/* -*- mode: c; tab-width: 4; indent-tabs-mode: t; c-basic-offset: 4 -*-
 *
 * $Id$
 *
 * Copyright (c) 2009-2014, Erik Lindahl & David van der Spoel
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <stdlib.h>
#include "xdrfile.h"
#include "xdrfile_xtc.h"

#define MAGIC 1995

enum
{
	FALSE,
	TRUE
};

static int xtc_header(XDRFILE *xd, int *natoms, int *step, float *time, mybool bRead)
{
	int result, magic, n = 1;

	/* Note: read is same as write. He he he */
	magic = MAGIC;
	if ((result = xdrfile_write_int(&magic, n, xd)) != n)
	{
		if (bRead)
			return exdrENDOFFILE;
		else
			return exdrINT;
	}
	if (magic != MAGIC)
		return exdrMAGIC;
	if ((result = xdrfile_write_int(natoms, n, xd)) != n)
		return exdrINT;
	if ((result = xdrfile_write_int(step, n, xd)) != n)
		return exdrINT;
	if ((result = xdrfile_write_float(time, n, xd)) != n)
		return exdrFLOAT;

	return exdrOK;
}

static int xtc_coord(XDRFILE *xd, int *natoms, matrix box, rvec *x, float *prec,
					 mybool bRead)
{
	int result;

	/* box */
	result = xdrfile_read_float(box[0], DIM * DIM, xd);
	if (DIM * DIM != result)
		return exdrFLOAT;
	else
	{
		if (bRead)
		{
			result = xdrfile_decompress_coord_float(x[0], natoms, prec, xd);
			if (result != *natoms)
				return exdr3DX;
		}
		else
		{
			result = xdrfile_compress_coord_float(x[0], *natoms, *prec, xd);
			if (result != *natoms)
				return exdr3DX;
		}
	}
	return exdrOK;
}

int read_xtc_natoms(const char *fn, int *natoms)
{
	XDRFILE *xd;
	int step, result;
	float time;

	xd = xdrfile_open(fn, "r");
	if (NULL == xd)
		return exdrFILENOTFOUND;
	result = xtc_header(xd, natoms, &step, &time, TRUE);
	xdrfile_close(xd);

	return result;
}

int read_xtc(XDRFILE *xd,
			 int natoms, int *step, float *time,
			 matrix box, rvec *x, float *prec)
/* Read subsequent frames */
{
	int result;

	if ((result = xtc_header(xd, &natoms, step, time, TRUE)) != exdrOK)
		return result;

	if ((result = xtc_coord(xd, &natoms, box, x, prec, 1)) != exdrOK)
		return result;

	return exdrOK;
}

int write_xtc(XDRFILE *xd,
			  int natoms, int step, float time,
			  matrix box, rvec *x, float prec)
/* Write a frame to xtc file */
{
	int result;

	if ((result = xtc_header(xd, &natoms, &step, &time, FALSE)) != exdrOK)
		return result;

	if ((result = xtc_coord(xd, &natoms, box, x, &prec, 0)) != exdrOK)
		return result;

	return exdrOK;
}