#include <psemek/gfx/pixmap.hpp>

#include <psemek/log/log.hpp>
#include <psemek/util/at_scope_exit.hpp>

#include <png.h>

namespace psemek::gfx
{

	template <typename Pixel>
	basic_pixmap<Pixel> read_png_impl(io::istream & is, png_byte expected_color_type)
	{
		png_error_ptr error = [](png_structp, png_const_charp str)
		{
			throw std::runtime_error(str);
		};

		png_error_ptr warn = [](png_structp, png_const_charp str)
		{
			log::warning() << str;
		};

		auto png = png_create_read_struct(PNG_LIBPNG_VER_STRING, nullptr, error, warn);
		if (!png) throw std::runtime_error("png_create_read_struct returned null");

		png_set_error_fn(png, nullptr, error, warn);

		png_infop info = nullptr;
		png_infop end_info = nullptr;

		[[maybe_unused]] auto png_dtor = util::at_scope_exit([&]{
			png_destroy_read_struct(&png, &info, &end_info);
		});

		info = png_create_info_struct(png);
		if (!info) throw std::runtime_error("png_create_info_struct returned null");

		end_info = png_create_info_struct(png);
		if (!end_info) throw std::runtime_error("png_create_info_struct returned null");

		png_rw_ptr read = [](png_structp png, png_bytep ptr, size_t count){
			reinterpret_cast<io::istream *>(png_get_io_ptr(png))->read(reinterpret_cast<char *>(ptr), count);
		};
		png_set_read_fn(png, &is, read);

		png_read_info(png, info);

		auto const width = png_get_image_width(png, info);
		auto const height = png_get_image_height(png, info);
		auto const color_type = png_get_color_type(png, info);
		auto const bit_depth = png_get_bit_depth(png, info);

		if (color_type != expected_color_type)
			throw std::runtime_error("PNG color type not supported");

		if (bit_depth == 16)
			png_set_strip_16(png);

		if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
			png_set_expand_gray_1_2_4_to_8(png);

		png_read_update_info(png, info);

		basic_pixmap<Pixel> result({width, height});

		auto const row_bytes = png_get_rowbytes(png, info);
		if (row_bytes != width * sizeof(Pixel))
			throw std::runtime_error("PNG row bytes mismatch");

		for (std::uint32_t i = 0; i < height; ++i)
			png_read_row(png, reinterpret_cast<png_bytep>(result.data() + i * width), nullptr);

		return result;
	}

	pixmap_rgba read_png(io::istream && is)
	{
		return read_png_impl<color_rgba>(is, PNG_COLOR_TYPE_RGBA);
	}

	pixmap_monochrome read_png_monochrome(io::istream && is)
	{
		return read_png_impl<std::uint8_t>(is, PNG_COLOR_TYPE_GRAY);
	}

}