/***************************************************************************
 kmath.c Copyright (C) 1999 Christoph Reichenbach


 This program may be modified and copied freely according to the terms of
 the GNU general public license (GPL), as long as the above copyright
 notice and the licensing information contained herein are preserved.

 Please refer to www.gnu.org for licensing details.

 This work is provided AS IS, without warranty of any kind, expressed or
 implied, including but not limited to the warranties of merchantibility,
 noninfringement, and fitness for a specific purpose. The author will not
 be held liable for any damage caused by this work or derivatives of it.

 By using this source code, you agree to the licensing terms as stated
 above.


 Please contact the maintainer for bug reports or inquiries.

 Current Maintainer:

    Christoph Reichenbach (CJR) [jameson@linuxgames.com]

***************************************************************************/

#include "sci/include/engine.h"


reg_t
kRandom(state_t *s, int funct_nr, int argc, reg_t *argv)
{
	return make_reg(0, 
			SKPV(0) + (int) ((SKPV(1) + 1.0 - SKPV(0)) * (rand() / (RAND_MAX + 1.0))));
}


reg_t
kAbs(state_t *s, int funct_nr, int argc, reg_t *argv)
{
	/* This is a hack, but so is the code in Hoyle1 that needs it. */
	if (argv[0].segment)
		return make_reg(0, 0x3e8); /* Yes people, this is an object */
	return make_reg(0, abs(SKPV(0)));
}


reg_t
kSqrt(state_t *s, int funct_nr, int argc, reg_t *argv)
{
	return make_reg(0, (gint16) sqrt((float) abs(SKPV(0))));
}


int
get_angle(int xrel, int yrel)
{
	if ((xrel == 0) && (yrel == 0))
		return 0;
	else {
		int val = (int) (180.0/PI * atan2(xrel, -yrel));
		if (val < 0)
			val += 360;

		/* Take care of OB1 differences between SSCI and
		FSCI. SCI games sometimes check for equality with
		"round" angles */
		if (val % 45 == 44)
			val++; 
		else if (val % 45 == 1)
			val--;

		return val;
	}
}

reg_t
kGetAngle(state_t *s, int funct_nr, int argc, reg_t *argv)
{
	/* Based on behavior observed with a test program created with
	** SCI Studio.
	*/
	int x1 = SKPV(0);
	int y1 = SKPV(1);
	int x2 = SKPV(2);
	int y2 = SKPV(3);
	int xrel = x2 - x1;
	int yrel = y1 - y2; /* y-axis is mirrored. */
	int angle;

	/* Move (xrel, yrel) to first quadrant. */ 
	if (y1 < y2)
		yrel = -yrel;
	if (x2 < x1)
		xrel = -xrel;

	/* Compute angle in grads. */
	if (yrel == 0 && xrel == 0)
		angle = 0;
	else
		angle = 100 * xrel / (xrel + yrel);

	/* Fix up angle for actual quadrant of (xrel, yrel). */
	if (y1 < y2)
		angle = 200 - angle;
	if (x2 < x1)
		angle = 400 - angle;

	/* Convert from grads to degrees by merging grad 0 with grad 1,
	** grad 10 with grad 11, grad 20 with grad 21, etc. This leads to
	** "degrees" that equal either one or two grads.
	*/
	angle -= (angle + 9) / 10;

	return make_reg(0, angle);
}


reg_t
kGetDistance(state_t *s, int funct_nr, int argc, reg_t *argv)
{
	int xrel = (int) (((float) SKPV(1) - SKPV_OR_ALT(3, 0))/cos(SKPV_OR_ALT(5, 0)* PI / 180.0)); /* This works because cos(0)==1 */
	int yrel = SKPV(0) - SKPV_OR_ALT(2, 0); 

	return make_reg(0, (gint16)sqrt((float) xrel*xrel + yrel*yrel));
}

reg_t
kTimesSin(state_t *s, int funct_nr, int argc, reg_t *argv)
{
	int angle = SKPV(0);
	int factor = SKPV(1);

	return make_reg(0, (int) (factor * 1.0 * sin(angle * PI / 180.0)));
}


reg_t
kTimesCos(state_t *s, int funct_nr, int argc, reg_t *argv)
{
	int angle = SKPV(0);
	int factor = SKPV(1);

	return make_reg(0, (int) (factor * 1.0 * cos(angle * PI / 180.0)));
}

reg_t
kCosDiv(state_t *s, int funct_nr, int argc, reg_t *argv)
{
	int angle = SKPV(0);
	int value = SKPV(1);
	double cosval = cos(angle * PI / 180.0);

	if ((cosval < 0.0001) && (cosval > 0.0001)) {
		SCIkwarn(SCIkWARNING,"Attepted division by zero\n");
		return make_reg(0, (gint16)0x8000);
	} else
		return make_reg(0, (gint16) (value/cosval));
}

reg_t
kSinDiv(state_t *s, int funct_nr, int argc, reg_t *argv)
{
	int angle = SKPV(0);
	int value = SKPV(1);
	double sinval = sin(angle * PI / 180.0);

	if ((sinval < 0.0001) && (sinval > 0.0001)) {
		SCIkwarn(SCIkWARNING,"Attepted division by zero\n");
		return make_reg(0, (gint16)0x8000);
	} else
		return make_reg(0, (gint16) (value/sinval));
}

reg_t
kTimesTan(state_t *s, int funct_nr, int argc, reg_t *argv)
{
	int param = SKPV(0);
	int scale = SKPV_OR_ALT(1, 1);

	param -= 90;
	if ((param % 90) == 0) {
		SCIkwarn(SCIkWARNING, "Attempted tan(pi/2)");
		return make_reg(0, (gint16)0x8000);
	} else
		return make_reg(0, (gint16) -(tan(param * PI / 180.0) * scale));
}

reg_t
kTimesCot(state_t *s, int funct_nr, int argc, reg_t *argv)
{
	int param = SKPV(0);
	int scale = SKPV_OR_ALT(1, 1);

	if ((param % 90) == 0) {
		SCIkwarn(SCIkWARNING, "Attempted tan(pi/2)");
		return make_reg(0, (gint16)0x8000);
	} else
		return make_reg(0, (gint16) (tan(param * PI / 180.0) * scale));
}