"""Compile-time variable supply contracts, separate from physical flow direction.

Equation ports may participate in a simultaneous solve. Fixed ports (for example
an Amesim node's reference/branch ports) require complementary local supplies.
These declarations do not add numerical state or Python evaluation callbacks.
"""
from __future__ import annotations

from dataclasses import dataclass
from typing import TYPE_CHECKING, Literal, Mapping

if TYPE_CHECKING:
    from .ports import PortDefinition


VARIABLE_LABELS = {
    "p": "压力", "T": "温度", "m_flow": "质量流率", "H_flow": "能量流率",
}


@dataclass(frozen=True)
class PortComputation:
    inputs: tuple[str, ...] = ()
    outputs: tuple[str, ...] = ()
    mode: Literal["equation", "fixed"] = "equation"
    # Output p/T aliases an input on another port of the same component.
    reference_port: str | None = None

    def __post_init__(self) -> None:
        if self.mode not in {"equation", "fixed"}:
            raise ValueError(f"Unknown port computation mode: {self.mode}")
        members = (*self.inputs, *self.outputs)
        if len(set(members)) != len(members) or set(members) - VARIABLE_LABELS.keys():
            raise ValueError("Port computation variables must be unique, supported quantities.")
        if self.reference_port and not {"p", "T"}.issubset(self.outputs):
            raise ValueError("A reference alias must supply pressure and temperature.")

    def as_dict(self) -> dict[str, object]:
        return {
            "mode": self.mode,
            "inputs": list(self.inputs),
            "outputs": list(self.outputs),
            **({"referencePort": self.reference_port} if self.reference_port else {}),
        }


THERMODYNAMIC_SUPPLY = PortComputation(inputs=("m_flow", "H_flow"), outputs=("p", "T"))
FLOW_SUPPLY = PortComputation(inputs=("p", "T"), outputs=("m_flow", "H_flow"))
ZERO_FLOW_SUPPLY = PortComputation(outputs=("m_flow", "H_flow"))
IMPLICIT_PNEUMATIC = PortComputation()
NODE_REFERENCE = PortComputation(inputs=("p", "T"), outputs=("m_flow", "H_flow"), mode="fixed")
NODE_BRANCH = PortComputation(inputs=("m_flow", "H_flow"), outputs=("p", "T"),
                              mode="fixed", reference_port="port_2")


@dataclass(frozen=True)
class PortSupplyIssue:
    code: str
    message: str
    endpoint: tuple[str, str] | None = None


class PortSupplyError(ValueError):
    def __init__(self, issue: PortSupplyIssue):
        self.issue = issue
        super().__init__(f"{issue.code}: {issue.message}")


def port_supply_issue(first: PortDefinition, second: PortDefinition,
                      first_label: str | None = None, second_label: str | None = None
                      ) -> PortSupplyIssue | None:
    """Check fixed causality; ordinary equation-to-equation links stay legal."""
    if first.kind != second.kind or first.domain != second.domain:
        return None  # Domain/type checks own their existing, more specific errors.
    a, b = first.computation, second.computation
    if not any(item and item.mode == "fixed" for item in (a, b)):
        return None
    for consumer, supplier, consumer_label, supplier_label in (
        (a, b, first_label or first.name, second_label or second.name),
        (b, a, second_label or second.name, first_label or first.name),
    ):
        if consumer is None:
            continue
        missing = [name for name in consumer.inputs
                   if supplier is None or name not in supplier.outputs]
        if missing:
            quantities = "、".join(VARIABLE_LABELS[name] for name in missing)
            return PortSupplyIssue(
                "CONNECTION_VARIABLE_SUPPLY_MISSING",
                f"{consumer_label} 需要对端提供{quantities}，但 {supplier_label} 未提供；"
                "请检查参考口与支路口的连接。气体流向反转不会改变这一供需关系。",
            )
    return None


def reference_supply_issues(
    ports: Mapping[tuple[str, str], PortDefinition],
    adjacency: Mapping[tuple[str, str], tuple[str, str]],
) -> list[PortSupplyIssue]:
    """Follow declared aliases to reject a reference ring without an origin.

    This is a supply check, not a whole-system execution scheduler. Reference
    chains are iterative to support deep networks without Python recursion.
    """
    issues = []
    resolved: dict[str, set[tuple[str, str]]] = {'p': set(), 'T': set()}
    for endpoint, port in ports.items():
        contract = port.computation
        if not contract or contract.mode != "fixed" or not {"p", "T"}.issubset(contract.inputs):
            continue
        if endpoint not in adjacency:
            continue  # Existing unconnected-port checks handle incomplete drawings.
        for variable in ("p", "T"):
            current = endpoint
            visited: set[tuple[str, str]] = set()
            chain: list[str] = []
            while True:
                if current in resolved[variable]:
                    resolved[variable].update(visited)
                    break
                if current in visited:
                    issues.append(PortSupplyIssue(
                        "REFERENCE_SUPPLY_CYCLE",
                        f"{'.'.join(endpoint)} 的{VARIABLE_LABELS[variable]}参考形成循环，"
                        f"没有实际提供者：{' → '.join(chain)} → {'.'.join(current)}。",
                        endpoint,
                    ))
                    break
                visited.add(current)
                chain.append('.'.join(current))
                supplier = adjacency.get(current)
                if supplier is None:
                    issues.append(PortSupplyIssue(
                        "REFERENCE_SUPPLY_UNCONNECTED",
                        f"{'.'.join(endpoint)} 的{VARIABLE_LABELS[variable]}参考链在 "
                        f"{'.'.join(current)} 中断：该参考输入尚未连接。", endpoint,
                    ))
                    break
                supplied = ports.get(supplier)
                supply = supplied.computation if supplied else None
                if supply is None or variable not in supply.outputs:
                    # Direct errors are already reported per connection. An
                    # indirect failure is explained at that failing connection.
                    break
                if supply.reference_port is None:
                    resolved[variable].update(visited)
                    break
                chain.append('.'.join(supplier))
                current = supplier[0], supply.reference_port
                if current not in ports:
                    raise ValueError(f"Invalid reference port declaration: {current}")
    return issues