#include <SDL.h>
#include <SDL_image.h>
#include <algorithm>
#include <cerrno>
#include <cctype>
#include <climits>
#include <cstdint>
#include <cstdlib>
#include <iostream>
#include <string>
#include <vector>
#include "Image.h"
#include "SpriteAssetLoader.h"

#if defined(_WIN32)
#define WIN32_LEAN_AND_MEAN
#define NOMINMAX
#include <windows.h>
#else
#include <dirent.h>
#include <sys/stat.h>
#include <sys/types.h>
#endif

namespace
{
	enum class TransformMode
	{
		None,
		Resize,
		Fit,
		Tom800x480Preset
	};

	struct TransformOptions
	{
		TransformMode mode;
		int32_t width;
		int32_t height;

		TransformOptions() : mode(TransformMode::None), width(0), height(0) {}
	};

	static bool IsPathSeparator(char value)
	{
		return value == '/' || value == '\\';
	}

	static std::string ToLower(std::string text)
	{
		std::transform(text.begin(), text.end(), text.begin(), [](char value) {
			return static_cast<char>(std::tolower(static_cast<unsigned char>(value)));
		});
		return text;
	}

	static std::string JoinPath(const std::string& directory, const std::string& fileName)
	{
		if (directory.empty())
		{
			return fileName;
		}

		if (IsPathSeparator(directory[directory.size() - 1]))
		{
			return directory + fileName;
		}

		return directory + "/" + fileName;
	}

	static std::string GetFileName(const std::string& path)
	{
		const size_t slash = path.find_last_of("/\\");
		if (slash == std::string::npos)
		{
			return path;
		}

		return path.substr(slash + 1);
	}

	static std::string GetParentPath(const std::string& path)
	{
		const size_t slash = path.find_last_of("/\\");
		if (slash == std::string::npos)
		{
			return std::string();
		}
		if (slash == 0)
		{
			return path.substr(0, 1);
		}

		return path.substr(0, slash);
	}

	static std::string ChangeExtensionToSprite(const std::string& fileName)
	{
		const size_t slash = fileName.find_last_of("/\\");
		const size_t dot = fileName.find_last_of('.');
		if (dot != std::string::npos && (slash == std::string::npos || dot > slash))
		{
			return fileName.substr(0, dot) + Asset::SpriteAssetLoader::GetFileExtension();
		}

		return fileName + Asset::SpriteAssetLoader::GetFileExtension();
	}

	static bool HasPngExtension(const std::string& path)
	{
		const std::string lower = ToLower(path);
		return lower.size() >= 4 && lower.substr(lower.size() - 4) == ".png";
	}

	static bool ParsePositiveInt(const char* text, int32_t& value)
	{
		if (text == nullptr || text[0] == '\0')
		{
			return false;
		}

		errno = 0;
		char* end = nullptr;
		const long parsed = std::strtol(text, &end, 10);
		if (errno != 0 || end == text || *end != '\0' || parsed <= 0 || parsed > INT_MAX)
		{
			return false;
		}

		value = static_cast<int32_t>(parsed);
		return true;
	}

	static bool DirectoryExists(const std::string& path)
	{
#if defined(_WIN32)
		const DWORD attrs = GetFileAttributesA(path.c_str());
		return attrs != INVALID_FILE_ATTRIBUTES && (attrs & FILE_ATTRIBUTE_DIRECTORY) != 0;
#else
		struct stat info;
		return stat(path.c_str(), &info) == 0 && S_ISDIR(info.st_mode);
#endif
	}

	static bool CreateSingleDirectory(const std::string& path)
	{
		if (path.empty() || DirectoryExists(path))
		{
			return true;
		}

#if defined(_WIN32)
		if (CreateDirectoryA(path.c_str(), nullptr) != 0)
		{
			return true;
		}
		return GetLastError() == ERROR_ALREADY_EXISTS && DirectoryExists(path);
#else
		if (mkdir(path.c_str(), 0755) == 0)
		{
			return true;
		}
		return errno == EEXIST && DirectoryExists(path);
#endif
	}

	static bool EnsureDirectoryTree(const std::string& path)
	{
		if (path.empty())
		{
			return true;
		}

		std::string normalized = path;
		while (!normalized.empty() && IsPathSeparator(normalized[normalized.size() - 1]))
		{
			normalized.erase(normalized.size() - 1);
		}

		if (normalized.empty())
		{
			return true;
		}

		size_t start = 0;
		if (normalized.size() >= 2 && normalized[1] == ':')
		{
			start = 2;
		}
		if (start < normalized.size() && IsPathSeparator(normalized[start]))
		{
			++start;
		}

		for (size_t i = start; i <= normalized.size(); ++i)
		{
			if (i != normalized.size() && !IsPathSeparator(normalized[i]))
			{
				continue;
			}

			const std::string part = normalized.substr(0, i);
			if (part.empty() || (part.size() == 2 && part[1] == ':'))
			{
				continue;
			}

			if (!CreateSingleDirectory(part))
			{
				std::cerr << "Create directory failed: " << part << std::endl;
				return false;
			}
		}

		return DirectoryExists(normalized);
	}

	static bool EnsureParentDirectory(const std::string& path)
	{
		return EnsureDirectoryTree(GetParentPath(path));
	}

	static bool ListPngFiles(const std::string& directory, std::vector<std::string>& fileNames)
	{
		fileNames.clear();

#if defined(_WIN32)
		const std::string searchPath = JoinPath(directory, "*");
		WIN32_FIND_DATAA data;
		HANDLE handle = FindFirstFileA(searchPath.c_str(), &data);
		if (handle == INVALID_HANDLE_VALUE)
		{
			return false;
		}

		do
		{
			if ((data.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) == 0 &&
				HasPngExtension(data.cFileName))
			{
				fileNames.push_back(data.cFileName);
			}
		}
		while (FindNextFileA(handle, &data) != 0);

		FindClose(handle);
#else
		DIR* dir = opendir(directory.c_str());
		if (dir == nullptr)
		{
			return false;
		}

		dirent* entry = nullptr;
		while ((entry = readdir(dir)) != nullptr)
		{
			const std::string name = entry->d_name;
			if (name == "." || name == ".." || !HasPngExtension(name))
			{
				continue;
			}

			fileNames.push_back(name);
		}

		closedir(dir);
#endif

		std::sort(fileNames.begin(), fileNames.end(), [](const std::string& left, const std::string& right) {
			return ToLower(left) < ToLower(right);
		});
		return true;
	}
}

static bool LoadPngImage(const std::string& path, RenderData::Image& image)
{
	SDL_Surface* loadedSurface = IMG_Load(path.c_str());
	if (loadedSurface == nullptr)
	{
		std::cerr << "IMG_Load failed: " << path << " : " << IMG_GetError() << std::endl;
		return false;
	}

	SDL_Surface* rgbaSurface = SDL_ConvertSurfaceFormat(loadedSurface, SDL_PIXELFORMAT_RGBA8888, 0);
	SDL_FreeSurface(loadedSurface);
	if (rgbaSurface == nullptr)
	{
		std::cerr << "SDL_ConvertSurfaceFormat failed: " << SDL_GetError() << std::endl;
		return false;
	}

	std::vector<uint32_t> pixels(static_cast<size_t>(rgbaSurface->w) * rgbaSurface->h, 0);
	if (SDL_LockSurface(rgbaSurface) != 0)
	{
		std::cerr << "SDL_LockSurface failed: " << SDL_GetError() << std::endl;
		SDL_FreeSurface(rgbaSurface);
		return false;
	}

	for (int32_t y = 0; y < rgbaSurface->h; ++y)
	{
		const uint8_t* srcRow = static_cast<const uint8_t*>(rgbaSurface->pixels) + y * rgbaSurface->pitch;
		const uint32_t* srcPixels = reinterpret_cast<const uint32_t*>(srcRow);
		for (int32_t x = 0; x < rgbaSurface->w; ++x)
		{
			pixels[static_cast<size_t>(y) * rgbaSurface->w + x] = srcPixels[x];
		}
	}
	SDL_UnlockSurface(rgbaSurface);

	image = RenderData::Image(rgbaSurface->w, rgbaSurface->h, pixels);
	SDL_FreeSurface(rgbaSurface);
	return image.is_valid();
}

static RenderData::Image ResizeImageNearest(const RenderData::Image& source, int32_t width, int32_t height)
{
	if (!source.is_valid() || width <= 0 || height <= 0)
	{
		return RenderData::Image();
	}

	RenderData::Image result(width, height);
	for (int32_t y = 0; y < height; ++y)
	{
		const int32_t sourceY = y * source.get_height() / height;
		for (int32_t x = 0; x < width; ++x)
		{
			const int32_t sourceX = x * source.get_width() / width;
			result.set_pixel(x, y, source.get_pixel_fast(sourceX, sourceY));
		}
	}

	return result;
}

static RenderData::Image ResizeImageToFit(const RenderData::Image& source, int32_t maxWidth, int32_t maxHeight)
{
	if (!source.is_valid() || maxWidth <= 0 || maxHeight <= 0)
	{
		return RenderData::Image();
	}

	const float scaleX = static_cast<float>(maxWidth) / source.get_width();
	const float scaleY = static_cast<float>(maxHeight) / source.get_height();
	const float scale = std::min(scaleX, scaleY);

	const int32_t width = std::max(1, static_cast<int32_t>(source.get_width() * scale));
	const int32_t height = std::max(1, static_cast<int32_t>(source.get_height() * scale));
	return ResizeImageNearest(source, width, height);
}

static TransformOptions ResolveTransformForInput(
	const std::string& inputPath,
	const TransformOptions& requested)
{
	if (requested.mode != TransformMode::Tom800x480Preset)
	{
		return requested;
	}

	TransformOptions resolved;
	const std::string fileName = ToLower(GetFileName(inputPath));
	if (fileName == "background.png")
	{
		resolved.mode = TransformMode::Resize;
		resolved.width = 800;
		resolved.height = 480;
	}
	else if (fileName.find("tom-") == 0)
	{
		resolved.mode = TransformMode::Fit;
		resolved.width = 560;
		resolved.height = 360;
	}
	else if (fileName.find("ui-") == 0)
	{
		resolved.mode = TransformMode::Fit;
		resolved.width = 72;
		resolved.height = 72;
	}

	return resolved;
}

static bool ApplyTransform(const std::string& inputPath, const TransformOptions& options, RenderData::Image& image)
{
	const TransformOptions resolved = ResolveTransformForInput(inputPath, options);
	switch (resolved.mode)
	{
	case TransformMode::None:
		return image.is_valid();

	case TransformMode::Resize:
		image = ResizeImageNearest(image, resolved.width, resolved.height);
		return image.is_valid();

	case TransformMode::Fit:
		image = ResizeImageToFit(image, resolved.width, resolved.height);
		return image.is_valid();

	case TransformMode::Tom800x480Preset:
		return false;
	}

	return false;
}

static bool ConvertFile(
	const std::string& inputPath,
	const std::string& outputPath,
	const TransformOptions& transformOptions)
{
	RenderData::Image image;
	if (!LoadPngImage(inputPath, image))
	{
		return false;
	}

	if (!ApplyTransform(inputPath, transformOptions, image))
	{
		std::cerr << "Image transform failed: " << inputPath << std::endl;
		return false;
	}

	if (!EnsureParentDirectory(outputPath))
	{
		return false;
	}

	if (!Asset::SpriteAssetLoader::Save(outputPath, image))
	{
		std::cerr << "Save failed: " << outputPath << std::endl;
		return false;
	}

	std::cout << inputPath << " -> " << outputPath
		<< " (" << image.get_width() << "x" << image.get_height() << ")" << std::endl;
	return true;
}

static bool ConvertBatch(
	const std::string& inputDirectory,
	const std::string& outputDirectory,
	const TransformOptions& transformOptions)
{
	std::vector<std::string> files;
	if (!ListPngFiles(inputDirectory, files) || files.empty())
	{
		std::cerr << "No PNG files found: " << inputDirectory << std::endl;
		return false;
	}

	if (!EnsureDirectoryTree(outputDirectory))
	{
		return false;
	}

	size_t successCount = 0;
	for (size_t i = 0; i < files.size(); ++i)
	{
		const std::string inputPath = JoinPath(inputDirectory, files[i]);
		const std::string outputPath = JoinPath(outputDirectory, ChangeExtensionToSprite(files[i]));
		if (ConvertFile(inputPath, outputPath, transformOptions))
		{
			++successCount;
		}
	}

	std::cout << "Converted " << successCount << " / " << files.size() << " PNG files." << std::endl;
	return successCount == files.size();
}

static bool ParseTransformOptions(int argc, char* argv[], int startIndex, TransformOptions& options)
{
	if (startIndex >= argc)
	{
		options = TransformOptions();
		return true;
	}

	const std::string mode = argv[startIndex];
	if (mode == "--resize" || mode == "--fit")
	{
		if (startIndex + 2 >= argc)
		{
			return false;
		}

		int32_t width = 0;
		int32_t height = 0;
		if (!ParsePositiveInt(argv[startIndex + 1], width) ||
			!ParsePositiveInt(argv[startIndex + 2], height) ||
			startIndex + 3 != argc)
		{
			return false;
		}

		options.mode = mode == "--resize" ? TransformMode::Resize : TransformMode::Fit;
		options.width = width;
		options.height = height;
		return true;
	}

	if (mode == "--preset")
	{
		if (startIndex + 2 != argc)
		{
			return false;
		}

		const std::string presetName = argv[startIndex + 1];
		if (presetName != "tom-800x480")
		{
			std::cerr << "Unknown preset: " << presetName << std::endl;
			return false;
		}

		options.mode = TransformMode::Tom800x480Preset;
		return true;
	}

	return false;
}

static void PrintUsage()
{
	std::cout << "Usage:" << std::endl;
	std::cout << "  SpriteAssetTool input.png output.sprite [--resize width height]" << std::endl;
	std::cout << "  SpriteAssetTool input.png output.sprite [--fit maxWidth maxHeight]" << std::endl;
	std::cout << "  SpriteAssetTool --batch inputDir outputDir [--resize width height]" << std::endl;
	std::cout << "  SpriteAssetTool --batch inputDir outputDir [--fit maxWidth maxHeight]" << std::endl;
	std::cout << "  SpriteAssetTool --batch game/assets/raw game/assets/sprites --preset tom-800x480" << std::endl;
}

int main(int argc, char* argv[])
{
	if (argc < 3)
	{
		PrintUsage();
		return 1;
	}

	const int imageFlags = IMG_INIT_PNG;
	if ((IMG_Init(imageFlags) & imageFlags) != imageFlags)
	{
		std::cerr << "IMG_Init failed: " << IMG_GetError() << std::endl;
		return 1;
	}

	TransformOptions transformOptions;
	bool ok = false;
	const std::string command = argv[1];
	if (command == "--batch")
	{
		if (argc < 4 || !ParseTransformOptions(argc, argv, 4, transformOptions))
		{
			PrintUsage();
			IMG_Quit();
			return 1;
		}

		ok = ConvertBatch(argv[2], argv[3], transformOptions);
	}
	else
	{
		if (!ParseTransformOptions(argc, argv, 3, transformOptions))
		{
			PrintUsage();
			IMG_Quit();
			return 1;
		}

		ok = ConvertFile(argv[1], argv[2], transformOptions);
	}

	IMG_Quit();
	return ok ? 0 : 1;
}