using System;
using System.Collections.Generic;
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; the outer loop in
    // CPartArray::FindObjCollisions iterates all parts regardless of
    // CylSpheres/Spheres.  ShadowShapeBuilder.FromSetup mirrors this by emitting
    // one BSP shape per part that `hasPhysicsBsp` returns true for.
    [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);
    }
}