/*
 * shape.c - Toolpaths for basic shapes
 *
 * Written 2010-2011 by Werner Almesberger
 * Copyright 2010-2011 Werner Almesberger
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */


#include <math.h>

#include "path.h"
#include "shape.h"


static double arc2angle(double arc, double r)
{
	return acos(1-arc*arc/(r*r)/2);
}


static void half_circle(struct path *path,
    double cx, double cy, double rx, double ry, double z, double s)
{
	double m[4];
	double x = rx, y = ry, tmp;
	double a;

	m[0] = cos(s);
	m[1] = -sin(s);
	m[2] = -m[1];
	m[3] = m[0];

	for (a = 0; a < M_PI; a += s) {
		path_add(path, cx+x, cy+y, z);
		tmp = x*m[0]+y*m[1];
		y = x*m[2]+y*m[3];
		x = tmp;
	}
	path_add(path, cx-rx, cy-ry, z);
}


struct path *slot(double xa, double ya, double xb, double yb, double z,
    double sr, double tr, double step, const char *id)
{
	struct path *path;
	double dx = xb-xa;
	double dy = yb-ya;
	double s = arc2angle(step, sr);
	double nx, ny;
	double f;

	path = path_new(tr, id);
	if (sr <= tr) {
		path_add(path, xa, ya, z);
		path_add(path, xb, yb, z);
	} else {
		f = (sr-tr)/hypot(dx, dy);
		nx = -dy*f;
		ny = dx*f;

		half_circle(path, xa, ya, nx, ny, z, s);
		half_circle(path, xb, yb, -nx, -ny, z, s);
		path_add(path, xa+nx, ya+ny, z);
	}
	return path;
}


struct path *circle(double cx, double cy, double cz, double cr, double tr,
    double step, const char *id)
{
	struct path *path;
	double s = arc2angle(step, cr);
	double a;

	path = path_new(tr, id);
	if (cr <= tr) {
		path_add(path, cx, cy, cz);
	} else {
		for (a = 0; a < 2*M_PI; a += s)
			path_add(path,
			    cx+(cr-tr)*cos(a), cy+(cr-tr)*sin(a), cz);
		path_add(path, cx+(cr-tr), cy, cz);
	}
	return path;
}