// Copyright 2018 yuzu Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.

#include <cmath>
#include <cstring>
#include "common/assert.h"
#include "core/memory.h"
#include "video_core/gpu.h"
#include "video_core/textures/decoders.h"
#include "video_core/textures/texture.h"

namespace Tegra::Texture {

/**
 * Calculates the offset of an (x, y) position within a swizzled texture.
 * Taken from the Tegra X1 TRM.
 */
static u32 GetSwizzleOffset(u32 x, u32 y, u32 image_width, u32 bytes_per_pixel, u32 block_height) {
    // Round up to the next gob
    const u32 image_width_in_gobs{(image_width * bytes_per_pixel + 63) / 64};

    u32 GOB_address = 0 + (y / (8 * block_height)) * 512 * block_height * image_width_in_gobs +
                      (x * bytes_per_pixel / 64) * 512 * block_height +
                      (y % (8 * block_height) / 8) * 512;
    x *= bytes_per_pixel;
    u32 address = GOB_address + ((x % 64) / 32) * 256 + ((y % 8) / 2) * 64 + ((x % 32) / 16) * 32 +
                  (y % 2) * 16 + (x % 16);

    return address;
}

void CopySwizzledData(u32 width, u32 height, u32 bytes_per_pixel, u32 out_bytes_per_pixel,
                      u8* swizzled_data, u8* unswizzled_data, bool unswizzle, u32 block_height) {
    u8* data_ptrs[2];
    for (unsigned y = 0; y < height; ++y) {
        for (unsigned x = 0; x < width; ++x) {
            u32 swizzle_offset = GetSwizzleOffset(x, y, width, bytes_per_pixel, block_height);
            u32 pixel_index = (x + y * width) * out_bytes_per_pixel;

            data_ptrs[unswizzle] = swizzled_data + swizzle_offset;
            data_ptrs[!unswizzle] = &unswizzled_data[pixel_index];

            std::memcpy(data_ptrs[0], data_ptrs[1], bytes_per_pixel);
        }
    }
}

u32 BytesPerPixel(TextureFormat format) {
    switch (format) {
    case TextureFormat::DXT1:
    case TextureFormat::DXN1:
        // In this case a 'pixel' actually refers to a 4x4 tile.
        return 8;
    case TextureFormat::DXT23:
    case TextureFormat::DXT45:
    case TextureFormat::DXN2:
    case TextureFormat::BC7U:
    case TextureFormat::BC6H_UF16:
    case TextureFormat::BC6H_SF16:
        // In this case a 'pixel' actually refers to a 4x4 tile.
        return 16;
    case TextureFormat::R32_G32_B32:
        return 12;
    case TextureFormat::ASTC_2D_4X4:
    case TextureFormat::ASTC_2D_8X8:
    case TextureFormat::A8R8G8B8:
    case TextureFormat::A2B10G10R10:
    case TextureFormat::BF10GF11RF11:
    case TextureFormat::R32:
    case TextureFormat::R16_G16:
        return 4;
    case TextureFormat::A1B5G5R5:
    case TextureFormat::B5G6R5:
    case TextureFormat::G8R8:
    case TextureFormat::R16:
        return 2;
    case TextureFormat::R8:
        return 1;
    case TextureFormat::R16_G16_B16_A16:
        return 8;
    case TextureFormat::R32_G32_B32_A32:
        return 16;
    case TextureFormat::R32_G32:
        return 8;
    default:
        UNIMPLEMENTED_MSG("Format not implemented");
        break;
    }
}

std::vector<u8> UnswizzleTexture(VAddr address, u32 tile_size, u32 bytes_per_pixel, u32 width,
                                 u32 height, u32 block_height) {
    std::vector<u8> unswizzled_data(width * height * bytes_per_pixel);
    CopySwizzledData(width / tile_size, height / tile_size, bytes_per_pixel, bytes_per_pixel,
                     Memory::GetPointer(address), unswizzled_data.data(), true, block_height);
    return unswizzled_data;
}

std::vector<u8> DecodeTexture(const std::vector<u8>& texture_data, TextureFormat format, u32 width,
                              u32 height) {
    std::vector<u8> rgba_data;

    // TODO(Subv): Implement.
    switch (format) {
    case TextureFormat::DXT1:
    case TextureFormat::DXT23:
    case TextureFormat::DXT45:
    case TextureFormat::DXN1:
    case TextureFormat::DXN2:
    case TextureFormat::BC7U:
    case TextureFormat::BC6H_UF16:
    case TextureFormat::BC6H_SF16:
    case TextureFormat::ASTC_2D_4X4:
    case TextureFormat::ASTC_2D_8X8:
    case TextureFormat::A8R8G8B8:
    case TextureFormat::A2B10G10R10:
    case TextureFormat::A1B5G5R5:
    case TextureFormat::B5G6R5:
    case TextureFormat::R8:
    case TextureFormat::G8R8:
    case TextureFormat::BF10GF11RF11:
    case TextureFormat::R32_G32_B32_A32:
    case TextureFormat::R32_G32:
    case TextureFormat::R32:
    case TextureFormat::R16:
    case TextureFormat::R16_G16:
    case TextureFormat::R32_G32_B32:
        // TODO(Subv): For the time being just forward the same data without any decoding.
        rgba_data = texture_data;
        break;
    default:
        UNIMPLEMENTED_MSG("Format not implemented");
        break;
    }

    return rgba_data;
}

} // namespace Tegra::Texture
