Kelsidavis-WoWee/include/pipeline/blp_loader.hpp

#pragma once

#include <vector>
#include <cstdint>
#include <string>

namespace wowee {
namespace pipeline {

/**
 * BLP image format (Blizzard Picture)
 */
enum class BLPFormat {
    UNKNOWN = 0,
    BLP0 = 1,      // Alpha channel only
    BLP1 = 2,      // DXT compression or uncompressed
    BLP2 = 3       // DXT compression with mipmaps
};

/**
 * BLP compression type
 */
enum class BLPCompression {
    NONE = 0,
    PALETTE = 1,     // 256-color palette
    DXT1 = 2,        // DXT1 compression (no alpha or 1-bit alpha)
    DXT3 = 3,        // DXT3 compression (4-bit alpha)
    DXT5 = 4,        // DXT5 compression (interpolated alpha)
    ARGB8888 = 5     // Uncompressed 32-bit ARGB
};

/**
 * Loaded BLP image data
 */
struct BLPImage {
    int width = 0;
    int height = 0;
    int channels = 4;
    int mipLevels = 1;
    BLPFormat format = BLPFormat::UNKNOWN;
    BLPCompression compression = BLPCompression::NONE;
    std::vector<uint8_t> data;      // RGBA8 pixel data (decompressed)
    std::vector<std::vector<uint8_t>> mipmaps;  // Mipmap levels

    bool isValid() const { return width > 0 && height > 0 && !data.empty(); }
};

/**
 * BLP texture loader
 *
 * Supports BLP0, BLP1, BLP2 formats
 * Handles DXT1/3/5 compression and palette formats
 * Format specification: https://wowdev.wiki/BLP
 */
class BLPLoader {
public:
    /**
     * Load BLP image from byte data
     * @param blpData Raw BLP file data
     * @return Loaded image (check isValid())
     */
    static BLPImage load(const std::vector<uint8_t>& blpData);

    /**
     * Get format name for debugging
     */
    static const char* getFormatName(BLPFormat format);
    static const char* getCompressionName(BLPCompression compression);

private:
    // BLP1 file header — all fields after magic are uint32
    // Used by classic WoW through WotLK for many textures
    struct BLP1Header {
        char magic[4];           // 'BLP1'
        uint32_t compression;    // 0=JPEG, 1=palette (uncompressed/indexed)
        uint32_t alphaBits;      // 0, 1, 4, or 8
        uint32_t width;
        uint32_t height;
        uint32_t extra;          // Flags/unknown (often 4 or 5)
        uint32_t hasMips;        // 0 or 1
        uint32_t mipOffsets[16];
        uint32_t mipSizes[16];
        uint32_t palette[256];   // 256-color BGRA palette (for compression=1)
    };

    // BLP2 file header — compression fields are uint8
    // Used by WoW from TBC onwards (coexists with BLP1 in WotLK)
    struct BLP2Header {
        char magic[4];           // 'BLP2'
        uint32_t version;        // Always 1
        uint8_t compression;     // 1=uncompressed/palette, 2=DXTC, 3=A8R8G8B8
        uint8_t alphaDepth;      // 0, 1, 4, or 8
        uint8_t alphaEncoding;   // 0=DXT1, 1=DXT3, 7=DXT5
        uint8_t hasMips;         // Has mipmaps
        uint32_t width;
        uint32_t height;
        uint32_t mipOffsets[16];
        uint32_t mipSizes[16];
        uint32_t palette[256];   // 256-color BGRA palette (for compression=1)
    };

    static BLPImage loadBLP1(const uint8_t* data, size_t size);
    static BLPImage loadBLP2(const uint8_t* data, size_t size);
    static void decompressDXT1(const uint8_t* src, uint8_t* dst, int width, int height);
    static void decompressDXT3(const uint8_t* src, uint8_t* dst, int width, int height);
    static void decompressDXT5(const uint8_t* src, uint8_t* dst, int width, int height);
    static void decompressPalette(const uint8_t* src, uint8_t* dst, const uint32_t* palette, int width, int height, uint8_t alphaDepth = 8);
};

} // namespace pipeline
} // namespace wowee