[gnome-photos] local-item: Embed XMP metadata identifying shared copies

[Debarshi Ray <debarshir src gnome org>]

commit cdfb023c25dd62277177d7c86e11e680921b1ce1
Author: Umang Jain <mailumangjain gmail com>
Date:   Tue Sep 6 20:46:05 2016 +0200

    local-item: Embed XMP metadata identifying shared copies
    
    It is rumoured (ask in #darktable on Freenode) that modifying the
    metadata of RAW files is risky and has caused such files to get
    corrupted. Therefore, we play it safe and only touch PNGs, JPEGs and
    JPEG-2000s.
    
    Some changes by Debarshi Ray.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=770267

 src/photos-local-item.c |  109 +++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 109 insertions(+), 0 deletions(-)
---
diff --git a/src/photos-local-item.c b/src/photos-local-item.c
index 5cba1da..6478fec 100644
--- a/src/photos-local-item.c
+++ b/src/photos-local-item.c
@@ -26,6 +26,7 @@
 
 #include "config.h"
 
+#include <gexiv2/gexiv2.h>
 #include <gio/gio.h>
 #include <glib.h>
 #include <glib/gi18n.h>
@@ -170,6 +171,113 @@ photos_local_item_get_source_widget (PhotosBaseItem *item)
 }
 
 
+static gboolean
+photos_local_item_metadata_add_shared (PhotosBaseItem  *item,
+                                       const gchar     *provider_type,
+                                       const gchar     *account_identity,
+                                       const gchar     *shared_id,
+                                       GCancellable    *cancellable,
+                                       GError         **error)
+{
+  GVariant *shared_variant = NULL;
+  GVariantBuilder builder;
+  const GVariantType *tuple_items[] = {G_VARIANT_TYPE_STRING,   /* provider-type */
+                                       G_VARIANT_TYPE_STRING,   /* account-identity */
+                                       G_VARIANT_TYPE_STRING};  /* shared-id */
+  GVariantType *array_type = NULL;
+  GVariantType *tuple_type = NULL;
+  GExiv2Metadata *metadata = NULL;
+  gboolean ret_val = FALSE;
+  const gchar *mime_type;
+  const gchar *shared_tag = "Xmp.gnome.photos-shared";
+  const gchar *version_tag = "Xmp.gnome.photos-xmp-version";
+  gchar *path = NULL;
+  gchar *shared_string = NULL;
+  gchar *tuple_type_format = NULL;
+
+  mime_type = photos_base_item_get_mime_type (item);
+  if (g_strcmp0 (mime_type, "image/png") != 0
+      && g_strcmp0 (mime_type, "image/jp2") != 0
+      && g_strcmp0 (mime_type, "image/jpeg") != 0)
+    {
+      ret_val = TRUE;
+      goto out;
+    }
+
+  path = photos_base_item_download (item, cancellable, error);
+  if (path == NULL)
+    goto out;
+
+  metadata = gexiv2_metadata_new ();
+
+  if (!gexiv2_metadata_open_path (metadata, path, error))
+    goto out;
+
+  if (!gexiv2_metadata_set_tag_long (metadata, version_tag, 0))
+    {
+      g_set_error (error, PHOTOS_ERROR, 0, "Failed to update %s", version_tag);
+      goto out;
+    }
+
+  tuple_type = g_variant_type_new_tuple (tuple_items, G_N_ELEMENTS (tuple_items));
+  tuple_type_format = g_variant_type_dup_string (tuple_type);
+
+  array_type = g_variant_type_new_array (tuple_type);
+
+  g_variant_builder_init (&builder, array_type);
+  g_variant_builder_add (&builder, tuple_type_format, provider_type, account_identity, shared_id);
+
+  shared_string = gexiv2_metadata_get_tag_string (metadata, shared_tag);
+  if (shared_string != NULL)
+    {
+      GVariant *old_shared_variant = NULL;
+      GVariant *child = NULL;
+      GVariantIter iter;
+
+      old_shared_variant = g_variant_parse (array_type, shared_string, NULL, NULL, error);
+      if (old_shared_variant == NULL)
+        goto out;
+
+      g_variant_iter_init (&iter, old_shared_variant);
+      child = g_variant_iter_next_value (&iter);
+      while (child != NULL)
+        {
+          g_variant_builder_add_value (&builder, child);
+          g_variant_unref (child);
+          child = g_variant_iter_next_value (&iter);
+        }
+
+      g_variant_unref (old_shared_variant);
+    }
+
+  shared_variant = g_variant_builder_end (&builder);
+
+  g_free (shared_string);
+  shared_string = g_variant_print (shared_variant, TRUE);
+
+  if (!gexiv2_metadata_set_tag_string (metadata, shared_tag, shared_string))
+    {
+      g_set_error (error, PHOTOS_ERROR, 0, "Failed to update %s", shared_tag);
+      goto out;
+    }
+
+  if (!gexiv2_metadata_save_file (metadata, path, error))
+    goto out;
+
+  ret_val = TRUE;
+
+ out:
+  g_clear_object (&metadata);
+  g_clear_pointer (&array_type, (GDestroyNotify) g_variant_type_free);
+  g_clear_pointer (&tuple_type, (GDestroyNotify) g_variant_type_free);
+  g_clear_pointer (&shared_variant, (GDestroyNotify) g_variant_unref);
+  g_free (path);
+  g_free (shared_string);
+  g_free (tuple_type_format);
+  return ret_val;
+}
+
+
 static void
 photos_local_item_trash_finish (GObject *source_object, GAsyncResult *res, gpointer user_data)
 {
@@ -271,5 +379,6 @@ photos_local_item_class_init (PhotosLocalItemClass *class)
   base_item_class->create_thumbnail = photos_local_item_create_thumbnail;
   base_item_class->download = photos_local_item_download;
   base_item_class->get_source_widget = photos_local_item_get_source_widget;
+  base_item_class->metadata_add_shared = photos_local_item_metadata_add_shared;
   base_item_class->trash = photos_local_item_trash;
 }