using System.Collections.Generic;
using System.Numerics;
using DatReaderWriter.Enums;
using DatReaderWriter.Types;
using AcDream.Core.Physics;
using Xunit;
using Xunit.Abstractions;

namespace AcDream.Core.Tests.Physics;

/// <summary>
/// Issue #265 capture-driven bisection: "Steep-slope response set" (uphill-jump
/// bounce, lost roof slide, edge wedge). This harness replays a REAL trajectory
/// mined from a live capture (<c>ACDREAM_CAPTURE_RESOLVE</c>,
/// <c>artifacts/matrix-session2-resolve.jsonl</c>, records 3415-3434) through a
/// synthetic single-polygon <see cref="PhysicsEngine"/> built from the EXACT
/// polygon the live capture landed on
/// (<c>bodyAfter.walkableVertices</c>: (240,0,88),(264,0,80),(264,24,68),
/// normal (2,3,6)/7 = (0.2857,0.4286,0.8571) — a moderate, WALKABLE-BY-THRESHOLD
/// roof slope, <c>normal.Z=0.857 &gt; PhysicsGlobals.FloorZ (0.6642)</c>).
///
/// <para>
/// <b>Live symptom this reproduces (mining evidence):</b> the player falls
/// (v ≈ (11.15, 14.13, -23.14) m/s at landing) onto this roof slope. Live capture
/// record 3433 shows <c>collisionNormalValid=true</c>, the correct real polygon
/// normal, and <c>walkablePolygonValid=true</c> — a legitimate walkable landing.
/// Record 3434 (the very next tick) shows the body FROZEN: velocity forced to
/// exactly (0,0,0), transientState=7 (Contact|OnWalkable|Sliding), and the
/// position stays byte-identical for the remaining 12,292 captured ticks (to
/// the end of the file) — i.e. the player never moves again. A second,
/// independent instance of the same shape appears at records 3153-3199+ (a
/// shallower ~18° roof edge, frozen for 46+ captured ticks). Full mining
/// evidence: <c>docs/research/2026-07-30-265-capture-bisect.md</c>.
/// </para>
///
/// <para>
/// <b>Candidate mechanism (S1):</b> commit <c>db2889af</c> ("#116 shape-1")
/// changed <c>BSPQuery.cs</c>'s Path-6 <c>hasSphere1</c> (head-sphere-only hit
/// while airborne, foot sphere clear) branch from a steepness-gated
/// SetCollide→Adjusted (shallow, Z≥FloorZ) / slide-tangent-then-Slid (steep,
/// Z&lt;FloorZ) dual path — IDENTICAL in shape to the still-unchanged sphere0
/// (foot) branch a few lines above it — to an UNCONDITIONAL
/// <c>SetCollisionNormal + return Collided</c>, regardless of steepness. A
/// `Collided` return short-circuits <c>TransitionalInsert</c> immediately
/// (<c>if (transitState == TransitionState.Collided) return
/// TransitionState.Collided;</c>) — it never reaches the retry loop's Phase 3
/// (<c>if (sp.Collide) ...DoCheckWalkable...Placement retry...</c>), which is
/// the ONLY place a shallow/walkable head-sphere hit can smoothly commit to a
/// real <c>ContactPlane</c> + <c>OnWalkable</c> via the SetCollide+Adjusted
/// path. This test's real captured polygon has <c>normal.Z=0.857</c> — well
/// ABOVE <c>FloorZ</c> (0.6642) — so it is the SHALLOW case, not the steep one;
/// S1 removed the steepness branch entirely, so this shallow graze now takes
/// the SAME hard-stop path a steep hit would.
/// </para>
///
/// <para>
/// <b>Method:</b> <see cref="ReplayRealRoofLanding"/> integrates the EXACT
/// captured ballistic state (position + velocity) from record 3415 forward
/// with real gravity (dt=1/30s, matching retail's tick rate), calling
/// <see cref="PhysicsEngine.ResolveWithTransition"/> every tick exactly like
/// <see cref="AcDream.Runtime.Gameplay.PlayerMovementController"/> does at the
/// Core boundary (this harness intentionally stops at that boundary — it does
/// NOT call <c>PhysicsObjUpdate.HandleAllCollisions</c> or model the R6
/// animation-root-motion grounded-movement zeroing, both of which live outside
/// Core and are confirmed NOT part of the S1/S2 candidate set — see the research
/// doc). Once the mover reports <c>IsOnGround</c>, the harness keeps REQUESTING
/// forward motion each tick (simulating held input) so a genuine "does the
/// engine allow continued advance across this surface" signal is observable,
/// rather than trivially replaying the live capture's own (already-frozen,
/// no-input) subsequent targets.
/// </para>
///
/// <para>
/// <b>A/B protocol (see the research doc for the executed results):</b> this
/// same test is run unmodified against (i) HEAD, (ii) <c>BSPQuery.cs</c> with
/// the S1 sphere1 branch reverted to mirror the still-current sphere0 shape
/// (local, uncommitted diagnostic edit), (iii) production unaffected by S2
/// (calc_friction's AP-7 threshold) since S2 has zero call sites outside its
/// own unit test — confirmed by <c>grep -rn "\.calc_friction(" src/</c> — so no
/// S2 toggle is needed for THIS harness, and (iv) both. The per-tick dump
/// (<see cref="TickSample"/> list, printed via <see cref="ITestOutputHelper"/>)
/// is the diff target.
/// </para>
/// </summary>
public class Issue265SteepSlopeCaptureBisectTests
{
    private readonly ITestOutputHelper _out;
    public Issue265SteepSlopeCaptureBisectTests(ITestOutputHelper output) => _out = output;

    // ── Real captured polygon (bodyAfter.walkableVertices, record 3433) ──────
    // artifacts/matrix-session2-resolve.jsonl, tick 3433, cell 0xAAB40011.
    // normal = cross(v1-v0, v2-v0) normalized = (2,3,6)/7 exactly.
    private static readonly Vector3 RoofV0 = new(240f, 0f, 88f);
    private static readonly Vector3 RoofV1 = new(264f, 0f, 80f);
    private static readonly Vector3 RoofV2 = new(264f, 24f, 68f);

    // Outdoor cell suffix MUST be < 0x0100 (retail's indoor/outdoor LandCell
    // convention — CellTransit.BuildShadowCellSet branches on it) and its
    // block index must be (0,0) so that the flood's landblock-local grid math
    // (CellTransit.AddAllOutsideCells, an 8x8 24-m-cell grid over the 192-m
    // landblock) treats this harness's coordinates as directly landblock-local
    // — CellGraph.TryGetTerrainOrigin has no registered terrain for this
    // synthetic landblock so it Zero-falls-back, meaning raw "world" position
    // IS landblock-local position (documented anchor-frame convention, same
    // one Ts4SteepRoofWedgeCaptureTests/DoorBugTrajectoryReplayTests rely on).
    // The harness's very first run registered the shadow object at the REAL
    // captured world coordinates (X≈256) under this convention — 256 is
    // outside the valid [0,192) landblock-local range, so the flood produced
    // an empty cell set and the object was silently never registered at all
    // (zero collisions the whole replay). Fix: re-anchor the entire synthetic
    // scene (triangle + approach trajectory) at the roof centroid so every
    // coordinate here is small and landblock-local (see the research doc's
    // harness-commissioning note).
    // Suffix 0x0001 is the canonical (gridX=0, gridY=0) outdoor LandCell — the
    // grid cell whose local origin is (0,0) — matching this harness's
    // re-anchored roof centroid at world (0,0,0) (see the note above). An
    // earlier attempt used suffix 0x0011; CellTransit.AddAllOutsideCells'
    // LandDefs.AdjustToOutside re-derives the (lx,ly) grid cell from the
    // sphere's ACTUAL position and silently corrects a mismatched seed, so the
    // registration landed in cell 0x00000001 regardless of the literal seed
    // passed — GetObjectsInCell(0x00000011) found nothing (see the research
    // doc's harness-commissioning note).
    private const uint CellId = 0x00000001u;
    private const uint LandblockId = 0x00000000u;
    private const uint SyntheticGfxId = 0x265BEEF1u;

    private const int TicksPerSecond = 30;
    private const float Gravity = -9.8f;
    private const float SphereRadius = 0.48f;   // production human Setup 0x02000001
    private const float SphereHeight = 1.835f;  // production human Setup 0x02000001

    // Real captured state, record index 3415 (session2, tick 3415) — 18 ticks
    // before the landing/freeze at record 3433/3434. vx/vy are constant across
    // this whole approach (pure ballistic fall, no further horizontal drive).
    // Re-anchored: subtract RoofCentroid from the real captured world position
    // (see the landblock-local note above) — the RELATIVE approach geometry
    // (distance, direction, velocity) is preserved exactly.
    private static readonly Vector3 ApproachStartPosReal = new(244.59f, -0.81f, 92.79f);
    private static readonly Vector3 ApproachStartVel = new(11.1509495f, 14.129979f, -16.72f);

    // ShadowObjects.Register's broad-phase culls candidates by distance from
    // `worldPos` within `radius` — registering at Vector3.Zero with the real
    // (far-from-origin) captured world coordinates put the polygon ~264 units
    // from the query point, well outside any sane radius, so the very first
    // run of this harness found ZERO collisions at all (see the research doc's
    // "harness commissioning" note). Fix: register the entity at the
    // triangle's centroid and express the polygon in LOCAL coordinates
    // relative to that centroid (identity rotation, scale 1 — world = local +
    // worldPos reconstructs the exact real-world triangle).
    private static readonly Vector3 RoofCentroid = (RoofV0 + RoofV1 + RoofV2) / 3f;

    private static PhysicsEngine MakeRoofEngine()
    {
        var resolved = new Dictionary<ushort, ResolvedPolygon>();
        var verts = new[] { RoofV0 - RoofCentroid, RoofV1 - RoofCentroid, RoofV2 - RoofCentroid };
        var normal = Vector3.Normalize(Vector3.Cross(verts[1] - verts[0], verts[2] - verts[0]));
        float d = -Vector3.Dot(normal, verts[0]);
        resolved[1] = new ResolvedPolygon
        {
            Vertices = verts,
            Plane = new Plane(normal, d),
            NumPoints = 3,
            SidesType = CullMode.None,
        };

        var leaf = new PhysicsBSPNode
        {
            Type = BSPNodeType.Leaf,
            BoundingSphere = new Sphere { Origin = Vector3.Zero, Radius = 30f },
        };
        leaf.Polygons.Add(1);

        var heights = new byte[81];
        var heightTab = new float[256];
        for (int i = 0; i < 256; i++) heightTab[i] = -1000f; // terrain never interferes

        var engine = new PhysicsEngine();
        engine.AddLandblock(
            LandblockId,
            new TerrainSurface(heights, heightTab),
            System.Array.Empty<CellSurface>(),
            System.Array.Empty<PortalPlane>(),
            worldOffsetX: 0f, worldOffsetY: 0f);

        var cache = new PhysicsDataCache();
        var bspTree = new PhysicsBSPTree { Root = leaf };
        var physics = new GfxObjPhysics
        {
            BSP = bspTree,
            PhysicsPolygons = new Dictionary<ushort, Polygon>(),
            Vertices = new VertexArray(),
            Resolved = resolved,
            BoundingSphere = new Sphere { Origin = Vector3.Zero, Radius = 30f },
        };
        cache.RegisterGfxObjForTest(SyntheticGfxId, physics);
        engine.DataCache = cache;

        // ShadowObjectRegistry is the per-cell shadow-object index (BR-7/A6.P4):
        // Register() FLOODS from a SEED CELL outward and registers the entity
        // into the resulting cell set; the query side (GetObjectsInCell) looks
        // up strictly by the mover's CURRENT cell id. Leaving seedCellId at its
        // default (0u) makes Register() call DeriveOutdoorSeed(worldPos, ...),
        // which computes its OWN outdoor landcell id from world position — for
        // the real captured coordinates used here (worldPos.X=256, well outside
        // landblock 0xAAB40000's own 192 m span) that derives to a DIFFERENT
        // cell than the literal CellId this harness resolves against, so the
        // very first run of this fixture found zero collisions (see the
        // research doc's harness-commissioning note). Passing seedCellId
        // explicitly bypasses the derivation and floods from the exact cell
        // the replay loop queries.
        engine.ShadowObjects.Register(
            entityId: SyntheticGfxId,
            gfxObjId: SyntheticGfxId,
            worldPos: Vector3.Zero,
            rotation: Quaternion.Identity,
            radius: 30f,
            worldOffsetX: 0f,
            worldOffsetY: 0f,
            landblockId: LandblockId,
            collisionType: ShadowCollisionType.BSP,
            scale: 1.0f,
            seedCellId: CellId);

        return engine;
    }

    public sealed record TickSample(
        int Tick,
        Vector3 Pos,
        float Advance,
        bool CollisionNormalValid,
        Vector3 CollisionNormal,
        bool OnGround,
        int FrozenStreak);

    /// <summary>
    /// Replays the real captured ballistic approach + landing, then keeps
    /// REQUESTING forward motion (simulating held input) for
    /// <paramref name="postLandingTicks"/> additional ticks once grounded, to
    /// see whether the engine allows continued advance across the roof surface
    /// or wedges in place. Returns one <see cref="TickSample"/> per tick.
    /// </summary>
    public static List<TickSample> ReplayRealRoofLanding(int postLandingTicks = 60)
    {
        var engine = MakeRoofEngine();
        const float dt = 1f / TicksPerSecond;

        var body = new PhysicsBody { TransientState = TransientStateFlags.Active };

        Vector3 pos = ApproachStartPosReal - RoofCentroid;
        Vector3 vel = ApproachStartVel;
        uint cell = CellId;
        bool grounded = false;
        int frozenStreak = 0;
        int ticksSinceGrounded = -1;

        var samples = new List<TickSample>();

        // Budget: enough ticks to cover the ~18-tick ballistic approach plus the
        // requested post-landing continuation window.
        int maxTicks = 18 + postLandingTicks + 20;

        for (int tick = 0; tick < maxTicks; tick++)
        {
            if (!grounded)
                vel = new Vector3(vel.X, vel.Y, vel.Z + Gravity * dt);
            // Once grounded, keep requesting the SAME horizontal advance each
            // tick (simulating held forward input) — this is the "does a
            // slide continue" probe. Vertical requested delta is zero (resting
            // against the surface, not still falling).
            Vector3 requestedVel = grounded ? new Vector3(vel.X, vel.Y, 0f) : vel;
            Vector3 target = pos + requestedVel * dt;

            var result = engine.ResolveWithTransition(
                currentPos: pos,
                targetPos: target,
                cellId: cell,
                sphereRadius: SphereRadius,
                sphereHeight: SphereHeight,
                stepUpHeight: 0.6f,
                stepDownHeight: 1.5f,
                isOnGround: grounded,
                body: body,
                moverFlags: ObjectInfoState.IsPlayer | ObjectInfoState.EdgeSlide,
                movingEntityId: 0x01000000u);

            float advance = Vector3.Distance(result.Position, pos);
            if (advance < 0.001f)
                frozenStreak++;
            else
                frozenStreak = 0;

            samples.Add(new TickSample(
                tick, result.Position, advance,
                result.CollisionNormalValid, result.CollisionNormal,
                result.IsOnGround, frozenStreak));

            pos = result.Position;
            cell = result.CellId;
            body.Position = pos;

            if (!grounded && result.IsOnGround)
            {
                grounded = true;
                ticksSinceGrounded = 0;
            }
            else if (grounded)
            {
                ticksSinceGrounded++;
                if (ticksSinceGrounded >= postLandingTicks)
                    break;
            }
        }

        return samples;
    }

    /// <summary>
    /// Characterization test: dumps the full per-tick trajectory so the A/B
    /// bisect (this file's class doc) can diff HEAD vs the S1-reverted local
    /// edit. Always passes — this is a diagnostic capture, matching the
    /// project's existing <c>LiveCompare_FirstCap_DiagnosticDump</c>-style
    /// tests. The actual pass/fail verdict is recorded in
    /// <c>docs/research/2026-07-30-265-capture-bisect.md</c>, not as a
    /// hardcoded assertion here, because the correct fix shape (and therefore
    /// the correct future regression assertion) is still being decided.
    /// </summary>
    [Fact]
    public void RealCapturedRoofLanding_CharacterizeCurrentBehavior()
    {
        PhysicsDiagnostics.ResetForTest();
        PhysicsDiagnostics.ProbeIndoorBspEnabled = true;
        PhysicsDiagnostics.ProbeBuildingEnabled = true;
        try
        {
            var samples = ReplayRealRoofLanding();

            int maxFrozen = 0;
            int landedAtTick = -1;
            foreach (var s in samples)
            {
                maxFrozen = System.Math.Max(maxFrozen, s.FrozenStreak);
                if (landedAtTick < 0 && s.OnGround) landedAtTick = s.Tick;
                _out.WriteLine(string.Format(
                    System.Globalization.CultureInfo.InvariantCulture,
                    "t{0,3}: pos=({1:F3},{2:F3},{3:F3}) adv={4:F4} cnv={5} n=({6:F3},{7:F3},{8:F3}) onGround={9} frozen={10}",
                    s.Tick, s.Pos.X, s.Pos.Y, s.Pos.Z, s.Advance,
                    s.CollisionNormalValid, s.CollisionNormal.X, s.CollisionNormal.Y, s.CollisionNormal.Z,
                    s.OnGround, s.FrozenStreak));
            }

            _out.WriteLine($"=== landedAtTick={landedAtTick} maxFrozenStreak={maxFrozen} totalTicks={samples.Count} ===");

            // Sanity-only assertion: the replay must actually reach the roof
            // (land) within the ballistic approach window — if this fails the
            // synthetic fixture itself is wrong, not a physics-engine finding.
            Assert.True(landedAtTick is >= 0 and < 30,
                $"Replay never reached the synthetic roof polygon (landedAtTick={landedAtTick}); " +
                "fixture geometry or approach trajectory needs adjustment before this is a valid oracle.");
        }
        finally
        {
            PhysicsDiagnostics.ResetForTest();
        }
    }
}