#include "png_encoder.h"
#include "common.h"

#define STB_IMAGE_WRITE_IMPLEMENTATION
#include "stb_image_write.h"

static void stbi_write_to_vector(void* context, void* data, int size) {
    auto* vec = static_cast<std::vector<uint8_t>*>(context);
    auto* bytes = static_cast<uint8_t*>(data);
    vec->insert(vec->end(), bytes, bytes + size);
}

std::vector<uint8_t> EncodeBgraToPng(const uint8_t* bgra, int width, int height, int stride) {
    // BGRA -> RGBA channel swap (D-14)
    std::vector<uint8_t> rgba(static_cast<size_t>(width) * height * 4);
    for (int y = 0; y < height; y++) {
        const uint8_t* src = bgra + y * stride;
        uint8_t* dst = rgba.data() + y * width * 4;
        for (int x = 0; x < width; x++) {
            dst[x * 4 + 0] = src[x * 4 + 2]; // R <- B
            dst[x * 4 + 1] = src[x * 4 + 1]; // G <- G
            dst[x * 4 + 2] = src[x * 4 + 0]; // B <- R
            dst[x * 4 + 3] = src[x * 4 + 3]; // A <- A
        }
    }

    std::vector<uint8_t> png;
    stbi_write_png_to_func(stbi_write_to_vector, &png, width, height, 4, rgba.data(), width * 4);
    if (png.empty()) {
        DWM_LOG("ERROR: stbi_write_png_to_func returned empty output");
    }
    return png;
}