/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */

#include "ImageLoaderPnm.hpp"

#include <sstream>
#include <fstream>

namespace OpenVulkano::Image
{
	std::unique_ptr<Image> ImageLoaderPnm::loadFromFile(const std::string& filePath)
	{
		std::ifstream file(filePath, std::ios::binary);
		if (!file.is_open())
		{
			throw std::runtime_error("Failed to open file: " + filePath);
		}

		std::vector<uint8_t> buffer((std::istreambuf_iterator<char>(file)), std::istreambuf_iterator<char>());
		return loadFromMemory(buffer);
	}

	std::unique_ptr<Image> ImageLoaderPnm::loadFromMemory(const std::vector<uint8_t>& buffer)
	{
		std::istringstream stream(std::string(buffer.begin(), buffer.end()));
		PnmHeader header = parseHeader(stream);

		std::unique_ptr<Image> result = std::make_unique<Image>();
		result->resolution.x = header.width;
		result->resolution.y = header.height;
		result->resolution.z = 1;

		if (header.magic == 1 || header.magic == 2 || header.magic == 3)
		{
			result->data = readTextData(stream, header);
		}
		else if (header.magic == 4 || header.magic == 5 || header.magic == 6)
		{
			result->data = readBinaryData(stream, header);
		}
		else
		{
			throw std::runtime_error("Unsupported format: P" + (header.magic + '0'));
		}

		if (header.magic == 1 || header.magic == 2 || header.magic == 4 || header.magic == 5)
		{
			result->dataFormat = DataFormat::Format::R8_UINT;
		}
		else
		{
			result->dataFormat = DataFormat::Format::R8G8B8_UINT;
		}

		return result;
	}

	Math::Vector2i ImageLoaderPnm::GetImageDimensions(const std::string& filename)
	{
		std::ifstream file(filename, std::ios::binary);
		if (!file.is_open())
		{
			throw std::runtime_error("Failed to open file: " + filename);
		}

		PnmHeader header = parseHeader(file);
		return Math::Vector2i(header.width, header.height);
	}

	PnmHeader ImageLoaderPnm::parseHeader(std::istream& stream)
	{
		PnmHeader header;

		char pMagic;
		stream >> pMagic;
		if (pMagic != 'P')
		{
			throw std::runtime_error("Unsupported magic");
		}

		stream >> header.magic;
		header.magic -= '0';
		if (header.magic != 1 && header.magic != 2 && header.magic != 3 && header.magic != 4 && header.magic != 5
		    && header.magic != 6)
		{
			throw std::runtime_error("Unsupported magic number: P" + (header.magic + '0'));
		}

		stream >> header.width >> header.height;
		if (header.magic != 1 && header.magic != 4)
		{
			stream >> header.maxVal;
		}

		stream.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
		return header;
	}

	Array<uint8_t> ImageLoaderPnm::readBinaryData(std::istream& stream, const PnmHeader& header)
	{
		size_t dataSize = header.width * header.height * ((header.magic == 6) ? 3 : 1);
		Array<uint8_t> data(dataSize);

		if (header.magic == 4)
		{
			size_t rowBytes = (header.width + 7) / 8;
			Array<uint8_t> rowBuffer(rowBytes);
			size_t index = 0;

			for (int y = 0; y < header.height; ++y)
			{
				stream.read(reinterpret_cast<char*>(rowBuffer.Data()), rowBytes);
				for (int x = 0; x < header.width; ++x)
				{
					size_t byteIndex = x / 8;
					size_t bitIndex = 7 - (x % 8);
					data[index++] = (rowBuffer[byteIndex] >> bitIndex) & 1 ? 255 : 0;
				}
			}
		}
		else
		{
			stream.read(reinterpret_cast<char*>(data.Data()), dataSize);
		}

		return data;
	}

	Array<uint8_t> ImageLoaderPnm::readTextData(std::istream& stream, const PnmHeader& header)
	{
		Array<uint8_t> data(header.width * header.height * ((header.magic == 3) ? 3 : 1));
		for (size_t i = 0; i < data.Size(); ++i)
		{
			int value;
			stream >> value;
			if (header.magic == 1 || header.magic == 4)
			{
				data[i] = static_cast<uint8_t>(value * 255);
			}
			else
			{
				data[i] = static_cast<uint8_t>((value * 255) / header.maxVal);
			}
		}
		return data;
	}
};