#include "PersistenceWriter.h"

#include <windows.h>

#include <filesystem>
#include <fstream>

bool PersistenceWriter::WriteSnapshot(const PersistenceSnapshot& snapshot, std::string& error) const
{
	if (snapshot.targetPath.empty())
	{
		error = "Persistence snapshot target path is empty.";
		return false;
	}

	std::error_code fsError;
	std::filesystem::create_directories(snapshot.targetPath.parent_path(), fsError);

	const std::filesystem::path temporaryPath = snapshot.targetPath.string() + ".tmp";
	std::ofstream output(temporaryPath, std::ios::binary | std::ios::trunc);
	if (!output)
	{
		error = "Could not write file: " + temporaryPath.string();
		return false;
	}

	output << snapshot.contents;
	output.close();
	if (!output.good())
	{
		error = "Could not finish writing file: " + temporaryPath.string();
		return false;
	}

	if (!MoveFileExA(temporaryPath.string().c_str(), snapshot.targetPath.string().c_str(), MOVEFILE_REPLACE_EXISTING | MOVEFILE_WRITE_THROUGH))
	{
		const DWORD lastError = GetLastError();
		std::filesystem::remove(temporaryPath, fsError);
		error = "Could not replace file: " + snapshot.targetPath.string() + " (Win32 error " + std::to_string(lastError) + ")";
		return false;
	}

	return true;
}