#include <mbgl/util/image.hpp>
#include <mbgl/util/string.hpp>
#include <mbgl/util/premultiply.hpp>

#include <png.h>

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-variable"
// Check png library version.
const static bool png_version_check = []() {
    const png_uint_32 version = png_access_version_number();
    if (version != PNG_LIBPNG_VER) {
        throw std::runtime_error(mbgl::util::sprintf<96>(
            "libpng version mismatch: headers report %d.%d.%d, but library reports %d.%d.%d",
            PNG_LIBPNG_VER / 10000, (PNG_LIBPNG_VER / 100) % 100, PNG_LIBPNG_VER % 100,
            version / 10000, (version / 100) % 100, version % 100));
    }
    return true;
}();
#pragma GCC diagnostic pop
namespace mbgl {

std::string encodePNG(const PremultipliedImage& pre) {
    PremultipliedImage copy { pre.width, pre.height };
    std::copy(pre.data.get(), pre.data.get() + pre.size(), copy.data.get());

    UnassociatedImage src = util::unpremultiply(std::move(copy));

    png_voidp error_ptr = 0;
    png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, error_ptr, NULL, NULL);
    if (!png_ptr) {
        throw std::runtime_error("couldn't create png_ptr");
    }

    png_infop info_ptr = png_create_info_struct(png_ptr);
    if (!png_ptr) {
        png_destroy_write_struct(&png_ptr, (png_infopp)0);
        throw std::runtime_error("couldn't create info_ptr");
    }

    png_set_IHDR(png_ptr, info_ptr, src.width, src.height, 8, PNG_COLOR_TYPE_RGB_ALPHA, PNG_INTERLACE_NONE,
                 PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);

    jmp_buf *jmp_context = (jmp_buf *)png_get_error_ptr(png_ptr);
    if (jmp_context) {
        png_destroy_write_struct(&png_ptr, &info_ptr);
        throw std::runtime_error("png error");
    }

    std::string result;
    png_set_write_fn(png_ptr, &result, [](png_structp png_ptr_, png_bytep data, png_size_t length) {
        std::string *out = static_cast<std::string *>(png_get_io_ptr(png_ptr_));
        out->append(reinterpret_cast<char *>(data), length);
    }, NULL);

    struct ptrs {
        ptrs(size_t count) : rows(new png_bytep[count]) {}
        ~ptrs() { delete[] rows; }
        png_bytep *rows = nullptr;
    } pointers(src.height);

    for (size_t i = 0; i < src.height; i++) {
        pointers.rows[i] = src.data.get() + src.stride() * i;
    }

    png_set_rows(png_ptr, info_ptr, pointers.rows);
    png_write_png(png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, NULL);
    png_destroy_write_struct(&png_ptr, &info_ptr);

    return result;
}

PremultipliedImage decodePNG(const uint8_t*, size_t);
PremultipliedImage decodeJPEG(const uint8_t*, size_t);

PremultipliedImage decodeImage(const std::string& string) {
    const uint8_t* data = reinterpret_cast<const uint8_t*>(string.data());
    const size_t size = string.size();

    if (size >= 4) {
        unsigned int magic = (data[0] << 24) | (data[1] << 16) | (data[2] << 8) | data[3];
        if (magic == 0x89504E47U) {
            return decodePNG(data, size);
        }
    }

    if (size >= 2) {
        unsigned int magic = ((data[0] << 8) | data[1]) & 0xffff;
        if (magic == 0xffd8) {
            return decodeJPEG(data, size);
        }
    }

    throw std::runtime_error("unsupported image type");
}

}