/*
 * overlap.c - Overlap two parallel faces
 *
 * Written 2010 by Werner Almesberger
 * Copyright 2010 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 <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <limits.h>
#include <gtk/gtk.h>

#include "face.h"
#include "solid.h"
#include "overlap.h"


#define	UNDEF_F	HUGE_VAL
#define BORDER 10	/* pixels around the minimum drawing area */


static int sx(const struct solid *s)
{
	return (s->a->sx > s->b->sx ? s->a->sx : s->b->sx)+2*BORDER;
}


static int sy(const struct solid *s)
{
	return (s->a->sy > s->b->sy ? s->a->sy : s->b->sy)+2*BORDER;
}


static double ramp(int z0, double w0, int z1, double w1)
{
	if (z0 != UNDEF && z1 != UNDEF)
		return w0 == 0 && w1 == 0 ? z0 : z0*w0+z1*w1;
	if (z0 == UNDEF && z0 == UNDEF)
		return UNDEF_F;
	if (z0 == UNDEF && w0 < w1)
		return z1;
	if (z1 == UNDEF && w0 > w1)
		return z0;
	return UNDEF_F;
}


static double zmix(struct face *f, double x, double y)
{
	int xa, xb, ya, yb;
	double zx0, zx1;

	xa = floor(x);
	xb = ceil(x);
	ya = floor(y);
	yb = ceil(y);

	zx0 = ramp(
	    get_bounded(f->a, xa, ya), yb-y,
	    get_bounded(f->a, xa, yb), y-ya);
	zx1 = ramp(
	    get_bounded(f->a, xb, ya), yb-y,
	    get_bounded(f->a, xb, yb), y-ya);

	return ramp(zx0, xb-x, zx1, x-xa);
}


static void point(const struct solid *s, int x, int y, guchar *p)
{
	double za, zb, z;
	int xa = x+s->a->a->min_x;
	int ya = y+s->a->a->min_y;
	int yb = sy(s)-1-y+s->a->a->min_y;

	za = zmix(s->a,
	    xa*s->a->m.a[0][0]+ya*s->a->m.a[0][1]+s->a->m.b[0],
	    xa*s->a->m.a[1][0]+ya*s->a->m.a[1][1]+s->a->m.b[1]);

	zb = zmix(s->b,
	    xa*s->b->m.a[0][0]+yb*s->b->m.a[0][1]+s->b->m.b[0],
	    xa*s->b->m.a[1][0]+yb*s->b->m.a[1][1]+s->b->m.b[1]);

	if (za == UNDEF_F && zb == UNDEF_F)
		return;

	if (za == UNDEF_F) {
		z = 128.0*(zb-s->b->a->min_z)/(s->b->a->max_z-s->b->a->min_z);
		if (z < 0)
			z = 0;
		if (z > 255)
			z = 255;
		p[0] = 255;
		p[1] = z;
		p[2] = z;
		return;
	}
	if (zb == UNDEF_F) {
		z = 128.0*(za-s->a->a->min_z)/(s->a->a->max_z-s->a->a->min_z);
		if (z < 0)
			z = 0;
		if (z > 255)
			z = 255;
		p[0] = z;
		p[1] = 255;
		p[2] = z;
		return;
	}

	z = za;
	za -= face_z0(s->a, xa, ya);
	zb -= face_z0(s->b, xa, yb);

	if (za+zb < -s->dist) {
		p[0] = 0;
		p[1] = 0;
		p[2] = 255;
		return;
	}

	z = 256.0*(z-s->a->a->min_z)/(s->a->a->max_z-s->a->a->min_z);
	if (z < 0)
		z = 0;
	if (z > 255)
		z = 255;
	p[0] = z;
	p[1] = z;
	p[2] = z;
}


static void draw_image(GtkWidget *widget, struct solid *s)
{
	guchar *rgbbuf, *p;
	int x, y;

	rgbbuf = p = calloc(sx(s)*sy(s), 3);
	if (!rgbbuf) {
		perror("calloc");
		exit(1);
	}
	for (y = sy(s)-1; y >= 0; y--)
		for (x = 0; x != sx(s) ; x++) {
			point(s, x, y, p);
			p += 3;
		}
	gdk_draw_rgb_image(widget->window,
	    widget->style->fg_gc[GTK_STATE_NORMAL],
	    0, 0, sx(s), sy(s), GDK_RGB_DITHER_MAX, rgbbuf, sx(s)*3);
	free(rgbbuf);
}


/*
 * Rotate such that a point at distance "r" moves one unit. Rotate
 * counter-clockwise for r > 1, clockwise for r < 0.
 */

static void rotate(struct matrix *m, double r)
{
	struct matrix t;
	double s, c;

	s = 1/r;
	c = sqrt(1-s*s);
	t.a[0][0] = m->a[0][0]*c-m->a[1][0]*s;
	t.a[0][1] = m->a[0][1]*c-m->a[1][1]*s;
	t.a[1][0] = m->a[1][0]*c+m->a[0][0]*s;
	t.a[1][1] = m->a[1][1]*c+m->a[0][1]*s;
	t.b[0] = m->b[0]*c-m->b[1]*s;
	t.b[1] = m->b[0]*s+m->b[1]*c;
	*m = t;
}


static void do_shift(struct matrix *m, int dx, int dy)
{
	m->b[0] -= dx;
	m->b[1] += dy;
}


static void shift(struct matrix *m, int dx, int dy, int dir)
{
	if (dx > 0 && dy < dx && dy > -dx)
		do_shift(m, dir, 0);
	if (dx < 0 && dy < -dx && dy > dx)
		do_shift(m, -dir, 0);
	if (dy > 0 && dx < dy && dx > -dy)
		do_shift(m, 0, dir);
	if (dy < 0 && dx < -dy && dx > dy)
		do_shift(m, 0, -dir);
}


static gboolean scroll_event(GtkWidget *widget, GdkEventScroll *event,
    gpointer data)
{
	GtkWidget *darea = gtk_bin_get_child(GTK_BIN(widget));
	struct solid *s = data;
	int dx = event->x-sx(s)/2;
	int dy = event->y-sy(s)/2;
	double r = hypot(dx, dy);
	int center = r/hypot(sx(s), sy(s)) < 0.25;

	if (r < 1)
		return TRUE;
	switch (event->direction) {
	case GDK_SCROLL_UP:
		if (center)
			shift(&s->a->m, dx, dy, 1);
		else
			rotate(&s->a->m, r);
		draw_image(darea, s);
		break;
	case GDK_SCROLL_DOWN:
		if (center)
			shift(&s->a->m, dx, dy, -1);
		else
			rotate(&s->a->m, -r);
		draw_image(darea, s);
		break;
	default:
		/* ignore */;
	}
	return TRUE;
}


static gboolean expose_event(GtkWidget *widget, GdkEventExpose *event,
    gpointer user_data)
{
	draw_image(widget, user_data);
	return TRUE;
}



void overlap(GtkWidget *canvas, struct solid *s)
{
	GtkWidget *evbox, *darea;

	evbox = gtk_event_box_new();
	darea = gtk_drawing_area_new();
	gtk_widget_set_size_request(darea, sx(s), sy(s));
	gtk_container_add(GTK_CONTAINER(canvas), evbox);
	gtk_container_add(GTK_CONTAINER(evbox), darea);

	draw_image(darea, s);

	g_signal_connect(G_OBJECT(evbox), "scroll-event",
	    G_CALLBACK(scroll_event), s);
	g_signal_connect(G_OBJECT(darea), "expose-event",
	    G_CALLBACK(expose_event), s);
}