using System;
using System.Collections.Generic;
using EMPlannerVerificationHost;
using MultiWheelC.TrajectoryPlanning.CoarsePath;
using MultiWheelC.TrajectoryPlanning.CoarsePath.Vehicle;
using MultiWheelC.TrajectoryPlanning.PathSmoothing;

namespace MultiWheelC.TrajectoryPlanning.EMPlanner;

internal static class LateralModelChecks
{
    public static void Run()
    {
        VerifiesDeterministicVariableLayout();
        VerifiesExactDiscreteDynamicsForUnequalStations();
        VerifiesPlanningInputBoundariesAndDefensiveCopies();
        VerifiesLateralResultPublicationContract();
    }

    private static void VerifiesDeterministicVariableLayout()
    {
        LateralVariableLayout layout = CreateLayout(4);

        Verification.Equal(15, layout.VariableCount, "layout variable count");
        for (int index = 0; index < 4; index++)
        {
            Verification.Equal(index, layout.L(index), "l index " + index);
            Verification.Equal(4 + index, layout.DL(index), "dl index " + index);
            Verification.Equal(8 + index, layout.DDL(index), "ddl index " + index);
        }
        for (int index = 0; index < 3; index++)
            Verification.Equal(12 + index, layout.DDDL(index), "dddl index " + index);

        ExpectArgumentException(() => CreateLayout(1), "layout rejects fewer than two stations");
        ExpectArgumentException(() => layout.L(4), "l index bounds check");
        ExpectArgumentException(() => layout.DL(-1), "dl index bounds check");
        ExpectArgumentException(() => layout.DDL(4), "ddl index bounds check");
        ExpectArgumentException(() => layout.DDDL(3), "dddl index bounds check");
    }

    private static void VerifiesExactDiscreteDynamicsForUnequalStations()
    {
        double[] stations = { 0d, 0.4d, 1.25d, 2.5d };
        double[] jerks = { 0.5d, -0.3d, 0.2d };
        LateralCandidate candidate = LateralCandidate.Integrate(stations, 0.1d, -0.2d, 0.3d, jerks);

        for (int index = 0; index < jerks.Length; index++)
        {
            double ds = stations[index + 1] - stations[index];
            Verification.NearlyEqual(candidate.DDL[index] + ds * candidate.DDDL[index], candidate.DDL[index + 1],
                "exact ddl integration " + index);
            Verification.NearlyEqual(candidate.DL[index] + ds * candidate.DDL[index] + 0.5d * ds * ds * candidate.DDDL[index],
                candidate.DL[index + 1], "exact dl integration " + index);
            Verification.NearlyEqual(candidate.L[index] + ds * candidate.DL[index] + 0.5d * ds * ds * candidate.DDL[index] +
                ds * ds * ds * candidate.DDDL[index] / 6d, candidate.L[index + 1], "exact l integration " + index);
        }
        Verification.True(candidate.SatisfiesExactDiscreteDynamics(1e-12d), "integrated candidate validates exact dynamics");

        LateralCandidate inconsistent = new LateralCandidate(new[] { 0d, 1d }, new[] { 0d, 1d },
            new[] { 0d, 0d }, new[] { 0d, 0d }, new[] { 0d });
        Verification.True(!inconsistent.SatisfiesExactDiscreteDynamics(1e-12d), "candidate detects inconsistent dynamics");
        ExpectArgumentException(() => new LateralCandidate(new[] { 0d, 0d }, new[] { 0d, 0d },
            new[] { 0d, 0d }, new[] { 0d, 0d }, new[] { 0d }), "candidate rejects non-increasing stations");
    }

    private static void VerifiesPlanningInputBoundariesAndDefensiveCopies()
    {
        DirectionSegmentView segment = CreateStraightSegment();
        var corridorStations = new[]
        {
            new LateralInterval(0d, -0.3d, 0.3d, 0d),
            new LateralInterval(1d, -0.3d, 0.3d, 0d),
            new LateralInterval(2d, -0.3d, 0.3d, 0d),
        };
        var seeds = new[]
        {
            new FrenetProjection(ReferencePathInterpolator.Interpolate(segment, 0d), 0d, 0d, 0d),
        };
        LateralPlanningInput input = new LateralPlanningInput(segment, new StaticCorridor(corridorStations), seeds[0],
            EmTerminalType.Goal, CreateVehicle(), EmPlannerConfiguration.CreateDefault(), seeds);
        corridorStations[1] = new LateralInterval(1d, -0.1d, 0.1d, 0d);
        seeds[0] = new FrenetProjection(ReferencePathInterpolator.Interpolate(segment, 0d), 0.2d, 0d, 0d);

        Verification.NearlyEqual(-0.3d, input.Corridor.Stations[1].MinimumL, "input copies corridor stations");
        Verification.NearlyEqual(0d, input.PreviousTrajectorySeed[0].LateralOffset, "input copies seed list");
        ExpectArgumentException(() => new LateralPlanningInput(segment,
            new StaticCorridor(new[] { new LateralInterval(0d, -0.3d, 0.3d, 0d) }),
            input.StartProjection, EmTerminalType.Goal, CreateVehicle(), EmPlannerConfiguration.CreateDefault(), Array.Empty<FrenetProjection>()),
            "input rejects fewer than two stations");
        ExpectArgumentException(() => new LateralPlanningInput(segment,
            new StaticCorridor(new[]
            {
                new LateralInterval(0d, -0.3d, 0.3d, 0d),
                new LateralInterval(0d, -0.3d, 0.3d, 0d),
            }), input.StartProjection, EmTerminalType.Goal, CreateVehicle(), EmPlannerConfiguration.CreateDefault(), Array.Empty<FrenetProjection>()),
            "input rejects non-increasing corridor stations");
        ExpectArgumentException(() => new LateralPlanningInput(segment,
            new StaticCorridor(new[]
            {
                new LateralInterval(0.1d, -0.3d, 0.3d, 0d),
                new LateralInterval(2d, -0.3d, 0.3d, 0d),
            }), input.StartProjection, EmTerminalType.Goal, CreateVehicle(), EmPlannerConfiguration.CreateDefault(), Array.Empty<FrenetProjection>()),
            "input rejects start-corridor station mismatch");
        ExpectArgumentException(() => new LateralPlanningInput(segment,
            new StaticCorridor(new[]
            {
                new LateralInterval(0d, -0.1d, 0.1d, 0d),
                new LateralInterval(2d, -0.1d, 0.1d, 0d),
            }), new FrenetProjection(ReferencePathInterpolator.Interpolate(segment, 0d), 0.2d, 0d, 0d),
            EmTerminalType.Goal, CreateVehicle(), EmPlannerConfiguration.CreateDefault(), Array.Empty<FrenetProjection>()),
            "input rejects start projection outside first hard interval");
    }

    private static void VerifiesLateralResultPublicationContract()
    {
        LateralPath unvalidated = new LateralPath(new[] { CreatePathPoint(0d) }, false);
        LateralPath validated = new LateralPath(new[] { CreatePathPoint(0d), CreatePathPoint(1d) }, true);

        ExpectArgumentException(() => new LateralPlanningResult(EmPlanningStatus.Success, unvalidated, string.Empty),
            "success requires an independently validated path");
        ExpectArgumentException(() => new LateralPlanningResult(EmPlanningStatus.SuccessWithFallback,
            new LateralPath(Array.Empty<LateralPathPoint>(), true), string.Empty),
            "fallback requires a non-empty path");
        ExpectArgumentException(() => new LateralPlanningResult(EmPlanningStatus.LateralInfeasible, validated, string.Empty),
            "failed result has no candidate");
        LateralPlanningResult result = new LateralPlanningResult(EmPlanningStatus.SuccessWithFallback, validated, "fallback");
        Verification.Equal(validated, result.Path, "fallback path is preserved");
    }

    private static DirectionSegmentView CreateStraightSegment()
    {
        var points = new List<SmoothedPathPoint>
        {
            Point(0d, 0d),
            Point(1d, 1d),
            Point(2d, 2d),
        };
        return new DirectionSegmentView(0, TravelDirection.Forward, points,
            new ReferenceBoundary(0, 0d, EmBoundaryType.None, 0d),
            new ReferenceBoundary(0, 2d, EmBoundaryType.Goal, 2d), 0d);
    }

    private static SmoothedPathPoint Point(double x, double s)
    {
        return new SmoothedPathPoint(x, 0d, 0d, 0d, s, TravelDirection.Forward, 0d, 0d, 0d, 1d,
            false, SmoothedPathPointSource.Anchor);
    }

    private static VehicleParameters CreateVehicle()
    {
        return new VehicleParameters
        {
            LengthMeters = 0.1d,
            WidthMeters = 0.1d,
            SafetyMarginMeters = 0d,
            MaximumCurvaturePerMeter = 1d,
        };
    }

    private static LateralPathPoint CreatePathPoint(double referenceS)
    {
        return new LateralPathPoint(referenceS, referenceS, 0d, 0d, 0d, 0d, referenceS, 0d, 0d, 0d, 0d, 0d);
    }

    private static LateralVariableLayout CreateLayout(int stationCount)
    {
        return new LateralVariableLayout(stationCount);
    }

    private static void ExpectArgumentException(Action action, string name)
    {
        try
        {
            action();
        }
        catch (ArgumentException)
        {
            return;
        }
        throw new InvalidOperationException(name + " did not throw ArgumentException.");
    }
}