/*
 * Copyright © 2004 David Reveman, Peter Nilsson
 *
 * Permission to use, copy, modify, distribute, and sell this software
 * and its documentation for any purpose is hereby granted without
 * fee, provided that the above copyright notice appear in all copies
 * and that both that copyright notice and this permission notice
 * appear in supporting documentation, and that the names of
 * David Reveman and Peter Nilsson not be used in advertising or
 * publicity pertaining to distribution of the software without
 * specific, written prior permission. David Reveman and Peter Nilsson
 * makes no representations about the suitability of this software for
 * any purpose. It is provided "as is" without express or implied warranty.
 *
 * DAVID REVEMAN AND PETER NILSSON DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL DAVID REVEMAN AND
 * PETER NILSSON BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA
 * OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
 * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 *
 * Authors: David Reveman <c99drn@cs.umu.se>
 *          Peter Nilsson <c99pnn@cs.umu.se>
 */

#include <stdio.h>
#include <stdlib.h>
#include <cairo.h>
#include <math.h>

#include "fdface.h"
#include "fdhand.h"

#define PRECISION int /* int/float */
#define TRUNC(x) ((PRECISION) (x))

static cairo_surface_t *clock_bg_surface;
static cairo_surface_t *clock_surface;
static cairo_surface_t *glider_surface;
static cairo_surface_t *fakewin_surface;
static cairo_surface_t *bg_surface;
static int bg_width, bg_height;

#define CLOCK_W 256
#define CLOCK_H 245

static int fakewin_width;
static int fakewin_height;

static int glider_width;
static int glider_height;

static double glider_angle = 0;
static double glider_pos_x = 80;
static double glider_pos_y = 50;
static double glider_dir_x = 1;
static double glider_dir_y = 1;

static void
render_fakewin (void)
{
    cairo_t *cr;

    cr = cairo_create (fakewin_surface);
    cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
    cairo_set_source_rgb (cr, 1.0, 1.0, 1.0);
    cairo_move_to (cr, 0, 0);
    cairo_rectangle (cr, 17, 34, fakewin_width - 32, fakewin_height - 50);
    cairo_fill (cr);
    cairo_set_operator (cr, CAIRO_OPERATOR_OVER);
    cairo_translate (cr, TRUNC (glider_pos_x), TRUNC (glider_pos_y));

    cairo_set_source_surface (cr, glider_surface, 0.0, 0.0);
    cairo_paint (cr);
    cairo_destroy (cr);

    glider_pos_x += glider_dir_x;
    glider_pos_y += glider_dir_y;

    if (glider_pos_x <= 18)
	glider_dir_x = -glider_dir_x;

    if (glider_pos_y <= 35)
	glider_dir_y = -glider_dir_y;

    if (glider_pos_x >= (fakewin_width - 16 - 37))
	glider_dir_x = -glider_dir_x;

    if (glider_pos_y >= (fakewin_height - 19 - 37))
	glider_dir_y = -glider_dir_y;
}

static void
render_clock (void)
{
    cairo_t *cr;

    cr = cairo_create (clock_surface);
    cairo_set_operator (cr, CAIRO_OPERATOR_CLEAR);
    cairo_paint (cr);
    cairo_set_operator (cr, CAIRO_OPERATOR_OVER);

    cairo_set_source_surface (cr, clock_bg_surface, 0.0, 0.0);
    cairo_paint (cr);

    fdhand_draw_now (cr, CLOCK_W, CLOCK_H, 1);
    cairo_destroy (cr);
}

void
shadow_setup (cairo_surface_t *target, int w, int h)
{
    cairo_surface_t *image;
    cairo_t *cr;

    clock_surface = cairo_surface_create_similar (target,
	    CAIRO_CONTENT_COLOR_ALPHA,
	    CLOCK_W, CLOCK_H);

    clock_bg_surface = cairo_surface_create_similar (target,
	    CAIRO_CONTENT_COLOR_ALPHA,
	    CLOCK_W, CLOCK_H);
    image = cairo_image_surface_create_from_png ("desktop.png");
    if (cairo_surface_status (image)) {
	printf ("error reading desktop.png: %s\n",
		cairo_status_to_string (cairo_surface_status (image)));
	exit(1);
    }

    bg_width = cairo_image_surface_get_width (image);
    bg_height = cairo_image_surface_get_height (image);

    bg_surface = cairo_surface_create_similar (target,
	    cairo_surface_get_content (image),
	    bg_width, bg_height);

    cr = cairo_create (bg_surface);
    cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
    cairo_set_source_surface (cr, image, 0.0, 0.0);
    cairo_paint (cr);
    cairo_destroy (cr);

    cairo_surface_destroy (image);

    image = cairo_image_surface_create_from_png ("fakewin.png");
    if (cairo_surface_status (image)) {
	printf ("error reading fakewin.png: %s\n",
		cairo_status_to_string (cairo_surface_status (image)));
	exit(1);
    }

    fakewin_width = cairo_image_surface_get_width (image);
    fakewin_height = cairo_image_surface_get_height (image);

    fakewin_surface = cairo_surface_create_similar (target,
	    cairo_surface_get_content (image),
	    fakewin_width + 2,
	    fakewin_height + 2);

    cr = cairo_create (fakewin_surface);
    cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
    cairo_set_source_surface (cr, image, 0.0, 0.0);
    cairo_paint (cr);
    cairo_destroy (cr);

    image = cairo_image_surface_create_from_png ("glider.png");
    if (cairo_surface_status (image)) {
	printf ("error reading glider.png: %s\n",
		cairo_status_to_string (cairo_surface_status (image)));
	exit(1);
    }

    glider_width = cairo_image_surface_get_width (image);
    glider_height = cairo_image_surface_get_height (image);

    glider_surface = cairo_surface_create_similar (target,
	    cairo_surface_get_content (image),
	    glider_width, glider_height);

    cr = cairo_create (glider_surface);
    cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
    cairo_set_source_surface (cr, image, 0.0, 0.0);
    cairo_paint (cr);
    cairo_destroy (cr);

    cr = cairo_create (clock_bg_surface);
    cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
    cairo_set_source_rgba(cr, 1.0, 1.0, 1.0, 0.0);
    cairo_rectangle (cr, 0, 0, CLOCK_W, CLOCK_H);
    cairo_fill (cr);

    cairo_save (cr);
    cairo_set_source_rgba (cr, 1.0, 1.0, 1.0, 0.25);
    cairo_set_operator (cr, CAIRO_OPERATOR_OVER);
    cairo_scale (cr, CLOCK_W, CLOCK_H);
    cairo_translate (cr, 0.5, 0.5);
    cairo_arc (cr, 0, 0, 0.5, 0, 2 * M_PI);
    cairo_fill (cr);
    cairo_restore (cr);

    cairo_set_source_rgb (cr, 1.0, 1.0, 1.0);
    cairo_set_operator (cr, CAIRO_OPERATOR_OVER);

    fdface_draw (cr, CLOCK_W, CLOCK_H);
    cairo_destroy (cr);

    cairo_surface_destroy (image);

    render_clock ();
    render_fakewin ();
}

static long int shadow_cnt = 0;

static double fw_x = 250.0, fw_y = 20.0;
static double cl_x = 50.0, cl_y = 180.0;
static double dst_x = 20.0, dst_y = 270.0;
static double start_x = 250.0, start_y = 20.0;

static int which = 1;

static int
shadow_move_towards_point (double *current_x, double *current_y)
{
    double to_go_x = dst_x - *current_x;
    double to_go_y = dst_y - *current_y;
    double done_x = *current_x - start_x;
    double done_y = *current_y - start_y;

    double dist_from_start = fabs (to_go_x) + fabs (to_go_y);
    double dist_from_goal = fabs (done_x) + fabs (done_y);
    double speed = (dist_from_start < dist_from_goal) ?
	dist_from_start: dist_from_goal;
    double speed_div;
    double angle;

    speed *= 10.0;

    speed_div = fabs (dst_x - start_x) + fabs (dst_y - start_y);

    speed /= (speed_div > 1.0)? speed_div: 1.0;
    speed += 0.1;

    angle = fabs (atan (to_go_y / to_go_x));

    *current_x += speed * cos (angle) * ((dst_x > start_x)? 1.0: -1.0);
    *current_y += speed * sin (angle) * ((dst_y > start_y)? 1.0: -1.0);

    if (start_x <= dst_x) {
	if (*current_x >= dst_x)
	    return 1;
    } else {
	if (*current_x <= dst_x)
	    return 1;
    }

    if (start_y <= dst_y) {
	if (*current_y >= dst_y)
	    return 1;
    } else {
	if (*current_y <= dst_y)
	    return 1;
    }

    return 0;
}

static double shadow_alpha = 0.4;
static double max_shadow_offset = 60.0;

void
shadow_render (cairo_t *cr, int w, int h)
{
    double scale_x, scale_y;
    int move_done;
    double shadow_offset_x, shadow_offset_y;
    double light_x, light_y;

    light_x = w / 2.0;
    light_y = h / 2.0;

    cairo_save (cr);

    cairo_save (cr);
    cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);

    scale_x = ((double) w) / (double) bg_width;
    scale_y = ((double) h) / (double) bg_height;

    cairo_scale (cr, scale_x, scale_y);
    cairo_set_source_surface (cr, bg_surface, 0.0, 0.0);
    cairo_paint (cr);
    cairo_restore (cr);

    cairo_set_operator (cr, CAIRO_OPERATOR_OVER);

    if (!(shadow_cnt % 10))
	render_clock ();
    else
	if (!(shadow_cnt % 5))
	    render_fakewin ();

    shadow_cnt++;

    if (shadow_cnt >= 1000000)
	shadow_cnt = 0;

    shadow_offset_x = max_shadow_offset *
	((fw_x + fakewin_width / 2) - light_x) / (w / 2.0);
    shadow_offset_y = max_shadow_offset *
	((fw_y + fakewin_height / 2) - light_y) / (h / 2.0);

    /* hard shadow */
    cairo_set_source_rgba (cr, 0.0, 0.0, 0.0, shadow_alpha);
    cairo_mask_surface (cr, fakewin_surface,
	    TRUNC (fw_x + shadow_offset_x - 0.05 * fakewin_width),
	    TRUNC (fw_y + shadow_offset_y - 0.05 * fakewin_height));
    cairo_paint (cr);

    cairo_set_source_surface (cr, fakewin_surface, TRUNC (fw_x), TRUNC (fw_y));
    cairo_paint (cr);

    shadow_offset_x = max_shadow_offset *
	((cl_x + CLOCK_W / 2) - light_x) / (w / 2.0);
    shadow_offset_y = max_shadow_offset *
	((cl_y + CLOCK_H / 2) - light_y) / (h / 2.0);

    /* soft (translucent) shadow */
    cairo_set_source_surface (cr, clock_surface,
	    TRUNC (cl_x + shadow_offset_x - 0.05 * CLOCK_W),
	    TRUNC (cl_y + shadow_offset_y - 0.05 * CLOCK_H));
    cairo_paint_with_alpha (cr, shadow_alpha);

    cairo_set_source_surface (cr, clock_surface, TRUNC (cl_x), TRUNC (cl_y));
    cairo_paint (cr);


    if (which) {
	move_done = shadow_move_towards_point (&fw_x, &fw_y);
    } else {
	move_done = shadow_move_towards_point (&cl_x, &cl_y);
    }

    if (move_done) {
	which = (int) (drand48 () + 0.5);

	dst_x = drand48 () *
	    (w - ((which)? fakewin_width : CLOCK_W) -
	     max_shadow_offset);
	dst_y = drand48 () *
	    (h - ((which)? fakewin_height: CLOCK_H) -
	     max_shadow_offset);

	if (which) {
	    start_x = fw_x;
	    start_y = fw_y;
	} else {
	    start_x = cl_x;
	    start_y = cl_y;
	}
    }

    cairo_restore (cr);
}