/*
 * slice.c - Generate slices
 *
 * Written 2015 by Werner Almesberger
 * Copyright 2015 by 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 <stdbool.h>
#include <math.h>
#include <glib.h>

#include "util.h"
#include "stl.h"
#include "slice.h"


struct line {
	float ax, ay;
	float bx, by;
	float cz;
	struct line *next;
};


struct z {
	float z;
	bool present;
	struct line *lines;
};


static GTree *tree;


static inline bool eq(float a, float b)
{
	return fabsf(a - b) < 1e-6;
}


static struct z *get_z(float z)
{
	struct z *base;

	base = g_tree_lookup(tree, &z);
	if (base)
		return base;
	base = alloc_type(struct z);
	base->z = z;
	base->present = 0;
	base->lines = NULL;
	g_tree_insert(tree, &base->z, base);
	return base;
}


static void mark_z(float z)
{
	struct z *base;

	base = get_z(z);
	base->present = 1;
}


static void add(const struct v *a, const struct v *b, const struct v *c)
{
	float cross;
	struct z *z;
	struct line *line;

	if (eq(a->x, b->x) && eq(a->y, b->y)) {
fprintf(stderr, "zero point\n");
		return;
	}

	if (c->z < a->z)
		return;

	cross = (b->x - a->x) * (c->y - a->y) - (b->y - a->y) * (c->x - a->x);
	if (!eq(cross, 0)) {
		fprintf(stderr,
		    "inclined facet\n\t%f %f %f\n\t%f %f %f\n\t%f %f %f\n",
		    a->x, a->y, a->z, b->x, b->y, b->z, c->x, c->y, c->z);
		exit(1);
	}

	z = get_z(a->z);
	line = alloc_type(struct line);
	line->ax = a->x;
	line->ay = a->y;
	line->bx = b->x;
	line->by = b->y;
	line->cz = c->z;
	line->next = z->lines;
	z->lines = line;
}


void slice(struct v f[3])
{
	bool ab = eq(f[0].z, f[1].z);
	bool bc = eq(f[1].z, f[2].z);
	bool ac = eq(f[0].z, f[2].z);

	if (ab && bc)
		mark_z(f[0].z);
	else if (ab)
		add(f + 0, f + 1, f + 2);
	else if (bc)
		add(f + 1, f + 2, f + 0);
	else if (ac)
		add(f + 0, f + 2, f + 1);
}


/* ----- Dumping ----------------------------------------------------------- */


static gboolean dump_layer(gpointer key, gpointer value, gpointer data)
{
	const struct z *z0 = data;
	const struct z *z1 = value;
	const struct line *line;

	if (z0->z > z1->z)
		return 0;
	if (!z1->present)
		return 0;
	for (line = z0->lines; line; line = line->next)
		if (line->cz >= z1->z)
			printf("%f %f %f\n%f %f %f\n\n\n",
			    line->ax, line->ay, z1->z,
			    line->bx, line->by, z1->z);
	return 0;
}


static gboolean dump_range(gpointer key, gpointer value, gpointer data)
{
	const struct z *z = value;

	if (z->present)
		g_tree_foreach(tree, dump_layer, value);
	return 0;
}


void slice_dump(void)
{
	g_tree_foreach(tree, dump_range, NULL);
}


/* ----- Initialization ---------------------------------------------------- */


static gint comp(gconstpointer a, gconstpointer b)
{
	const float *za = a;
	const float *zb = b;

	return eq(*za, *zb) ? 0 : *za < *zb ? -1 : 1;

}


void slice_init(void)
{
	tree = g_tree_new(comp);
}