using System;
using System.Collections.Generic;
using System.IO;
using System.Numerics;
using AcDream.Core.Physics;
using DatReaderWriter;
using DatReaderWriter.DBObjs;
using DatReaderWriter.Enums;
using DatReaderWriter.Options;
using Xunit;
using Xunit.Abstractions;
using Env = System.Environment;
using Plane = System.Numerics.Plane;

namespace AcDream.Core.Tests.Physics;

/// <summary>
/// A6.P4 door fix (2026-05-24) — apparatus test. Loads door Setup
/// <c>0x020019FF</c> + GfxObj <c>0x010044B5</c> (the collision-bearing
/// frame/slab part — see
/// <see cref="DoorSetupGfxObjInspectionTests"/>) from the real dat,
/// registers a synthetic door entity at a known world position via
/// <see cref="ShadowObjectRegistry.RegisterMultiPart"/>, and sweeps a
/// player sphere into the door from multiple angles.
///
/// <para>
/// Purpose: with the dat inspection having confirmed that
/// <c>0x010044B5</c> has a complete 1.9 × 0.26 × 2.5 m door-slab
/// PhysicsBSP, this test isolates whether our
/// <see cref="BSPQuery.FindCollisions"/> + the
/// <see cref="RegisterMultiPart"/> registration path actually fires
/// collisions against that BSP. If it does, the live Holtburg door
/// bug is somewhere DOWNSTREAM (live registration race, entity
/// rotation, cell scoping). If it doesn't, the bug is here in
/// the integration we can fix with confidence.
/// </para>
///
/// <para>
/// The test skips gracefully when the dat directory isn't present so
/// CI stays green. Local developer machines always have it.
/// </para>
/// </summary>
public class DoorCollisionApparatusTests
{
    private readonly ITestOutputHelper _out;
    public DoorCollisionApparatusTests(ITestOutputHelper output) => _out = output;

    private const uint DoorSetupId = 0x020019FFu;
    private const uint DoorFrameGfxObjId = 0x010044B5u;
    private const uint DoorEntityId = 0xF424Fu;
    private const uint TestLandblockId = 0xA9B40000u;

    // Cell (0, 0) in landblock 0xA9B40000 — outdoor 24-m cell, low byte
    // = (0 * 8) + 0 + 1 = 1.
    private const uint TestCellId = TestLandblockId | 0x0001u;

    private const float SphereRadius   = 0.48f;   // ~retail player capsule radius
    private const float SphereHeight   = 1.20f;
    private const float StepUpHeight   = 0.60f;
    private const float StepDownHeight = 0.04f;

    /// <summary>
    /// Walk the sphere toward the closed door, dead-center, from
    /// the door's -Y front face approach. Expect a CollisionNormalValid
    /// = true AND the sphere stops before passing through the door.
    /// </summary>
    [Fact]
    public void Apparatus_DeadCenter_FrontApproach_BlocksOnBSP()
    {
        if (!TryBuildScenario(out var ctx)) return;

        // Door at world (12, 12, 0). The frame's BSP slab extends
        // entity-local Y∈[-0.009, 0.252] (poly Y range plus frame[0] offset).
        // Approach from -Y at sphere Y=11 (1 m before the front face),
        // walk +Y at 0.10 m/tick.
        var start = new Vector3(12f, 11f, 0.5f);
        var perTick = new Vector3(0f, 0.10f, 0f);

        var (blocked, finalPos, normal, ticks) = SweepUntilBlocked(
            ctx.engine, start, perTick, maxTicks: 30);

        _out.WriteLine($"Final pos = ({finalPos.X:F3}, {finalPos.Y:F3}, {finalPos.Z:F3}) " +
                       $"after {ticks} ticks; blocked={blocked} normal=({normal.X:F3},{normal.Y:F3},{normal.Z:F3})");

        Assert.True(blocked,
            $"Expected collision before passing through the door. Sphere reached " +
            $"({finalPos.X:F3},{finalPos.Y:F3},{finalPos.Z:F3}) after {ticks} ticks " +
            $"without firing CollisionNormalValid.");
        Assert.True(finalPos.Y < 12.0f,
            $"Sphere should stop before the door's front face (Y ≈ 11.99). " +
            $"Got Y={finalPos.Y:F3}");
    }

    /// <summary>
    /// 50 cm off-center: the small Sphere shape (r=0.10) can't catch
    /// this, but the BSP slab (1.9 m wide) MUST. This is the live
    /// regression — pre-fix the user can walk around the cylinder.
    /// </summary>
    [Fact]
    public void Apparatus_50cmOffCenter_FrontApproach_BlocksOnBSP()
    {
        if (!TryBuildScenario(out var ctx)) return;

        // Same setup, but start 0.5 m off-center in X. Slab X range
        // is approximately [11.05, 12.97] (frame[0].X offset = -0.006).
        var start = new Vector3(12.5f, 11f, 0.5f);
        var perTick = new Vector3(0f, 0.10f, 0f);

        var (blocked, finalPos, normal, ticks) = SweepUntilBlocked(
            ctx.engine, start, perTick, maxTicks: 30);

        _out.WriteLine($"Final pos = ({finalPos.X:F3}, {finalPos.Y:F3}, {finalPos.Z:F3}) " +
                       $"after {ticks} ticks; blocked={blocked} normal=({normal.X:F3},{normal.Y:F3},{normal.Z:F3})");

        Assert.True(blocked,
            $"Expected BSP collision off-center. Sphere reached " +
            $"({finalPos.X:F3},{finalPos.Y:F3},{finalPos.Z:F3}) after {ticks} ticks " +
            $"without firing CollisionNormalValid.");
        Assert.True(finalPos.Y < 12.0f,
            $"Sphere should stop before door front face. Got Y={finalPos.Y:F3}");
    }

    /// <summary>
    /// Reverse approach: walk from the door's +Y back side toward -Y.
    /// SidesType=Landblock polys are two-sided, so this must also block.
    /// This pins the live "walking out from inside passes through" bug
    /// in its simplest geometric form.
    /// </summary>
    [Fact]
    public void Apparatus_DeadCenter_BackApproach_BlocksOnBSP()
    {
        if (!TryBuildScenario(out var ctx)) return;

        // Start past the door at Y=13, walk back toward -Y.
        var start = new Vector3(12f, 13f, 0.5f);
        var perTick = new Vector3(0f, -0.10f, 0f);

        var (blocked, finalPos, normal, ticks) = SweepUntilBlocked(
            ctx.engine, start, perTick, maxTicks: 30);

        _out.WriteLine($"Final pos = ({finalPos.X:F3}, {finalPos.Y:F3}, {finalPos.Z:F3}) " +
                       $"after {ticks} ticks; blocked={blocked} normal=({normal.X:F3},{normal.Y:F3},{normal.Z:F3})");

        Assert.True(blocked,
            $"Expected BSP collision from back side (two-sided Landblock poly). " +
            $"Sphere reached ({finalPos.X:F3},{finalPos.Y:F3},{finalPos.Z:F3}) " +
            $"after {ticks} ticks.");
        Assert.True(finalPos.Y > 12.30f,
            $"Sphere should stop after the door's back face (Y ≈ 12.25). " +
            $"Got Y={finalPos.Y:F3}");
    }

    /// <summary>
    /// Diagnostic dump: drive 5 ticks with probes on, just to see
    /// what the engine reports per-tick. Useful when the assertion
    /// tests above fail — the diagnostic test shows the FULL log
    /// without yielding a green/red verdict.
    /// </summary>
    [Fact]
    public void Apparatus_DiagnosticDump_FrontApproach()
    {
        if (!TryBuildScenario(out var ctx)) return;

        PhysicsDiagnostics.ProbeResolveEnabled    = true;
        PhysicsDiagnostics.ProbeBuildingEnabled   = true;
        try
        {
            var pos = new Vector3(12f, 11f, 0.5f);
            var perTick = new Vector3(0f, 0.10f, 0f);
            uint cellId = TestCellId;
            bool isOnGround = false;

            for (int tick = 0; tick < 8; tick++)
            {
                Vector3 target = pos + perTick;
                var result = ctx.engine.ResolveWithTransition(
                    pos, target, cellId,
                    SphereRadius, SphereHeight,
                    StepUpHeight, StepDownHeight,
                    isOnGround,
                    body: null,
                    moverFlags: ObjectInfoState.IsPlayer,
                    movingEntityId: 0);
                _out.WriteLine($"tick={tick} pos=({pos.X:F3},{pos.Y:F3},{pos.Z:F3}) → " +
                               $"({result.Position.X:F3},{result.Position.Y:F3},{result.Position.Z:F3}) " +
                               $"hit={result.CollisionNormalValid} " +
                               $"normal=({result.CollisionNormal.X:F3},{result.CollisionNormal.Y:F3},{result.CollisionNormal.Z:F3})");
                pos = result.Position;
                cellId = result.CellId;
                isOnGround = result.IsOnGround;
            }

            Assert.True(true, "Diagnostic test — always passes; check stdout.");
        }
        finally
        {
            PhysicsDiagnostics.ProbeResolveEnabled    = false;
            PhysicsDiagnostics.ProbeBuildingEnabled   = false;
        }
    }

    /// <summary>
    /// Reproduces the LIVE bug: a grounded player (isOnGround=true with
    /// seeded ContactPlane) walking off-center toward a closed door
    /// passes through. The path-difference test: this hits Path 5
    /// (Contact branch + StepSphereUp), while the other apparatus
    /// tests above hit Path 6 (Default). If Path 5 incorrectly
    /// declares step-up success the BSP collision returns OK and the
    /// sphere walks through — exactly what the user reports in the
    /// live Holtburg session 2026-05-24.
    /// </summary>
    [Fact]
    public void Apparatus_Grounded_50cmOffCenter_FrontApproach_DocumentsBug()
    {
        if (!TryBuildScenario(out var ctx)) return;

        PhysicsDiagnostics.ProbeResolveEnabled  = true;
        PhysicsDiagnostics.ProbeBuildingEnabled = true;
        Env.SetEnvironmentVariable("ACDREAM_DUMP_STEPUP", "1");

        // Synthetic floor plane at Z = 0 so the grounded sphere has a
        // walkable plane to rest on. Sphere foot center starts at Z=radius
        // = 0.48, head at 0.48 + 1.20 = 1.68.
        var floorPlane = new Plane(0f, 0f, 1f, 0f); // z = 0 plane
        var floorVerts = new[]
        {
            new Vector3( 0f,  0f, 0f),
            new Vector3(24f,  0f, 0f),
            new Vector3(24f, 24f, 0f),
            new Vector3( 0f, 24f, 0f),
        };

        var body = new PhysicsBody
        {
            Position             = new Vector3(12.5f, 11f, 0.48f),
            Orientation          = Quaternion.Identity,
            ContactPlaneValid    = true,
            ContactPlane         = floorPlane,
            ContactPlaneCellId   = TestCellId,
            WalkablePolygonValid = true,
            WalkablePlane        = floorPlane,
            WalkableVertices     = floorVerts,
            WalkableUp           = Vector3.UnitZ,
            TransientState       = TransientStateFlags.Contact | TransientStateFlags.OnWalkable,
        };

        var perTick = new Vector3(0f, 0.10f, 0f);
        Vector3 pos = body.Position;
        uint cellId = TestCellId;
        bool isOnGround = true;
        bool blocked = false;
        Vector3 lastNormal = Vector3.Zero;
        int ticks = 0;

        for (int tick = 0; tick < 30; tick++)
        {
            Vector3 target = pos + perTick;
            var result = ctx.engine.ResolveWithTransition(
                pos, target, cellId,
                SphereRadius, SphereHeight,
                StepUpHeight, StepDownHeight,
                isOnGround,
                body:           body,
                moverFlags:     ObjectInfoState.IsPlayer | ObjectInfoState.EdgeSlide,
                movingEntityId: 0);

            ticks = tick;
            body.Position = result.Position;
            pos = result.Position;
            cellId = result.CellId;
            isOnGround = result.IsOnGround;
            lastNormal = result.CollisionNormal;

            if (result.CollisionNormalValid)
            {
                blocked = true;
                _out.WriteLine($"Tick {tick}: BLOCKED at pos=({pos.X:F3},{pos.Y:F3},{pos.Z:F3}) normal=({lastNormal.X:F3},{lastNormal.Y:F3},{lastNormal.Z:F3})");
                break;
            }
        }

        _out.WriteLine($"Final pos = ({pos.X:F3}, {pos.Y:F3}, {pos.Z:F3}) after {ticks + 1} ticks; blocked={blocked}");
        _out.WriteLine($"Grounded={isOnGround}");

        // EXPECTED FAILURE (documents-the-bug): the grounded sphere walks
        // straight through, reaching the far side at Y > 12.30. When the
        // fix lands, flip this to Assert.True(blocked) — same shape as
        // the Path-6 apparatus tests above.
        PhysicsDiagnostics.ProbeResolveEnabled  = false;
        PhysicsDiagnostics.ProbeBuildingEnabled = false;
        Env.SetEnvironmentVariable("ACDREAM_DUMP_STEPUP", null);

        Assert.True(pos.Y > 12.30f,
            $"This test documents the production bug. If this is failing " +
            $"because the sphere now blocks, the door fix worked — flip " +
            $"the assertion to Assert.True(blocked) and Assert.True(pos.Y < 12.0f). " +
            $"Current pos=({pos.X:F3},{pos.Y:F3},{pos.Z:F3}) blocked={blocked}");
    }

    // ───────────────────────────────────────────────────────────────
    // Apparatus setup
    // ───────────────────────────────────────────────────────────────

    private sealed record Context(
        PhysicsEngine engine,
        PhysicsDataCache cache,
        Setup setup,
        IReadOnlyList<ShadowShape> registeredShapes);

    /// <summary>
    /// Build the engine + cache + landblock + registered door entity.
    /// Returns false if the dat directory is missing (test skips).
    /// </summary>
    private bool TryBuildScenario(out Context ctx)
    {
        ctx = default!;
        var datDir = Env.GetEnvironmentVariable("ACDREAM_DAT_DIR")
            ?? Path.Combine(Env.GetFolderPath(Env.SpecialFolder.UserProfile),
                            "Documents", "Asheron's Call");
        if (!Directory.Exists(datDir))
        {
            _out.WriteLine($"SKIP: dat directory not found at {datDir}");
            return false;
        }

        using var dats = new DatCollection(datDir, DatAccessType.Read);

        // Load + cache the door's collision-bearing part.
        var doorFrameGfx = dats.Get<GfxObj>(DoorFrameGfxObjId);
        Assert.NotNull(doorFrameGfx);
        var cache = new PhysicsDataCache();
        cache.CacheGfxObj(DoorFrameGfxObjId, doorFrameGfx!);
        Assert.NotNull(cache.GetGfxObj(DoorFrameGfxObjId));

        var engine = new PhysicsEngine { DataCache = cache };

        // Stub landblock at world (0, 0) so TryGetLandblockContext succeeds
        // for player XY in the [0, 192) range. Flat far-below terrain so it
        // doesn't interact with the door collision.
        var heights = new byte[81];
        var heightTable = new float[256];
        for (int i = 0; i < 256; i++) heightTable[i] = -1000f;
        engine.AddLandblock(
            landblockId:    TestLandblockId,
            terrain:        new TerrainSurface(heights, heightTable),
            cells:          Array.Empty<CellSurface>(),
            portals:        Array.Empty<PortalPlane>(),
            worldOffsetX:   0f,
            worldOffsetY:   0f);

        // Load door setup, build shapes via the production builder.
        var setup = dats.Get<Setup>(DoorSetupId);
        Assert.NotNull(setup);
        var shapes = ShadowShapeBuilder.FromSetup(
            setup!,
            entScale: 1.0f,
            hasPhysicsBsp: id => cache.GetGfxObj(id)?.BSP?.Root is not null);

        _out.WriteLine($"Shapes from FromSetup: {shapes.Count} entries");
        foreach (var s in shapes)
        {
            _out.WriteLine($"  type={s.CollisionType} gfxObj=0x{s.GfxObjId:X8} " +
                           $"localPos=({s.LocalPosition.X:F3},{s.LocalPosition.Y:F3},{s.LocalPosition.Z:F3}) " +
                           $"radius={s.Radius:F3} cylH={s.CylHeight:F3}");
        }

        // Register the door at world (12, 12, 0). That's cell (0,0) of
        // landblock 0xA9B40000.
        Vector3 doorWorldPos = new(12f, 12f, 0f);
        Quaternion doorWorldRot = Quaternion.Identity;
        const uint doorState = 0x10008u; // PhysicsState.HasPhysicsBSP | HasDefaultScript (typical)

        engine.ShadowObjects.RegisterMultiPart(
            entityId:        DoorEntityId,
            entityWorldPos:  doorWorldPos,
            entityWorldRot:  doorWorldRot,
            shapes:          shapes,
            state:           doorState,
            flags:           EntityCollisionFlags.None,
            worldOffsetX:    0f,
            worldOffsetY:    0f,
            landblockId:     TestLandblockId);

        ctx = new Context(engine, cache, setup!, shapes);
        return true;
    }

    /// <summary>
    /// Drive a sphere from <paramref name="start"/> by
    /// <paramref name="perTick"/> each tick until either
    /// <c>CollisionNormalValid</c> fires or <paramref name="maxTicks"/>
    /// elapse. Returns the outcome + final position.
    /// </summary>
    private (bool blocked, Vector3 finalPos, Vector3 normal, int ticks)
        SweepUntilBlocked(PhysicsEngine engine, Vector3 start, Vector3 perTick, int maxTicks)
    {
        Vector3 pos = start;
        uint cellId = TestCellId;
        bool isOnGround = false;
        Vector3 lastNormal = Vector3.Zero;

        for (int tick = 0; tick < maxTicks; tick++)
        {
            Vector3 target = pos + perTick;
            var result = engine.ResolveWithTransition(
                pos, target, cellId,
                SphereRadius, SphereHeight,
                StepUpHeight, StepDownHeight,
                isOnGround,
                body: null,
                moverFlags: ObjectInfoState.IsPlayer | ObjectInfoState.EdgeSlide,
                movingEntityId: 0);

            if (result.CollisionNormalValid)
                return (true, result.Position, result.CollisionNormal, tick);

            pos = result.Position;
            cellId = result.CellId;
            isOnGround = result.IsOnGround;
            lastNormal = result.CollisionNormal;
        }

        return (false, pos, lastNormal, maxTicks);
    }
}