using System;

using System.IO;

using System.Runtime.InteropServices;

using BCnEncoder.Shared;

namespace BCnEncoder.Decoder

{

internal class Bc7Decoder : IBcBlockDecoder

{

public RawBlock4X4Rgba32[,] Decode(ReadOnlySpan<byte> data, int pixelWidth, int pixelHeight, out int blockWidth, out int blockHeight) {

blockWidth = (int)MathF.Ceiling(pixelWidth / 4.0f);

blockHeight = (int)MathF.Ceiling(pixelHeight / 4.0f);

if (data.Length != (blockWidth * blockHeight * Marshal.SizeOf<Bc7Block>())) {

throw new InvalidDataException();

}

var encodedBlocks = MemoryMarshal.Cast<byte, Bc7Block>(data);

RawBlock4X4Rgba32[,] output = new RawBlock4X4Rgba32[blockWidth, blockHeight];

for (int x = 0; x < blockWidth; x++) {

for (int y = 0; y < blockHeight; y++) {

var rawBlock = encodedBlocks[x + y * blockWidth];

output[x, y] = rawBlock.Decode();

}

}

return output;

}

}

}