using AcDream.Core.Textures;
using DatReaderWriter.DBObjs;
using DatReaderWriter.Enums;

namespace AcDream.Core.Tests.Textures;

public class SurfaceDecoderTests
{
    [Fact]
    public void Decode_A8R8G8B8_ConvertsToRgba8()
    {
        // Source format is B, G, R, A in memory (little-endian ARGB).
        // One 2x2 image: red, green, blue, white pixels.
        var src = new byte[]
        {
            0x00, 0x00, 0xFF, 0xFF,  // red   (B=0, G=0, R=255, A=255)
            0x00, 0xFF, 0x00, 0xFF,  // green
            0xFF, 0x00, 0x00, 0xFF,  // blue
            0xFF, 0xFF, 0xFF, 0xFF,  // white
        };
        var rs = new RenderSurface
        {
            Width = 2,
            Height = 2,
            Format = PixelFormat.PFID_A8R8G8B8,
            SourceData = src,
        };

        var decoded = SurfaceDecoder.DecodeRenderSurface(rs);

        Assert.Equal(2, decoded.Width);
        Assert.Equal(2, decoded.Height);
        Assert.Equal(16, decoded.Rgba8.Length);  // 2*2*4
        // red pixel, in RGBA: 255, 0, 0, 255
        Assert.Equal(0xFF, decoded.Rgba8[0]);
        Assert.Equal(0x00, decoded.Rgba8[1]);
        Assert.Equal(0x00, decoded.Rgba8[2]);
        Assert.Equal(0xFF, decoded.Rgba8[3]);
    }

    [Fact]
    public void Decode_UnsupportedFormat_ReturnsMagenta()
    {
        var rs = new RenderSurface
        {
            Width = 4,
            Height = 4,
            Format = PixelFormat.PFID_INDEX16,  // not implemented path
            SourceData = new byte[32],
        };

        var decoded = SurfaceDecoder.DecodeRenderSurface(rs);

        Assert.Same(DecodedTexture.Magenta, decoded);
    }

    [Fact]
    public void Decode_NullSourceData_ReturnsMagenta()
    {
        var rs = new RenderSurface
        {
            Width = 4,
            Height = 4,
            Format = PixelFormat.PFID_A8R8G8B8,
            SourceData = null!,
        };

        var decoded = SurfaceDecoder.DecodeRenderSurface(rs);

        Assert.Same(DecodedTexture.Magenta, decoded);
    }

    [Fact]
    public void Decode_TruncatedA8R8G8B8_ReturnsMagenta()
    {
        // Buffer too small for width*height*4.
        var rs = new RenderSurface
        {
            Width = 2,
            Height = 2,
            Format = PixelFormat.PFID_A8R8G8B8,
            SourceData = new byte[8],  // should be 16
        };

        var decoded = SurfaceDecoder.DecodeRenderSurface(rs);

        Assert.Same(DecodedTexture.Magenta, decoded);
    }
}