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

namespace AcDream.Core.Tests.Physics;

/// <summary>
/// Guards the DAT-only shape-source rule (Slice 1 of the unified
/// collision-inclusion phase, 2026-06-24).
///
/// <para>
/// Retail oracle: <c>CPartArray::InitParts@0x00517F40</c> (parts come from
/// the Setup list only), <c>CGfxObj::Serialize@0x00534970</c> (physics_bsp
/// gated on serialized-flags bit-0), <c>CPhysicsPart::find_obj_collisions@0x0050D8D0</c>
/// (returns OK / passable when <c>physics_bsp == null</c>). Render-mesh bounds
/// never enter collision.
/// </para>
/// </summary>
public class ShadowShapeBuilderShapeSourceTests
{
    // Retail: an object with no DAT physics shape (no CylSphere, no Sphere,
    // no part with a PhysicsBSP) emits NO collision shape and is passable.
    // CPhysicsPart::find_obj_collisions@0x0050D8D0 returns OK when physics_bsp==null.
    [Fact]
    public void Setup_WithNoCylSpheres_NoSpheres_NoPhysicsBspParts_YieldsEmptyShapeList()
    {
        var setup = new Setup
        {
            CylSpheres      = new List<CylSphere>(),
            Spheres         = new List<Sphere>(),
            Parts           = { 0x01000ABCu },
            PlacementFrames = new Dictionary<Placement, AnimationFrame>(),
        };
        var shapes = ShadowShapeBuilder.FromSetup(setup, entScale: 1f, hasPhysicsBsp: _ => false);
        Assert.Empty(shapes);
    }

    // D4+W1 (2026-06-24) — BSP-only furniture weenie guard.
    //
    // A Setup with no CylSpheres, no Spheres, no Radius, but whose Part has a
    // PhysicsBSP (e.g. a candle holder or floor candelabra) MUST produce a BSP
    // ShadowShape. The premature `if (!hasCyl && !hasSphere && !hasRadius) return`
    // gate in GameWindow.RegisterLiveEntityCollision was dropped because it fired
    // BEFORE ShadowShapeBuilder ran and discarded these entities entirely.
    //
    // Retail oracle: CPhysicsPart::find_obj_collisions@0x0050D8D0 -- when
    // physics_bsp is non-null the part IS tested, and the outer loop in
    // CPartArray::FindObjCollisions@0x00518180 iterates ALL parts.
    // ShadowShapeBuilder.FromSetup mirrors this by emitting one BSP shape per
    // part that `hasPhysicsBsp` returns true for.
    //
    // AP-152 correction (2026-08-06): that "regardless of CylSpheres/Spheres"
    // used to be stated here and was then used to justify emitting the BSP
    // shapes IN ADDITION TO the primitives. It does not support that. The
    // per-part loop is reached only from the BSP branch of
    // CPhysicsObj::FindObjCollisions@0x0050f050, which is entered on
    // HAS_PHYSICS_BSP_PS (0x0050f165 test / 0x0050f16f je) and left by the
    // UNCONDITIONAL 0x0050f19d jmp 0x50f2b0 — past both primitive loops. The
    // dispatch is exclusive and BSP wins; this fixture's Setup simply has no
    // primitive to lose.
    [Fact]
    public void Setup_WithBspPart_NoCylSpheres_EmitsBspShape()
    {
        // hasPhysicsBsp predicate returns true for 0x0100AAAAu, simulating a
        // GfxObj that has a PhysicsBSP but no CylSpheres/Spheres.
        const uint BspGfxObjId = 0x0100AAAAu;
        var setup = new Setup
        {
            CylSpheres      = new List<CylSphere>(),
            Spheres         = new List<Sphere>(),
            Parts           = { BspGfxObjId },
            PlacementFrames = new Dictionary<Placement, AnimationFrame>(),
        };
        var shapes = ShadowShapeBuilder.FromSetup(setup, entScale: 1f,
            hasPhysicsBsp: id => id == BspGfxObjId);

        Assert.Contains(shapes, s => s.CollisionType == ShadowCollisionType.BSP);
    }

    // Complementary regression guard: a Setup with no CylSpheres, no Spheres,
    // and a Part that has NO PhysicsBSP must still produce an empty shape list.
    // The premature gate removal does not accidentally register shapeless entities.
    [Fact]
    public void Setup_WithPartButNoBsp_NoCylSpheres_YieldsEmptyShapeList()
    {
        const uint NoBspGfxObjId = 0x0100BBBBu;
        var setup = new Setup
        {
            CylSpheres      = new List<CylSphere>(),
            Spheres         = new List<Sphere>(),
            Parts           = { NoBspGfxObjId },
            PlacementFrames = new Dictionary<Placement, AnimationFrame>(),
        };
        var shapes = ShadowShapeBuilder.FromSetup(setup, entScale: 1f,
            hasPhysicsBsp: _ => false);

        Assert.Empty(shapes);
    }

    // 2026-07-07 — the PREMISE of the player-vs-monster crowd-collision fix (the
    // CSphere family port): a humanoid Setup carries body Spheres and NO
    // CylSpheres, so FromSetup emits Sphere-type shadows → collision runs through
    // Transition.SphereCollision (the retail CSphere::intersects_sphere family),
    // NOT the cylinder path. Mirrors the human Setup 0x02000001 (two body spheres
    // at 0.475 / 1.350, r=0.48 — TS-46 / the physics digest). If this ever flips
    // to CylSphere-first, the crowd fix would be aimed at the wrong dispatcher.
    [Fact]
    public void Setup_WithBodySpheres_NoCylSpheres_EmitsSphereShapes()
    {
        var setup = new Setup
        {
            CylSpheres = new List<CylSphere>(),
            Spheres = new List<Sphere>
            {
                new Sphere { Origin = new Vector3(0f, 0f, 0.475f), Radius = 0.48f },
                new Sphere { Origin = new Vector3(0f, 0f, 1.350f), Radius = 0.48f },
            },
            Parts           = new List<QualifiedDataId<GfxObj>>(),
            PlacementFrames = new Dictionary<Placement, AnimationFrame>(),
        };

        var shapes = ShadowShapeBuilder.FromSetup(setup, entScale: 1f, hasPhysicsBsp: _ => false);

        Assert.Equal(2, shapes.Count);
        Assert.All(shapes, s => Assert.Equal(ShadowCollisionType.Sphere, s.CollisionType));
    }
}