using AcDream.Core.Meshing;
using DatReaderWriter.Enums;

namespace AcDream.Core.Tests.Meshing;

/// <summary>
/// Verifies that <see cref="TranslucencyKindExtensions.FromSurfaceType"/> maps
/// SurfaceType flag combinations to the correct <see cref="TranslucencyKind"/>
/// according to the documented priority order:
///   Additive &gt; InvAlpha &gt; AlphaBlend (Alpha|Translucent) &gt; ClipMap &gt; Opaque
/// </summary>
public class TranslucencyKindTests
{
    // ── Opaque cases ────────────────────────────────────────────────────────

    [Fact]
    public void Opaque_FromZeroFlags_ReturnsOpaque()
        => Assert.Equal(TranslucencyKind.Opaque, TranslucencyKindExtensions.FromSurfaceType((SurfaceType)0));

    [Fact]
    public void Opaque_FromBase1SolidFlag_ReturnsOpaque()
        => Assert.Equal(TranslucencyKind.Opaque, TranslucencyKindExtensions.FromSurfaceType(SurfaceType.Base1Solid));

    [Fact]
    public void Opaque_FromBase1ImageFlag_ReturnsOpaque()
        => Assert.Equal(TranslucencyKind.Opaque, TranslucencyKindExtensions.FromSurfaceType(SurfaceType.Base1Image));

    // ── ClipMap cases ───────────────────────────────────────────────────────

    [Fact]
    public void ClipMap_FromBase1ClipMapFlag_ReturnsClipMap()
        => Assert.Equal(TranslucencyKind.ClipMap, TranslucencyKindExtensions.FromSurfaceType(SurfaceType.Base1ClipMap));

    [Fact]
    public void ClipMap_WithOtherOpaqueFlags_ReturnsClipMap()
        => Assert.Equal(TranslucencyKind.ClipMap,
            TranslucencyKindExtensions.FromSurfaceType(SurfaceType.Base1ClipMap | SurfaceType.Gouraud));

    // ── AlphaBlend cases ────────────────────────────────────────────────────

    [Fact]
    public void AlphaBlend_FromAlphaFlag_ReturnsAlphaBlend()
        => Assert.Equal(TranslucencyKind.AlphaBlend, TranslucencyKindExtensions.FromSurfaceType(SurfaceType.Alpha));

    [Fact]
    public void AlphaBlend_FromTranslucentFlag_ReturnsAlphaBlend()
        => Assert.Equal(TranslucencyKind.AlphaBlend, TranslucencyKindExtensions.FromSurfaceType(SurfaceType.Translucent));

    [Fact]
    public void AlphaBlend_FromAlphaAndTranslucentFlags_ReturnsAlphaBlend()
        => Assert.Equal(TranslucencyKind.AlphaBlend,
            TranslucencyKindExtensions.FromSurfaceType(SurfaceType.Alpha | SurfaceType.Translucent));

    [Fact]
    public void AlphaBlend_AlphaWithClipMap_AlphaWins()
        => Assert.Equal(TranslucencyKind.AlphaBlend,
            TranslucencyKindExtensions.FromSurfaceType(SurfaceType.Alpha | SurfaceType.Base1ClipMap));

    // ── InvAlpha cases ──────────────────────────────────────────────────────

    [Fact]
    public void InvAlpha_FromInvAlphaFlag_ReturnsInvAlpha()
        => Assert.Equal(TranslucencyKind.InvAlpha, TranslucencyKindExtensions.FromSurfaceType(SurfaceType.InvAlpha));

    [Fact]
    public void InvAlpha_InvAlphaBeatsAlpha()
        => Assert.Equal(TranslucencyKind.InvAlpha,
            TranslucencyKindExtensions.FromSurfaceType(SurfaceType.InvAlpha | SurfaceType.Alpha));

    // ── Additive cases ──────────────────────────────────────────────────────

    [Fact]
    public void Additive_FromAdditiveFlag_ReturnsAdditive()
        => Assert.Equal(TranslucencyKind.Additive, TranslucencyKindExtensions.FromSurfaceType(SurfaceType.Additive));

    [Fact]
    public void Additive_AdditiveBeatsAllOther()
        => Assert.Equal(TranslucencyKind.Additive,
            TranslucencyKindExtensions.FromSurfaceType(
                SurfaceType.Additive | SurfaceType.InvAlpha | SurfaceType.Alpha | SurfaceType.Base1ClipMap));
}