/*
 * Copyright © 2018 Benjamin Otte
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library. If not, see <http://www.gnu.org/licenses/>.
 *
 * Authors: Benjamin Otte <otte@gnome.org>
 */

#include "config.h"

#include "updatesoverlay.h"

#include "gtkintl.h"
#include "gtkwidget.h"

#include "gsk/gskrendernodeprivate.h"

/* duration before we start fading in us */
#define GDK_DRAW_REGION_MIN_DURATION 50 * 1000
/* duration when fade is finished in us */
#define GDK_DRAW_REGION_MAX_DURATION 200 * 1000

typedef struct {
  gint64 timestamp;
  cairo_region_t *region;
} GtkUpdate;

typedef struct {
  GQueue *updates;
  GskRenderNode *last;
  GtkWidget *widget;
  guint tick_callback;
  gulong unmap_callback;
} GtkWidgetUpdates;

struct _GtkUpdatesOverlay
{
  GtkInspectorOverlay parent_instance;

  GHashTable *toplevels; /* widget => GtkWidgetUpdates */
};

struct _GtkUpdatesOverlayClass
{
  GtkInspectorOverlayClass parent_class;
};

G_DEFINE_TYPE (GtkUpdatesOverlay, gtk_updates_overlay, GTK_TYPE_INSPECTOR_OVERLAY)

static void
gtk_update_free (gpointer data)
{
  GtkUpdate *region = data;

  cairo_region_destroy (region->region);
  g_slice_free (GtkUpdate, region);
}

static void
gtk_widget_updates_release_widget (GtkWidgetUpdates *updates)
{
  g_assert (updates->widget);
  g_signal_handler_disconnect (updates->widget, updates->unmap_callback);
  if (updates->tick_callback)
    gtk_widget_remove_tick_callback (updates->widget, updates->tick_callback);
  updates->tick_callback = 0;
  updates->widget = NULL;
}

static void
gtk_widget_updates_free (gpointer data)
{
  GtkWidgetUpdates *updates = data;

  g_queue_free_full (updates->updates, gtk_update_free);
  g_clear_pointer (&updates->last, gsk_render_node_unref);
  if (updates->widget)
    gtk_widget_updates_release_widget (updates);

  g_slice_free (GtkWidgetUpdates, updates);
}

static gboolean
gtk_widget_updates_tick (GtkWidget     *widget,
                         GdkFrameClock *clock,
                         gpointer       data)
{
  GtkWidgetUpdates *updates = data;
  GtkUpdate *draw;
  gint64 now;

  now = gdk_frame_clock_get_frame_time (clock);

  for (draw = g_queue_pop_tail (updates->updates);
       draw != NULL && (now - draw->timestamp >= GDK_DRAW_REGION_MAX_DURATION);
       draw = g_queue_pop_tail (updates->updates))
    {
      gtk_update_free (draw);
    }

  gdk_surface_queue_expose (gtk_widget_get_surface (widget));
  if (draw)
    {
      g_queue_push_tail (updates->updates, draw);
      return G_SOURCE_CONTINUE;
    }
  else
    {
      updates->tick_callback = 0;
      return G_SOURCE_REMOVE;
    }
}

static GtkWidgetUpdates *
gtk_update_overlay_lookup_for_widget (GtkUpdatesOverlay *self,
                                      GtkWidget         *widget,
                                      gboolean           create)
{
  GtkWidgetUpdates *updates = g_hash_table_lookup (self->toplevels, widget);

  if (updates || !create)
    return updates;

  updates = g_slice_new0 (GtkWidgetUpdates);
  updates->updates = g_queue_new ();
  updates->widget = widget;
  updates->unmap_callback = g_signal_connect_swapped (widget, "unmap", G_CALLBACK (gtk_widget_updates_release_widget), updates);

  g_hash_table_insert (self->toplevels, g_object_ref (widget), updates);
  return updates;
}

static void
gtk_widget_updates_add (GtkWidgetUpdates *updates,
                        gint64            timestamp,
                        cairo_region_t   *region)
{
  GtkUpdate *update;
  GList *l;

  update = g_slice_new0 (GtkUpdate);
  update->timestamp = timestamp;
  update->region = region;
  for (l = g_queue_peek_head_link (updates->updates); l != NULL; l = l->next)
    {
      GtkUpdate *u = l->data;
      cairo_region_subtract (u->region, region);
    }
  g_queue_push_head (updates->updates, update);
  if (updates->tick_callback == 0)
    updates->tick_callback = gtk_widget_add_tick_callback (updates->widget, gtk_widget_updates_tick, updates, NULL);
}

static void
gtk_updates_overlay_snapshot (GtkInspectorOverlay *overlay,
                              GtkSnapshot         *snapshot,
                              GskRenderNode       *node,
                              GtkWidget           *widget)
{
  GtkUpdatesOverlay *self = GTK_UPDATES_OVERLAY (overlay);
  GtkWidgetUpdates *updates;
  GtkUpdate *draw;
  gint64 now;
  GList *l;

  updates = gtk_update_overlay_lookup_for_widget (self, widget, TRUE);
  now = gdk_frame_clock_get_frame_time (gtk_widget_get_frame_clock (widget));

  if (updates->last)
    {
      cairo_region_t *diff;

      diff = cairo_region_create ();
      gsk_render_node_diff (updates->last, node, diff);
      if (cairo_region_is_empty (diff))
        cairo_region_destroy (diff);
      else
        gtk_widget_updates_add (updates, now, diff);
    }
  else
    {
      cairo_region_t *region;
      graphene_rect_t bounds;

      gsk_render_node_get_bounds (node, &bounds);
      region = cairo_region_create_rectangle (&(cairo_rectangle_int_t) {
                                                  floor (bounds.origin.x),
                                                  floor (bounds.origin.y),
                                                  ceil (bounds.origin.x + bounds.size.width) - floor (bounds.origin.x),
                                                  ceil (bounds.origin.y + bounds.size.height) - floor (bounds.origin.y)
                                              });
      gtk_widget_updates_add (updates, now, region);
    }
  g_clear_pointer (&updates->last, gsk_render_node_unref);
  updates->last = gsk_render_node_ref (node);

  for (l = g_queue_peek_head_link (updates->updates); l != NULL; l = l->next)
    {
      double progress;
      guint i;

      draw = l->data;

      if (now - draw->timestamp < GDK_DRAW_REGION_MIN_DURATION)
        progress = 0.0;
      else if (now - draw->timestamp < GDK_DRAW_REGION_MAX_DURATION)
        progress = (double) (now - draw->timestamp - GDK_DRAW_REGION_MIN_DURATION)
                   / (GDK_DRAW_REGION_MAX_DURATION - GDK_DRAW_REGION_MIN_DURATION);
      else
        break;

      for (i = 0; i < cairo_region_num_rectangles (draw->region); i++)
        {
          GdkRectangle rect;

          cairo_region_get_rectangle (draw->region, i, &rect);
          gtk_snapshot_append_color (snapshot,
                                     &(GdkRGBA) { 1, 0, 0, 0.4 * (1 - progress) },
                                     &GRAPHENE_RECT_INIT(rect.x, rect.y, rect.width, rect.height));
        }
    }
}

static void
gtk_updates_overlay_queue_draw (GtkInspectorOverlay *overlay)
{
  GtkUpdatesOverlay *self = GTK_UPDATES_OVERLAY (overlay);
  GHashTableIter iter;
  gpointer widget;

  g_hash_table_iter_init (&iter, self->toplevels);
  while (g_hash_table_iter_next (&iter, &widget, NULL))
    gdk_surface_queue_expose (gtk_widget_get_surface (widget));
}

static void
gtk_updates_overlay_dispose (GObject *object)
{
  GtkUpdatesOverlay *self = GTK_UPDATES_OVERLAY (object);

  g_hash_table_unref (self->toplevels);

  G_OBJECT_CLASS (gtk_updates_overlay_parent_class)->dispose (object);
}

static void
gtk_updates_overlay_class_init (GtkUpdatesOverlayClass *klass)
{
  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
  GtkInspectorOverlayClass *overlay_class = GTK_INSPECTOR_OVERLAY_CLASS (klass);

  overlay_class->snapshot = gtk_updates_overlay_snapshot;
  overlay_class->queue_draw = gtk_updates_overlay_queue_draw;

  gobject_class->dispose = gtk_updates_overlay_dispose;
}

static void
gtk_updates_overlay_init (GtkUpdatesOverlay *self)
{
  self->toplevels = g_hash_table_new_full (g_direct_hash, g_direct_equal, NULL, gtk_widget_updates_free);
}

GtkInspectorOverlay *
gtk_updates_overlay_new (void)
{
  return g_object_new (GTK_TYPE_UPDATES_OVERLAY, NULL);
}