/* DEC	**DepreciateDecliningTable(depr, remval, book, salv,dbf,life,partial);
 *
 * ARGUMENT
 *	DEC	**depr,	**remval, *book, *salv,	*dbf, *partial;
 *	int	life;
 *
 * DESCRIPTION
 *	Calculate several years' depreciation and remaining depreciable
 *   value according to	declining balance depreciation.
 *   With a declining balance factor of	dbf, the item has book value
 *   book, salvage value salv, and lifetime life (which	may include a partial
 *   period).  At year#	i, the depreciation and	remaining value	are
 *   computed and stored in depr[i] and	remval[i].  The	first year is always
 *   the partial year.	The results are	calculated for the entire lifetime.
 *
 * SIDE	EFFECTS
 *	depr and remval	are changed.
 *
 * RETURNS
 *	depr if	successful, otherwise GM_NULLARR.
 *
 * POSSIBLE ERRORS
 *	GM_NULLPOINTER
 *	GM_ARGVAL
 *
 * AUTHOR
 *  Jared Levy
 *   Copyright (C) 1988-1990 Greenleaf Software	Inc.  All rights reserved.
 *
 * MODIFICATIONS
 *
 *
 */

#include <stdio.h>
#include "gm.h"
#include "gmsystem.h"

DEC	**DepreciateDecliningTable(depr, remval, book, salv,dbf,life, partial)
DEC	**depr,	**remval, *book, *salv,	*dbf, *partial;
int	life;
{
	int	i, plife;
	DEC	drbv, *rbv=&drbv, dfol,	*fol=&dfol;
	DEC	dtemp, *temp=&dtemp, dnsalv, *nsalv=&dnsalv;

	_MacStart(GM_DPDBTBL);

	if (!depr||!remval||!book||!salv||!partial||!dbf)  {
		_MacErr(GM_NULLPOINTER);
		_MacRet(GM_NULLARR);
	}
	if (_MacBad(salv)||_MacBad(partial)||_MacBad(dbf))  {
		_MacErr(GM_INIT);
		_MacRet(GM_NULLARR);
	}

	plife=life+(_MacIsDecZ(partial)?0:1);

	for (i=0;i<=plife;i++)
		if(!depr[i]||!remval[i])  {
			_MacErr(GM_NULLPOINTER);
			_MacRet(GM_NULLARR);
		}

/* check life>=1, 0<=partial<=1	*/
	if (life<1||_MacIsDecN(partial)||CompareDecimal(partial,&decOne)==1
		||_MacIsDecN(dbf)
		||_MacIsDecN(book)||_MacIsDecN(salv))  {
		_MacErr(GM_ARGVAL);
		_MacRet(GM_NULLARR);
	}

	(void) _ScaleDec80Bit(rbv, book, 2);
	(void) _ScaleDec80Bit(nsalv, salv, 2);
	(void) _SubDec80Bit(remval[0],rbv,nsalv);

	_MacDZero(depr[0]);

	(void) ConvLongToDecimal(temp, (long) life * 100L);
	(void) _DivDec80Bit(fol, dbf, temp);

/* handle partial first	year */
	if (_MacIsDecZ(partial))  {
		i=0;
	}
	else  {
		(void) _MulDec80Bit(temp,rbv,fol);
		(void) _MulDec80Bit(depr[1], temp, partial);
		(void) _ScaleDec80Bit(depr[1],depr[1],2);
		(void) _SubDec80Bit(remval[1], remval[0], depr[1]);
/* remaining value can't be negative */
		if (_MacIsDecN(remval[1]))  {
			(void) _AddDec80Bit(depr[1], depr[1], remval[1]);
			_MacDZero(remval[1]);
		}
		(void) _SubDec80Bit(rbv,rbv,depr[1]);
		i=1;
	}

/* handle remaining years */

	while (i<plife)	 {
		i++;
		(void) _MulDec80Bit(depr[i], rbv, fol);
		(void) _ScaleDec80Bit(depr[i],depr[i],2);
		(void) _SubDec80Bit(remval[i], remval[i-1], depr[i]);
/* remaining value can't be negative */
		if (_MacIsDecN(remval[i]))  {
			(void) _AddDec80Bit(depr[i], depr[i], remval[i]);
			_MacDZero(remval[i]);
		}
		(void) _SubDec80Bit(rbv,rbv,depr[i]);
	}

/* remaining depreciable value after last year should be 0 */
	if (!_MacIsDecZ(remval[plife]))	 {
		(void) _AddDec80Bit(depr[plife],depr[plife],remval[plife]);
		_MacDZero(remval[plife]);
	}

	_MacRet(depr);
}