from __future__ import annotations

import os
import unittest
from unittest.mock import patch

from app.main import compile_reactflow_network
from app.simulation.solvers.algebraic import (
    CAUSAL_FAST_PATH_ENVIRONMENT_VARIABLE,
)
from app.simulation.systems.generic import GenericFluidSystem
from tests.test_amesim_mechanical_xml import zero_force_mass_project
from tests.test_amesim_pnvo001_signal_xml import (
    high_pressure_helium_step_project,
)
from tests.test_generic_system_xml_simulation import chain_project


def _system(project) -> GenericFluidSystem:
    return GenericFluidSystem(compile_reactflow_network(project))


class PressureFlowCausalExecutionTests(unittest.TestCase):
    def test_strict_causal_rhs_matches_environment_disabled_legacy_bitwise(
        self,
    ) -> None:
        optimized = _system(high_pressure_helium_step_project())
        with patch.dict(
            os.environ,
            {CAUSAL_FAST_PATH_ENVIRONMENT_VARIABLE: "0"},
        ):
            legacy = _system(high_pressure_helium_step_project())

        optimized_state = optimized.initial_state_vector()
        legacy_state = legacy.initial_state_vector()
        for time in (0.0, 0.041, 0.8):
            optimized_derivative = optimized.rhs(time, optimized_state)
            legacy_derivative = legacy.rhs(time, legacy_state)
            self.assertEqual(optimized_derivative, legacy_derivative)
            self.assertEqual(
                tuple(
                    unknown.read()
                    for unknown in optimized.pressure_flow_solver.unknowns
                ),
                tuple(
                    unknown.read()
                    for unknown in legacy.pressure_flow_solver.unknowns
                ),
            )

        global_diagnostics = (
            optimized.pressure_flow_solver.causal_execution_diagnostics()
        )
        self.assertTrue(global_diagnostics["eligible"])
        self.assertGreater(global_diagnostics["fastSolveCount"], 0)
        self.assertGreaterEqual(
            global_diagnostics["fullResidualAuditCount"],
            1,
        )
        secondary = (
            optimized._thermofluid_closure_plan.secondary_block_solvers[0]
        )
        secondary_diagnostics = secondary.causal_execution_diagnostics()
        self.assertTrue(secondary_diagnostics["eligible"])
        self.assertGreater(secondary_diagnostics["fastSolveCount"], 0)

        legacy_diagnostics = (
            legacy.pressure_flow_solver.causal_execution_diagnostics()
        )
        self.assertFalse(legacy_diagnostics["enabled"])
        self.assertEqual(
            legacy_diagnostics["disabledReason"],
            "disabledByEnvironment",
        )
        self.assertEqual(legacy_diagnostics["fastSolveCount"], 0)

    def test_multiple_effort_anchors_conservatively_keep_legacy_path(self) -> None:
        system = _system(chain_project())
        diagnostics = (
            system.pressure_flow_solver.causal_execution_diagnostics()
        )

        self.assertFalse(diagnostics["eligible"])
        self.assertFalse(diagnostics["enabled"])
        self.assertEqual(
            diagnostics["fallbackReason"],
            "effortGroupDoesNotHaveOneAnchor",
        )

    def test_runtime_flow_coverage_failure_fuses_to_verified_legacy_path(
        self,
    ) -> None:
        system = _system(zero_force_mass_project())
        state = system.initial_state_vector()
        system.rhs(0.0, state)
        solver = system.pressure_flow_solver
        original = solver._solve_explicit_flow_unknowns

        def hide_coverage(*args, **kwargs):
            original(*args, **kwargs)
            return set()

        with patch.object(
            solver,
            "_solve_explicit_flow_unknowns",
            side_effect=hide_coverage,
        ):
            diagnostics = solver.solve(effort_variables=("p",))

        self.assertTrue(diagnostics.success)
        self.assertTrue(diagnostics.residual_verified_this_solve)
        execution = solver.causal_execution_diagnostics()
        self.assertFalse(execution["enabled"])
        self.assertEqual(
            execution["disabledReason"],
            "causalRuntimeGateFailed",
        )
        self.assertEqual(execution["legacyFallbackCount"], 1)

    def test_periodic_audit_failure_disables_fast_path_before_fallback(self) -> None:
        system = _system(zero_force_mass_project())
        state = system.initial_state_vector()
        system.rhs(0.0, state)
        solver = system.pressure_flow_solver
        solver._causal_audit_interval = 0
        original_values = solver._pressure_flow_equation_values
        call_count = 0

        def one_bad_audit_value():
            nonlocal call_count
            call_count += 1
            values = original_values()
            if call_count != 1:
                return values
            return (values[0] + 1.0, *values[1:])

        with patch.object(
            solver,
            "_pressure_flow_equation_values",
            side_effect=one_bad_audit_value,
        ):
            diagnostics = solver.solve(effort_variables=("p",))

        self.assertTrue(diagnostics.success)
        execution = solver.causal_execution_diagnostics()
        self.assertFalse(execution["enabled"])
        self.assertEqual(
            execution["disabledReason"],
            "causalResidualAuditFailed",
        )
        self.assertEqual(execution["auditFailureCount"], 1)
        self.assertEqual(execution["legacyFallbackCount"], 1)

    def test_requested_audit_interrupts_periodic_fast_sequence(self) -> None:
        system = _system(zero_force_mass_project())
        state = system.initial_state_vector()
        solver = system.pressure_flow_solver

        system.rhs(0.0, state)
        system.rhs(0.0, state)
        before = solver.causal_execution_diagnostics()
        self.assertEqual(before["fullResidualAuditCount"], 1)
        self.assertEqual(before["fastSolveCount"], 1)

        solver.request_causal_audit()
        system.rhs(0.0, state)
        after = solver.causal_execution_diagnostics()
        self.assertEqual(after["fullResidualAuditCount"], 2)
        self.assertEqual(after["fastSolveCount"], 1)

    def test_fast_solve_skips_the_full_residual_evaluator(self) -> None:
        system = _system(zero_force_mass_project())
        state = system.initial_state_vector()
        solver = system.pressure_flow_solver
        system.rhs(0.0, state)

        with patch.object(
            solver,
            "_pressure_flow_equation_values",
            wraps=solver._pressure_flow_equation_values,
        ) as evaluate_all:
            system.rhs(0.0, state)

        evaluate_all.assert_not_called()
        self.assertTrue(solver.last_diagnostics.causal_fast_path_used)
        self.assertFalse(
            solver.last_diagnostics.residual_verified_this_solve
        )

    def test_nonfinite_explicit_assignment_fuses_and_verifies_same_solve(
        self,
    ) -> None:
        system = _system(zero_force_mass_project())
        state = system.initial_state_vector()
        system.rhs(0.0, state)
        solver = system.pressure_flow_solver
        original = solver._evaluate_explicit_flow_stage
        call_count = 0

        def one_nonfinite_assignment(stage):
            nonlocal call_count
            call_count += 1
            values = original(stage)
            if call_count != 1:
                return values
            return (float("nan"), *values[1:])

        with patch.object(
            solver,
            "_evaluate_explicit_flow_stage",
            side_effect=one_nonfinite_assignment,
        ):
            diagnostics = solver.solve(effort_variables=("p",))

        self.assertTrue(diagnostics.success)
        self.assertTrue(diagnostics.residual_verified_this_solve)
        execution = solver.causal_execution_diagnostics()
        self.assertFalse(execution["enabled"])
        self.assertEqual(
            execution["disabledReason"],
            "causalRuntimeGateFailed",
        )
        self.assertEqual(execution["legacyFallbackCount"], 1)

    def test_nonpositive_pressure_fuses_and_verifies_same_solve(self) -> None:
        system = _system(high_pressure_helium_step_project())
        state = system.initial_state_vector()
        system.rhs(0.0, state)
        solver = system.pressure_flow_solver
        original = solver._solve_explicit_flow_unknowns
        pressure = next(
            unknown for unknown in solver.unknowns if unknown.variable == "p"
        )

        def make_pressure_invalid(*args, **kwargs):
            seeded = original(*args, **kwargs)
            pressure.write(-1.0)
            return seeded

        with patch.object(
            solver,
            "_solve_explicit_flow_unknowns",
            side_effect=make_pressure_invalid,
        ):
            diagnostics = solver.solve(effort_variables=("p",))

        self.assertTrue(diagnostics.success)
        self.assertTrue(diagnostics.residual_verified_this_solve)
        self.assertGreater(pressure.read(), 0.0)
        execution = solver.causal_execution_diagnostics()
        self.assertFalse(execution["enabled"])
        self.assertEqual(
            execution["disabledReason"],
            "causalRuntimeGateFailed",
        )
        self.assertEqual(execution["legacyFallbackCount"], 1)

    def test_default_periodic_audit_runs_after_sixty_four_fast_solves(self) -> None:
        system = _system(zero_force_mass_project())
        state = system.initial_state_vector()
        solver = system.pressure_flow_solver
        system.rhs(0.0, state)

        for _iteration in range(64):
            system.rhs(0.0, state)
        before_boundary = solver.causal_execution_diagnostics()
        self.assertEqual(before_boundary["auditInterval"], 64)
        self.assertEqual(before_boundary["fastSolveCount"], 64)
        self.assertEqual(before_boundary["fullResidualAuditCount"], 1)

        system.rhs(0.0, state)
        after_boundary = solver.causal_execution_diagnostics()
        self.assertEqual(after_boundary["fastSolveCount"], 64)
        self.assertEqual(after_boundary["fullResidualAuditCount"], 2)


if __name__ == "__main__":
    unittest.main()