/*
 * 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 facet {
	struct v a, b, c;
	struct facet *next;
};


struct z {
	float z;
};


static GTree *tree;
static struct facet *facets = NULL;


/* ----- Bounding box ------------------------------------------------------ */


static bool first = 1;
static float min_x, max_x, min_y, max_y;


static void bbox(float x, float y)
{
	if (first) {
		min_x = max_x = x;
		min_y = max_y = y;
		first = 0;
	} else {
		if (x < min_x)
			min_x = x;
		if (y < min_y)
			min_y = y;
		if (x > max_x)
			max_x = x;
		if (y > max_y)
			max_y = y;
	}
}


/* ----- Data collection --------------------------------------------------- */


static inline bool eq(float a, float b)
{
	return fabsf(a - b) < 1e-5;
}


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

	e = g_tree_lookup(tree, &z);
	if (e)
		return;
	e = alloc_type(struct z);
	e->z = z;
	g_tree_insert(tree, &e->z, e);
}


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

	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);
	}

	bbox(a->x, a->y);
	bbox(b->x, b->y);
	bbox(c->x, c->y);

	f = alloc_type(struct facet);
	f->a = *a;
	f->b = *b;
	f->c = *c;
	f->next = facets;
	facets = f;
}


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

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


/* ----- Insert intermediate layers ---------------------------------------- */


struct ctx {
	float z_step;
	bool first;
	float z0;	/* only defined if !first */
	bool more;	/* returned due to having made changes */
};


static gboolean check_z(gpointer key, gpointer value, gpointer data)
{
	const struct z *z = value;
	struct ctx *ctx = data;
	float d;
	int n, i;

	if (ctx->first) {
		ctx->first = 0;
		ctx->z0 = z->z;
		return 0;
	}

	d = z->z - ctx->z0;
	if (d <= ctx->z_step) {
		ctx->z0 = z->z;
		return 0;
	}

	n = (d / ctx->z_step) + 1;
	for (i = 1; i < n; i++)
		mark_z(ctx->z0 + d / n * i);

	ctx->more = 1;
	return 1;
}


void slice_intermediate(float z_step)
{
	struct ctx ctx = {
		.z_step	= z_step,
	};

	do {
		ctx.first = 1;
		ctx.more = 0;
		g_tree_foreach(tree, check_z, &ctx);
	}
	while (ctx.more);
}


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


static bool cut(const struct v *a, const struct v *b, float z, struct v *res)
{
	float dx, dy, dz;
	float f;

	if (a->z > b->z)
		return cut(b, a, z, res);
	if (eq(a->z, b->z))
		return 0;
	if (a->z > z || b->z < z || eq(b->z, z))
		return 0;

	dx = b->x - a->x;
	dy = b->y - a->y;
	dz = b->z - a->z;

	f = (z - a->z) / dz;

	res->x = f * dx + a->x;
	res->y = f * dy + a->y;
	res->z = z;

	return 1;
}


static gboolean dump_layer(gpointer key, gpointer value, gpointer data)
{
	const struct z *z = value;
	const struct facet *f;
	struct v p1, p2;

	for (f = facets; f; f = f->next) {
		if (cut(&f->a, &f->b, z->z, &p1)) {
			if (!cut(&f->a, &f->c, z->z, &p2) &&
			    !cut(&f->b, &f->c, z->z, &p2))
				continue;
		} else if (!cut(&f->a, &f->c, z->z, &p1) ||
		    !cut(&f->b, &f->c, z->z, &p2)) {
			continue;
		}
		printf("%f %f %f\n%f %f %f\n\n\n",
		    p1.x, p1.y, z->z, p2.x, p2.y, z->z);

	}
	return 0;
}


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

	printf("%f %f %f\n%f %f %f\n%f %f %f\n%f %f %f\n%f %f %f\n\n\n",
	    min_x - box, min_y - box, z->z,
	    max_x + box, min_y - box, z->z,
	    max_x + box, max_y + box, z->z,
	    min_x - box, max_y + box, z->z,
	    min_x - box, min_y - box, z->z);
	
	return 0;
}


void slice_dump(float box)
{
	g_tree_foreach(tree, dump_layer, NULL);
	if (box && !first)
		g_tree_foreach(tree, dump_box, &box);
}


/* ----- 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);
}