using System.Collections.Generic;
using System.Linq;
using System.Numerics;
using AcDream.Core.Physics;
using Xunit;

namespace AcDream.Core.Tests.Physics;

public class ShadowObjectRegistryMultiPartTests
{
    private const uint LbId = 0xA9B40000u;
    private const float OffX = 0f;
    private const float OffY = 0f;

    private static IReadOnlyList<ShadowShape> DoorShapes() => new[]
    {
        ShadowShape.Cylinder(
            gfxObjId:      0u,
            localPosition: new Vector3(0f, 0f, 0.018f),
            localRotation: Quaternion.Identity,
            scale:         1.0f,
            radius:        0.100f,
            cylHeight:     0.200f),
        ShadowShape.Bsp(
            gfxObjId:      0x010044B5u,
            localPosition: Vector3.Zero,
            localRotation: Quaternion.Identity,
            scale:         1.0f,
            localGeometry:   ShadowPartGeometry.Create(new FlatCollisionSphere(Vector3.Zero, 2.0f), null)),
        ShadowShape.Bsp(
            gfxObjId:      0x010044B6u,
            localPosition: Vector3.Zero,
            localRotation: Quaternion.Identity,
            scale:         1.0f,
            localGeometry:   ShadowPartGeometry.Create(new FlatCollisionSphere(Vector3.Zero, 2.0f), null)),
        ShadowShape.Bsp(
            gfxObjId:      0x010044B6u,
            localPosition: Vector3.Zero,
            localRotation: Quaternion.Identity,
            scale:         1.0f,
            localGeometry:   ShadowPartGeometry.Create(new FlatCollisionSphere(Vector3.Zero, 2.0f), null))
    };

    [Fact]
    public void RegisterMultiPart_FourShapes_AllShareEntityId()
    {
        var reg = new ShadowObjectRegistry();
        const uint doorEntityId = 0x000F4244u;

        reg.RegisterMultiPart(
            entityId:        doorEntityId,
            entityWorldPos:  new Vector3(132.6f, 17.1f, 94.08f),
            entityWorldRot:  Quaternion.Identity,
            shapes:          DoorShapes(),
            state:           0x10008u,
            flags:           EntityCollisionFlags.None,
            worldOffsetX:    OffX,
            worldOffsetY:    OffY,
            landblockId:     LbId);

        int found = 0;
        foreach (var entry in reg.AllEntriesForDebug())
        {
            if (entry.EntityId == doorEntityId) found++;
        }
        Assert.True(found >= 4,
            $"Expected at least 4 entries for door entity (one per shape); found {found}");
    }

    [Fact]
    public void RegisterMultiPart_EmptyShapeList_NoOp()
    {
        var reg = new ShadowObjectRegistry();
        reg.RegisterMultiPart(
            entityId:       0x1u,
            entityWorldPos: Vector3.Zero,
            entityWorldRot: Quaternion.Identity,
            shapes:         System.Array.Empty<ShadowShape>(),
            state:          0u,
            flags:          EntityCollisionFlags.None,
            worldOffsetX:   OffX, worldOffsetY: OffY, landblockId: LbId);

        Assert.Equal(0, reg.TotalRegistered);
    }

    [Fact]
    public void Deregister_RemovesAllParts()
    {
        var reg = new ShadowObjectRegistry();
        const uint doorEntityId = 0x000F4244u;
        reg.RegisterMultiPart(doorEntityId, new Vector3(132.6f, 17.1f, 94.08f),
                               Quaternion.Identity, DoorShapes(), 0x10008u,
                               EntityCollisionFlags.None, OffX, OffY, LbId);

        reg.Deregister(doorEntityId);

        Assert.Equal(0, reg.TotalRegistered);
        foreach (var entry in reg.AllEntriesForDebug())
            Assert.NotEqual(doorEntityId, entry.EntityId);
    }

    [Fact]
    public void UpdatePhysicsState_PropagatesEtherealToAllParts()
    {
        var reg = new ShadowObjectRegistry();
        const uint doorEntityId = 0x000F4244u;
        reg.RegisterMultiPart(doorEntityId, new Vector3(132.6f, 17.1f, 94.08f),
                               Quaternion.Identity, DoorShapes(), 0x10008u,
                               EntityCollisionFlags.None, OffX, OffY, LbId);

        reg.UpdatePhysicsState(doorEntityId, 0x1000Cu); // 0x10008 | 0x4

        int updated = 0;
        foreach (var entry in reg.AllEntriesForDebug())
        {
            if (entry.EntityId != doorEntityId) continue;
            Assert.Equal(0x1000Cu, entry.State);
            updated++;
        }
        Assert.True(updated >= 4, $"Expected all parts updated, only {updated} were");
    }

    [Fact]
    public void RegisterMultiPart_PartsAcrossMultipleCells_AllCellsListed()
    {
        var reg = new ShadowObjectRegistry();
        // Two shapes 30m apart in X — must span two outdoor 24m cells.
        var shapes = new[]
        {
            ShadowShape.Cylinder(0u, new Vector3(  0f, 0f, 0f), Quaternion.Identity, 1f, 1f, 2f),
            ShadowShape.Cylinder(0u, new Vector3(30f, 0f, 0f), Quaternion.Identity, 1f, 1f, 2f),
        };
        reg.RegisterMultiPart(0x1u, new Vector3(12f, 12f, 50f), Quaternion.Identity,
                               shapes, 0u, EntityCollisionFlags.None, OffX, OffY, LbId);

        // Part 1 at world (12, 12) → cell (0,0) = LbId | 1
        // Part 2 at world (42, 12) → cell (1,0) = LbId | 9
        var entriesIn1 = reg.GetObjectsInCell(LbId | 1u);
        var entriesIn9 = reg.GetObjectsInCell(LbId | 9u);
        Assert.Contains(entriesIn1, e => e.EntityId == 0x1u);
        Assert.Contains(entriesIn9, e => e.EntityId == 0x1u);
    }

    [Fact]
    public void Register_SingleShapeCompat_Unchanged()
    {
        var reg = new ShadowObjectRegistry();
        reg.Register(42u, 0x01000001u, new Vector3(12f, 12f, 50f),
                     Quaternion.Identity, 1f, OffX, OffY, LbId);

        Assert.Equal(1, reg.TotalRegistered);
        Assert.Single(reg.GetObjectsInCell(LbId | 1u),
                      e => e.EntityId == 42u);
    }

    [Fact]
    public void UpdatePosition_MovesAllPartsWithEntity()
    {
        var reg = new ShadowObjectRegistry();
        const uint movingEntityId = 0xA1u;

        var shapes = new[]
        {
            ShadowShape.Cylinder(0u, new Vector3(0f, 0f, 0f), Quaternion.Identity, 1f, 0.5f, 1f),
            ShadowShape.Cylinder(0u, new Vector3(1f, 0f, 0f), Quaternion.Identity, 1f, 0.5f, 1f),
        };
        reg.RegisterMultiPart(movingEntityId, new Vector3(10f, 10f, 50f),
                               Quaternion.Identity, shapes, 0u,
                               EntityCollisionFlags.None, OffX, OffY, LbId);

        // Move entity to (50, 10, 50). Parts should be at (50, 10, 50) and (51, 10, 50).
        reg.UpdatePosition(movingEntityId,
                           new Vector3(50f, 10f, 50f), Quaternion.Identity,
                           OffX, OffY, LbId);

        Vector3 expectedPart0 = new(50f, 10f, 50f);
        Vector3 expectedPart1 = new(51f, 10f, 50f);
        var atNew = reg.AllEntriesForDebug().Where(e => e.EntityId == movingEntityId).ToList();
        Assert.Equal(2, atNew.Count);
        bool found0 = atNew.Any(e => Vector3.Distance(e.Position, expectedPart0) < 0.01f);
        bool found1 = atNew.Any(e => Vector3.Distance(e.Position, expectedPart1) < 0.01f);
        Assert.True(found0 && found1,
            "Expected both parts at new world positions (50, 10, 50) and (51, 10, 50)");
    }

    [Fact]
    public void Deregister_ClearsEntityShapesCache_NoStaleUpdatePositionRebuild()
    {
        // A6.P4 door fix (2026-05-24) regression: after Deregister, a stray
        // UpdatePosition with the same entityId must NOT resurrect the entity
        // via the _entityShapes path. The Deregister cleanup added in Task 4
        // (which folded Task 6 into the multi-part registration commit) clears
        // _entityShapes[entityId] alongside the cell-list cleanup.
        var reg = new ShadowObjectRegistry();
        const uint doorEntityId = 0x000F4244u;
        reg.RegisterMultiPart(doorEntityId, new Vector3(132.6f, 17.1f, 94.08f),
                               Quaternion.Identity, DoorShapes(), 0x10008u,
                               EntityCollisionFlags.None, OffX, OffY, LbId);

        reg.Deregister(doorEntityId);

        // Stray UpdatePosition should be a no-op now (no entry to find AND
        // no _entityShapes entry to rebuild from).
        reg.UpdatePosition(doorEntityId, new Vector3(200f, 200f, 50f),
                           Quaternion.Identity, OffX, OffY, LbId);

        Assert.Equal(0, reg.TotalRegistered);
    }

    // ---------------------------------------------------------------------
    // AP-152 — cross-cell dispatch. CPhysicsObj::calc_cross_cells @0x00515230
    // tests HAS_PHYSICS_BSP_PS at 0x00515285 and routes a BSP-bearing object
    // to CPhysicsObj::find_bbox_cell_list @0x00510fc0 through
    // 0x0051528f jne 0x515305. The cylsphere branch (0x005152d1
    // CObjCell::find_cell_list @0x0052b9f0) and the sorting-sphere branch
    // (0x005152fb ... @0x0052b990) are BOTH below that jump and unreachable
    // from it. BuildFloodSpheres used to prefer Cylinders over everything
    // whenever any Cylinder was present, which is retail's SECOND priority
    // applied ahead of its first.
    // ---------------------------------------------------------------------

    /// <summary>Cells of the landblock that hold at least one row for owner.</summary>
    private static List<uint> OutdoorCellsHolding(ShadowObjectRegistry reg, uint ownerId)
    {
        var cells = new List<uint>();
        for (uint index = 1u; index <= 64u; index++)
        {
            uint cellId = LbId | index;
            if (reg.GetObjectsInCell(cellId).Any(e => e.EntityId == ownerId))
                cells.Add(cellId);
        }
        return cells;
    }

    private static ShadowShape Cyl(float radius, Vector3 localPosition = default)
        => ShadowShape.Cylinder(
            gfxObjId: 0u,
            localPosition: localPosition,
            localRotation: Quaternion.Identity,
            scale: 1f,
            radius: radius,
            cylHeight: radius * 2f);

    /// <summary>
    /// A physics-BSP part shape. <paramref name="boundsCenter"/> defaults
    /// OFF-CENTRE because that is the DAT-real configuration: a GfxObj's
    /// physics BSP is authored in the GfxObj's own coordinates and 376 of the
    /// 973 installed physics-BSP parts have a root bounding sphere further
    /// from the part origin than half their own radius. A fixture pinned at
    /// <c>Vector3.Zero</c> is the one configuration in which discarding the
    /// centre is invisible.
    /// </summary>
    private static ShadowShape Bsp(
        float radius,
        Vector3 boundsCenter = default,
        Vector3 localPosition = default,
        Quaternion localRotation = default)
        => ShadowShape.Bsp(
            gfxObjId: 0x010044B5u,
            localPosition: localPosition,
            localRotation: localRotation == default ? Quaternion.Identity : localRotation,
            scale: 1f,
            localGeometry: ShadowPartGeometry.Create(
                new FlatCollisionSphere(
                    boundsCenter == default ? new Vector3(0f, 6f, 0f) : boundsCenter,
                    radius),
                null));

    private static List<uint> FloodCellsFor(params ShadowShape[] shapes)
    {
        var reg = new ShadowObjectRegistry();
        const uint ownerId = 0xBEEF01u;
        // Centre of the landblock's cell (1,1) so a 14 m footprint stays
        // inside the block's own 8x8 outdoor grid on every side.
        reg.RegisterMultiPart(
            ownerId, new Vector3(36f, 36f, 50f), Quaternion.Identity,
            shapes, 0x10008u, EntityCollisionFlags.None, OffX, OffY, LbId);
        return OutdoorCellsHolding(reg, ownerId);
    }

    [Fact]
    public void BuildFloodSpheres_BspBearingOwner_FloodsFromBspNotFromCylinder()
    {
        List<uint> cylinderOnly = FloodCellsFor(Cyl(0.5f));
        List<uint> bspOnly      = FloodCellsFor(Bsp(14f));
        List<uint> mixed        = FloodCellsFor(Cyl(0.5f), Bsp(14f));


        // Controls: the two footprints must actually differ, or the fact below
        // is satisfiable by any dispatch rule at all.
        Assert.Equal([LbId | 10u], cylinderOnly);
        Assert.True(bspOnly.Count > 1,
            $"BSP footprint control failed: expected >1 cell, got {bspOnly.Count}");

        // The fact: a mixed list floods from the BSP shapes, exactly as if the
        // cylinder were not there. Retail 0x0051528f.
        Assert.Equal(bspOnly, mixed);
        Assert.NotEqual(cylinderOnly, mixed);
    }

    /// <summary>
    /// AP-156. Retail's per-part cross-cell walk transforms the BSP root
    /// bounding sphere's CENTRE through the part's own frame before it uses
    /// the radius: <c>CGfxObj::physics_sphere</c> is
    /// <c>BSPTREE::GetSphere(physics_bsp)</c> @0x005397e0 (root
    /// <c>BSPNODE</c> + 4, past its vftable), and
    /// <c>CEnvCell::find_transit_cells</c> @0x0052cae0 — the part-array
    /// overload reached from <c>find_bbox_cell_list</c> @0x00510fc0 through
    /// <c>CPartArray::calc_cross_cells_static</c> @0x00518160's
    /// <c>[vtbl+0x7c]</c> — loads it at <c>0x0052cb36 mov esi,[ecx+0x74]</c>,
    /// runs <c>Position::localtolocal</c> on it against
    /// <c>[part+0x30]</c> (<c>0x0052cb4c add eax,0x30</c>), and only then
    /// reads <c>[esi+0xc]</c> for the radius.
    ///
    /// <para>
    /// acdream used to flood from the part ORIGIN with the sphere's radius.
    /// Over the installed DAT that failed to contain the parts' own physics
    /// polygons for 428 of the 530 BSP-bearing Setups, shortfall up to
    /// 35.869 m at entity scale 1.75 (0x0200129A) — under-inclusive
    /// membership, the #98 / #168 class. (172 is AP-152's DISPATCH
    /// population; the AP-156 row's original "170 of 172" understated this
    /// 2.5x and was corrected at the fix review.)
    /// </para>
    /// </summary>
    [Fact]
    public void BuildFloodSpheres_BspShape_CentresOnTheBoundsCentreNotThePartOrigin()
    {
        // Same sphere, three placements of the SAME 6 m radius:
        //   a) part origin at (0,0,0), bounds centre at the origin too;
        //   b) part origin at (0,0,0), bounds centre 30 m along +Y;
        //   c) part origin 30 m along +Y, bounds centre at the origin.
        // (b) and (c) describe the identical world sphere, so they must flood
        // the identical cells — and neither may equal (a).
        List<uint> concentric = FloodCellsFor(
            Bsp(6f, boundsCenter: new Vector3(0.001f, 0f, 0f)));
        List<uint> viaBoundsCentre = FloodCellsFor(
            Bsp(6f, boundsCenter: new Vector3(0f, 30f, 0f)));
        List<uint> viaPartOrigin = FloodCellsFor(
            Bsp(6f,
                boundsCenter: new Vector3(0.001f, 0f, 0f),
                localPosition: new Vector3(0f, 30f, 0f)));

        // Control: the offset must actually move the footprint, or the
        // equality below is satisfiable by ignoring BoundsCenter entirely.
        Assert.NotEqual(concentric, viaBoundsCentre);

        Assert.Equal(viaPartOrigin, viaBoundsCentre);
    }

    /// <summary>
    /// Retail's 10-sphere clamp is on the CYLSPHERE branch and nowhere else.
    /// <c>CObjCell::find_cell_list</c> @0x0052b9f0 clamps the cylsphere count
    /// (<c>0x0052ba21 cmp eax,0xa</c> / <c>0x0052ba28 mov ebp,0xa</c>); the
    /// BSP branch — <c>find_bbox_cell_list</c> @0x00510fc0 →
    /// <c>CPartArray::calc_cross_cells_static</c> @0x00518160 →
    /// <c>CEnvCell::find_transit_cells</c> @0x0052cae0 — walks every part with
    /// no cap, and the sorting-sphere overload @0x0052b990 takes one sphere.
    /// 7 installed Setups carry more than 10 physics-BSP parts (max 49,
    /// Setup 0x02001A91) and landblock-baked stair runs and fences routinely
    /// do, so clamping the BSP branch dropped their tail parts out of the
    /// flood entirely.
    /// </summary>
    [Fact]
    public void BuildFloodSpheres_CapsCylSpheresAtTenButNeverTheBspParts()
    {
        // Ten shapes on the owner's own cell, then an eleventh 72 m north.
        var near = new Vector3(0f, 0f, 0f);
        var far = new Vector3(0f, 72f, 0f);
        uint ownCell = LbId | (uint)(1 * 8 + 1 + 1);   // (x=1, y=1)
        uint farCell = LbId | (uint)(1 * 8 + 4 + 1);   // (x=1, y=4)

        var bsp = new ShadowShape[11];
        for (int i = 0; i < 10; i++)
            bsp[i] = Bsp(1f, boundsCenter: new Vector3(0.001f, 0f, 0f));
        bsp[10] = Bsp(1f, boundsCenter: far);
        List<uint> bspCells = FloodCellsFor(bsp);

        var cyls = new ShadowShape[11];
        for (int i = 0; i < 10; i++)
            cyls[i] = Cyl(1f, near);
        cyls[10] = Cyl(1f, far);
        List<uint> cylCells = FloodCellsFor(cyls);

        Assert.Contains(ownCell, bspCells);
        Assert.Contains(ownCell, cylCells);

        // The eleventh BSP part still floods; the eleventh cylsphere does not.
        Assert.Contains(farCell, bspCells);
        Assert.DoesNotContain(farCell, cylCells);
    }

    /// <summary>
    /// The BoundsCentre is expressed in the SHAPE's own frame, so the part's
    /// LocalRotation must carry it — exactly as retail transforms the sphere
    /// centre through <c>[part+0x30]</c>, the part's full Position, not just
    /// its origin. A +Y offset on a part yawed 180 degrees must land at -Y.
    /// </summary>
    [Fact]
    public void BuildFloodSpheres_BspShape_RotatesTheBoundsCentreByThePartRotation()
    {
        Quaternion yaw180 = Quaternion.CreateFromAxisAngle(Vector3.UnitZ, MathF.PI);

        List<uint> yawed = FloodCellsFor(
            Bsp(6f, boundsCenter: new Vector3(0f, 20f, 0f), localRotation: yaw180));
        List<uint> negatedUnrotated = FloodCellsFor(
            Bsp(6f, boundsCenter: new Vector3(0f, -20f, 0f)));
        List<uint> unrotated = FloodCellsFor(
            Bsp(6f, boundsCenter: new Vector3(0f, 20f, 0f)));

        Assert.NotEqual(unrotated, negatedUnrotated);   // control
        Assert.Equal(negatedUnrotated, yawed);
    }

    /// <summary>
    /// The AP-152 delta end-to-end: a CylSphere+BSP Setup (73 of the 172
    /// affected installed Setups are this shape) registered through the
    /// production builder. Before the fix the emitted list carried both, and
    /// BuildFloodSpheres' cylinder preference confined the owner to the
    /// cylinder's cell while its slab BSP reached further — an object absent
    /// from shadow cells it physically occupies, the #98 / #168 symptom class.
    ///
    /// <para>
    /// The BSP bounds are supplied through the production seam
    /// (<c>physicsBspBounds</c>, the same resolver
    /// <c>LiveEntityCollisionBuilder</c> passes) and are OFF-CENTRE, so the
    /// flood is asserted where the geometry is rather than where the part
    /// origin is.
    /// </para>
    /// </summary>
    [Fact]
    public void FromSetup_CylSphereAndBspSetup_FloodsTheBspFootprint()
    {
        const uint part = 0x010044B5u;
        var setup = new DatReaderWriter.DBObjs.Setup
        {
            Parts      = { part },
            CylSpheres = { new DatReaderWriter.Types.CylSphere
                { Radius = 0.5f, Height = 1f, Origin = Vector3.Zero } },
        };

        // 14 m stands in for a slab wide enough to leave its own landcell;
        // the +18 m Y offset stands in for the 376-of-973 installed parts
        // whose root sphere is nowhere near the part origin.
        var bounds = new FlatCollisionSphere(new Vector3(0f, 18f, 0f), 14f);
        IReadOnlyList<ShadowShape> shapes = ShadowShapeBuilder.FromSetup(
            setup,
            entScale: 1f,
            hasPhysicsBsp: id => id == part,
            physicsBspBounds: id => id == part
                ? ShadowPartGeometry.Create(bounds, null)
                : (ShadowPartGeometry?)null);

        ShadowShape only = Assert.Single(shapes);
        Assert.Equal(ShadowCollisionType.BSP, only.CollisionType);
        Assert.Equal(14f, only.Radius);
        Assert.Equal(new Vector3(0f, 18f, 0f), only.BoundsCenter);

        var reg = new ShadowObjectRegistry();
        const uint ownerId = 0xBEEF02u;
        reg.RegisterMultiPart(
            ownerId, new Vector3(36f, 36f, 50f), Quaternion.Identity,
            shapes, 0x10008u, EntityCollisionFlags.None, OffX, OffY, LbId);

        List<uint> cells = OutdoorCellsHolding(reg, ownerId);
        Assert.True(cells.Count > 1,
            $"Expected the slab footprint to span more than its own landcell; got {cells.Count}");
        // Landcells are 24 m. The slab's sphere is centred at y = 54 m with
        // r = 14 m, so it spans y in [40, 68] — rows 1 and 2, and it comes no
        // closer than 16 m to row 0 (y < 24). Flooding it around the PART
        // ORIGIN instead (y = 36 m, span [22, 50]) would drag row 0 in.
        Assert.Contains(LbId | (uint)(1 * 8 + 2 + 1), cells);        // (x=1, y=2)
        Assert.DoesNotContain(LbId | (uint)(1 * 8 + 0 + 1), cells);  // (x=1, y=0)
    }
}