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

namespace AcDream.Core.Tests.Physics;

/// <summary>
/// Issue #101 (2026-05-25) — phantom-stair fix. Retail's
/// <c>CPartArray::InitParts</c> emits collision shapes only from
/// Setup-level <c>CylSpheres</c>/<c>Spheres</c> or per-Part
/// <c>PhysicsBSP</c>. There is NO synthesis from visual mesh AABB.
/// Acdream's <c>mesh-aabb-fallback</c> path at
/// <c>GameWindow.cs:6127</c> previously fired for ANY entity that
/// reached it with <c>entityBsp==0 &amp;&amp; entityCyl==0</c>,
/// including GfxObj-only stabs whose GfxObj has
/// <c>HasPhysics=False</c>. This produced the 10 phantom 0.80 m
/// cylinders that block the Holtburg upper-floor staircase (see
/// <c>docs/research/2026-05-25-a6-stairs-cyl-retail-investigation.md</c>).
///
/// <para>
/// <see cref="PhysicsDataCache.IsPhantomGfxObjSource"/> captures the
/// retail rule as a predicate: "the entity's source is a GfxObj
/// (high byte 0x01) AND the cache has no <see cref="GfxObjPhysics"/>
/// entry for it." When this returns true, the caller suppresses the
/// fallback synthesis.
/// </para>
/// </summary>
public class PhysicsDataCachePhantomSourceTests
{
    [Fact]
    public void IsPhantomGfxObjSource_SetupHighByte_ReturnsFalse()
    {
        // Setup source (high byte 0x02) is never the GfxObj-phantom case.
        // The existing isPhantomSetup check at GameWindow.cs:6090 handles
        // the Setup-side phantom. This predicate is scoped to GfxObj only.
        var cache = new PhysicsDataCache();
        Assert.False(cache.IsPhantomGfxObjSource(0x020019FFu));   // door setup
        Assert.False(cache.IsPhantomGfxObjSource(0x02000266u));   // some setup
    }

    [Fact]
    public void IsPhantomGfxObjSource_GfxObjUncached_ReturnsTrue()
    {
        // GfxObj source (high byte 0x01) with NO cached GfxObjPhysics
        // = the phantom case. The stair-step GfxObj 0x0100081A from
        // issue #101's broken-stairs capture has HasPhysics=False and
        // does not enter the cache. Acdream should treat it as phantom.
        var cache = new PhysicsDataCache();
        Assert.True(cache.IsPhantomGfxObjSource(0x0100081Au));
    }

    [Fact]
    public void IsPhantomGfxObjSource_GfxObjCached_ReturnsFalse()
    {
        // GfxObj source (high byte 0x01) WITH a cached GfxObjPhysics
        // (i.e. the GfxObj's HasPhysics flag was set and its PhysicsBSP
        // root is non-null) is NOT phantom. The staircase BSP entity
        // 0x40B50089 from issue #101's capture, backed by GfxObj
        // 0x01000C16 with hasPhys=True, is this case.
        var cache = new PhysicsDataCache();
        var leaf = new PhysicsBSPNode { Type = BSPNodeType.Leaf };
        var fakePhysics = new GfxObjPhysics
        {
            BSP             = new PhysicsBSPTree { Root = leaf },
            PhysicsPolygons = new Dictionary<ushort, Polygon>(),
            Vertices        = new VertexArray(),
            Resolved        = new Dictionary<ushort, ResolvedPolygon>(),
        };
        cache.RegisterGfxObjForTest(0x01000C16u, fakePhysics);
        Assert.False(cache.IsPhantomGfxObjSource(0x01000C16u));
    }
}