using System;
using System.Collections.Generic;
using System.Numerics;
using AcDream.App.Rendering;
using DatReaderWriter;
using DatReaderWriter.Options;
using Xunit;
using Xunit.Abstractions;

namespace AcDream.App.Tests.Rendering;

/// <summary>
/// #118 exit-walk harness (handoff 2026-06-11 §5): the character is clipped and then
/// vanishes for a moment when exiting a house — the window where the player is just
/// outside the door while the collided viewer (camera) is still indoors.
///
/// Per step of a deterministic eye+player path crossing the exit doorway of the
/// Holtburg corner building (cell 0xA9B40170, dat-loaded via the CornerFloodReplay
/// fixture loader), this drives the PRODUCTION decision stack headlessly:
/// viewer-cell resolution (healthy-sweep model, see below) →
/// <see cref="PortalVisibilityBuilder.Build"/> → <see cref="ClipFrameAssembler.Assemble"/> →
/// <see cref="ViewconeCuller.Build"/> → the exact DrawDynamicsLast visibility predicate
/// (RetailPViewRenderer.cs:375-401), PLUS the depth relationship DrawDynamicsLast is
/// subject to: under an INTERIOR root the exit-portal SEAL stamps the door fan at TRUE
/// depth (GameWindow.DrawRetailPViewPortalDepthWrite, forceFarZ=false) after the full
/// depth clear, and dynamics draw depth-tested AFTER it.
///
/// The four candidates this pins (handoff §5 + this session's read):
///  1. eye/cell incoherence under damping — EXONERATED BY READ for clean exits:
///     RetailChaseCamera publishes (Position, ViewerCellId) from the SAME SweepEye call
///     (RetailChaseCamera.cs:188-203), published==damped when nothing collides (an open
///     doorway), and GameWindow updates the camera (≈:6889) BEFORE the visibility read
///     (≈:7361) in the same frame.
///  2. exit-portal side test culling at an ε-outside eye → OutsideView EMPTY →
///     SphereVisibleOutside culls ALL outdoor dynamics. Quantified by the stale-root
///     diagnostic below (the healthy walk should never produce the incoherent pair).
///  3. doorway-aperture cone tightness → tested per step by the predicate replica.
///  4. (new, this session) SEAL-DEPTH vs dynamics-last ordering: a player whose
///     fragments lie BEYOND the door plane z-fails against the seal across the whole
///     aperture → invisible while fully outside (and clipped at the plane while
///     straddling). Tested per step by the CPU depth check (same viewProj math the GPU
///     consumes).
///
/// Healthy-sweep model: the corner-seal replay (b21bb28) + the camera read above prove
/// the sweep resolves the eye's ACTUAL cell same-frame, so the harness derives the
/// viewer cell geometrically: door-plane side decides indoor/outdoor; AABB containment
/// (smallest containing volume) picks the interior cell. The outdoor root is
/// <see cref="OutdoorCellNode.Build"/> exactly as GameWindow builds it (full-screen
/// OutsideView ⇒ outdoor dynamics trivially cone-pass).
/// </summary>
public class HouseExitWalkReplayTests
{
    private readonly ITestOutputHelper _out;
    public HouseExitWalkReplayTests(ITestOutputHelper output) => _out = output;

    private const uint ExitCellId = CornerFloodReplayTests.Landblock | 0x0170u;

    // Production humanoid entity sphere (RetailPViewRenderer.EntitySphere: AABB center +
    // half-diagonal). A ~1.8 m × 0.6 m character AABB gives center ≈ feet+0.9, r ≈ 1.0.
    private const float PlayerSphereRadius = 1.0f;
    private static readonly Vector3 PlayerSphereCenterOffset = new(0f, 0f, 0.9f);

    private sealed record ExitDoor(
        int PortalIndex,
        Vector3[] WorldVerts,
        Vector3 WorldCentroid,
        Vector3 OutwardNormal,   // unit, world space, pointing OUT of the building
        float FloorZ);

    private sealed record WalkStep(
        int Index,
        float WalkS,             // raw walk parameter (feet travel along the XY exit direction)
        float CenterS,           // signed distance of the SPHERE CENTER to the door plane (the production quantity)
        float EyeS,              // signed distance of the published eye
        Vector3 PlayerFeet,
        Vector3 Eye,
        uint RootCellId,         // 0 = outdoor root
        uint PlayerParentCellId,
        bool ConeVisible,
        bool OutsideStage,       // production stage assignment (DynamicDrawsInOutsideStage)
        bool DepthCheckApplies,
        bool DepthPass,
        int OutsidePolys,
        int FloodCells);

    // ── fixture / geometry ──────────────────────────────────────────────

    private static ExitDoor FindExitDoor(LoadedCell cell)
    {
        int best = -1;
        float bestMinZ = float.MaxValue;
        for (int i = 0; i < cell.Portals.Count; i++)
        {
            if (cell.Portals[i].OtherCellId != 0xFFFF) continue;
            if (i >= cell.PortalPolygons.Count) continue;
            var poly = cell.PortalPolygons[i];
            if (poly is null || poly.Length < 3) continue;

            float minZ = float.MaxValue;
            foreach (var v in poly)
                minZ = MathF.Min(minZ, Vector3.Transform(v, cell.WorldTransform).Z);
            // a DOOR reaches the floor; a window doesn't — pick the lowest-silled exit portal
            if (minZ < bestMinZ) { bestMinZ = minZ; best = i; }
        }
        Assert.True(best >= 0, $"cell 0x{cell.CellId:X8} has no exit portal (OtherCellId==0xFFFF)");

        var local = cell.PortalPolygons[best];
        var world = new Vector3[local.Length];
        var centroid = Vector3.Zero;
        float floorZ = float.MaxValue;
        for (int v = 0; v < local.Length; v++)
        {
            world[v] = Vector3.Transform(local[v], cell.WorldTransform);
            centroid += world[v];
            floorZ = MathF.Min(floorZ, world[v].Z);
        }
        centroid /= local.Length;

        // Outward = away from the cell interior. ClipPlanes[i].InsideSide encodes which
        // side the cell centroid is on (CornerFloodReplayTests.LoadCell): InsideSide==0
        // ⇒ interior satisfies dot ≥ 0 ⇒ outward is −Normal; InsideSide==1 ⇒ +Normal.
        var plane = cell.ClipPlanes[best];
        var outwardLocal = plane.InsideSide == 0 ? -plane.Normal : plane.Normal;
        var outwardWorld = Vector3.Normalize(Vector3.TransformNormal(outwardLocal, cell.WorldTransform));

        return new ExitDoor(best, world, centroid, outwardWorld, floorZ);
    }

    private static float SignedSide(ExitDoor door, Vector3 p)
        => Vector3.Dot(door.OutwardNormal, p - door.WorldCentroid);

    private static uint? ResolveInteriorCellByAabb(
        Dictionary<uint, LoadedCell> cells, Vector3 worldPoint, float margin = 0.05f)
    {
        uint? best = null;
        float bestVolume = float.MaxValue;
        foreach (var (id, cell) in cells)
        {
            var local = Vector3.Transform(worldPoint, cell.InverseWorldTransform);
            var min = cell.LocalBoundsMin - new Vector3(margin);
            var max = cell.LocalBoundsMax + new Vector3(margin);
            if (local.X < min.X || local.Y < min.Y || local.Z < min.Z
                || local.X > max.X || local.Y > max.Y || local.Z > max.Z)
                continue;
            var ext = cell.LocalBoundsMax - cell.LocalBoundsMin;
            float volume = MathF.Max(ext.X, 1e-3f) * MathF.Max(ext.Y, 1e-3f) * MathF.Max(ext.Z, 1e-3f);
            if (volume < bestVolume) { bestVolume = volume; best = id; }
        }
        return best;
    }

    // Outdoor landcell id for a landblock-local position (dat EnvCell positions are
    // landblock-local). Only the (low word < 0x100) classification is load-bearing for
    // the DrawDynamicsLast predicate; the exact landcell is kept honest anyway.
    private static uint OutdoorLandcellId(Vector3 landblockLocalPos)
    {
        int cx = Math.Clamp((int)MathF.Floor(landblockLocalPos.X / 24f), 0, 7);
        int cy = Math.Clamp((int)MathF.Floor(landblockLocalPos.Y / 24f), 0, 7);
        return CornerFloodReplayTests.Landblock | (uint)(cx * 8 + cy + 1);
    }

    // Exact replica of RetailPViewRenderer.DrawDynamicsLast's visibility predicate
    // (RetailPViewRenderer.cs:386-391). Keep in lockstep with production.
    private static bool DynamicsConeVisible(ViewconeCuller cone, uint parentCellId, Vector3 c, float r)
    {
        bool indoor = (parentCellId & 0xFFFFu) >= 0x0100u && (parentCellId & 0xFFFFu) != 0xFFFFu;
        return indoor
            ? cone.SphereVisibleInCell(parentCellId, c, r)
            : cone.SphereVisibleOutside(c, r);
    }

    // ── the walk ────────────────────────────────────────────────────────

    private List<WalkStep>? RunExitWalk()
    {
        var datDir = CornerFloodReplayTests.ResolveDatDir();
        if (datDir is null) { _out.WriteLine("SKIP: dats unavailable"); return null; }

        using var dats = new DatCollection(datDir, DatAccessType.Read);
        var cells = CornerFloodReplayTests.LoadBuilding(dats);
        Func<uint, LoadedCell?> lookup = id => cells.TryGetValue(id, out var c) ? c : null;

        var exitCell = cells[ExitCellId];
        var door = FindExitDoor(exitCell);
        _out.WriteLine(FormattableString.Invariant(
            $"exit door: cell=0x{ExitCellId:X8} portal[{door.PortalIndex}] centroid=({door.WorldCentroid.X:F2},{door.WorldCentroid.Y:F2},{door.WorldCentroid.Z:F2}) outward=({door.OutwardNormal.X:F2},{door.OutwardNormal.Y:F2},{door.OutwardNormal.Z:F2}) floorZ={door.FloorZ:F2} verts={door.WorldVerts.Length}"));

        // Walk straight out through the door centroid along the outward normal's XY
        // projection (doors are vertical; assert so).
        var out2d = Vector3.Normalize(new Vector3(door.OutwardNormal.X, door.OutwardNormal.Y, 0f));
        Assert.True(MathF.Abs(door.OutwardNormal.Z) < 0.3f, "exit door is not vertical — walk path invalid");

        float yaw = MathF.Atan2(out2d.Y, out2d.X);
        const float dt = 1f / 60f;
        const float stepLen = 0.02f;                 // 2 cm per frame = 1.2 m/s walk
        const float sStart = -1.2f, sEnd = 3.0f;     // door plane at s=0
        var velocity = out2d * (stepLen / dt);

        var camera = new RetailChaseCamera { Aspect = 1280f / 720f };

        Vector3 FeetAt(float s) => new(
            door.WorldCentroid.X + out2d.X * s,
            door.WorldCentroid.Y + out2d.Y * s,
            door.FloorZ);

        // Warm the damped boom to convergence at the start pose (retail's convergence
        // snap freezes it once the lerp step is sub-epsilon).
        for (int i = 0; i < 240; i++)
            camera.Update(FeetAt(sStart), yaw, Vector3.Zero, isOnGround: true, Vector3.UnitZ, dt);

        var clipFrame = ClipFrame.NoClip();
        var steps = new List<WalkStep>();
        int stepCount = (int)MathF.Round((sEnd - sStart) / stepLen);

        for (int i = 0; i <= stepCount; i++)
        {
            float s = sStart + i * stepLen;
            var feet = FeetAt(s);
            camera.Update(feet, yaw, velocity, isOnGround: true, Vector3.UnitZ, dt);
            var eye = camera.Position;
            var viewProj = camera.View * camera.Projection;

            float eyeS = SignedSide(door, eye);
            var sphereC = feet + PlayerSphereCenterOffset;
            float playerS = SignedSide(door, sphereC);

            // membership model: the controller's pick is center point-in-cell (physics
            // digest, P1) — the player's ParentCellId flips when the sphere CENTER
            // crosses the door plane.
            uint playerCell = playerS <= 0f
                ? ExitCellId
                : OutdoorLandcellId(feet);

            // healthy-sweep viewer resolution: plane side decides indoor/outdoor;
            // AABB containment picks the interior cell the eye is in.
            uint rootCellId = 0u;
            LoadedCell? root = null;
            if (eyeS <= 0f)
            {
                var contained = ResolveInteriorCellByAabb(cells, eye);
                Assert.True(contained.HasValue,
                    FormattableString.Invariant(
                        $"step {i}: eye=({eye.X:F2},{eye.Y:F2},{eye.Z:F2}) (eyeS={eyeS:F2}) is inside the door plane but no loaded cell AABB contains it — adjust the walk"));
                rootCellId = contained.Value;
                root = cells[rootCellId];
            }
            else
            {
                root = OutdoorCellNode.Build(OutdoorLandcellId(eye));
            }

            var pv = PortalVisibilityBuilder.Build(root, eye, lookup, viewProj);
            var asm = ClipFrameAssembler.Assemble(clipFrame, pv);
            var cone = ViewconeCuller.Build(asm, viewProj);

            bool coneVisible = DynamicsConeVisible(cone, playerCell, sphereC, PlayerSphereRadius);

            // Production stage assignment (#118 fix): an outside-stage dynamic draws
            // BEFORE the depth clear + seal (retail LScape::draw → DrawSortCell), so
            // the seal PROTECTS its pixels instead of z-killing them.
            var drawable = new HashSet<uint>(pv.OrderedVisibleCells);
            bool outsideStage = rootCellId != 0u
                && RetailPViewRenderer.DynamicDrawsInOutsideStage(
                    playerCell, sphereC, PlayerSphereRadius, drawable, lookup);

            // Candidate 4: the seal depth check. Applies when the root is INTERIOR
            // (ClearDepthForInterior + the TRUE-depth seal run, GameWindow:7719-7729),
            // the player sphere center lies BEYOND the door plane on the ray from the
            // eye, AND the player draws in the post-seal last pass (not outside-stage).
            bool depthApplies = false, depthPass = true;
            if (rootCellId != 0u && coneVisible && playerS > 0f && eyeS < 0f && !outsideStage)
            {
                depthApplies = TrySealDepthCheck(door, eye, sphereC, viewProj, out depthPass);
            }

            steps.Add(new WalkStep(
                i, s, playerS, eyeS, feet, eye, rootCellId, playerCell, coneVisible, outsideStage,
                depthApplies, depthPass,
                pv.OutsideView.Polygons.Count, pv.OrderedVisibleCells.Count));
        }

        return steps;
    }

    /// <summary>
    /// CPU model of the depth relationship at the player-sphere-center pixel:
    /// the SEAL (door fan at true depth, drawn after the full depth clear and before
    /// dynamics — PortalDepthMaskRenderer, forceFarZ=false) vs the player fragment.
    /// Returns true (out: pass) when the player's NDC depth at that pixel is ≤ the
    /// seal's. Returns false (check N/A) when the eye→center ray misses the door fan
    /// (the seal doesn't cover that pixel; depth there is the cleared far plane).
    /// </summary>
    private static bool TrySealDepthCheck(
        ExitDoor door, Vector3 eye, Vector3 sphereCenter, in Matrix4x4 viewProj, out bool depthPass)
    {
        depthPass = true;

        float dEye = Vector3.Dot(door.OutwardNormal, eye - door.WorldCentroid);
        float dC = Vector3.Dot(door.OutwardNormal, sphereCenter - door.WorldCentroid);
        if (dEye >= 0f || dC <= 0f) return false;          // plane not between eye and center
        float t = dEye / (dEye - dC);
        var hit = eye + (sphereCenter - eye) * t;

        // is the ray-plane hit inside the door polygon? (2D point-in-polygon in the
        // plane's basis — the seal only stamps pixels inside the fan)
        if (!PointInPolygon(door, hit)) return false;

        var pc = Vector4.Transform(new Vector4(sphereCenter, 1f), viewProj);
        var hc = Vector4.Transform(new Vector4(hit, 1f), viewProj);
        if (pc.W <= 1e-6f || hc.W <= 1e-6f) return false;  // behind the eye — no pixel

        float playerZ = pc.Z / pc.W;
        float sealZ = hc.Z / hc.W;
        // GL depth test default LESS/LEQUAL: smaller NDC z = nearer = passes.
        depthPass = playerZ <= sealZ + 1e-4f;
        return true;
    }

    private static bool PointInPolygon(ExitDoor door, Vector3 worldPoint)
    {
        // build a 2D basis in the door plane
        var n = door.OutwardNormal;
        var u = Vector3.Normalize(Vector3.Cross(n, Vector3.UnitZ));
        if (u.LengthSquared() < 1e-6f) u = Vector3.UnitX;
        var v = Vector3.Cross(n, u);

        Vector2 Project(Vector3 p) => new(
            Vector3.Dot(p - door.WorldCentroid, u),
            Vector3.Dot(p - door.WorldCentroid, v));

        var pt = Project(worldPoint);
        bool inside = false;
        for (int i = 0, j = door.WorldVerts.Length - 1; i < door.WorldVerts.Length; j = i++)
        {
            var a = Project(door.WorldVerts[i]);
            var b = Project(door.WorldVerts[j]);
            if ((a.Y > pt.Y) != (b.Y > pt.Y)
                && pt.X < (b.X - a.X) * (pt.Y - a.Y) / (b.Y - a.Y) + a.X)
                inside = !inside;
        }
        return inside;
    }

    private void DumpSteps(IEnumerable<WalkStep> steps, Func<WalkStep, bool>? filter = null)
    {
        foreach (var st in steps)
        {
            if (filter is not null && !filter(st)) continue;
            string root = st.RootCellId == 0 ? "OUTDOOR " : FormattableString.Invariant($"0x{st.RootCellId:X8}");
            string cone = st.ConeVisible ? "VIS " : "CULL";
            string stage = st.OutsideStage ? "outside" : "last   ";
            string depth = st.DepthCheckApplies ? (st.DepthPass ? "pass" : "FAIL") : "n/a ";
            _out.WriteLine(FormattableString.Invariant(
                $"step={st.Index,3} s={st.WalkS,6:F2} cS={st.CenterS,6:F2} eyeS={st.EyeS,6:F2} root={root} pCell=0x{st.PlayerParentCellId:X8} cone={cone} stage={stage} depth={depth} outPolys={st.OutsidePolys} flood={st.FloodCells}"));
        }
    }

    // ── the pins ────────────────────────────────────────────────────────

    /// <summary>
    /// Candidates 1–3 (cone level): per step of the exit walk, the player sphere must
    /// survive the exact DrawDynamicsLast cone predicate. A failing step pins the
    /// side-test / cone-tightness / incoherence family with its exact geometry.
    /// </summary>
    [Fact]
    public void ExitWalk_PlayerStaysConeVisible_EveryStep()
    {
        var steps = RunExitWalk();
        if (steps is null) return;

        var failures = steps.FindAll(s => !s.ConeVisible);
        if (failures.Count > 0)
        {
            _out.WriteLine($"--- {failures.Count} cone-CULLED steps ---");
            DumpSteps(failures);
        }
        Assert.True(failures.Count == 0,
            $"{failures.Count}/{steps.Count} steps cone-cull the player (first at step {(failures.Count > 0 ? failures[0].Index : -1)}) — see output");
    }

    /// <summary>
    /// Candidate 4 (depth level): on every step where the root is interior and the
    /// cone admits the outdoor player, the player's fragments must also SURVIVE the
    /// exit-portal SEAL's depth — otherwise DrawDynamicsLast paints nothing (the
    /// vanish) and a straddling body is cut at the door plane (the clip).
    /// </summary>
    [Fact]
    public void ExitWalk_PlayerSurvivesSealDepth_WhenConeVisible()
    {
        var steps = RunExitWalk();
        if (steps is null) return;

        var applicable = steps.FindAll(s => s.DepthCheckApplies);
        _out.WriteLine($"depth check applies on {applicable.Count}/{steps.Count} steps");
        var failures = applicable.FindAll(s => !s.DepthPass);
        if (failures.Count > 0)
        {
            _out.WriteLine($"--- {failures.Count} seal-depth-FAILED steps ---");
            DumpSteps(failures);
        }
        Assert.True(failures.Count == 0,
            $"{failures.Count}/{applicable.Count} applicable steps z-fail the player against the exit-portal seal — " +
            "dynamics drawn after the TRUE-depth seal cannot appear beyond the door plane (see output)");
    }

    /// <summary>
    /// The straddle ("clipped") phase: while the player sphere crosses the door
    /// plane under an interior root, it must be assigned to the OUTSIDE stage
    /// (drawn pre-seal — for indoor-classified straddlers that is retail's
    /// per-overlapped-shadow-cell dual draw, DrawBlock pc:430056-430064), or the
    /// beyond-plane body half is cut at the plane by the seal.
    /// </summary>
    [Fact]
    public void ExitWalk_StraddlingPlayerDrawsInOutsideStage()
    {
        var steps = RunExitWalk();
        if (steps is null) return;

        var straddling = steps.FindAll(s =>
            s.RootCellId != 0u && MathF.Abs(s.CenterS) < PlayerSphereRadius);
        Assert.True(straddling.Count > 0, "walk produced no interior-root straddle steps — geometry changed?");
        var failures = straddling.FindAll(s => !s.OutsideStage);
        if (failures.Count > 0)
        {
            _out.WriteLine($"--- {failures.Count} straddle steps NOT outside-stage ---");
            DumpSteps(failures);
        }
        Assert.True(failures.Count == 0,
            $"{failures.Count}/{straddling.Count} straddle steps are not outside-stage-assigned — the seal clips the body at the door plane");
    }

    /// <summary>Full per-step table for the handoff doc.</summary>
    [Fact]
    public void Diagnostic_ExitWalk_PerStepTable()
    {
        var steps = RunExitWalk();
        if (steps is null) return;
        DumpSteps(steps);
        // transition summary
        int firstOutPlayer = steps.FindIndex(s => s.CenterS > 0f);
        int firstOutRoot = steps.FindIndex(s => s.RootCellId == 0u);
        _out.WriteLine(FormattableString.Invariant(
            $"player center exits at step {firstOutPlayer}; viewer root flips outdoor at step {firstOutRoot}; interior-root/outdoor-player window = {Math.Max(0, firstOutRoot - firstOutPlayer)} steps"));
    }

    /// <summary>
    /// Candidate 2 quantifier (synthetic): the INCOHERENT (root=interior, eye outside)
    /// pair the healthy sweep never produces. Documents how the flood degrades if the
    /// root ever lagged the eye: within PortalSideEpsilon the exit portal still
    /// traverses; beyond it the side test culls and OutsideView goes EMPTY (which would
    /// cull ALL outdoor content — terrain included, not just the player).
    /// </summary>
    [Fact]
    public void Diagnostic_StaleRootWindow_EyeJustOutside()
    {
        var datDir = CornerFloodReplayTests.ResolveDatDir();
        if (datDir is null) { _out.WriteLine("SKIP: dats unavailable"); return; }

        using var dats = new DatCollection(datDir, DatAccessType.Read);
        var cells = CornerFloodReplayTests.LoadBuilding(dats);
        Func<uint, LoadedCell?> lookup = id => cells.TryGetValue(id, out var c) ? c : null;
        var exitCell = cells[ExitCellId];
        var door = FindExitDoor(exitCell);

        var out2d = Vector3.Normalize(new Vector3(door.OutwardNormal.X, door.OutwardNormal.Y, 0f));
        var eyeBase = new Vector3(door.WorldCentroid.X, door.WorldCentroid.Y, door.FloorZ + 1.8f);
        var playerC = eyeBase + out2d * 1.5f;   // player just outside, in front of the eye

        var clipFrame = ClipFrame.NoClip();
        foreach (float d in new[] { 0.005f, 0.02f, 0.05f, 0.10f, 0.25f })
        {
            var eye = eyeBase + out2d * d;
            var view = Matrix4x4.CreateLookAt(eye, eye + out2d, Vector3.UnitZ);
            var proj = Matrix4x4.CreatePerspectiveFieldOfView(MathF.PI / 3f, 1280f / 720f, 0.1f, 5000f);
            var viewProj = view * proj;

            var pv = PortalVisibilityBuilder.Build(exitCell, eye, lookup, viewProj);
            var asm = ClipFrameAssembler.Assemble(clipFrame, pv);
            var cone = ViewconeCuller.Build(asm, viewProj);
            bool playerVisible = cone.SphereVisibleOutside(playerC, PlayerSphereRadius);

            _out.WriteLine(FormattableString.Invariant(
                $"eye {d * 100,5:F1} cm OUTSIDE + root still 0x{ExitCellId:X8}: outPolys={pv.OutsideView.Polygons.Count} flood={pv.OrderedVisibleCells.Count} playerConeVisible={playerVisible}"));
        }
    }
}