using System.IO;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using GmodAssetImporter;

[TestClass]
public class VtfReaderTests
{
	[TestMethod]
	public void DecodesBgra8888Vtf()
	{
		var image = VtfReader.Load( BuildVtf71( withThumbnail: false ) );
		Assert.AreEqual( 2, image.Width );
		Assert.AreEqual( 2, image.Height );
		Assert.AreEqual( 255, image.Rgba[0] ); // R
		Assert.AreEqual( 0, image.Rgba[1] );
		Assert.AreEqual( 0, image.Rgba[2] );
	}

	[TestMethod]
	public void SkipsLowResThumbnailBeforeHighResImage()
	{
		var image = VtfReader.Load( BuildVtf71( withThumbnail: true ) );
		Assert.AreEqual( 255, image.Rgba[0] ); // first high-res pixel is red, not the thumbnail
		Assert.AreEqual( 0, image.Rgba[1] );
		Assert.AreEqual( 0, image.Rgba[2] );
		Assert.AreEqual( 255, image.Rgba[13] ); // last pixel white
	}

	/// <summary>Minimal VTF 7.1 with a 2x2 BGRA8888 image and optional 1x1 BGRA8888 thumbnail.</summary>
	static byte[] BuildVtf71( bool withThumbnail )
	{
		using var ms = new MemoryStream();
		using ( var bw = new BinaryWriter( ms, System.Text.Encoding.ASCII, leaveOpen: true ) )
		{
			bw.Write( new byte[] { (byte)'V', (byte)'T', (byte)'F', 0 } );
			bw.Write( 7u ); // major
			bw.Write( 1u ); // minor
			bw.Write( 64u ); // headerSize
			bw.Write( (ushort)2 ); // width
			bw.Write( (ushort)2 ); // height
			bw.Write( 0u ); // flags
			bw.Write( (ushort)1 ); // frames
			bw.Write( (ushort)0 ); // firstFrame
			bw.Write( new byte[4] ); // pad
			bw.Write( 1f ); bw.Write( 1f ); bw.Write( 1f ); // reflectivity
			bw.Write( new byte[4] ); // pad
			bw.Write( 1f ); // bump
			bw.Write( 12 ); // high format BGRA8888
			bw.Write( (byte)1 ); // mipcount
			bw.Write( withThumbnail ? 12 : -1 ); // low format (int)
			bw.Write( (byte)(withThumbnail ? 1 : 0) ); // low w
			bw.Write( (byte)(withThumbnail ? 1 : 0) ); // low h
			bw.Flush();
			while ( ms.Length < 64 )
				ms.WriteByte( 0 );

			ms.Position = 64;
			if ( withThumbnail )
				bw.Write( new byte[] { 9, 9, 9, 255 } );

			bw.Write( new byte[]
			{
				0, 0, 255, 255, // red in BGRA
				0, 255, 0, 255, // green
				255, 0, 0, 255, // blue
				255, 255, 255, 255 // white
			} );
			bw.Flush();
		}

		return ms.ToArray();
	}
}