/*
 * stl.c - Genererate STL slice from polygon set
 *
 * Written 2013 by Werner Almesberger
 * Copyright 2013 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 <stdlib.h>
#include <stdio.h>
#include <math.h>

#include "poly2d.h"

#include "path.h"
#include "stl.h"


static void facet(FILE *file, const struct f2d *f, int a, int b, int c,
    double za, double zb, double zc,  double nx, double ny, double nz)
{
	double d;

	d = sqrt(nx*nx+ny*ny+nz*nz);
	if (!d)
		d = 1;

	fprintf(file, "facet normal %e %e %e\n", nx/d, ny/d, nz/d);
	fprintf(file, "\touter loop\n");
	fprintf(file, "\t\tvertex %e %e %e\n", f->x[a], f->y[a], za);
	fprintf(file, "\t\tvertex %e %e %e\n", f->x[b], f->y[b], zb);
	fprintf(file, "\t\tvertex %e %e %e\n", f->x[c], f->y[c], zc);
	fprintf(file, "\tendloop\n");
	fprintf(file, "endfacet\n");
}


static void surface(FILE *file, const struct f2d *f)
{
	facet(file, f, 0, 1, 2, 1, 1, 1, 0, 0, 1);
	facet(file, f, 2, 1, 0, 0, 0, 0, 0, 0, -1);
}


static void side(FILE *file, const struct f2d *f, int a, int b)
{
	double nx, ny;

	nx = f->y[b]-f->y[a];
	ny = f->x[a]-f->x[b];
	facet(file, f, a, b, b, 0, 0, 1, nx, ny, 0);
	facet(file, f, b, a, a, 1, 1, 0, nx, ny, 0);
}


static void stl_write(FILE *file, const struct path *paths)
{
	struct p2d *polys;
	struct f2d *faces;
	const struct f2d *f;
	int i;

	fprintf(file, "solid cameo\n");
	polys = paths_to_polys(paths);
	faces = f2d_tri(polys);
	for (f = faces; f; f = f->next) {
		surface(file, f);
		for (i = 0; i != 3; i++)
			if (f->side[i])
				side(file, f, i, (i+1) % 3);
	}
	p2d_free_all(polys);
	f2d_free_all(faces);
	fprintf(file, "endsolid cameo\n");
}


void stl(const char *name, const struct path *paths)
{
	FILE *file = stdout;

	if (name) {
		file = fopen(name, "w");
		if (!file) {
			perror(name);
			exit(1);
		}
	}
	stl_write(file, paths);
	if (name && fclose(file)) {
		perror(name);
		exit(1);
	}
}