import { useEffect, useMemo, useRef, useState } from "react";
import type {
  ChangeEvent as ReactChangeEvent,
  DragEvent,
  KeyboardEvent as ReactKeyboardEvent,
  PointerEvent as ReactPointerEvent,
} from "react";
import {
  ChartNoAxesCombined,
  ChartSpline,
  Crosshair,
  FileDown,
  FolderOpen,
  ImageDown,
  ListChecks,
  Move,
  Scaling,
  Sheet,
  Trash2,
  X,
} from "lucide-react";
import {
  Background,
  ConnectionLineType,
  ConnectionMode,
  Controls,
  ReactFlow,
  type Edge,
  type Node,
  type NodeTypes,
} from "@xyflow/react";
import {
  WorkspaceViewTabs,
  type WorkspaceView,
} from "./WorkspaceViewTabs";
import { AutoFitView } from "./AutoFitView";
import {
  CONTACT_AWARE_EDGE_TYPE,
  contactAwareEdgeTypes,
} from "./ContactAwareEdge";

type ResultPortDefinition = {
  name: string;
  kind: string;
  domain: string;
  nominalRole: string;
  positiveFlowDirection?: string;
  side: "left" | "right";
};

type ResultNodeData = {
  label: string;
  componentType: string;
  modelType: string;
  ports: ResultPortDefinition[];
  parameters: Record<string, number | string>;
  parameterUnits?: Record<string, string>;
  rotation: 0 | 90 | 180 | 270;
  mirrored: boolean;
};

type ResultRenderedNodeData = ResultNodeData & {
  portConnectionStates: Record<string, "idle" | "connected">;
};

type ResultProjectNode = {
  id: string;
  type: "simulationComponent";
  position: {
    x: number;
    y: number;
  };
  data: ResultNodeData;
};

type ResultProjectEdge = {
  id: string;
  source: string;
  target: string;
  sourceHandle: string | null;
  targetHandle: string | null;
};

type ResultSimulationConfig = {
  t_start: number;
  t_stop: number;
  step: number;
  max_step: number;
  method: string;
};

export type ResultVariableMetadata = {
  key: string;
  componentId: string;
  componentType: string;
  scope: "component" | "port";
  portName: string | null;
  name: string;
  label: string;
  quantity: string;
  unit: string;
  category: string;
  order: number;
};

type ResultPayload = {
  success: boolean;
  status?: "completed" | "stopped" | "stalled" | "failed";
  partial?: boolean;
  message: string;
  simulatedUntil?: number;
  requestedStopTime?: number;
  variables: ResultVariableMetadata[];
  final: Record<string, number>;
  series: Record<string, number[]>;
  diagnostics: {
    pressureFlow: {
      solveCount: number;
      maxScaledResidual: number;
      maxEvaluationsPerSolve: number;
    };
    stream: {
      maxIterationsPerSolve: number;
    };
    stateCount: number;
    sampleCount: number;
  };
};

export type SimulationResultsSnapshot = {
  id: string;
  createdAt: string;
  project: {
    name: string;
    presentationLayoutVersion?: 1 | null;
    nodes: ResultProjectNode[];
    edges: ResultProjectEdge[];
    simulation: ResultSimulationConfig;
  };
  result: ResultPayload;
};

type SimulationResultFile = {
  fileType: "system-simulation-result";
  formatVersion: 1;
  exportedAt: string;
  metadata: {
    projectName: string;
    resultCreatedAt: string;
    simulation: ResultSimulationConfig & {
      simulatedUntil: number | null;
    };
    resultStatus: NonNullable<ResultPayload["status"]>;
    componentCount: number;
    connectionCount: number;
    sampleCount: number;
    componentParameters: Array<{
      id: string;
      name: string;
      componentType: string;
      parameters: Record<string, number | string>;
      parameterUnits: Record<string, string>;
    }>;
  };
  snapshot: SimulationResultsSnapshot;
};

type SimulationResultsViewProps = {
  snapshot: SimulationResultsSnapshot;
  nodeTypes: NodeTypes;
  onViewChange: (view: WorkspaceView) => void;
  onSnapshotLoad: (snapshot: SimulationResultsSnapshot) => void;
};

type EmptySimulationResultsViewProps = {
  onViewChange: (view: WorkspaceView) => void;
  onSnapshotLoad: (snapshot: SimulationResultsSnapshot) => void;
};

type ChartWindow = {
  id: string;
  kind: "single" | "multi" | "mixed";
  variableKey: string;
  variableKeys: string[];
  hiddenVariableKeys: string[];
  variableUnits: Record<string, string>;
  x: number;
  y: number;
  width: number;
  height: number;
  unit: string;
  cursorEnabled: boolean;
  zIndex: number;
};

type ResultUnitOption = {
  value: string;
  label: string;
  fromBase: (value: number) => number;
};

type WindowDragState = {
  windowId: string;
  pointerId: number;
  offsetX: number;
  offsetY: number;
  width: number;
  height: number;
};

type WindowResizeState = {
  windowId: string;
  pointerId: number;
  startX: number;
  startY: number;
  startWidth: number;
  startHeight: number;
  windowX: number;
  windowY: number;
};

type ResultsPaneLayout = {
  inspectorWidth: number;
  systemHeight: number;
};

type PaneResizeKind = "inspector-width" | "system-height";

type PaneResizeState = {
  kind: PaneResizeKind;
  pointerId: number;
  startX: number;
  startY: number;
  startSize: number;
};

const RESULT_VARIABLE_MIME = "application/x-system-simulation-variable";
const RESULT_FILE_TYPE = "system-simulation-result";
const RESULT_FILE_FORMAT_VERSION = 1;
const RESULT_FILE_MIME = "application/vnd.system-simulation.result+json";
const MAX_RESULT_FILE_SIZE = 250 * 1024 * 1024;
const RESULT_LAYOUT_KEY_PREFIX = "system-simulation-flow:result-layout:";
const RESULT_PANE_LAYOUT_KEY = "system-simulation-flow:result-pane-layout";
const CHART_WINDOW_WIDTH = 420;
const CHART_WINDOW_HEIGHT = 260;
const MULTI_CHART_WINDOW_WIDTH = 560;
const MULTI_CHART_WINDOW_HEIGHT = 340;
const MIN_CHART_WINDOW_WIDTH = 360;
const MIN_CHART_WINDOW_HEIGHT = 240;
const PANE_SPLITTER_SIZE = 7;
const MIN_INSPECTOR_WIDTH = 320;
const MIN_CHART_WIDTH = 440;
const MIN_SYSTEM_HEIGHT = 180;
const MIN_VARIABLE_HEIGHT = 180;
const PANE_KEYBOARD_STEP = 20;
const CHART_COLORS = [
  "#1d6fb8",
  "#c2413b",
  "#2f7d55",
  "#b36b16",
  "#6b5ca5",
  "#087f8c",
  "#9a4f76",
];
const PRESSURE_RESULT_UNITS = [
  scaledResultUnit("Pa", "Pa", 1),
  scaledResultUnit("kPa", "kPa", 1e3),
  scaledResultUnit("MPa", "MPa", 1e6),
  scaledResultUnit("bar", "bar", 1e5),
];
const SPECIFIC_ENERGY_RESULT_UNITS = [
  scaledResultUnit("J/kg", "J/kg", 1),
  scaledResultUnit("kJ/kg", "kJ/kg", 1e3),
  scaledResultUnit("MJ/kg", "MJ/kg", 1e6),
];
const RESULT_UNIT_OPTIONS: Record<string, ResultUnitOption[]> = {
  area: [
    scaledResultUnit("m2", "m²", 1),
    scaledResultUnit("cm2", "cm²", 1e-4),
    scaledResultUnit("mm2", "mm²", 1e-6),
  ],
  heat_transfer_coefficient: [
    scaledResultUnit("W/(m2*K)", "W/(m²·K)", 1),
  ],
  pressure: PRESSURE_RESULT_UNITS,
  absolute_pressure: PRESSURE_RESULT_UNITS,
  temperature: [
    scaledResultUnit("K", "K", 1),
    { value: "degC", label: "°C", fromBase: (value) => value - 273.15 },
  ],
  mass: [
    scaledResultUnit("kg", "kg", 1),
    scaledResultUnit("g", "g", 1e-3),
    scaledResultUnit("t", "t", 1e3),
  ],
  internal_energy: [
    scaledResultUnit("J", "J", 1),
    scaledResultUnit("kJ", "kJ", 1e3),
    scaledResultUnit("MJ", "MJ", 1e6),
  ],
  energy: [
    scaledResultUnit("J", "J", 1),
    scaledResultUnit("kJ", "kJ", 1e3),
    scaledResultUnit("MJ", "MJ", 1e6),
  ],
  specific_internal_energy: SPECIFIC_ENERGY_RESULT_UNITS,
  specific_enthalpy: SPECIFIC_ENERGY_RESULT_UNITS,
  density: [
    scaledResultUnit("kg/m³", "kg/m³", 1),
    scaledResultUnit("g/cm³", "g/cm³", 1e3),
  ],
  mass_flow: [
    scaledResultUnit("kg/s", "kg/s", 1),
    scaledResultUnit("g/s", "g/s", 1e-3),
    scaledResultUnit("kg/min", "kg/min", 1 / 60),
    scaledResultUnit("kg/h", "kg/h", 1 / 3600),
  ],
  volume: [
    scaledResultUnit("m3", "m³", 1),
    scaledResultUnit("L", "L", 1e-3),
    scaledResultUnit("mL", "mL", 1e-6),
  ],
  length: [
    scaledResultUnit("m", "m", 1),
    scaledResultUnit("cm", "cm", 1e-2),
    scaledResultUnit("mm", "mm", 1e-3),
  ],
  velocity: [
    scaledResultUnit("m/s", "m/s", 1),
  ],
};

export function SimulationResultsView({
  snapshot,
  nodeTypes,
  onViewChange,
  onSnapshotLoad,
}: SimulationResultsViewProps) {
  const resultStatus = simulationResultStatus(snapshot.result);
  const [selectedNodeId, setSelectedNodeId] = useState<string | null>(
    snapshot.project.nodes[0]?.id ?? null,
  );
  const [chartWindows, setChartWindows] = useState<ChartWindow[]>(() =>
    loadChartWindows(snapshot.id),
  );
  const [paneLayout, setPaneLayout] = useState<ResultsPaneLayout>(
    loadResultsPaneLayout,
  );
  const [activePaneResize, setActivePaneResize] =
    useState<PaneResizeKind | null>(null);
  const [csvDownloadPending, setCsvDownloadPending] = useState(false);
  const [activeMultiPickerWindowId, setActiveMultiPickerWindowId] =
    useState<string | null>(null);
  const [multiDropTargetWindowId, setMultiDropTargetWindowId] =
    useState<string | null>(null);
  const workbenchRef = useRef<HTMLElement>(null);
  const workspaceRef = useRef<HTMLDivElement>(null);
  const dragStateRef = useRef<WindowDragState | null>(null);
  const resizeStateRef = useRef<WindowResizeState | null>(null);
  const paneResizeStateRef = useRef<PaneResizeState | null>(null);
  const nextWindowIdRef = useRef(nextChartWindowNumber(chartWindows));
  const topZIndexRef = useRef(
    Math.max(1, ...chartWindows.map((window) => window.zIndex)),
  );

  useEffect(() => {
    storeChartWindows(snapshot.id, chartWindows);
  }, [chartWindows, snapshot.id]);

  useEffect(() => {
    storeResultsPaneLayout(paneLayout);
  }, [paneLayout]);

  useEffect(() => {
    const clampLayoutToWorkbench = () => {
      const bounds = workbenchRef.current?.getBoundingClientRect();
      if (!bounds) {
        return;
      }
      setPaneLayout((current) => {
        const next = clampResultsPaneLayout(current, bounds.width, bounds.height);
        return sameResultsPaneLayout(current, next) ? current : next;
      });
    };
    clampLayoutToWorkbench();
    window.addEventListener("resize", clampLayoutToWorkbench);
    return () => window.removeEventListener("resize", clampLayoutToWorkbench);
  }, []);

  useEffect(() => {
    const workspace = workspaceRef.current;
    if (!workspace || typeof ResizeObserver === "undefined") {
      return;
    }
    const observer = new ResizeObserver(([entry]) => {
      if (!entry) {
        return;
      }
      const { width, height } = entry.contentRect;
      setChartWindows((current) => {
        let changed = false;
        const next = current.map((chartWindow) => {
          const size = clampChartWindowDimensions(
            chartWindow.width,
            chartWindow.height,
            width,
            height,
          );
          const x = clampWindowCoordinate(
            chartWindow.x,
            width,
            size.width,
          );
          const y = clampWindowCoordinate(
            chartWindow.y,
            height,
            size.height,
          );
          const windowChanged =
            x !== chartWindow.x ||
            y !== chartWindow.y ||
            size.width !== chartWindow.width ||
            size.height !== chartWindow.height;
          changed ||= windowChanged;
          return windowChanged
            ? { ...chartWindow, ...size, x, y }
            : chartWindow;
        });
        return changed ? next : current;
      });
    });
    observer.observe(workspace);
    return () => observer.disconnect();
  }, []);

  const selectedNode =
    snapshot.project.nodes.find((node) => node.id === selectedNodeId) ?? null;
  const connectedPortKeys = useMemo(() => {
    const keys = new Set<string>();
    snapshot.project.edges.forEach((edge) => {
      if (edge.sourceHandle) {
        keys.add(`${edge.source}:${edge.sourceHandle}`);
      }
      if (edge.targetHandle) {
        keys.add(`${edge.target}:${edge.targetHandle}`);
      }
    });
    return keys;
  }, [snapshot.project.edges]);
  const readOnlyNodes = useMemo<
    Node<ResultRenderedNodeData, "simulationComponent">[]
  >(
    () =>
      snapshot.project.nodes.map((node) => ({
        ...node,
        className: "results-readonly-node",
        connectable: false,
        draggable: false,
        focusable: true,
        selectable: true,
        selected: node.id === selectedNodeId,
        data: {
          ...node.data,
          portConnectionStates: Object.fromEntries(
            node.data.ports.map((port) => [
              port.name,
              connectedPortKeys.has(`${node.id}:${port.name}`)
                ? "connected"
                : "idle",
            ]),
          ),
        },
      })),
    [connectedPortKeys, selectedNodeId, snapshot.project.nodes],
  );
  const readOnlyEdges = useMemo<Edge[]>(
    () =>
      snapshot.project.edges.map((edge) => ({
        ...edge,
        focusable: false,
        selectable: false,
        type: CONTACT_AWARE_EDGE_TYPE,
      })),
    [snapshot.project.edges],
  );
  const selectedVariables = useMemo(
    () =>
      selectedNode
        ? resultVariablesForNode(
            snapshot.result.variables,
            snapshot.result.series,
            selectedNode.id,
          )
        : [],
    [selectedNode, snapshot.result.series, snapshot.result.variables],
  );
  const componentVariables = selectedVariables.filter(
    (variable) => variable.scope === "component",
  );
  const portVariables = selectedVariables.filter(
    (variable) => variable.scope === "port",
  );
  const plottableResultVariables = useMemo(
    () =>
      snapshot.result.variables
        .filter(
          (variable) =>
            (snapshot.result.series[variable.key]?.length ?? 0) > 0,
        )
        .sort((first, second) =>
          first.key.localeCompare(second.key, "zh-CN"),
        ),
    [snapshot.result.series, snapshot.result.variables],
  );
  const setPaneSize = (kind: PaneResizeKind, requestedSize: number) => {
    const bounds = workbenchRef.current?.getBoundingClientRect();
    if (!bounds) {
      return;
    }
    setPaneLayout((current) =>
      clampResultsPaneLayout(
        {
          ...current,
          ...(kind === "inspector-width"
            ? { inspectorWidth: requestedSize }
            : { systemHeight: requestedSize }),
        },
        bounds.width,
        bounds.height,
      ),
    );
  };

  const startPaneResize = (
    event: ReactPointerEvent<HTMLDivElement>,
    kind: PaneResizeKind,
  ) => {
    event.preventDefault();
    paneResizeStateRef.current = {
      kind,
      pointerId: event.pointerId,
      startX: event.clientX,
      startY: event.clientY,
      startSize:
        kind === "inspector-width"
          ? paneLayout.inspectorWidth
          : paneLayout.systemHeight,
    };
    event.currentTarget.setPointerCapture(event.pointerId);
    setActivePaneResize(kind);
  };

  const movePaneResize = (event: ReactPointerEvent<HTMLDivElement>) => {
    const resize = paneResizeStateRef.current;
    if (!resize || resize.pointerId !== event.pointerId) {
      return;
    }
    const delta =
      resize.kind === "inspector-width"
        ? event.clientX - resize.startX
        : event.clientY - resize.startY;
    setPaneSize(resize.kind, resize.startSize + delta);
  };

  const stopPaneResize = (event: ReactPointerEvent<HTMLDivElement>) => {
    if (paneResizeStateRef.current?.pointerId !== event.pointerId) {
      return;
    }
    if (event.currentTarget.hasPointerCapture(event.pointerId)) {
      event.currentTarget.releasePointerCapture(event.pointerId);
    }
    paneResizeStateRef.current = null;
    setActivePaneResize(null);
  };

  const resizePaneWithKeyboard = (
    event: ReactKeyboardEvent<HTMLDivElement>,
    kind: PaneResizeKind,
  ) => {
    const decreaseKey = kind === "inspector-width" ? "ArrowLeft" : "ArrowUp";
    const increaseKey = kind === "inspector-width" ? "ArrowRight" : "ArrowDown";
    if (event.key !== decreaseKey && event.key !== increaseKey) {
      return;
    }
    event.preventDefault();
    const currentSize =
      kind === "inspector-width"
        ? paneLayout.inspectorWidth
        : paneLayout.systemHeight;
    setPaneSize(
      kind,
      currentSize +
        (event.key === increaseKey ? PANE_KEYBOARD_STEP : -PANE_KEYBOARD_STEP),
    );
  };

  const resetPaneSize = (kind: PaneResizeKind) => {
    const defaults = defaultResultsPaneLayout();
    setPaneSize(
      kind,
      kind === "inspector-width"
        ? defaults.inspectorWidth
        : defaults.systemHeight,
    );
  };

  const focusChartWindow = (windowId: string) => {
    const zIndex = ++topZIndexRef.current;
    setChartWindows((current) =>
      current.map((window) =>
        window.id === windowId ? { ...window, zIndex } : window,
      ),
    );
  };

  const addChartWindow = (
    variableKey: string,
    requestedPosition?: { x: number; y: number },
  ) => {
    const workspace = workspaceRef.current;
    if (!workspace) {
      return;
    }
    const existing = chartWindows.find(
      (window) =>
        window.kind === "single" && window.variableKey === variableKey,
    );
    if (existing) {
      focusChartWindow(existing.id);
      return;
    }
    const bounds = workspace.getBoundingClientRect();
    const size = clampChartWindowDimensions(
      CHART_WINDOW_WIDTH,
      CHART_WINDOW_HEIGHT,
      bounds.width,
      bounds.height,
    );
    const variable = snapshot.result.variables.find(
      (item) => item.key === variableKey,
    );
    const index = chartWindows.length;
    const fallback = {
      x: 18 + (index % 3) * 26,
      y: 18 + (index % 4) * 26,
    };
    const position = requestedPosition ?? fallback;
    const zIndex = ++topZIndexRef.current;
    setChartWindows((current) => [
      ...current,
      {
        id: `chart-${nextWindowIdRef.current++}`,
        kind: "single",
        variableKey,
        variableKeys: [variableKey],
        hiddenVariableKeys: [],
        variableUnits: { [variableKey]: variable?.unit ?? "" },
        x: clampWindowCoordinate(
          position.x,
          bounds.width,
          size.width,
        ),
        y: clampWindowCoordinate(
          position.y,
          bounds.height,
          size.height,
        ),
        width: size.width,
        height: size.height,
        unit: variable?.unit ?? "",
        cursorEnabled: false,
        zIndex,
      },
    ]);
  };

  const addCombinedChartWindow = (
    kind: "multi" | "mixed",
    requestedPosition?: { x: number; y: number },
  ) => {
    const workspace = workspaceRef.current;
    if (!workspace) {
      return;
    }

    const bounds = workspace.getBoundingClientRect();
    const size = clampChartWindowDimensions(
      MULTI_CHART_WINDOW_WIDTH,
      MULTI_CHART_WINDOW_HEIGHT,
      bounds.width,
      bounds.height,
    );
    const index = chartWindows.length;
    const position = requestedPosition ?? {
      x: (kind === "mixed" ? 38 : 28) + (index % 3) * 28,
      y: (kind === "mixed" ? 38 : 28) + (index % 4) * 28,
    };
    const id = `chart-${nextWindowIdRef.current++}`;
    const zIndex = ++topZIndexRef.current;
    setChartWindows((current) => [
      ...current,
      {
        id,
        kind,
        variableKey: "",
        variableKeys: [],
        hiddenVariableKeys: [],
        variableUnits: {},
        x: clampWindowCoordinate(position.x, bounds.width, size.width),
        y: clampWindowCoordinate(position.y, bounds.height, size.height),
        width: size.width,
        height: size.height,
        unit: "",
        cursorEnabled: false,
        zIndex,
      },
    ]);
    setActiveMultiPickerWindowId(null);
  };

  const toggleChartCurveVisibility = (
    windowId: string,
    variableKey: string,
  ) => {
    setChartWindows((current) =>
      current.map((window) => {
        if (window.id !== windowId || window.kind === "single") {
          return window;
        }
        const hiddenVariableKeys = window.hiddenVariableKeys.includes(variableKey)
          ? window.hiddenVariableKeys.filter((key) => key !== variableKey)
          : [...window.hiddenVariableKeys, variableKey];
        return {
          ...window,
          hiddenVariableKeys,
        };
      }),
    );
  };

  const removeChartCurve = (windowId: string, variableKey: string) => {
    const resetsWindow = chartWindows.some(
      (window) =>
        window.id === windowId &&
        window.kind !== "single" &&
        window.variableKeys.length === 1,
    );
    setChartWindows((current) =>
      current.map((window) => {
        if (window.id !== windowId || window.kind === "single") {
          return window;
        }
        if (window.variableKeys.length === 1) {
          return {
            ...window,
            variableKey: "",
            variableKeys: [],
            hiddenVariableKeys: [],
            variableUnits: {},
            unit: "",
            cursorEnabled: false,
          };
        }
        const variableKeys = window.variableKeys.filter(
          (key) => key !== variableKey,
        );
        return {
          ...window,
          variableKey: variableKeys[0],
          variableKeys,
          hiddenVariableKeys: window.hiddenVariableKeys.filter(
            (key) => key !== variableKey,
          ),
          variableUnits: Object.fromEntries(
            Object.entries(window.variableUnits).filter(
              ([key]) => key !== variableKey,
            ),
          ),
        };
      }),
    );
    if (resetsWindow) {
      setActiveMultiPickerWindowId(null);
    }
  };

  const addDroppedVariableToMultiChart = (
    event: DragEvent<HTMLElement>,
    chartWindow: ChartWindow,
  ) => {
    event.preventDefault();
    event.stopPropagation();
    setMultiDropTargetWindowId(null);
    const variableKey = event.dataTransfer.getData(RESULT_VARIABLE_MIME);
    const variable = snapshot.result.variables.find(
      (item) => item.key === variableKey,
    );
    const primaryVariable =
      snapshot.result.variables.find(
        (item) => item.key === chartWindow.variableKey,
      ) ??
      chartWindow.variableKeys
        .map((key) =>
          snapshot.result.variables.find((item) => item.key === key),
        )
        .find((item): item is ResultVariableMetadata => item !== undefined);
    if (!variableKey || !variable || chartWindow.kind === "single") {
      return;
    }
    if (
      chartWindow.kind === "multi" &&
      primaryVariable &&
      variable.unit !== primaryVariable.unit
    ) {
      window.alert(
        `无法加入曲线：该窗口只接受 SI 单位为 ${primaryVariable.unit || "无量纲"} 的变量。`,
      );
      return;
    }
    setChartWindows((current) =>
      current.map((window) => {
        if (window.id !== chartWindow.id || window.kind === "single") {
          return window;
        }
        if (window.variableKeys.length === 0 || !primaryVariable) {
          return {
            ...window,
            variableKey,
            variableKeys: [variableKey],
            hiddenVariableKeys: [],
            variableUnits: { [variableKey]: variable.unit },
            unit: variable.unit,
          };
        }
        if (window.variableKeys.includes(variableKey)) {
          return {
            ...window,
            hiddenVariableKeys: window.hiddenVariableKeys.filter(
              (key) => key !== variableKey,
            ),
          };
        }
        return {
          ...window,
          variableKeys: [...window.variableKeys, variableKey],
          hiddenVariableKeys: window.hiddenVariableKeys.filter(
            (key) => key !== variableKey,
          ),
          variableUnits: {
            ...window.variableUnits,
            [variableKey]: variable.unit,
          },
        };
      }),
    );
  };

  const handleVariableDragStart = (
    event: DragEvent<HTMLButtonElement>,
    variableKey: string,
  ) => {
    event.dataTransfer.effectAllowed = "copy";
    event.dataTransfer.setData(RESULT_VARIABLE_MIME, variableKey);
  };

  const handleWorkspaceDrop = (event: DragEvent<HTMLDivElement>) => {
    event.preventDefault();
    const variableKey = event.dataTransfer.getData(RESULT_VARIABLE_MIME);
    const workspace = workspaceRef.current;
    if (!variableKey || !workspace) {
      return;
    }
    const bounds = workspace.getBoundingClientRect();
    addChartWindow(variableKey, {
      x: event.clientX - bounds.left - CHART_WINDOW_WIDTH / 2,
      y: event.clientY - bounds.top - 34,
    });
  };

  const startWindowDrag = (
    event: ReactPointerEvent<HTMLDivElement>,
    chartWindow: ChartWindow,
  ) => {
    const windowElement = event.currentTarget.closest(".result-chart-window");
    if (!(windowElement instanceof HTMLElement)) {
      return;
    }
    const bounds = windowElement.getBoundingClientRect();
    dragStateRef.current = {
      windowId: chartWindow.id,
      pointerId: event.pointerId,
      offsetX: event.clientX - bounds.left,
      offsetY: event.clientY - bounds.top,
      width: chartWindow.width,
      height: chartWindow.height,
    };
    event.currentTarget.setPointerCapture(event.pointerId);
    focusChartWindow(chartWindow.id);
  };

  const moveChartWindow = (event: ReactPointerEvent<HTMLDivElement>) => {
    const dragState = dragStateRef.current;
    const workspace = workspaceRef.current;
    if (
      !dragState ||
      dragState.pointerId !== event.pointerId ||
      !workspace
    ) {
      return;
    }
    const bounds = workspace.getBoundingClientRect();
    const x = clampWindowCoordinate(
      event.clientX - bounds.left - dragState.offsetX,
      bounds.width,
      dragState.width,
    );
    const y = clampWindowCoordinate(
      event.clientY - bounds.top - dragState.offsetY,
      bounds.height,
      dragState.height,
    );
    setChartWindows((current) =>
      current.map((window) =>
        window.id === dragState.windowId ? { ...window, x, y } : window,
      ),
    );
  };

  const stopWindowDrag = (event: ReactPointerEvent<HTMLDivElement>) => {
    if (dragStateRef.current?.pointerId !== event.pointerId) {
      return;
    }
    if (event.currentTarget.hasPointerCapture(event.pointerId)) {
      event.currentTarget.releasePointerCapture(event.pointerId);
    }
    dragStateRef.current = null;
  };

  const startWindowResize = (
    event: ReactPointerEvent<HTMLButtonElement>,
    chartWindow: ChartWindow,
  ) => {
    event.preventDefault();
    event.stopPropagation();
    resizeStateRef.current = {
      windowId: chartWindow.id,
      pointerId: event.pointerId,
      startX: event.clientX,
      startY: event.clientY,
      startWidth: chartWindow.width,
      startHeight: chartWindow.height,
      windowX: chartWindow.x,
      windowY: chartWindow.y,
    };
    event.currentTarget.setPointerCapture(event.pointerId);
    focusChartWindow(chartWindow.id);
  };

  const resizeChartWindow = (event: ReactPointerEvent<HTMLButtonElement>) => {
    const resize = resizeStateRef.current;
    const workspace = workspaceRef.current;
    if (!resize || resize.pointerId !== event.pointerId || !workspace) {
      return;
    }
    event.preventDefault();
    const bounds = workspace.getBoundingClientRect();
    const width = clampChartWindowDimension(
      resize.startWidth + event.clientX - resize.startX,
      bounds.width - resize.windowX - 12,
      MIN_CHART_WINDOW_WIDTH,
    );
    const height = clampChartWindowDimension(
      resize.startHeight + event.clientY - resize.startY,
      bounds.height - resize.windowY - 12,
      MIN_CHART_WINDOW_HEIGHT,
    );
    setChartWindows((current) =>
      current.map((window) =>
        window.id === resize.windowId ? { ...window, width, height } : window,
      ),
    );
  };

  const stopWindowResize = (event: ReactPointerEvent<HTMLButtonElement>) => {
    if (resizeStateRef.current?.pointerId !== event.pointerId) {
      return;
    }
    if (event.currentTarget.hasPointerCapture(event.pointerId)) {
      event.currentTarget.releasePointerCapture(event.pointerId);
    }
    resizeStateRef.current = null;
  };

  const removeChartWindow = (windowId: string) => {
    setChartWindows((current) =>
      current.filter((window) => window.id !== windowId),
    );
    setActiveMultiPickerWindowId((current) =>
      current === windowId ? null : current,
    );
  };

  const updateChartWindowUnit = (windowId: string, unit: string) => {
    setChartWindows((current) =>
      current.map((window) =>
        window.id === windowId ? { ...window, unit } : window,
      ),
    );
  };

  const updateChartCurveUnit = (
    windowId: string,
    variableKey: string,
    unit: string,
  ) => {
    setChartWindows((current) =>
      current.map((window) =>
        window.id === windowId
          ? {
              ...window,
              variableUnits: {
                ...window.variableUnits,
                [variableKey]: unit,
              },
            }
          : window,
      ),
    );
  };

  const toggleChartWindowCursor = (windowId: string) => {
    setChartWindows((current) =>
      current.map((window) =>
        window.id === windowId
          ? { ...window, cursorEnabled: !window.cursorEnabled }
          : window,
      ),
    );
  };

  const downloadResultsCsv = async () => {
    if (csvDownloadPending) {
      return;
    }
    setCsvDownloadPending(true);
    try {
      const response = await fetch("/api/simulation-results/csv", {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({
          projectName: snapshot.project.name,
          variables: snapshot.result.variables,
          series: snapshot.result.series,
        }),
      });
      if (!response.ok) {
        throw new Error(await responseErrorMessage(response));
      }
      const filename = responseDownloadFilename(
        response,
        `${safeFileStem(snapshot.project.name)}-results.csv`,
      );
      downloadBlob(await response.blob(), filename);
    } catch (error) {
      window.alert(`CSV 下载失败：${errorMessage(error)}`);
    } finally {
      setCsvDownloadPending(false);
    }
  };

  return (
    <div className="results-shell">
      <header className="results-topbar">
        <div>
          <div className="product-name">System Simulation Flow</div>
          <div className="product-meta">仿真结果查看</div>
        </div>
        <WorkspaceViewTabs
          activeView="results"
          hasResults
          onViewChange={onViewChange}
        />
        <div className="results-run-actions">
          <ResultsFileToolbar
            csvDownloadPending={csvDownloadPending}
            onDownloadCsv={() => void downloadResultsCsv()}
            onSnapshotLoad={onSnapshotLoad}
            snapshot={snapshot}
          />
          <div className="results-run-meta">
            <strong>{snapshot.project.name}</strong>
            {resultStatus !== "completed" ? (
              <span className={`results-run-status ${resultStatus}`}>
                {simulationResultStatusText(snapshot.result, resultStatus)}
              </span>
            ) : null}
            <span>
              {snapshot.result.diagnostics.sampleCount} 个采样点 ·{" "}
              {formatResultTimestamp(snapshot.createdAt)}
            </span>
          </div>
        </div>
      </header>

      <main
        className={`results-workbench ${
          activePaneResize ? `resizing-${activePaneResize}` : ""
        }`}
        ref={workbenchRef}
        style={{
          gridTemplateColumns: `${paneLayout.inspectorWidth}px ${PANE_SPLITTER_SIZE}px minmax(${MIN_CHART_WIDTH}px, 1fr)`,
        }}
      >
        <div
          className="results-inspector-pane"
          style={{
            gridTemplateRows: `${paneLayout.systemHeight}px ${PANE_SPLITTER_SIZE}px minmax(${MIN_VARIABLE_HEIGHT}px, 1fr)`,
          }}
        >
          <section className="results-system-panel">
            <div className="results-section-heading">
              <strong>系统图</strong>
              <span>{snapshot.project.nodes.length} 个组件</span>
            </div>
            <div className="results-system-canvas">
              <ReactFlow
                colorMode="light"
                connectionLineType={ConnectionLineType.Step}
                connectionMode={ConnectionMode.Loose}
                deleteKeyCode={null}
                edges={readOnlyEdges}
                edgeTypes={contactAwareEdgeTypes}
                edgesFocusable={false}
                edgesReconnectable={false}
                elementsSelectable
                minZoom={0.1}
                nodeTypes={nodeTypes}
                nodes={readOnlyNodes}
                nodesConnectable={false}
                nodesDraggable={false}
                nodesFocusable
                onNodeClick={(_, node) => setSelectedNodeId(node.id)}
                onPaneClick={() => setSelectedNodeId(null)}
                panOnDrag
                selectionOnDrag={false}
                zoomOnDoubleClick={false}
              >
                <AutoFitView
                  enabled={readOnlyNodes.length > 0}
                  expectedNodeCount={readOnlyNodes.length}
                  fitOnMount
                  requestKey={snapshot.id}
                />
                <Background gap={18} />
                <Controls
                  fitViewOptions={{ duration: 180, minZoom: 0.1, padding: 0.18 }}
                />
              </ReactFlow>
            </div>
          </section>

          <div
            aria-label="调整系统图和结果变量区域高度"
            aria-orientation="horizontal"
            aria-valuemin={MIN_SYSTEM_HEIGHT}
            aria-valuenow={Math.round(paneLayout.systemHeight)}
            className="results-pane-splitter horizontal"
            onDoubleClick={() => resetPaneSize("system-height")}
            onKeyDown={(event) =>
              resizePaneWithKeyboard(event, "system-height")
            }
            onPointerCancel={stopPaneResize}
            onPointerDown={(event) =>
              startPaneResize(event, "system-height")
            }
            onPointerMove={movePaneResize}
            onPointerUp={stopPaneResize}
            role="separator"
            tabIndex={0}
            title="拖动调整上下区域，双击恢复默认"
          >
            <span aria-hidden="true" />
          </div>

          <aside className="results-variable-panel">
            <div className="results-section-heading">
              <strong>结果变量</strong>
              <span>{selectedVariables.length}</span>
            </div>
            <div className="results-variable-content">
              {selectedNode ? (
                <>
                  <div className="results-selected-component">
                    <strong>{selectedNode.data.label}</strong>
                    <span>{selectedNode.data.modelType}</span>
                  </div>
                  <VariableGroup
                    chartWindows={chartWindows}
                    onClick={addChartWindow}
                    onDragStart={handleVariableDragStart}
                    title="组件变量"
                    variables={componentVariables}
                  />
                  <VariableGroup
                    chartWindows={chartWindows}
                    onClick={addChartWindow}
                    onDragStart={handleVariableDragStart}
                    title="端口变量"
                    variables={portVariables}
                  />
                </>
              ) : (
                <div className="results-variable-empty">未选择组件</div>
              )}
            </div>
          </aside>
        </div>

        <div
          aria-label="调整系统与曲线区域宽度"
          aria-orientation="vertical"
          aria-valuemin={MIN_INSPECTOR_WIDTH}
          aria-valuenow={Math.round(paneLayout.inspectorWidth)}
          className="results-pane-splitter vertical"
          onDoubleClick={() => resetPaneSize("inspector-width")}
          onKeyDown={(event) =>
            resizePaneWithKeyboard(event, "inspector-width")
          }
          onPointerCancel={stopPaneResize}
          onPointerDown={(event) =>
            startPaneResize(event, "inspector-width")
          }
          onPointerMove={movePaneResize}
          onPointerUp={stopPaneResize}
          role="separator"
          tabIndex={0}
          title="拖动调整左右区域，双击恢复默认"
        >
          <span aria-hidden="true" />
        </div>

        <section className="results-chart-panel">
          <div className="results-section-heading results-chart-heading">
            <strong>曲线窗口</strong>
            <div className="results-chart-heading-tools">
              <span>
                {chartWindows.length} 个窗口 ·{" "}
                {chartWindows.reduce(
                  (count, window) => count + window.variableKeys.length,
                  0,
                )}{" "}
                条曲线
              </span>
              <div className="results-multi-create">
                <button
                  aria-label="新建同单位多曲线对比窗口"
                  disabled={plottableResultVariables.length === 0}
                  onClick={() => addCombinedChartWindow("multi")}
                  title="新建同单位多曲线对比窗口"
                  type="button"
                >
                  <ChartNoAxesCombined
                    aria-hidden="true"
                    size={17}
                    strokeWidth={1.9}
                  />
                </button>
              </div>
              <div className="results-multi-create">
                <button
                  aria-label="新建异单位上下对比窗口"
                  disabled={plottableResultVariables.length === 0}
                  onClick={() => addCombinedChartWindow("mixed")}
                  title="新建异单位上下对比窗口"
                  type="button"
                >
                  <ChartSpline
                    aria-hidden="true"
                    size={17}
                    strokeWidth={1.9}
                  />
                </button>
              </div>
            </div>
          </div>
          <div
            className={`results-chart-workspace ${
              chartWindows.length === 0 ? "empty" : ""
            }`}
            onDragOver={(event) => {
              event.preventDefault();
              event.dataTransfer.dropEffect = "copy";
            }}
            onDrop={handleWorkspaceDrop}
            ref={workspaceRef}
          >
            {chartWindows.map((chartWindow) => {
              const isCombined = chartWindow.kind !== "single";
              const isMixed = chartWindow.kind === "mixed";
              const windowVariables = chartWindow.variableKeys
                .map((key) =>
                  snapshot.result.variables.find((item) => item.key === key),
                )
                .filter(
                  (item): item is ResultVariableMetadata => item !== undefined,
                );
              const variable =
                windowVariables.find(
                  (item) => item.key === chartWindow.variableKey,
                ) ?? windowVariables[0];
              if (!variable) {
                if (!isCombined) {
                  return null;
                }
                const pendingTitle = isMixed
                  ? "异单位上下对比"
                  : "同单位多曲线对比";
                return (
                  <article
                    aria-label={`${pendingTitle}窗口（待定）`}
                    className={`result-chart-window ${chartWindow.kind} pending ${
                      multiDropTargetWindowId === chartWindow.id
                        ? "drop-target"
                        : ""
                    }`}
                    data-chart-kind={chartWindow.kind}
                    data-pending="true"
                    key={chartWindow.id}
                    onDragLeave={(event) => {
                      if (
                        event.relatedTarget instanceof Element &&
                        event.currentTarget.contains(event.relatedTarget)
                      ) {
                        return;
                      }
                      if (multiDropTargetWindowId === chartWindow.id) {
                        setMultiDropTargetWindowId(null);
                      }
                    }}
                    onDragOver={(event) => {
                      event.preventDefault();
                      event.stopPropagation();
                      event.dataTransfer.dropEffect = "copy";
                      setMultiDropTargetWindowId(chartWindow.id);
                    }}
                    onDrop={(event) =>
                      addDroppedVariableToMultiChart(event, chartWindow)
                    }
                    onPointerDown={() => focusChartWindow(chartWindow.id)}
                    style={{
                      height: chartWindow.height,
                      left: chartWindow.x,
                      top: chartWindow.y,
                      width: chartWindow.width,
                      zIndex: chartWindow.zIndex,
                    }}
                  >
                    <div
                      className="result-chart-window-header"
                      onPointerCancel={stopWindowDrag}
                      onPointerDown={(event) =>
                        startWindowDrag(event, chartWindow)
                      }
                      onPointerMove={moveChartWindow}
                      onPointerUp={stopWindowDrag}
                    >
                      <div className="result-chart-window-title">
                        <strong>{pendingTitle}</strong>
                        <span>待定 · 请拖入第一条曲线</span>
                      </div>
                      <div className="result-chart-window-actions">
                        <button
                          aria-label={`关闭${pendingTitle}窗口`}
                          className="close"
                          onClick={(event) => {
                            event.stopPropagation();
                            removeChartWindow(chartWindow.id);
                          }}
                          onPointerDown={(event) => event.stopPropagation()}
                          title="关闭曲线窗口"
                          type="button"
                        >
                          <X aria-hidden="true" size={16} strokeWidth={1.9} />
                        </button>
                      </div>
                    </div>
                    <div className="result-chart-pending">
                      {isMixed ? (
                        <ChartSpline aria-hidden="true" size={34} strokeWidth={1.5} />
                      ) : (
                        <ChartNoAxesCombined
                          aria-hidden="true"
                          size={34}
                          strokeWidth={1.5}
                        />
                      )}
                      <strong>等待第一条曲线</strong>
                      <span>
                        拖入变量后，将以第一条曲线初始化单位和显示设置
                      </span>
                    </div>
                    <button
                      aria-label={`调整${pendingTitle}窗口大小`}
                      className="result-chart-resize-handle"
                      onLostPointerCapture={stopWindowResize}
                      onPointerCancel={stopWindowResize}
                      onPointerDown={(event) =>
                        startWindowResize(event, chartWindow)
                      }
                      onPointerMove={resizeChartWindow}
                      onPointerUp={stopWindowResize}
                      title="调整窗口大小"
                      type="button"
                    >
                      <Scaling aria-hidden="true" size={13} strokeWidth={1.8} />
                    </button>
                  </article>
                );
              }
              const label = resultVariableLabel(variable);
              const component = snapshot.project.nodes.find(
                (node) => node.id === variable.componentId,
              );
              const componentName =
                component?.data.label ?? variable.componentId;
              const chartTitle = resultVariableTitle(variable, componentName);
              const unitOptions = resultUnitOptions(variable);
              const selectedUnit = resolveResultUnitOption(
                variable,
                chartWindow.unit,
              );
              const displayValues = (
                snapshot.result.series[chartWindow.variableKey] ?? []
              ).map(selectedUnit.fromBase);
              const combinedVariables = windowVariables.filter(
                (item) => isMixed || item.unit === variable.unit,
              );
              const visibleCombinedVariables = combinedVariables.filter(
                (item) => !chartWindow.hiddenVariableKeys.includes(item.key),
              );
              const multiSeries = visibleCombinedVariables.map((item) => {
                const itemComponent = snapshot.project.nodes.find(
                  (node) => node.id === item.componentId,
                );
                const itemUnit = isMixed
                  ? resolveResultUnitOption(
                      item,
                      chartWindow.variableUnits[item.key] ?? item.unit,
                    )
                  : selectedUnit;
                return {
                  key: item.key,
                  label: resultVariableTitle(
                    item,
                    itemComponent?.data.label ?? item.componentId,
                  ),
                  color: colorForVariable(item.key),
                  unit: itemUnit.label,
                  values: (snapshot.result.series[item.key] ?? []).map(
                    itemUnit.fromBase,
                  ),
                };
              });
              return (
                <article
                  className={`result-chart-window ${isCombined ? chartWindow.kind : "single"} ${
                    multiDropTargetWindowId === chartWindow.id
                      ? "drop-target"
                      : ""
                  }`}
                  data-chart-kind={chartWindow.kind}
                  data-pending="false"
                  key={chartWindow.id}
                  onDragLeave={(event) => {
                    if (
                      event.relatedTarget instanceof Element &&
                      event.currentTarget.contains(event.relatedTarget)
                    ) {
                      return;
                    }
                    if (multiDropTargetWindowId === chartWindow.id) {
                      setMultiDropTargetWindowId(null);
                    }
                  }}
                  onDragOver={(event) => {
                    if (!isCombined) {
                      return;
                    }
                    event.preventDefault();
                    event.stopPropagation();
                    event.dataTransfer.dropEffect = "copy";
                    setMultiDropTargetWindowId(chartWindow.id);
                  }}
                  onDrop={(event) => {
                    if (isCombined) {
                      addDroppedVariableToMultiChart(event, chartWindow);
                    }
                  }}
                  onPointerDown={() => focusChartWindow(chartWindow.id)}
                  style={{
                    height: chartWindow.height,
                    left: chartWindow.x,
                    top: chartWindow.y,
                    width: chartWindow.width,
                    zIndex: chartWindow.zIndex,
                  }}
                >
                  <div
                    className="result-chart-window-header"
                    onPointerCancel={stopWindowDrag}
                    onPointerDown={(event) =>
                      startWindowDrag(event, chartWindow)
                    }
                    onPointerMove={moveChartWindow}
                    onPointerUp={stopWindowDrag}
                  >
                    <div className="result-chart-window-title">
                      <strong>
                        {isMixed
                          ? "异单位上下对比"
                          : isCombined
                            ? "同单位多曲线对比"
                            : label}
                      </strong>
                      <span>
                        {isCombined
                          ? `${visibleCombinedVariables.length}/${combinedVariables.length} 条显示 · ${isMixed ? "上下同步图" : variable.unit || "无量纲"}`
                          : componentName}
                      </span>
                    </div>
                    <div className="result-chart-window-actions">
                      <button
                        aria-label={`${chartWindow.cursorEnabled ? "关闭" : "打开"} ${isCombined ? "多曲线" : label} 曲线游标`}
                        aria-pressed={chartWindow.cursorEnabled}
                        className={`cursor ${chartWindow.cursorEnabled ? "active" : ""}`}
                        onClick={(event) => {
                          event.stopPropagation();
                          toggleChartWindowCursor(chartWindow.id);
                        }}
                        onPointerDown={(event) => event.stopPropagation()}
                        title={chartWindow.cursorEnabled ? "关闭游标" : "打开游标"}
                        type="button"
                      >
                        <Crosshair
                          aria-hidden="true"
                          size={16}
                          strokeWidth={1.9}
                        />
                      </button>
                      {isCombined ? (
                        <div
                          className="result-chart-multi-picker"
                          onBlur={(event) => {
                            if (
                              !(event.relatedTarget instanceof HTMLElement) ||
                              !event.currentTarget.contains(event.relatedTarget)
                            ) {
                              setActiveMultiPickerWindowId(null);
                            }
                          }}
                          onKeyDown={(event) => {
                            if (event.key === "Escape") {
                              event.stopPropagation();
                              setActiveMultiPickerWindowId(null);
                            }
                          }}
                          onPointerDown={(event) => event.stopPropagation()}
                        >
                          <button
                            aria-expanded={
                              activeMultiPickerWindowId === chartWindow.id
                            }
                            aria-label="管理多曲线窗口中的曲线"
                            className={
                              activeMultiPickerWindowId === chartWindow.id
                                ? "active"
                                : ""
                            }
                            onClick={(event) => {
                              event.stopPropagation();
                              setActiveMultiPickerWindowId((current) =>
                                current === chartWindow.id
                                  ? null
                                  : chartWindow.id,
                              );
                            }}
                            title="显示、隐藏或删除曲线"
                            type="button"
                          >
                            <ListChecks
                              aria-hidden="true"
                              size={17}
                              strokeWidth={1.9}
                            />
                          </button>
                          {activeMultiPickerWindowId === chartWindow.id ? (
                            <div
                              aria-label="管理已加入多曲线窗口的曲线"
                              className="result-chart-multi-menu"
                              role="group"
                            >
                              <div className="result-chart-multi-menu-title">
                                <span>曲线管理</span>
                                <strong>
                                  {isMixed
                                    ? "多单位"
                                    : variable.unit || "无量纲"}
                                </strong>
                              </div>
                              <div className="result-chart-multi-menu-list">
                                {combinedVariables.map((item) => {
                                  const visible =
                                    !chartWindow.hiddenVariableKeys.includes(
                                      item.key,
                                    );
                                  const itemComponent =
                                    snapshot.project.nodes.find(
                                      (node) => node.id === item.componentId,
                                    );
                                  const itemTitle = resultVariableTitle(
                                    item,
                                    itemComponent?.data.label ?? item.componentId,
                                  );
                                  const itemUnitOptions = resultUnitOptions(item);
                                  const itemUnit = resolveResultUnitOption(
                                    item,
                                    chartWindow.variableUnits[item.key] ??
                                      item.unit,
                                  );
                                  return (
                                    <div
                                      className="result-chart-multi-menu-row"
                                      key={item.key}
                                      title={itemTitle}
                                    >
                                      <input
                                        aria-label={`${visible ? "隐藏" : "显示"} ${itemTitle}`}
                                        checked={visible}
                                        onChange={() =>
                                          toggleChartCurveVisibility(
                                            chartWindow.id,
                                            item.key,
                                          )
                                        }
                                        type="checkbox"
                                      />
                                      <span
                                        className="result-variable-swatch"
                                        style={{
                                          backgroundColor: colorForVariable(
                                            item.key,
                                          ),
                                        }}
                                      />
                                      <span className="result-chart-multi-menu-label">
                                        <b>{itemTitle}</b>
                                        <small>
                                          {resultVariableLabel(item)} ·{" "}
                                          {itemUnit.label || "无量纲"}
                                        </small>
                                      </span>
                                      {isMixed && itemUnitOptions.length > 1 ? (
                                        <select
                                          aria-label={`${itemTitle}纵轴单位`}
                                          onChange={(event) =>
                                            updateChartCurveUnit(
                                              chartWindow.id,
                                              item.key,
                                              event.target.value,
                                            )
                                          }
                                          title="该曲线纵轴单位"
                                          value={itemUnit.value}
                                        >
                                          {itemUnitOptions.map((option) => (
                                            <option
                                              key={option.value}
                                              value={option.value}
                                            >
                                              {option.label}
                                            </option>
                                          ))}
                                        </select>
                                      ) : null}
                                      <button
                                        aria-label={`删除 ${itemTitle}`}
                                        className="remove"
                                        onClick={() =>
                                          removeChartCurve(
                                            chartWindow.id,
                                            item.key,
                                          )
                                        }
                                        title="从窗口中删除曲线"
                                        type="button"
                                      >
                                        <Trash2
                                          aria-hidden="true"
                                          size={14}
                                          strokeWidth={1.8}
                                        />
                                      </button>
                                    </div>
                                  );
                                })}
                              </div>
                            </div>
                          ) : null}
                        </div>
                      ) : null}
                      {!isMixed && unitOptions.length > 1 ? (
                        <select
                          aria-label={`${isCombined ? "多曲线" : label}纵轴单位`}
                          onChange={(event) =>
                            updateChartWindowUnit(
                              chartWindow.id,
                              event.target.value,
                            )
                          }
                          onPointerDown={(event) => event.stopPropagation()}
                          title="纵轴单位"
                          value={selectedUnit.value}
                        >
                          {unitOptions.map((option) => (
                            <option key={option.value} value={option.value}>
                              {option.label}
                            </option>
                          ))}
                        </select>
                      ) : null}
                      <button
                        aria-label={`下载 ${isCombined ? "多曲线" : label} 曲线图片`}
                        className="download"
                        onClick={(event) => {
                          event.stopPropagation();
                          void downloadChartImage(
                            event.currentTarget,
                            isCombined
                              ? `${snapshot.project.name}-${isMixed ? "异单位" : "同单位"}多曲线对比`
                              : chartTitle,
                          ).catch((error) => {
                            window.alert(`图片下载失败：${errorMessage(error)}`);
                          });
                        }}
                        onPointerDown={(event) => event.stopPropagation()}
                        title="下载 PNG"
                        type="button"
                      >
                        <ImageDown
                          aria-hidden="true"
                          size={16}
                          strokeWidth={1.9}
                        />
                      </button>
                      <button
                        aria-label={`关闭 ${isCombined ? "多曲线" : label} 曲线`}
                        className="close"
                        onClick={(event) => {
                          event.stopPropagation();
                          removeChartWindow(chartWindow.id);
                        }}
                        onPointerDown={(event) => event.stopPropagation()}
                        title="关闭曲线"
                        type="button"
                      >
                        <X aria-hidden="true" size={16} strokeWidth={1.9} />
                      </button>
                    </div>
                  </div>
                  {isMixed ? (
                    <StackedCurvePlot
                      cursorEnabled={chartWindow.cursorEnabled}
                      series={multiSeries}
                      time={snapshot.result.series.time ?? []}
                    />
                  ) : isCombined ? (
                    <MultiCurvePlot
                      cursorEnabled={chartWindow.cursorEnabled}
                      series={multiSeries}
                      time={snapshot.result.series.time ?? []}
                      title="多曲线对比"
                      unit={selectedUnit.label}
                    />
                  ) : (
                    <CurvePlot
                      color={colorForVariable(chartWindow.variableKey)}
                      cursorEnabled={chartWindow.cursorEnabled}
                      time={snapshot.result.series.time ?? []}
                      title={chartTitle}
                      unit={selectedUnit.label}
                      values={displayValues}
                    />
                  )}
                  <button
                    aria-label={`调整 ${isCombined ? "多曲线" : label} 曲线窗口大小`}
                    className="result-chart-resize-handle"
                    onLostPointerCapture={stopWindowResize}
                    onPointerCancel={stopWindowResize}
                    onPointerDown={(event) =>
                      startWindowResize(event, chartWindow)
                    }
                    onPointerMove={resizeChartWindow}
                    onPointerUp={stopWindowResize}
                    title="调整窗口大小"
                    type="button"
                  >
                    <Scaling aria-hidden="true" size={13} strokeWidth={1.8} />
                  </button>
                </article>
              );
            })}
            {chartWindows.length === 0 ? (
              <div className="results-workspace-empty">暂无曲线</div>
            ) : null}
          </div>
        </section>
      </main>
    </div>
  );
}

export function EmptySimulationResultsView({
  onViewChange,
  onSnapshotLoad,
}: EmptySimulationResultsViewProps) {
  return (
    <div className="results-shell">
      <header className="results-topbar">
        <div>
          <div className="product-name">System Simulation Flow</div>
          <div className="product-meta">仿真结果查看</div>
        </div>
        <WorkspaceViewTabs
          activeView="results"
          hasResults={false}
          onViewChange={onViewChange}
        />
        <div className="results-run-actions">
          <ResultsFileToolbar onSnapshotLoad={onSnapshotLoad} />
          <div className="results-run-meta empty">
            <span>尚无结果</span>
          </div>
        </div>
      </header>
      <main className="results-empty-view">
        <strong>尚未生成仿真结果</strong>
        <button onClick={() => onViewChange("modeling")} type="button">
          进入建模
        </button>
      </main>
    </div>
  );
}

type ResultsFileToolbarProps = {
  snapshot?: SimulationResultsSnapshot;
  csvDownloadPending?: boolean;
  onDownloadCsv?: () => void;
  onSnapshotLoad: (snapshot: SimulationResultsSnapshot) => void;
};

function ResultsFileToolbar({
  snapshot,
  csvDownloadPending = false,
  onDownloadCsv,
  onSnapshotLoad,
}: ResultsFileToolbarProps) {
  const fileInputRef = useRef<HTMLInputElement>(null);
  const [resultFileLoadPending, setResultFileLoadPending] = useState(false);

  const loadResultFile = async (
    event: ReactChangeEvent<HTMLInputElement>,
  ) => {
    const file = event.target.files?.[0];
    event.target.value = "";
    if (!file || resultFileLoadPending) {
      return;
    }
    setResultFileLoadPending(true);
    try {
      if (file.size > MAX_RESULT_FILE_SIZE) {
        throw new Error("结果文件超过 250 MB，无法在浏览器中安全加载。");
      }
      onSnapshotLoad(parseSimulationResultFile(await file.text()));
    } catch (error) {
      window.alert(`结果文件加载失败：${errorMessage(error)}`);
    } finally {
      setResultFileLoadPending(false);
    }
  };

  return (
    <div aria-label="结果文件工具" className="results-file-toolbar" role="toolbar">
      {snapshot ? (
        <button
          aria-label="下载结果文件"
          onClick={() => downloadSimulationResultFile(snapshot)}
          title="下载结果文件"
          type="button"
        >
          <FileDown aria-hidden="true" size={17} strokeWidth={1.9} />
        </button>
      ) : null}
      <button
        aria-busy={resultFileLoadPending}
        aria-label="加载结果文件"
        disabled={resultFileLoadPending}
        onClick={() => fileInputRef.current?.click()}
        title="加载结果文件"
        type="button"
      >
        <FolderOpen aria-hidden="true" size={17} strokeWidth={1.9} />
      </button>
      {snapshot && onDownloadCsv ? (
        <button
          aria-busy={csvDownloadPending}
          aria-label="下载结果 CSV"
          disabled={csvDownloadPending}
          onClick={onDownloadCsv}
          title="下载结果 CSV"
          type="button"
        >
          <Sheet aria-hidden="true" size={17} strokeWidth={1.9} />
        </button>
      ) : null}
      <input
        accept={`.simresult,${RESULT_FILE_MIME}`}
        className="results-file-input"
        onChange={(event) => void loadResultFile(event)}
        ref={fileInputRef}
        type="file"
      />
    </div>
  );
}

type VariableGroupProps = {
  title: string;
  variables: ResultVariableMetadata[];
  chartWindows: ChartWindow[];
  onClick: (variableKey: string) => void;
  onDragStart: (
    event: DragEvent<HTMLButtonElement>,
    variableKey: string,
  ) => void;
};

function VariableGroup({
  title,
  variables,
  chartWindows,
  onClick,
  onDragStart,
}: VariableGroupProps) {
  if (variables.length === 0) {
    return null;
  }
  return (
    <section className="results-variable-group">
      <div className="results-variable-group-title">{title}</div>
      <div className="results-variable-list">
        {variables.map((variable) => {
          const visible = chartWindows.some(
            (window) =>
              window.variableKeys.includes(variable.key) &&
              !window.hiddenVariableKeys.includes(variable.key),
          );
          const label = resultVariableLabel(variable);
          return (
            <button
              className={visible ? "visible" : ""}
              draggable
              key={variable.key}
              onClick={() => onClick(variable.key)}
              onDragStart={(event) => onDragStart(event, variable.key)}
              type="button"
            >
              <span
                className="result-variable-swatch"
                style={{ backgroundColor: colorForVariable(variable.key) }}
              />
              <span>
                <strong>{label}</strong>
                <small>{variable.unit || "无量纲"}</small>
              </span>
            </button>
          );
        })}
      </div>
    </section>
  );
}

type MultiCurveSeries = {
  key: string;
  label: string;
  color: string;
  unit: string;
  values: number[];
};

type MultiCurvePlotProps = {
  time: number[];
  series: MultiCurveSeries[];
  title: string;
  unit: string;
  cursorEnabled: boolean;
};

function MultiCurvePlot({
  time,
  series,
  title,
  unit,
  cursorEnabled,
}: MultiCurvePlotProps) {
  const bodyRef = useRef<HTMLDivElement>(null);
  const cursorPanelRef = useRef<HTMLDivElement>(null);
  const cursorPanelDragRef = useRef<CursorPanelDragState | null>(null);
  const cursorLineDragRef = useRef<CursorLineDragState | null>(null);
  const [chartSize, setChartSize] = useState({ width: 520, height: 270 });
  const [cursorIndex, setCursorIndex] = useState<number | null>(null);
  const [cursorPanelPosition, setCursorPanelPosition] =
    useState<CursorPanelPosition>({ x: 330, y: 9 });
  const plottedSeries = useMemo(
    () =>
      series
        .map((curve) => ({
          ...curve,
          samples: time
            .map((timeValue, index) => ({
              x: Number(timeValue),
              y: Number(curve.values[index]),
              dataIndex: index,
            }))
            .filter(
              (sample) =>
                Number.isFinite(sample.x) && Number.isFinite(sample.y),
            ),
        }))
        .filter((curve) => curve.samples.length >= 2),
    [series, time],
  );
  const cursorSamples = useMemo<CurveSample[]>(
    () =>
      time
        .map((timeValue, index) => ({
          x: Number(timeValue),
          y: index,
        }))
        .filter((sample) => Number.isFinite(sample.x)),
    [time],
  );

  useEffect(() => {
    const body = bodyRef.current;
    if (!body || typeof ResizeObserver === "undefined") {
      return;
    }
    const updateSize = (width: number, height: number) => {
      const nextSize = {
        width: Math.max(280, Math.round(width)),
        height: Math.max(150, Math.round(height)),
      };
      setChartSize((current) =>
        current.width === nextSize.width && current.height === nextSize.height
          ? current
          : nextSize,
      );
    };
    updateSize(body.clientWidth, body.clientHeight);
    const observer = new ResizeObserver(([entry]) => {
      if (entry) {
        updateSize(entry.contentRect.width, entry.contentRect.height);
      }
    });
    observer.observe(body);
    return () => observer.disconnect();
  }, []);

  useEffect(() => {
    if (!cursorEnabled || cursorSamples.length === 0) {
      return;
    }
    setCursorIndex((current) =>
      current !== null && current < cursorSamples.length
        ? current
        : Math.floor(cursorSamples.length / 2),
    );
  }, [cursorEnabled, cursorSamples.length]);

  useEffect(() => {
    const body = bodyRef.current;
    if (!cursorEnabled || !body || typeof ResizeObserver === "undefined") {
      return;
    }
    const clampPanel = () => {
      const panel = cursorPanelRef.current;
      if (!panel) {
        return;
      }
      setCursorPanelPosition((current) =>
        clampCursorPanelPosition(
          current,
          body.clientWidth,
          body.clientHeight,
          panel.offsetWidth,
          panel.offsetHeight,
        ),
      );
    };
    const animationFrame = window.requestAnimationFrame(clampPanel);
    const observer = new ResizeObserver(clampPanel);
    observer.observe(body);
    return () => {
      window.cancelAnimationFrame(animationFrame);
      observer.disconnect();
    };
  }, [cursorEnabled, plottedSeries.length]);

  if (plottedSeries.length === 0) {
    return (
      <div className="result-chart-body" ref={bodyRef}>
        <div className="result-chart-empty">无可绘制数据</div>
      </div>
    );
  }

  const { width, height } = chartSize;
  const maximumLegendRows = Math.max(
    1,
    Math.floor(Math.min(70, height * 0.26) / 14),
  );
  const legendColumns = Math.max(
    1,
    Math.ceil(plottedSeries.length / maximumLegendRows),
  );
  const legendRows = Math.ceil(plottedSeries.length / legendColumns);
  const allSamples = plottedSeries.flatMap((curve) => curve.samples);
  const rawYMin = Math.min(...allSamples.map((sample) => sample.y));
  const rawYMax = Math.max(...allSamples.map((sample) => sample.y));
  const sharedYPadding =
    rawYMin === rawYMax
      ? Math.max(Math.abs(rawYMin) * 0.05, 1)
      : (rawYMax - rawYMin) * 0.08;
  const sharedYScale = {
    minimum: rawYMin - sharedYPadding,
    maximum: rawYMax + sharedYPadding,
  };
  const margin = {
    top: 25 + legendRows * 14,
    right: 18,
    bottom: 40,
    left: 68,
  };
  const plotWidth = Math.max(40, width - margin.left - margin.right);
  const plotHeight = Math.max(30, height - margin.top - margin.bottom);
  const xMin = Math.min(...allSamples.map((sample) => sample.x));
  const xMax = Math.max(...allSamples.map((sample) => sample.x));
  const xRange = Math.max(xMax - xMin, 1e-12);
  const xPosition = (value: number) =>
    margin.left + ((value - xMin) / xRange) * plotWidth;
  const yPosition = (value: number) => {
    const range = Math.max(
      sharedYScale.maximum - sharedYScale.minimum,
      1e-12,
    );
    return (
      margin.top +
      (1 - (value - sharedYScale.minimum) / range) * plotHeight
    );
  };
  const xTicks = chartTicks(xMin, xMax, 5);
  const yTicks = chartTicks(
    sharedYScale.minimum,
    sharedYScale.maximum,
    5,
  );
  const legendWidth = plotWidth / legendColumns;
  const activeCursorIndex =
    cursorIndex === null
      ? Math.floor(cursorSamples.length / 2)
      : Math.min(cursorIndex, cursorSamples.length - 1);
  const cursorSample = cursorSamples[activeCursorIndex];
  const cursorReadings = cursorSample
    ? plottedSeries
        .map((curve, index) => ({
          color: curve.color,
          index,
          label: curve.label,
          unit: curve.unit,
          y: Number(curve.values[Math.round(cursorSample.y)]),
        }))
        .filter((reading) => Number.isFinite(reading.y))
    : [];

  const updateCursorByX = (clientX: number, svg: SVGSVGElement) => {
    const bounds = svg.getBoundingClientRect();
    if (bounds.width <= 0 || cursorSamples.length === 0) {
      return;
    }
    const svgX = ((clientX - bounds.left) / bounds.width) * width;
    const clampedX = Math.min(
      width - margin.right,
      Math.max(margin.left, svgX),
    );
    const targetX = xMin + ((clampedX - margin.left) / plotWidth) * xRange;
    setCursorIndex(nearestSampleIndex(cursorSamples, targetX));
  };

  const startCursorLineDrag = (
    event: ReactPointerEvent<SVGLineElement>,
  ) => {
    if (!cursorEnabled) {
      return;
    }
    event.preventDefault();
    event.stopPropagation();
    cursorLineDragRef.current = {
      pointerId: event.pointerId,
      axis: "x",
    };
    event.currentTarget.setPointerCapture(event.pointerId);
  };

  const moveCursorLine = (event: ReactPointerEvent<SVGLineElement>) => {
    const drag = cursorLineDragRef.current;
    const svg = event.currentTarget.ownerSVGElement;
    if (!drag || drag.pointerId !== event.pointerId || !svg) {
      return;
    }
    event.preventDefault();
    event.stopPropagation();
    updateCursorByX(event.clientX, svg);
  };

  const stopCursorLineDrag = (
    event: ReactPointerEvent<SVGLineElement>,
  ) => {
    if (cursorLineDragRef.current?.pointerId !== event.pointerId) {
      return;
    }
    event.stopPropagation();
    if (event.currentTarget.hasPointerCapture(event.pointerId)) {
      event.currentTarget.releasePointerCapture(event.pointerId);
    }
    cursorLineDragRef.current = null;
  };

  const startCursorPanelDrag = (
    event: ReactPointerEvent<HTMLButtonElement>,
  ) => {
    const body = bodyRef.current;
    const panel = cursorPanelRef.current;
    if (!body || !panel) {
      return;
    }
    event.preventDefault();
    event.stopPropagation();
    const panelBounds = panel.getBoundingClientRect();
    const bodyBounds = body.getBoundingClientRect();
    cursorPanelDragRef.current = {
      pointerId: event.pointerId,
      offsetX: event.clientX - panelBounds.left,
      offsetY: event.clientY - panelBounds.top,
    };
    setCursorPanelPosition({
      x: panelBounds.left - bodyBounds.left,
      y: panelBounds.top - bodyBounds.top,
    });
    event.currentTarget.setPointerCapture(event.pointerId);
  };

  const moveCursorPanel = (event: ReactPointerEvent<HTMLButtonElement>) => {
    const drag = cursorPanelDragRef.current;
    const body = bodyRef.current;
    const panel = cursorPanelRef.current;
    if (!drag || drag.pointerId !== event.pointerId || !body || !panel) {
      return;
    }
    event.preventDefault();
    event.stopPropagation();
    const bodyBounds = body.getBoundingClientRect();
    setCursorPanelPosition(
      clampCursorPanelPosition(
        {
          x: event.clientX - bodyBounds.left - drag.offsetX,
          y: event.clientY - bodyBounds.top - drag.offsetY,
        },
        body.clientWidth,
        body.clientHeight,
        panel.offsetWidth,
        panel.offsetHeight,
      ),
    );
  };

  const stopCursorPanelDrag = (
    event: ReactPointerEvent<HTMLButtonElement>,
  ) => {
    if (cursorPanelDragRef.current?.pointerId !== event.pointerId) {
      return;
    }
    event.stopPropagation();
    if (event.currentTarget.hasPointerCapture(event.pointerId)) {
      event.currentTarget.releasePointerCapture(event.pointerId);
    }
    cursorPanelDragRef.current = null;
  };

  return (
    <div className="result-chart-body" ref={bodyRef}>
      <svg
        aria-label={`${title}，包含 ${plottedSeries.length} 条曲线`}
        className={cursorEnabled ? "cursor-enabled" : undefined}
        data-result-chart="true"
        onPointerDown={(event) => {
          if (cursorEnabled) {
            event.preventDefault();
            updateCursorByX(event.clientX, event.currentTarget);
          }
        }}
        role="img"
        viewBox={`0 0 ${width} ${height}`}
      >
        <text
          className="result-chart-title"
          textAnchor="start"
          x={margin.left}
          y={13}
        >
          {title}
        </text>
        <text
          className="result-chart-unit"
          textAnchor="end"
          x={width - margin.right}
          y={13}
        >
          {unit || "无量纲"}
        </text>
        <g className="result-chart-legend">
          {plottedSeries.map((curve, index) => {
            const column = Math.floor(index / legendRows);
            const row = index % legendRows;
            const x = margin.left + column * legendWidth;
            const y = 27 + row * 14;
            return (
              <g key={curve.key}>
                <line
                  stroke={curve.color}
                  strokeWidth="2"
                  vectorEffect="non-scaling-stroke"
                  x1={x}
                  x2={x + 12}
                  y1={y - 3}
                  y2={y - 3}
                />
                <text x={x + 16} y={y}>
                  {truncateLegendLabel(
                    `Y${index + 1} ${curve.label}`,
                    legendWidth - 20,
                  )}
                </text>
              </g>
            );
          })}
        </g>
        {yTicks.map((tick, index) => {
          const y = yPosition(tick);
          return (
            <g key={`y-${index}`}>
              <line
                className="result-chart-grid-line"
                x1={margin.left}
                x2={margin.left + plotWidth}
                y1={y}
                y2={y}
              />
              <line
                className="result-chart-tick"
                x1={margin.left - 4}
                x2={margin.left}
                y1={y}
                y2={y}
              />
              <text
                className="result-chart-label"
                textAnchor="end"
                x={margin.left - 7}
                y={y + 3}
              >
                {formatChartNumber(tick)}
              </text>
            </g>
          );
        })}
        {xTicks.map((tick, index) => {
          const x = xPosition(tick);
          const textAnchor =
            index === 0
              ? "start"
              : index === xTicks.length - 1
                ? "end"
                : "middle";
          return (
            <g key={`x-${index}`}>
              <line
                className="result-chart-grid-line"
                x1={x}
                x2={x}
                y1={margin.top}
                y2={height - margin.bottom}
              />
              <line
                className="result-chart-tick"
                x1={x}
                x2={x}
                y1={height - margin.bottom}
                y2={height - margin.bottom + 4}
              />
              <text
                className="result-chart-label"
                textAnchor={textAnchor}
                x={x}
                y={height - margin.bottom + 15}
              >
                {formatChartNumber(tick)}
              </text>
            </g>
          );
        })}
        <line
          className="result-chart-axis"
          x1={margin.left}
          x2={margin.left}
          y1={margin.top}
          y2={height - margin.bottom}
        />
        <line
          className="result-chart-axis"
          x1={margin.left}
          x2={margin.left + plotWidth}
          y1={height - margin.bottom}
          y2={height - margin.bottom}
        />
        {plottedSeries.map((curve) => {
          const path = curve.samples
            .map(
              (sample, index) =>
                `${index === 0 ? "M" : "L"} ${xPosition(sample.x).toFixed(2)} ${yPosition(sample.y).toFixed(2)}`,
            )
            .join(" ");
          return (
            <path
              d={path}
              fill="none"
              key={curve.key}
              stroke={curve.color}
              strokeLinecap="round"
              strokeLinejoin="round"
              strokeWidth="2"
              vectorEffect="non-scaling-stroke"
            />
          );
        })}
        {cursorEnabled && cursorSample ? (
          <>
            <g className="result-chart-cursor" pointerEvents="none">
              <line
                x1={xPosition(cursorSample.x)}
                x2={xPosition(cursorSample.x)}
                y1={margin.top}
                y2={height - margin.bottom}
              />
              {cursorReadings.map((reading) => (
                <circle
                  cx={xPosition(cursorSample.x)}
                  cy={yPosition(reading.y)}
                  fill={reading.color}
                  key={`${reading.index}-${reading.label}`}
                  r="3.5"
                />
              ))}
            </g>
            <line
              className="result-chart-cursor-hit x"
              onLostPointerCapture={stopCursorLineDrag}
              onPointerCancel={stopCursorLineDrag}
              onPointerDown={startCursorLineDrag}
              onPointerMove={moveCursorLine}
              onPointerUp={stopCursorLineDrag}
              x1={xPosition(cursorSample.x)}
              x2={xPosition(cursorSample.x)}
              y1={margin.top}
              y2={height - margin.bottom}
            />
          </>
        ) : null}
        <text
          className="result-chart-axis-title"
          textAnchor="middle"
          x={margin.left + plotWidth / 2}
          y={height - 5}
        >
          时间 (s)
        </text>
      </svg>
      {cursorEnabled && cursorSample ? (
        <div
          className="result-chart-cursor-panel multi"
          onPointerDown={(event) => event.stopPropagation()}
          ref={cursorPanelRef}
          style={{
            left: cursorPanelPosition.x,
            top: cursorPanelPosition.y,
          }}
        >
          <button
            aria-label="移动多曲线游标读数窗口"
            className="result-chart-cursor-panel-header"
            onLostPointerCapture={stopCursorPanelDrag}
            onPointerCancel={stopCursorPanelDrag}
            onPointerDown={startCursorPanelDrag}
            onPointerMove={moveCursorPanel}
            onPointerUp={stopCursorPanelDrag}
            title="移动游标读数"
            type="button"
          >
            <Move aria-hidden="true" size={13} strokeWidth={1.8} />
            <span>游标</span>
          </button>
          <dl>
            <div>
              <dt>X</dt>
              <dd>{formatCursorNumber(cursorSample.x)} s</dd>
            </div>
            {cursorReadings.map((reading) => (
              <div
                key={`${reading.index}-${reading.label}`}
                title={`Y${reading.index + 1} · ${reading.label}`}
              >
                <dt>Y{reading.index + 1}</dt>
                <dd>
                  <span
                    aria-hidden="true"
                    className="result-chart-cursor-value-swatch"
                    style={{ backgroundColor: reading.color }}
                  />
                  <span>
                    {formatCursorNumber(reading.y)} {reading.unit}
                  </span>
                </dd>
              </div>
            ))}
          </dl>
        </div>
      ) : null}
    </div>
  );
}

type StackedCurvePlotProps = {
  time: number[];
  series: MultiCurveSeries[];
  cursorEnabled: boolean;
};

function StackedCurvePlot({
  time,
  series,
  cursorEnabled,
}: StackedCurvePlotProps) {
  const bodyRef = useRef<HTMLDivElement>(null);
  const cursorPanelRef = useRef<HTMLDivElement>(null);
  const cursorPanelDragRef = useRef<CursorPanelDragState | null>(null);
  const cursorLineDragRef = useRef<CursorLineDragState | null>(null);
  const [chartSize, setChartSize] = useState({ width: 520, height: 270 });
  const [cursorIndex, setCursorIndex] = useState<number | null>(null);
  const [cursorPanelPosition, setCursorPanelPosition] =
    useState<CursorPanelPosition>({ x: 330, y: 9 });
  const plottedSeries = useMemo(
    () =>
      series
        .map((curve) => ({
          ...curve,
          samples: time
            .map((timeValue, index) => ({
              x: Number(timeValue),
              y: Number(curve.values[index]),
              dataIndex: index,
            }))
            .filter(
              (sample) =>
                Number.isFinite(sample.x) && Number.isFinite(sample.y),
            ),
        }))
        .filter((curve) => curve.samples.length >= 2),
    [series, time],
  );
  const cursorSamples = useMemo<CurveSample[]>(
    () =>
      time
        .map((timeValue, index) => ({
          x: Number(timeValue),
          y: index,
        }))
        .filter((sample) => Number.isFinite(sample.x)),
    [time],
  );

  useEffect(() => {
    const body = bodyRef.current;
    if (!body || typeof ResizeObserver === "undefined") {
      return;
    }
    const updateSize = (width: number, height: number) => {
      const nextSize = {
        width: Math.max(280, Math.round(width)),
        height: Math.max(180, Math.round(height)),
      };
      setChartSize((current) =>
        current.width === nextSize.width && current.height === nextSize.height
          ? current
          : nextSize,
      );
    };
    updateSize(body.clientWidth, body.clientHeight);
    const observer = new ResizeObserver(([entry]) => {
      if (entry) {
        updateSize(entry.contentRect.width, entry.contentRect.height);
      }
    });
    observer.observe(body);
    return () => observer.disconnect();
  }, []);

  useEffect(() => {
    if (!cursorEnabled || cursorSamples.length === 0) {
      return;
    }
    setCursorIndex((current) =>
      current !== null && current < cursorSamples.length
        ? current
        : Math.floor(cursorSamples.length / 2),
    );
  }, [cursorEnabled, cursorSamples.length]);

  useEffect(() => {
    const body = bodyRef.current;
    if (!cursorEnabled || !body || typeof ResizeObserver === "undefined") {
      return;
    }
    const clampPanel = () => {
      const panel = cursorPanelRef.current;
      if (!panel) {
        return;
      }
      setCursorPanelPosition((current) =>
        clampCursorPanelPosition(
          current,
          body.clientWidth,
          body.clientHeight,
          panel.offsetWidth,
          panel.offsetHeight,
        ),
      );
    };
    const animationFrame = window.requestAnimationFrame(clampPanel);
    const observer = new ResizeObserver(clampPanel);
    observer.observe(body);
    return () => {
      window.cancelAnimationFrame(animationFrame);
      observer.disconnect();
    };
  }, [cursorEnabled, plottedSeries.length]);

  if (plottedSeries.length === 0) {
    return (
      <div className="result-chart-body" ref={bodyRef}>
        <div className="result-chart-empty">无可绘制数据</div>
      </div>
    );
  }

  const { width, height } = chartSize;
  const margin = {
    top: 4,
    right: 18,
    bottom: 28,
    left: 68,
  };
  const plotWidth = Math.max(40, width - margin.left - margin.right);
  const availableHeight = Math.max(
    80,
    height - margin.top - margin.bottom,
  );
  const bandHeight = availableHeight / plottedSeries.length;
  const allSamples = plottedSeries.flatMap((curve) => curve.samples);
  const xMin = Math.min(...allSamples.map((sample) => sample.x));
  const xMax = Math.max(...allSamples.map((sample) => sample.x));
  const xRange = Math.max(xMax - xMin, 1e-12);
  const xPosition = (value: number) =>
    margin.left + ((value - xMin) / xRange) * plotWidth;
  const xTicks = chartTicks(xMin, xMax, 5);
  const plotBands = plottedSeries.map((curve, index) => {
    const rawMinimum = Math.min(...curve.samples.map((sample) => sample.y));
    const rawMaximum = Math.max(...curve.samples.map((sample) => sample.y));
    const padding =
      rawMinimum === rawMaximum
        ? Math.max(Math.abs(rawMinimum) * 0.05, 1)
        : (rawMaximum - rawMinimum) * 0.08;
    const minimum = rawMinimum - padding;
    const maximum = rawMaximum + padding;
    const range = Math.max(maximum - minimum, 1e-12);
    const bandTop = margin.top + index * bandHeight;
    const plotTop = bandTop + 20;
    const plotBottom = Math.max(plotTop + 22, bandTop + bandHeight - 5);
    const plotHeight = plotBottom - plotTop;
    return {
      curve,
      index,
      bandTop,
      plotTop,
      plotBottom,
      yTicks: chartTicks(minimum, maximum, bandHeight < 105 ? 2 : 3),
      yPosition: (value: number) =>
        plotTop + (1 - (value - minimum) / range) * plotHeight,
    };
  });
  const activeCursorIndex =
    cursorIndex === null
      ? Math.floor(cursorSamples.length / 2)
      : Math.min(cursorIndex, cursorSamples.length - 1);
  const cursorSample = cursorSamples[activeCursorIndex];
  const cursorReadings = cursorSample
    ? plottedSeries
        .map((curve, index) => ({
          color: curve.color,
          index,
          label: curve.label,
          unit: curve.unit,
          y: Number(curve.values[Math.round(cursorSample.y)]),
        }))
        .filter((reading) => Number.isFinite(reading.y))
    : [];
  const cursorTop = plotBands[0].plotTop;
  const cursorBottom = plotBands[plotBands.length - 1].plotBottom;

  const updateCursorByX = (clientX: number, svg: SVGSVGElement) => {
    const bounds = svg.getBoundingClientRect();
    if (bounds.width <= 0 || cursorSamples.length === 0) {
      return;
    }
    const svgX = ((clientX - bounds.left) / bounds.width) * width;
    const clampedX = Math.min(
      width - margin.right,
      Math.max(margin.left, svgX),
    );
    const targetX = xMin + ((clampedX - margin.left) / plotWidth) * xRange;
    setCursorIndex(nearestSampleIndex(cursorSamples, targetX));
  };

  const startCursorLineDrag = (
    event: ReactPointerEvent<SVGLineElement>,
  ) => {
    if (!cursorEnabled) {
      return;
    }
    event.preventDefault();
    event.stopPropagation();
    cursorLineDragRef.current = {
      pointerId: event.pointerId,
      axis: "x",
    };
    event.currentTarget.setPointerCapture(event.pointerId);
  };

  const moveCursorLine = (event: ReactPointerEvent<SVGLineElement>) => {
    const drag = cursorLineDragRef.current;
    const svg = event.currentTarget.ownerSVGElement;
    if (!drag || drag.pointerId !== event.pointerId || !svg) {
      return;
    }
    event.preventDefault();
    event.stopPropagation();
    updateCursorByX(event.clientX, svg);
  };

  const stopCursorLineDrag = (
    event: ReactPointerEvent<SVGLineElement>,
  ) => {
    if (cursorLineDragRef.current?.pointerId !== event.pointerId) {
      return;
    }
    event.stopPropagation();
    if (event.currentTarget.hasPointerCapture(event.pointerId)) {
      event.currentTarget.releasePointerCapture(event.pointerId);
    }
    cursorLineDragRef.current = null;
  };

  const startCursorPanelDrag = (
    event: ReactPointerEvent<HTMLButtonElement>,
  ) => {
    const body = bodyRef.current;
    const panel = cursorPanelRef.current;
    if (!body || !panel) {
      return;
    }
    event.preventDefault();
    event.stopPropagation();
    const panelBounds = panel.getBoundingClientRect();
    const bodyBounds = body.getBoundingClientRect();
    cursorPanelDragRef.current = {
      pointerId: event.pointerId,
      offsetX: event.clientX - panelBounds.left,
      offsetY: event.clientY - panelBounds.top,
    };
    setCursorPanelPosition({
      x: panelBounds.left - bodyBounds.left,
      y: panelBounds.top - bodyBounds.top,
    });
    event.currentTarget.setPointerCapture(event.pointerId);
  };

  const moveCursorPanel = (event: ReactPointerEvent<HTMLButtonElement>) => {
    const drag = cursorPanelDragRef.current;
    const body = bodyRef.current;
    const panel = cursorPanelRef.current;
    if (!drag || drag.pointerId !== event.pointerId || !body || !panel) {
      return;
    }
    event.preventDefault();
    event.stopPropagation();
    const bodyBounds = body.getBoundingClientRect();
    setCursorPanelPosition(
      clampCursorPanelPosition(
        {
          x: event.clientX - bodyBounds.left - drag.offsetX,
          y: event.clientY - bodyBounds.top - drag.offsetY,
        },
        body.clientWidth,
        body.clientHeight,
        panel.offsetWidth,
        panel.offsetHeight,
      ),
    );
  };

  const stopCursorPanelDrag = (
    event: ReactPointerEvent<HTMLButtonElement>,
  ) => {
    if (cursorPanelDragRef.current?.pointerId !== event.pointerId) {
      return;
    }
    event.stopPropagation();
    if (event.currentTarget.hasPointerCapture(event.pointerId)) {
      event.currentTarget.releasePointerCapture(event.pointerId);
    }
    cursorPanelDragRef.current = null;
  };

  return (
    <div className="result-chart-body stacked" ref={bodyRef}>
      <svg
        aria-label={`上下曲线对比，包含 ${plottedSeries.length} 个同步子图`}
        className={cursorEnabled ? "cursor-enabled" : undefined}
        data-result-chart="true"
        onPointerDown={(event) => {
          if (cursorEnabled) {
            event.preventDefault();
            updateCursorByX(event.clientX, event.currentTarget);
          }
        }}
        role="img"
        viewBox={`0 0 ${width} ${height}`}
      >
        {plotBands.map((band) => {
          const isLast = band.index === plotBands.length - 1;
          const path = band.curve.samples
            .map(
              (sample, sampleIndex) =>
                `${sampleIndex === 0 ? "M" : "L"} ${xPosition(sample.x).toFixed(2)} ${band.yPosition(sample.y).toFixed(2)}`,
            )
            .join(" ");
          return (
            <g className="result-chart-stack-band" key={band.curve.key}>
              {band.index > 0 ? (
                <line
                  className="result-chart-stack-divider"
                  x1={8}
                  x2={width - 8}
                  y1={band.bandTop}
                  y2={band.bandTop}
                />
              ) : null}
              <text
                className="result-chart-title"
                textAnchor="start"
                x={margin.left}
                y={band.bandTop + 12}
              >
                {truncateLegendLabel(
                  `Y${band.index + 1} ${band.curve.label}`,
                  plotWidth - 66,
                )}
              </text>
              <text
                className="result-chart-unit"
                textAnchor="end"
                x={width - margin.right}
                y={band.bandTop + 12}
              >
                {band.curve.unit || "无量纲"}
              </text>
              {band.yTicks.map((tick, tickIndex) => {
                const y = band.yPosition(tick);
                return (
                  <g key={`${band.curve.key}-y-${tickIndex}`}>
                    <line
                      className="result-chart-grid-line"
                      x1={margin.left}
                      x2={margin.left + plotWidth}
                      y1={y}
                      y2={y}
                    />
                    <line
                      className="result-chart-tick"
                      x1={margin.left - 4}
                      x2={margin.left}
                      y1={y}
                      y2={y}
                    />
                    <text
                      className="result-chart-label"
                      textAnchor="end"
                      x={margin.left - 7}
                      y={y + 3}
                    >
                      {formatChartNumber(tick)}
                    </text>
                  </g>
                );
              })}
              {xTicks.map((tick, tickIndex) => {
                const x = xPosition(tick);
                const textAnchor =
                  tickIndex === 0
                    ? "start"
                    : tickIndex === xTicks.length - 1
                      ? "end"
                      : "middle";
                return (
                  <g key={`${band.curve.key}-x-${tickIndex}`}>
                    <line
                      className="result-chart-grid-line"
                      x1={x}
                      x2={x}
                      y1={band.plotTop}
                      y2={band.plotBottom}
                    />
                    {isLast ? (
                      <>
                        <line
                          className="result-chart-tick"
                          x1={x}
                          x2={x}
                          y1={band.plotBottom}
                          y2={band.plotBottom + 4}
                        />
                        <text
                          className="result-chart-label"
                          textAnchor={textAnchor}
                          x={x}
                          y={band.plotBottom + 14}
                        >
                          {formatChartNumber(tick)}
                        </text>
                      </>
                    ) : null}
                  </g>
                );
              })}
              <line
                className="result-chart-axis"
                x1={margin.left}
                x2={margin.left}
                y1={band.plotTop}
                y2={band.plotBottom}
              />
              <line
                className="result-chart-axis"
                x1={margin.left}
                x2={margin.left + plotWidth}
                y1={band.plotBottom}
                y2={band.plotBottom}
              />
              <path
                d={path}
                fill="none"
                stroke={band.curve.color}
                strokeLinecap="round"
                strokeLinejoin="round"
                strokeWidth="2"
                vectorEffect="non-scaling-stroke"
              />
            </g>
          );
        })}
        {cursorEnabled && cursorSample ? (
          <>
            <g className="result-chart-cursor" pointerEvents="none">
              {plotBands.map((band) => (
                <line
                  key={`${band.curve.key}-cursor-line`}
                  x1={xPosition(cursorSample.x)}
                  x2={xPosition(cursorSample.x)}
                  y1={band.plotTop}
                  y2={band.plotBottom}
                />
              ))}
              {cursorReadings.map((reading) => {
                const band = plotBands[reading.index];
                return band ? (
                  <circle
                    cx={xPosition(cursorSample.x)}
                    cy={band.yPosition(reading.y)}
                    fill={reading.color}
                    key={`${reading.index}-${reading.label}`}
                    r="3.5"
                  />
                ) : null;
              })}
            </g>
            <line
              className="result-chart-cursor-hit x"
              onLostPointerCapture={stopCursorLineDrag}
              onPointerCancel={stopCursorLineDrag}
              onPointerDown={startCursorLineDrag}
              onPointerMove={moveCursorLine}
              onPointerUp={stopCursorLineDrag}
              x1={xPosition(cursorSample.x)}
              x2={xPosition(cursorSample.x)}
              y1={cursorTop}
              y2={cursorBottom}
            />
          </>
        ) : null}
        <text
          className="result-chart-axis-title"
          textAnchor="middle"
          x={margin.left + plotWidth / 2}
          y={height - 4}
        >
          时间 (s)
        </text>
      </svg>
      {cursorEnabled && cursorSample ? (
        <div
          className="result-chart-cursor-panel multi"
          onPointerDown={(event) => event.stopPropagation()}
          ref={cursorPanelRef}
          style={{
            left: cursorPanelPosition.x,
            top: cursorPanelPosition.y,
          }}
        >
          <button
            aria-label="移动上下曲线游标读数窗口"
            className="result-chart-cursor-panel-header"
            onLostPointerCapture={stopCursorPanelDrag}
            onPointerCancel={stopCursorPanelDrag}
            onPointerDown={startCursorPanelDrag}
            onPointerMove={moveCursorPanel}
            onPointerUp={stopCursorPanelDrag}
            title="移动游标读数"
            type="button"
          >
            <Move aria-hidden="true" size={13} strokeWidth={1.8} />
            <span>同步游标</span>
          </button>
          <dl>
            <div>
              <dt>X</dt>
              <dd>{formatCursorNumber(cursorSample.x)} s</dd>
            </div>
            {cursorReadings.map((reading) => (
              <div key={`${reading.index}-${reading.label}`}>
                <dt>Y{reading.index + 1}</dt>
                <dd>
                  <span
                    aria-hidden="true"
                    className="result-chart-cursor-value-swatch"
                    style={{ backgroundColor: reading.color }}
                  />
                  <span>
                    {formatCursorNumber(reading.y)} {reading.unit}
                  </span>
                </dd>
              </div>
            ))}
          </dl>
        </div>
      ) : null}
    </div>
  );
}

type CurvePlotProps = {
  time: number[];
  values: number[];
  title: string;
  unit: string;
  color: string;
  cursorEnabled: boolean;
};

type CurveSample = {
  x: number;
  y: number;
};

type CursorPanelPosition = {
  x: number;
  y: number;
};

type CursorPanelDragState = {
  pointerId: number;
  offsetX: number;
  offsetY: number;
};

type CursorLineDragState = {
  pointerId: number;
  axis: "x" | "y";
};

function CurvePlot({
  time,
  values,
  title,
  unit,
  color,
  cursorEnabled,
}: CurvePlotProps) {
  const bodyRef = useRef<HTMLDivElement>(null);
  const cursorPanelRef = useRef<HTMLDivElement>(null);
  const cursorPanelDragRef = useRef<CursorPanelDragState | null>(null);
  const cursorLineDragRef = useRef<CursorLineDragState | null>(null);
  const [chartSize, setChartSize] = useState({ width: 400, height: 190 });
  const [cursorIndex, setCursorIndex] = useState<number | null>(null);
  const [cursorPanelPosition, setCursorPanelPosition] =
    useState<CursorPanelPosition>({ x: 238, y: 9 });
  const samples = useMemo<CurveSample[]>(
    () =>
      time
        .map((timeValue, index) => ({
          x: Number(timeValue),
          y: Number(values[index]),
        }))
        .filter(
          (sample) => Number.isFinite(sample.x) && Number.isFinite(sample.y),
        ),
    [time, values],
  );

  useEffect(() => {
    const body = bodyRef.current;
    if (!body || typeof ResizeObserver === "undefined") {
      return;
    }
    const updateSize = (width: number, height: number) => {
      const nextSize = {
        width: Math.max(280, Math.round(width)),
        height: Math.max(150, Math.round(height)),
      };
      setChartSize((current) =>
        current.width === nextSize.width && current.height === nextSize.height
          ? current
          : nextSize,
      );
    };
    updateSize(body.clientWidth, body.clientHeight);
    const observer = new ResizeObserver(([entry]) => {
      if (entry) {
        updateSize(entry.contentRect.width, entry.contentRect.height);
      }
    });
    observer.observe(body);
    return () => observer.disconnect();
  }, []);

  useEffect(() => {
    if (!cursorEnabled || samples.length === 0) {
      return;
    }
    setCursorIndex((current) =>
      current !== null && current < samples.length
        ? current
        : Math.floor(samples.length / 2),
    );
  }, [cursorEnabled, samples.length]);

  useEffect(() => {
    const body = bodyRef.current;
    if (!cursorEnabled || !body || typeof ResizeObserver === "undefined") {
      return;
    }
    const clampPanel = () => {
      const panel = cursorPanelRef.current;
      if (!panel) {
        return;
      }
      setCursorPanelPosition((current) =>
        clampCursorPanelPosition(
          current,
          body.clientWidth,
          body.clientHeight,
          panel.offsetWidth,
          panel.offsetHeight,
        ),
      );
    };
    const animationFrame = window.requestAnimationFrame(clampPanel);
    const observer = new ResizeObserver(clampPanel);
    observer.observe(body);
    return () => {
      window.cancelAnimationFrame(animationFrame);
      observer.disconnect();
    };
  }, [cursorEnabled]);

  if (samples.length < 2) {
    return (
      <div className="result-chart-body" ref={bodyRef}>
        <div className="result-chart-empty">无可绘制数据</div>
      </div>
    );
  }

  const { width, height } = chartSize;
  const margin = { top: 24, right: 18, bottom: 40, left: 68 };
  const plotWidth = width - margin.left - margin.right;
  const plotHeight = height - margin.top - margin.bottom;
  const xMin = Math.min(...samples.map((sample) => sample.x));
  const xMax = Math.max(...samples.map((sample) => sample.x));
  const rawYMin = Math.min(...samples.map((sample) => sample.y));
  const rawYMax = Math.max(...samples.map((sample) => sample.y));
  const yPadding =
    rawYMin === rawYMax
      ? Math.max(Math.abs(rawYMin) * 0.05, 1)
      : (rawYMax - rawYMin) * 0.08;
  const yMin = rawYMin - yPadding;
  const yMax = rawYMax + yPadding;
  const xRange = Math.max(xMax - xMin, 1e-12);
  const yRange = Math.max(yMax - yMin, 1e-12);
  const xPosition = (value: number) =>
    margin.left + ((value - xMin) / xRange) * plotWidth;
  const yPosition = (value: number) =>
    margin.top + (1 - (value - yMin) / yRange) * plotHeight;
  const xTicks = chartTicks(xMin, xMax, 5);
  const yTicks = chartTicks(yMin, yMax, 5);
  const path = samples
    .map(
      (sample, index) =>
        `${index === 0 ? "M" : "L"} ${xPosition(sample.x).toFixed(2)} ${yPosition(
          sample.y,
        ).toFixed(2)}`,
    )
    .join(" ");
  const activeCursorIndex =
    cursorIndex === null
      ? Math.floor(samples.length / 2)
      : Math.min(cursorIndex, samples.length - 1);
  const cursorSample = samples[activeCursorIndex];

  const updateCursorByX = (clientX: number, svg: SVGSVGElement) => {
    const bounds = svg.getBoundingClientRect();
    if (bounds.width <= 0) {
      return;
    }
    const svgX = ((clientX - bounds.left) / bounds.width) * width;
    const clampedX = Math.min(
      width - margin.right,
      Math.max(margin.left, svgX),
    );
    const targetX = xMin + ((clampedX - margin.left) / plotWidth) * xRange;
    setCursorIndex(nearestSampleIndex(samples, targetX));
  };

  const updateCursorByY = (clientY: number, svg: SVGSVGElement) => {
    const bounds = svg.getBoundingClientRect();
    if (bounds.height <= 0) {
      return;
    }
    const svgY = ((clientY - bounds.top) / bounds.height) * height;
    const clampedY = Math.min(
      height - margin.bottom,
      Math.max(margin.top, svgY),
    );
    const targetY = yMax - ((clampedY - margin.top) / plotHeight) * yRange;
    setCursorIndex((current) =>
      nearestSampleIndexByY(
        samples,
        targetY,
        current ?? activeCursorIndex,
      ),
    );
  };

  const startCursorLineDrag = (
    event: ReactPointerEvent<SVGLineElement>,
    axis: CursorLineDragState["axis"],
  ) => {
    if (!cursorEnabled) {
      return;
    }
    event.preventDefault();
    event.stopPropagation();
    cursorLineDragRef.current = {
      pointerId: event.pointerId,
      axis,
    };
    event.currentTarget.setPointerCapture(event.pointerId);
  };

  const moveCursorLine = (event: ReactPointerEvent<SVGLineElement>) => {
    const drag = cursorLineDragRef.current;
    const svg = event.currentTarget.ownerSVGElement;
    if (!drag || drag.pointerId !== event.pointerId || !svg) {
      return;
    }
    event.preventDefault();
    event.stopPropagation();
    if (drag.axis === "x") {
      updateCursorByX(event.clientX, svg);
    } else {
      updateCursorByY(event.clientY, svg);
    }
  };

  const stopCursorLineDrag = (
    event: ReactPointerEvent<SVGLineElement>,
  ) => {
    if (cursorLineDragRef.current?.pointerId !== event.pointerId) {
      return;
    }
    event.stopPropagation();
    if (event.currentTarget.hasPointerCapture(event.pointerId)) {
      event.currentTarget.releasePointerCapture(event.pointerId);
    }
    cursorLineDragRef.current = null;
  };

  const startCursorPanelDrag = (
    event: ReactPointerEvent<HTMLButtonElement>,
  ) => {
    const body = bodyRef.current;
    const panel = cursorPanelRef.current;
    if (!body || !panel) {
      return;
    }
    event.preventDefault();
    event.stopPropagation();
    const panelBounds = panel.getBoundingClientRect();
    const bodyBounds = body.getBoundingClientRect();
    cursorPanelDragRef.current = {
      pointerId: event.pointerId,
      offsetX: event.clientX - panelBounds.left,
      offsetY: event.clientY - panelBounds.top,
    };
    setCursorPanelPosition({
      x: panelBounds.left - bodyBounds.left,
      y: panelBounds.top - bodyBounds.top,
    });
    event.currentTarget.setPointerCapture(event.pointerId);
  };

  const moveCursorPanel = (event: ReactPointerEvent<HTMLButtonElement>) => {
    const drag = cursorPanelDragRef.current;
    const body = bodyRef.current;
    const panel = cursorPanelRef.current;
    if (!drag || drag.pointerId !== event.pointerId || !body || !panel) {
      return;
    }
    event.preventDefault();
    event.stopPropagation();
    const bodyBounds = body.getBoundingClientRect();
    setCursorPanelPosition(
      clampCursorPanelPosition(
        {
          x: event.clientX - bodyBounds.left - drag.offsetX,
          y: event.clientY - bodyBounds.top - drag.offsetY,
        },
        body.clientWidth,
        body.clientHeight,
        panel.offsetWidth,
        panel.offsetHeight,
      ),
    );
  };

  const stopCursorPanelDrag = (
    event: ReactPointerEvent<HTMLButtonElement>,
  ) => {
    if (cursorPanelDragRef.current?.pointerId !== event.pointerId) {
      return;
    }
    event.stopPropagation();
    if (event.currentTarget.hasPointerCapture(event.pointerId)) {
      event.currentTarget.releasePointerCapture(event.pointerId);
    }
    cursorPanelDragRef.current = null;
  };

  return (
    <div className="result-chart-body" ref={bodyRef}>
      <svg
        aria-label={`${title} 随时间变化曲线`}
        className={cursorEnabled ? "cursor-enabled" : undefined}
        data-result-chart="true"
        onPointerDown={(event) => {
          if (cursorEnabled) {
            event.preventDefault();
            updateCursorByX(event.clientX, event.currentTarget);
          }
        }}
        role="img"
        viewBox={`0 0 ${width} ${height}`}
      >
        <text
          className="result-chart-title"
          textAnchor="start"
          x={margin.left}
          y={13}
        >
          {title}
        </text>
        <text
          className="result-chart-unit"
          textAnchor="end"
          x={width - margin.right}
          y={13}
        >
          {unit || "无量纲"}
        </text>
        {yTicks.map((tick, index) => {
          const y = yPosition(tick);
          return (
            <g key={`y-${index}`}>
              <line
                className="result-chart-grid-line"
                x1={margin.left}
                x2={width - margin.right}
                y1={y}
                y2={y}
              />
              <line
                className="result-chart-tick"
                x1={margin.left - 4}
                x2={margin.left}
                y1={y}
                y2={y}
              />
              <text
                className="result-chart-label"
                textAnchor="end"
                x={margin.left - 7}
                y={y + 3}
              >
                {formatChartNumber(tick)}
              </text>
            </g>
          );
        })}
        {xTicks.map((tick, index) => {
          const x = xPosition(tick);
          const textAnchor =
            index === 0 ? "start" : index === xTicks.length - 1 ? "end" : "middle";
          return (
            <g key={`x-${index}`}>
              <line
                className="result-chart-grid-line"
                x1={x}
                x2={x}
                y1={margin.top}
                y2={height - margin.bottom}
              />
              <line
                className="result-chart-tick"
                x1={x}
                x2={x}
                y1={height - margin.bottom}
                y2={height - margin.bottom + 4}
              />
              <text
                className="result-chart-label"
                textAnchor={textAnchor}
                x={x}
                y={height - margin.bottom + 15}
              >
                {formatChartNumber(tick)}
              </text>
            </g>
          );
        })}
        <line
          className="result-chart-axis"
          x1={margin.left}
          x2={margin.left}
          y1={margin.top}
          y2={height - margin.bottom}
        />
        <line
          className="result-chart-axis"
          x1={margin.left}
          x2={width - margin.right}
          y1={height - margin.bottom}
          y2={height - margin.bottom}
        />
        <path
          d={path}
          fill="none"
          stroke={color}
          strokeLinecap="round"
          strokeLinejoin="round"
          strokeWidth="2"
          vectorEffect="non-scaling-stroke"
        />
        {cursorEnabled && cursorSample ? (
          <>
            <g className="result-chart-cursor" pointerEvents="none">
              <line
                x1={xPosition(cursorSample.x)}
                x2={xPosition(cursorSample.x)}
                y1={margin.top}
                y2={height - margin.bottom}
              />
              <line
                x1={margin.left}
                x2={width - margin.right}
                y1={yPosition(cursorSample.y)}
                y2={yPosition(cursorSample.y)}
              />
              <circle
                cx={xPosition(cursorSample.x)}
                cy={yPosition(cursorSample.y)}
                fill={color}
                r="3.5"
              />
            </g>
            <line
              className="result-chart-cursor-hit x"
              onLostPointerCapture={stopCursorLineDrag}
              onPointerCancel={stopCursorLineDrag}
              onPointerDown={(event) => startCursorLineDrag(event, "x")}
              onPointerMove={moveCursorLine}
              onPointerUp={stopCursorLineDrag}
              x1={xPosition(cursorSample.x)}
              x2={xPosition(cursorSample.x)}
              y1={margin.top}
              y2={height - margin.bottom}
            />
            <line
              className="result-chart-cursor-hit y"
              onLostPointerCapture={stopCursorLineDrag}
              onPointerCancel={stopCursorLineDrag}
              onPointerDown={(event) => startCursorLineDrag(event, "y")}
              onPointerMove={moveCursorLine}
              onPointerUp={stopCursorLineDrag}
              x1={margin.left}
              x2={width - margin.right}
              y1={yPosition(cursorSample.y)}
              y2={yPosition(cursorSample.y)}
            />
          </>
        ) : null}
        <text
          className="result-chart-axis-title"
          textAnchor="middle"
          x={margin.left + plotWidth / 2}
          y={height - 5}
        >
          时间 (s)
        </text>
      </svg>
      {cursorEnabled && cursorSample ? (
        <div
          className="result-chart-cursor-panel"
          onPointerDown={(event) => event.stopPropagation()}
          ref={cursorPanelRef}
          style={{
            left: cursorPanelPosition.x,
            top: cursorPanelPosition.y,
          }}
        >
          <button
            aria-label="移动游标读数窗口"
            className="result-chart-cursor-panel-header"
            onLostPointerCapture={stopCursorPanelDrag}
            onPointerCancel={stopCursorPanelDrag}
            onPointerDown={startCursorPanelDrag}
            onPointerMove={moveCursorPanel}
            onPointerUp={stopCursorPanelDrag}
            title="移动游标读数"
            type="button"
          >
            <Move aria-hidden="true" size={13} strokeWidth={1.8} />
            <span>游标</span>
          </button>
          <dl>
            <div>
              <dt>X</dt>
              <dd>{formatCursorNumber(cursorSample.x)} s</dd>
            </div>
            <div>
              <dt>Y</dt>
              <dd>
                {formatCursorNumber(cursorSample.y)} {unit}
              </dd>
            </div>
          </dl>
        </div>
      ) : null}
    </div>
  );
}

function nearestSampleIndex(samples: CurveSample[], targetX: number) {
  let low = 0;
  let high = samples.length - 1;
  while (low < high) {
    const middle = Math.floor((low + high) / 2);
    if (samples[middle].x < targetX) {
      low = middle + 1;
    } else {
      high = middle;
    }
  }
  if (low === 0) {
    return 0;
  }
  return Math.abs(samples[low].x - targetX) <
    Math.abs(samples[low - 1].x - targetX)
    ? low
    : low - 1;
}

function nearestSampleIndexByY(
  samples: CurveSample[],
  targetY: number,
  currentIndex: number,
) {
  let nearestIndex = 0;
  let nearestDistance = Number.POSITIVE_INFINITY;
  let nearestIndexDistance = Number.POSITIVE_INFINITY;
  samples.forEach((sample, index) => {
    const distance = Math.abs(sample.y - targetY);
    const indexDistance = Math.abs(index - currentIndex);
    if (
      distance < nearestDistance ||
      (distance === nearestDistance && indexDistance < nearestIndexDistance)
    ) {
      nearestIndex = index;
      nearestDistance = distance;
      nearestIndexDistance = indexDistance;
    }
  });
  return nearestIndex;
}

function clampCursorPanelPosition(
  position: CursorPanelPosition,
  containerWidth: number,
  containerHeight: number,
  panelWidth: number,
  panelHeight: number,
) {
  const margin = 6;
  return {
    x: Math.round(
      Math.min(
        Math.max(margin, position.x),
        Math.max(margin, containerWidth - panelWidth - margin),
      ),
    ),
    y: Math.round(
      Math.min(
        Math.max(margin, position.y),
        Math.max(margin, containerHeight - panelHeight - margin),
      ),
    ),
  };
}

function resultVariablesForNode(
  variables: ResultVariableMetadata[],
  series: Record<string, number[]>,
  nodeId: string,
) {
  return variables
    .filter((variable) => {
      const values = series[variable.key];
      return (
        variable.componentId === nodeId &&
        Array.isArray(values) &&
        values.length > 0
      );
    })
    .sort((first, second) => {
      if (first.scope !== second.scope) {
        return first.scope === "component" ? -1 : 1;
      }
      const portOrder = (first.portName ?? "").localeCompare(
        second.portName ?? "",
        "zh-CN",
      );
      if (portOrder !== 0) {
        return portOrder;
      }
      return (
        first.order - second.order ||
        first.label.localeCompare(second.label, "zh-CN")
      );
    });
}

function resultVariableLabel(variable: ResultVariableMetadata) {
  return variable.scope === "port" && variable.portName
    ? `${variable.portName} · ${variable.label}`
    : variable.label;
}

function resultVariableTitle(
  variable: ResultVariableMetadata,
  componentName: string,
) {
  const variablePath = variable.portName
    ? `${variable.portName}.${variable.name}`
    : variable.name;
  return `${componentName}.${variablePath}`;
}

function scaledResultUnit(
  value: string,
  label: string,
  baseUnitsPerDisplayUnit: number,
): ResultUnitOption {
  return {
    value,
    label,
    fromBase: (baseValue) => baseValue / baseUnitsPerDisplayUnit,
  };
}

function resultUnitOptions(variable: ResultVariableMetadata) {
  return (
    RESULT_UNIT_OPTIONS[variable.quantity] ?? [
      scaledResultUnit(variable.unit, variable.unit || "无量纲", 1),
    ]
  );
}

function resolveResultUnitOption(
  variable: ResultVariableMetadata,
  requestedUnit: string,
) {
  const options = resultUnitOptions(variable);
  return (
    options.find((option) => option.value === requestedUnit) ??
    options.find((option) => option.value === variable.unit) ??
    options[0]
  );
}

function chartTicks(minimum: number, maximum: number, intervalCount: number) {
  const range = maximum - minimum;
  return Array.from(
    { length: intervalCount + 1 },
    (_, index) => minimum + (range * index) / intervalCount,
  );
}

function truncateLegendLabel(label: string, availableWidth: number) {
  const maximumCharacters = Math.max(7, Math.floor(availableWidth / 5.8));
  return label.length <= maximumCharacters
    ? label
    : `${label.slice(0, maximumCharacters - 1)}…`;
}

async function downloadChartImage(
  button: HTMLButtonElement,
  filenameStem: string,
) {
  const chartWindow = button.closest(".result-chart-window");
  if (!(chartWindow instanceof HTMLElement)) {
    throw new Error("没有找到可导出的曲线窗口。");
  }
  const chartSurface = chartWindow.querySelector(".result-chart-body");
  if (!(chartSurface instanceof HTMLElement)) {
    throw new Error("没有找到可导出的绘图区。");
  }
  downloadBlob(
    await chartSurfaceToPngBlob(chartSurface),
    `${safeFileStem(filenameStem)}.png`,
  );
}

async function chartSurfaceToPngBlob(chartSurface: HTMLElement) {
  const { default: html2canvas } = await import("html2canvas");
  const canvas = await html2canvas(chartSurface, {
    backgroundColor: "#ffffff",
    imageTimeout: 0,
    logging: false,
    removeContainer: true,
    scale: Math.min(Math.max(window.devicePixelRatio || 1, 2), 3),
    useCORS: true,
  });
  return await canvasBlob(canvas, "image/png");
}

function canvasBlob(canvas: HTMLCanvasElement, type: string) {
  return new Promise<Blob>((resolve, reject) => {
    canvas.toBlob((blob) => {
      if (blob) {
        resolve(blob);
      } else {
        reject(new Error("曲线图片生成失败。"));
      }
    }, type);
  });
}

function createSimulationResultFile(
  snapshot: SimulationResultsSnapshot,
): SimulationResultFile {
  const lastSeriesTime = snapshot.result.series.time?.at(-1);
  const simulatedUntil = Number.isFinite(snapshot.result.simulatedUntil)
    ? Number(snapshot.result.simulatedUntil)
    : Number.isFinite(lastSeriesTime)
      ? Number(lastSeriesTime)
      : null;
  return {
    fileType: RESULT_FILE_TYPE,
    formatVersion: RESULT_FILE_FORMAT_VERSION,
    exportedAt: new Date().toISOString(),
    metadata: {
      projectName: snapshot.project.name,
      resultCreatedAt: snapshot.createdAt,
      simulation: {
        ...snapshot.project.simulation,
        simulatedUntil,
      },
      resultStatus: simulationResultStatus(snapshot.result),
      componentCount: snapshot.project.nodes.length,
      connectionCount: snapshot.project.edges.length,
      sampleCount: snapshot.result.diagnostics.sampleCount,
      componentParameters: snapshot.project.nodes.map((node) => ({
        id: node.id,
        name: node.data.label,
        componentType: node.data.componentType,
        parameters: { ...node.data.parameters },
        parameterUnits: { ...(node.data.parameterUnits ?? {}) },
      })),
    },
    snapshot,
  };
}

function downloadSimulationResultFile(snapshot: SimulationResultsSnapshot) {
  const payload = createSimulationResultFile(snapshot);
  const timestamp = compactFileTimestamp(payload.exportedAt);
  downloadBlob(
    new Blob([JSON.stringify(payload)], { type: RESULT_FILE_MIME }),
    `${safeFileStem(snapshot.project.name)}-${timestamp}.simresult`,
  );
}

function parseSimulationResultFile(raw: string): SimulationResultsSnapshot {
  let value: unknown;
  try {
    value = JSON.parse(raw);
  } catch {
    throw new Error("文件不是有效的 System Simulation 结果文件。");
  }
  if (!isRecord(value) || value.fileType !== RESULT_FILE_TYPE) {
    throw new Error("文件类型不正确，请选择 .simresult 文件。");
  }
  if (value.formatVersion !== RESULT_FILE_FORMAT_VERSION) {
    throw new Error(`不支持的结果文件版本：${String(value.formatVersion)}`);
  }
  if (!isRecord(value.metadata) || !isSimulationResultsSnapshotValue(value.snapshot)) {
    throw new Error("结果文件内容不完整或已经损坏。");
  }
  return {
    ...value.snapshot,
    id: `imported-${Date.now()}-${Math.random().toString(16).slice(2)}`,
  };
}

function isSimulationResultsSnapshotValue(
  value: unknown,
): value is SimulationResultsSnapshot {
  if (!isRecord(value) || typeof value.id !== "string" || typeof value.createdAt !== "string") {
    return false;
  }
  const project = value.project;
  const result = value.result;
  if (
    !isRecord(project) ||
    typeof project.name !== "string" ||
    (project.presentationLayoutVersion !== undefined &&
      project.presentationLayoutVersion !== null &&
      project.presentationLayoutVersion !== 1) ||
    !Array.isArray(project.nodes) ||
    !project.nodes.every(isResultProjectNode) ||
    !Array.isArray(project.edges) ||
    !project.edges.every(isResultProjectEdge) ||
    !isResultSimulationConfig(project.simulation) ||
    !isRecord(result) ||
    typeof result.success !== "boolean" ||
    typeof result.message !== "string" ||
    !Array.isArray(result.variables) ||
    !result.variables.every(isResultVariableMetadata) ||
    !isRecord(result.final) ||
    !isNumericRecord(result.final) ||
    !isRecord(result.series) ||
    !Object.values(result.series).every(isNumericArray) ||
    !Array.isArray(result.series.time) ||
    !isRecord(result.diagnostics) ||
    typeof result.diagnostics.sampleCount !== "number"
  ) {
    return false;
  }
  return (
    result.status === undefined ||
    ["completed", "stopped", "stalled", "failed"].includes(String(result.status))
  );
}

function isResultProjectNode(value: unknown): value is ResultProjectNode {
  if (!isRecord(value) || !isRecord(value.position) || !isRecord(value.data)) {
    return false;
  }
  const data = value.data;
  return (
    typeof value.id === "string" &&
    value.type === "simulationComponent" &&
    Number.isFinite(value.position.x) &&
    Number.isFinite(value.position.y) &&
    typeof data.label === "string" &&
    typeof data.componentType === "string" &&
    typeof data.modelType === "string" &&
    Array.isArray(data.ports) &&
    isRecord(data.parameters) &&
    (data.parameterUnits === undefined || isRecord(data.parameterUnits)) &&
    [0, 90, 180, 270].includes(Number(data.rotation)) &&
    typeof data.mirrored === "boolean"
  );
}

function isResultProjectEdge(value: unknown): value is ResultProjectEdge {
  return (
    isRecord(value) &&
    typeof value.id === "string" &&
    typeof value.source === "string" &&
    typeof value.target === "string" &&
    (value.sourceHandle === null || typeof value.sourceHandle === "string") &&
    (value.targetHandle === null || typeof value.targetHandle === "string")
  );
}

function isResultSimulationConfig(
  value: unknown,
): value is ResultSimulationConfig {
  return (
    isRecord(value) &&
    Number.isFinite(value.t_start) &&
    Number.isFinite(value.t_stop) &&
    Number.isFinite(value.step) &&
    Number.isFinite(value.max_step) &&
    typeof value.method === "string"
  );
}

function isResultVariableMetadata(
  value: unknown,
): value is ResultVariableMetadata {
  return (
    isRecord(value) &&
    typeof value.key === "string" &&
    typeof value.componentId === "string" &&
    typeof value.componentType === "string" &&
    (value.scope === "component" || value.scope === "port") &&
    (value.portName === null || typeof value.portName === "string") &&
    typeof value.name === "string" &&
    typeof value.label === "string" &&
    typeof value.quantity === "string" &&
    typeof value.unit === "string" &&
    typeof value.category === "string" &&
    Number.isFinite(value.order)
  );
}

function isNumericRecord(value: Record<string, unknown>) {
  return Object.values(value).every(
    (item) => typeof item === "number" && Number.isFinite(item),
  );
}

function isNumericArray(value: unknown): value is number[] {
  return (
    Array.isArray(value) &&
    value.every((item) => typeof item === "number" && Number.isFinite(item))
  );
}

function isRecord(value: unknown): value is Record<string, unknown> {
  return Boolean(value) && typeof value === "object" && !Array.isArray(value);
}

function compactFileTimestamp(value: string) {
  const timestamp = new Date(value);
  if (Number.isNaN(timestamp.getTime())) {
    return "result";
  }
  const pad = (part: number) => String(part).padStart(2, "0");
  return `${timestamp.getFullYear()}${pad(timestamp.getMonth() + 1)}${pad(
    timestamp.getDate(),
  )}-${pad(timestamp.getHours())}${pad(timestamp.getMinutes())}${pad(
    timestamp.getSeconds(),
  )}`;
}

function responseDownloadFilename(response: Response, fallback: string) {
  const disposition = response.headers.get("Content-Disposition") ?? "";
  const encoded = /filename\*=UTF-8''([^;]+)/i.exec(disposition)?.[1];
  if (encoded) {
    try {
      return decodeURIComponent(encoded);
    } catch {
      return fallback;
    }
  }
  return /filename="([^"]+)"/i.exec(disposition)?.[1] ?? fallback;
}

async function responseErrorMessage(response: Response) {
  try {
    const payload = (await response.json()) as { detail?: unknown };
    if (typeof payload.detail === "string") {
      return payload.detail;
    }
  } catch {
    // Use the HTTP status when the server did not return a JSON error body.
  }
  return `${response.status} ${response.statusText}`.trim();
}

function errorMessage(error: unknown) {
  return error instanceof Error ? error.message : String(error);
}

function safeFileStem(value: string) {
  const cleaned = value
    .trim()
    .replace(/[<>:"/\\|?*\u0000-\u001f]/g, "_")
    .replace(/[. ]+$/g, "");
  return cleaned.slice(0, 80) || "simulation";
}

function downloadBlob(blob: Blob, filename: string) {
  const url = URL.createObjectURL(blob);
  const anchor = document.createElement("a");
  anchor.href = url;
  anchor.download = filename;
  anchor.style.display = "none";
  document.body.append(anchor);
  anchor.click();
  anchor.remove();
  window.setTimeout(() => URL.revokeObjectURL(url), 1000);
}

function colorForVariable(key: string) {
  let hash = 0;
  for (const character of key) {
    hash = (hash * 31 + character.charCodeAt(0)) >>> 0;
  }
  return CHART_COLORS[hash % CHART_COLORS.length];
}

function defaultResultsPaneLayout(): ResultsPaneLayout {
  const viewportWidth = typeof window === "undefined" ? 1440 : window.innerWidth;
  const viewportHeight = typeof window === "undefined" ? 900 : window.innerHeight;
  return {
    inspectorWidth: Math.round(
      Math.min(560, Math.max(380, viewportWidth * 0.31)),
    ),
    systemHeight: Math.round(
      Math.min(580, Math.max(260, (viewportHeight - 62) * 0.54)),
    ),
  };
}

function loadResultsPaneLayout(): ResultsPaneLayout {
  const defaults = defaultResultsPaneLayout();
  try {
    const raw = localStorage.getItem(RESULT_PANE_LAYOUT_KEY);
    if (!raw) {
      return defaults;
    }
    const value = JSON.parse(raw) as Partial<ResultsPaneLayout>;
    return {
      inspectorWidth:
        typeof value.inspectorWidth === "number" &&
        Number.isFinite(value.inspectorWidth)
          ? value.inspectorWidth
          : defaults.inspectorWidth,
      systemHeight:
        typeof value.systemHeight === "number" &&
        Number.isFinite(value.systemHeight)
          ? value.systemHeight
          : defaults.systemHeight,
    };
  } catch {
    return defaults;
  }
}

function storeResultsPaneLayout(layout: ResultsPaneLayout) {
  try {
    localStorage.setItem(RESULT_PANE_LAYOUT_KEY, JSON.stringify(layout));
  } catch {
    // Keep the active layout in memory when browser storage is unavailable.
  }
}

function clampResultsPaneLayout(
  layout: ResultsPaneLayout,
  workbenchWidth: number,
  workbenchHeight: number,
): ResultsPaneLayout {
  const maximumInspectorWidth = Math.max(
    MIN_INSPECTOR_WIDTH,
    workbenchWidth - PANE_SPLITTER_SIZE - MIN_CHART_WIDTH,
  );
  const maximumSystemHeight = Math.max(
    MIN_SYSTEM_HEIGHT,
    workbenchHeight - PANE_SPLITTER_SIZE - MIN_VARIABLE_HEIGHT,
  );
  return {
    inspectorWidth: Math.round(
      Math.min(
        maximumInspectorWidth,
        Math.max(MIN_INSPECTOR_WIDTH, layout.inspectorWidth),
      ),
    ),
    systemHeight: Math.round(
      Math.min(
        maximumSystemHeight,
        Math.max(MIN_SYSTEM_HEIGHT, layout.systemHeight),
      ),
    ),
  };
}

function sameResultsPaneLayout(
  first: ResultsPaneLayout,
  second: ResultsPaneLayout,
) {
  return (
    first.inspectorWidth === second.inspectorWidth &&
    first.systemHeight === second.systemHeight
  );
}

function clampWindowCoordinate(
  value: number,
  containerSize: number,
  windowSize: number,
) {
  return Math.min(
    Math.max(12, value),
    Math.max(12, containerSize - windowSize - 12),
  );
}

function clampChartWindowDimension(
  requestedSize: number,
  availableSize: number,
  minimumSize: number,
) {
  const maximumSize = Math.max(1, availableSize);
  const effectiveMinimum = Math.min(minimumSize, maximumSize);
  return Math.round(
    Math.min(maximumSize, Math.max(effectiveMinimum, requestedSize)),
  );
}

function clampChartWindowDimensions(
  requestedWidth: number,
  requestedHeight: number,
  workspaceWidth: number,
  workspaceHeight: number,
) {
  return {
    width: clampChartWindowDimension(
      requestedWidth,
      workspaceWidth - 24,
      MIN_CHART_WINDOW_WIDTH,
    ),
    height: clampChartWindowDimension(
      requestedHeight,
      workspaceHeight - 24,
      MIN_CHART_WINDOW_HEIGHT,
    ),
  };
}

function loadChartWindows(snapshotId: string): ChartWindow[] {
  try {
    const raw = sessionStorage.getItem(`${RESULT_LAYOUT_KEY_PREFIX}${snapshotId}`);
    if (!raw) {
      return [];
    }
    const value = JSON.parse(raw) as unknown;
    if (!Array.isArray(value)) {
      return [];
    }
    return value.filter(isStoredChartWindow).map(normalizeStoredChartWindow);
  } catch {
    return [];
  }
}

function nextChartWindowNumber(windows: ChartWindow[]) {
  return (
    Math.max(
      0,
      ...windows.map((window) => {
        const match = /^chart-(\d+)$/.exec(window.id);
        return match ? Number(match[1]) : 0;
      }),
    ) + 1
  );
}

function storeChartWindows(snapshotId: string, windows: ChartWindow[]) {
  try {
    sessionStorage.setItem(
      `${RESULT_LAYOUT_KEY_PREFIX}${snapshotId}`,
      JSON.stringify(windows),
    );
  } catch {
    // The current mounted result view still retains its layout in memory.
  }
}

type StoredChartWindow = Pick<
  ChartWindow,
  "id" | "variableKey" | "x" | "y" | "zIndex"
> &
  Partial<
    Pick<
      ChartWindow,
      | "kind"
      | "variableKeys"
      | "hiddenVariableKeys"
      | "variableUnits"
      | "width"
      | "height"
      | "unit"
      | "cursorEnabled"
    >
  >;

function normalizeStoredChartWindow(window: StoredChartWindow): ChartWindow {
  const kind =
    window.kind === "multi" || window.kind === "mixed"
      ? window.kind
      : "single";
  const rawVariableKeys = window.variableKeys;
  const hasStoredVariableKeys = Array.isArray(rawVariableKeys);
  const storedVariableKeys = hasStoredVariableKeys
    ? rawVariableKeys.filter(
        (key, index, keys) =>
          typeof key === "string" && key.length > 0 && keys.indexOf(key) === index,
      )
    : [];
  const variableKeys =
    kind === "single"
      ? window.variableKey
        ? [window.variableKey]
        : []
      : hasStoredVariableKeys
        ? storedVariableKeys
        : window.variableKey
          ? [window.variableKey]
          : [];
  const hiddenVariableKeys = Array.isArray(window.hiddenVariableKeys)
    ? window.hiddenVariableKeys.filter(
        (key, index, keys) =>
          typeof key === "string" &&
          variableKeys.includes(key) &&
          keys.indexOf(key) === index,
      )
    : [];
  const variableUnits =
    window.variableUnits && isRecord(window.variableUnits)
      ? Object.fromEntries(
          Object.entries(window.variableUnits).filter(
            ([key, value]) =>
              variableKeys.includes(key) && typeof value === "string",
          ),
        )
      : {};
  return {
    ...window,
    kind,
    variableKey: variableKeys[0] ?? "",
    variableKeys,
    hiddenVariableKeys,
    variableUnits,
    width:
      typeof window.width === "number" && Number.isFinite(window.width)
        ? window.width
        : CHART_WINDOW_WIDTH,
    height:
      typeof window.height === "number" && Number.isFinite(window.height)
        ? window.height
        : CHART_WINDOW_HEIGHT,
    unit: typeof window.unit === "string" ? window.unit : "",
    cursorEnabled: window.cursorEnabled === true,
  };
}

function isStoredChartWindow(value: unknown): value is StoredChartWindow {
  if (!value || typeof value !== "object") {
    return false;
  }
  const window = value as Partial<ChartWindow>;
  return (
    typeof window.id === "string" &&
    typeof window.variableKey === "string" &&
    typeof window.x === "number" &&
    Number.isFinite(window.x) &&
    typeof window.y === "number" &&
    Number.isFinite(window.y) &&
    typeof window.zIndex === "number" &&
    Number.isFinite(window.zIndex)
  );
}

function simulationResultStatus(
  result: ResultPayload,
): NonNullable<ResultPayload["status"]> {
  return result.status ?? (result.success ? "completed" : "failed");
}

function simulationResultStatusText(
  result: ResultPayload,
  status: Exclude<NonNullable<ResultPayload["status"]>, "completed">,
) {
  const lastSeriesTime = result.series.time?.at(-1);
  const simulatedUntil = Number.isFinite(result.simulatedUntil)
    ? Number(result.simulatedUntil)
    : Number.isFinite(lastSeriesTime)
      ? Number(lastSeriesTime)
      : null;
  const timeText = simulatedUntil === null
    ? ""
    : ` · 计算至 t=${simulatedUntil.toLocaleString("zh-CN", { maximumFractionDigits: 6 })} s`;
  const labels = {
    stopped: "部分结果：仿真已手动终止",
    stalled: "部分结果：仿真因进度异常终止",
    failed: "部分结果：仿真因求解异常终止",
  } as const;
  return `${labels[status]}${timeText}`;
}

function formatResultTimestamp(value: string) {
  const parsed = new Date(value);
  return Number.isNaN(parsed.getTime())
    ? value
    : parsed.toLocaleString("zh-CN", {
        month: "2-digit",
        day: "2-digit",
        hour: "2-digit",
        minute: "2-digit",
      });
}

function formatChartNumber(value: number) {
  if (!Number.isFinite(value)) {
    return "-";
  }
  if (
    Math.abs(value) >= 100000 ||
    (Math.abs(value) > 0 && Math.abs(value) < 0.001)
  ) {
    return value.toExponential(2);
  }
  return value.toFixed(3).replace(/\.?0+$/, "");
}

function formatCursorNumber(value: number) {
  if (!Number.isFinite(value)) {
    return "-";
  }
  if (
    Math.abs(value) >= 1e7 ||
    (Math.abs(value) > 0 && Math.abs(value) < 1e-5)
  ) {
    return value.toExponential(6);
  }
  return value.toLocaleString("zh-CN", {
    maximumSignificantDigits: 8,
    useGrouping: false,
  });
}