#include "lowlevelfile.hpp"

#include <stdexcept>
#include <sstream>
#include <cassert>

#if FILE_API == FILE_API_POSIX
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#endif

#if FILE_API == FILE_API_STDIO
/*
 *
 *	Implementation of LowLevelFile methods using c stdio
 *
 */

LowLevelFile::LowLevelFile ()
{
	mHandle = NULL;
}

LowLevelFile::~LowLevelFile ()
{
	if (mHandle != NULL)
		fclose (mHandle);
}

void LowLevelFile::open (char const * filename)
{
	assert (mHandle == NULL);

	mHandle = fopen (filename, "rb");

	if (mHandle == NULL)
	{
		std::ostringstream os;
		os << "Failed to open '" << filename << "' for reading.";
		throw std::runtime_error (os.str ());
	}
}

void LowLevelFile::close ()
{
	assert (mHandle != NULL);

	fclose (mHandle);

	mHandle = NULL;
}

size_t LowLevelFile::size ()
{
	assert (mHandle != NULL);

	long oldPosition = ftell (mHandle);

	if (oldPosition == -1)
		throw std::runtime_error ("A query operation on a file failed.");

	if (fseek (mHandle, 0, SEEK_END) != 0)
		throw std::runtime_error ("A query operation on a file failed.");

	long Size = ftell (mHandle);

	if (Size == -1)
		throw std::runtime_error ("A query operation on a file failed.");

	if (fseek (mHandle, oldPosition, SEEK_SET) != 0)
		throw std::runtime_error ("A query operation on a file failed.");

	return size_t (Size);
}

void LowLevelFile::seek (size_t Position)
{
	assert (mHandle != NULL);

	if (fseek (mHandle, Position, SEEK_SET) != 0)
		throw std::runtime_error ("A seek operation on a file failed.");
}

size_t LowLevelFile::tell ()
{
	assert (mHandle != NULL);

	long Position = ftell (mHandle);

	if (Position == -1)
		throw std::runtime_error ("A query operation on a file failed.");

	return size_t (Position);
}

size_t LowLevelFile::read (void * data, size_t size)
{
	assert (mHandle != NULL);

	int amount = fread (data, 1, size, mHandle);

	if (amount == 0 && ferror (mHandle))
		throw std::runtime_error ("A read operation on a file failed.");

	return amount;
}

#elif FILE_API == FILE_API_POSIX
/*
 *
 *	Implementation of LowLevelFile methods using posix IO calls
 *
 */

LowLevelFile::LowLevelFile ()
{
	mHandle = -1;
}

LowLevelFile::~LowLevelFile ()
{
	if (mHandle != -1)
		::close (mHandle);
}

void LowLevelFile::open (char const * filename)
{
	assert (mHandle == -1);

#ifdef O_BINARY
	static const int openFlags = O_RDONLY | O_BINARY;
#else
	static const int openFlags = O_RDONLY;
#endif

	mHandle = ::open (filename, openFlags, 0);

	if (mHandle == -1)
	{
		std::ostringstream os;
		os << "Failed to open '" << filename << "' for reading.";
		throw std::runtime_error (os.str ());
	}
}

void LowLevelFile::close ()
{
	assert (mHandle != -1);

	::close (mHandle);

	mHandle = -1;
}

size_t LowLevelFile::size ()
{
	assert (mHandle != -1);

	size_t oldPosition = ::lseek (mHandle, 0, SEEK_CUR);

	if (oldPosition == size_t (-1))
		throw std::runtime_error ("A query operation on a file failed.");

	size_t Size = ::lseek (mHandle, 0, SEEK_END);

	if (Size == size_t (-1))
		throw std::runtime_error ("A query operation on a file failed.");

	if (lseek (mHandle, oldPosition, SEEK_SET) == -1)
		throw std::runtime_error ("A query operation on a file failed.");

	return Size;
}

void LowLevelFile::seek (size_t Position)
{
	assert (mHandle != -1);

	if (::lseek (mHandle, Position, SEEK_SET) == -1)
		throw std::runtime_error ("A seek operation on a file failed.");
}

size_t LowLevelFile::tell ()
{
	assert (mHandle != -1);

	size_t Position = ::lseek (mHandle, 0, SEEK_CUR);

	if (Position == size_t (-1))
		throw std::runtime_error ("A query operation on a file failed.");

	return Position;
}

size_t LowLevelFile::read (void * data, size_t size)
{
	assert (mHandle != -1);

	int amount = ::read (mHandle, data, size);

	if (amount == -1)
		throw std::runtime_error ("A read operation on a file failed.");

	return amount;
}

#elif FILE_API == FILE_API_WIN32
/*
 *
 *	Implementation of LowLevelFile methods using Win32 API calls
 *
 */

LowLevelFile::LowLevelFile ()
{
	mHandle = INVALID_HANDLE_VALUE;
}

LowLevelFile::~LowLevelFile ()
{
	if (mHandle != INVALID_HANDLE_VALUE)
		CloseHandle (mHandle);
}

void LowLevelFile::open (char const * filename)
{
	assert (mHandle == INVALID_HANDLE_VALUE);

	HANDLE handle = CreateFileA (filename, GENERIC_READ, FILE_SHARE_READ, 0, OPEN_EXISTING, 0, 0);

	if (handle == NULL)
	{
		std::ostringstream os;
		os << "Failed to open '" << filename << "' for reading.";
		throw std::runtime_error (os.str ());
	}

	mHandle = handle;
}

void LowLevelFile::close ()
{
	assert (mHandle != INVALID_HANDLE_VALUE);

	CloseHandle (mHandle);

	mHandle = INVALID_HANDLE_VALUE;
}

size_t LowLevelFile::size ()
{
	assert (mHandle != INVALID_HANDLE_VALUE);

	BY_HANDLE_FILE_INFORMATION info;

	if (!GetFileInformationByHandle (mHandle, &info))
		throw std::runtime_error ("A query operation on a file failed.");

	if (info.nFileSizeHigh != 0)
		throw std::runtime_error ("Files greater that 4GB are not supported.");

	return info.nFileSizeLow;
}

void LowLevelFile::seek (size_t Position)
{
	assert (mHandle != INVALID_HANDLE_VALUE);

	if (SetFilePointer (mHandle, Position, NULL, SEEK_SET) == INVALID_SET_FILE_POINTER)
		if (GetLastError () != NO_ERROR)
			throw std::runtime_error ("A seek operation on a file failed.");
}

size_t LowLevelFile::tell ()
{
	assert (mHandle != INVALID_HANDLE_VALUE);

	DWORD value = SetFilePointer (mHandle, 0, NULL, SEEK_CUR);

	if (value == INVALID_SET_FILE_POINTER && GetLastError () != NO_ERROR)
		throw std::runtime_error ("A query operation on a file failed.");

	return value;
}

size_t LowLevelFile::read (void * data, size_t size)
{
	assert (mHandle != INVALID_HANDLE_VALUE);

	DWORD read;

	if (!ReadFile (mHandle, data, size, &read, NULL))
		throw std::runtime_error ("A read operation on a file failed.");

	return read;
}

#endif
