Convert app_launch_index and page_index from int to StringOrdinal.

chrome/browser/extensions/extension_prefs.cc

Index: chrome/browser/extensions/extension_prefs.cc
diff --git a/chrome/browser/extensions/extension_prefs.cc b/chrome/browser/extensions/extension_prefs.cc
index ebe337cc0b60403f3c82af43d9fae8d2f6495a9b..8de504a99567fb60e841bc02b61ef5551030668f 100644
--- a/chrome/browser/extensions/extension_prefs.cc
+++ b/chrome/browser/extensions/extension_prefs.cc
@@ -110,10 +110,12 @@ const char kWebStoreLogin[] = "extensions.webstore_login";
 const char kPrefLaunchType[] = "launchType";
 
 // A preference determining the order of which the apps appear on the NTP.
-const char kPrefAppLaunchIndex[] = "app_launcher_index";
+const char kPrefAppLaunchIndexDeprecated[] = "app_launcher_index";
+const char kPrefAppLaunchOrdinal[] = "app_launcher_ordinal";
 
 // A preference determining the page on which an app appears in the NTP.
-const char kPrefPageIndex[] = "page_index";
+const char kPrefPageIndexDeprecated[] = "page_index";
+const char kPrefPageOrdinal[] = "page_ordinal";
 
 // A preference specifying if the user dragged the app on the NTP.
 const char kPrefUserDraggedApp[] = "user_dragged_app_ntp";
@@ -239,6 +241,28 @@ std::string JoinPrefs(std::string parent, const char* child) {
   return parent + "." + child;
 }
 
+// A simple structure used when sorting applications based on their app launch
+// index. This is used by the code that migrates the data from integers to
+// StringOrdinals.
+struct ApplicationNTPOldAppLaunch {
+  const std::string* application_id;
+  const int app_launch_index;
+
+  ApplicationNTPOldAppLaunch() : application_id(0),
+                                 app_launch_index(0) {}
+
+  ApplicationNTPOldAppLaunch(const std::string& app_id, int app_launch)
+      : application_id(&app_id),
+        app_launch_index(app_launch) {}
+};
+
+struct SortByNTPOldAppLaunch {
+  bool operator() (const ApplicationNTPOldAppLaunch& lhs,
+                   const ApplicationNTPOldAppLaunch& rhs) const {
+    return lhs.app_launch_index < rhs.app_launch_index;
+  }
+};
+
 }  // namespace
 
 ExtensionPrefs::ExtensionPrefs(
@@ -415,6 +439,17 @@ bool ExtensionPrefs::ReadExtensionPrefList(
   return true;
 }
 
+bool ExtensionPrefs::ReadExtensionPrefString(
+    const std::string& extension_id, const std::string& pref_key,
+    std::string* out_value) const {
+  const DictionaryValue* ext = GetExtensionPref(extension_id);
+
+  if (!ext || !ext->GetString(pref_key, out_value))
+    return false;
+
+  return true;
+}
+
 bool ExtensionPrefs::ReadExtensionPrefURLPatternSet(
     const std::string& extension_id,
     const std::string& pref_key,
@@ -858,6 +893,60 @@ void ExtensionPrefs::MigratePermissions(const ExtensionIdSet& extension_ids) {
   }
 }
 
+void ExtensionPrefs::MigrateAppIndex(const ExtensionIdSet& extension_ids) {
+  if (extension_ids.empty())
+    return;
+
+  // Convert all the page index values to page ordinals. If there are any
+  // app launch values that need to be migrated, inserted them into a sorted
+  // set to be dealt with later.
+  std::multiset<ApplicationNTPOldAppLaunch, SortByNTPOldAppLaunch>
+      app_launches_to_convert;
+  for (ExtensionIdSet::const_iterator ext_id = extension_ids.begin();
+       ext_id != extension_ids.end(); ++ext_id) {
+    int old_page_index = 0;
+    if (ReadExtensionPrefInteger(*ext_id,
+                                 kPrefPageIndexDeprecated,
+                                 &old_page_index)) {
+      SetPageOrdinal(*ext_id, PageIntegerAsStringOrdinal(old_page_index));
+      UpdateExtensionPref(*ext_id, kPrefPageIndexDeprecated, NULL);
+    }
+
+    int old_app_launch_index = 0;
+    if (ReadExtensionPrefInteger(*ext_id,
+                                 kPrefAppLaunchIndexDeprecated,
+                                 &old_app_launch_index)) {
+      // We can't update the app launch index value yet, because we use
+      // GetNextAppLaunchOrdinal to get the new ordinal value and it requires
+      // all the ordinals with lower values to have already been migrated.
+      app_launches_to_convert.insert(ApplicationNTPOldAppLaunch(
+          *ext_id,
+          old_app_launch_index));
+      UpdateExtensionPref(*ext_id, kPrefAppLaunchIndexDeprecated, NULL);
+    }
+  }
+
+  if (app_launches_to_convert.empty())
+    return;
+
+  // Create the new app launch ordinals and remove the old preferences. Since
+  // the set is sorted, each time we migrate an apps index, we know that all of
+  // the remaining apps will appear further down the NTP than it or on a
+  // different page.
+  for (std::multiset<ApplicationNTPOldAppLaunch, SortByNTPOldAppLaunch>
+           ::const_iterator ext = app_launches_to_convert.begin();
+       ext != app_launches_to_convert.end(); ++ext) {
+    StringOrdinal page = GetPageOrdinal(*(ext->application_id));
+    if (!page.IsValid()) {
+      page = GetNaturalAppPageOrdinal();
+      SetPageOrdinal(*(ext->application_id), page);
+    }
+
+    SetAppLaunchOrdinal(*(ext->application_id),
+                          GetNextAppLaunchOrdinal(page));
+  }
+}
+
 ExtensionPermissionSet* ExtensionPrefs::GetGrantedPermissions(
     const std::string& extension_id) {
   CHECK(Extension::IdIsValid(extension_id));
@@ -1068,11 +1157,22 @@ void ExtensionPrefs::SetToolbarOrder(
   SavePrefs();
 }
 
+void ExtensionPrefs::SetAppOrdinalValues(DictionaryValue* extension_dict,
+                                         const StringOrdinal& page_ordinal) {
+  extension_dict->Set(kPrefPageOrdinal,
+                      Value::CreateStringValue(page_ordinal.ToString()));
+  UpdatePageOrdinalMap(StringOrdinal(), page_ordinal);
+
+  extension_dict->Set(kPrefAppLaunchOrdinal,
+                      Value::CreateStringValue(
+                          GetNextAppLaunchOrdinal(page_ordinal).ToString()));
+}
+
 void ExtensionPrefs::OnExtensionInstalled(
     const Extension* extension,
     Extension::State initial_state,
     bool from_webstore,
-    int page_index) {
+    const StringOrdinal& page_ordinal) {
   const std::string& id = extension->id();
   CHECK(Extension::IdIsValid(id));
   ScopedExtensionPrefUpdate update(prefs_, id);
@@ -1104,13 +1204,12 @@ void ExtensionPrefs::OnExtensionInstalled(
   }
 
   if (extension->is_app()) {
-    if (page_index == -1)
-      page_index = GetNaturalAppPageIndex();
-    extension_dict->Set(kPrefPageIndex,
-                        Value::CreateIntegerValue(page_index));
-    extension_dict->Set(kPrefAppLaunchIndex,
-        Value::CreateIntegerValue(GetNextAppLaunchIndex(page_index)));
+    if (page_ordinal.IsValid())
+      SetAppOrdinalValues(extension_dict, page_ordinal);
+    else
+      SetAppOrdinalValues(extension_dict, GetNaturalAppPageOrdinal());
   }
+
   extension_pref_value_map_->RegisterExtension(
       id, install_time, initial_state == Extension::ENABLED);
   content_settings_store_->RegisterExtension(
@@ -1442,59 +1541,136 @@ void ExtensionPrefs::SetWebStoreLogin(const std::string& login) {
   SavePrefs();
 }
 
-int ExtensionPrefs::GetAppLaunchIndex(const std::string& extension_id) {
-  int value;
-  if (ReadExtensionPrefInteger(extension_id, kPrefAppLaunchIndex, &value))
-    return value;
+bool ExtensionPrefs::GetMaxAndMinAppLaunchOrdinalsOnPage(
+    const StringOrdinal& target_page_ordinal,
+    StringOrdinal* min_app_launch_value,
+    StringOrdinal* max_app_launch_value) const {
+  const DictionaryValue* extensions = prefs_->GetDictionary(kExtensionsPref);
+  CHECK(extensions);
+  CHECK(target_page_ordinal.IsValid());
+  CHECK(min_app_launch_value);
+  CHECK(max_app_launch_value);
+
+  StringOrdinal* min_value = NULL;
+  StringOrdinal* max_value = NULL;
+  for (DictionaryValue::key_iterator ext_it = extensions->begin_keys();
+       ext_it != extensions->end_keys(); ++ext_it) {
+    StringOrdinal page_ordinal = GetPageOrdinal(*ext_it);
+    if (page_ordinal.IsValid() && page_ordinal.Equal(target_page_ordinal)) {
+      StringOrdinal app_launch_ordinal = GetAppLaunchOrdinal(*ext_it);
+      if (app_launch_ordinal.IsValid()) {
+        if (min_value == NULL || !min_value->IsValid() ||
+            app_launch_ordinal.LessThan(*min_value))
+          min_value = &app_launch_ordinal;
+
+        if (max_value == NULL || !max_value->IsValid() ||
+            max_value->LessThan(app_launch_ordinal))
+          max_value = &app_launch_ordinal;
+      }
+    }
+  }
 
-  return -1;
-}
+  if (min_value != NULL)
+    *min_app_launch_value = *min_value;
+  if (max_value != NULL)
+    *max_app_launch_value = *max_value;
 
-void ExtensionPrefs::SetAppLaunchIndex(const std::string& extension_id,
-                                       int index) {
-  UpdateExtensionPref(extension_id, kPrefAppLaunchIndex,
-                      Value::CreateIntegerValue(index));
+  // If |min_app_launch_value| is valid then we had at least 1 app on the page,
+  // so both positions are valid.
+  return min_app_launch_value->IsValid();
 }
 
-int ExtensionPrefs::GetNextAppLaunchIndex(int on_page) {
+StringOrdinal ExtensionPrefs::GetFirstAppPage() const {
   const DictionaryValue* extensions = prefs_->GetDictionary(kExtensionsPref);
-  if (!extensions)
-    return 0;
+  CHECK(extensions);
 
-  int max_value = -1;
-  for (DictionaryValue::key_iterator extension_id = extensions->begin_keys();
-       extension_id != extensions->end_keys(); ++extension_id) {
-    int value = GetAppLaunchIndex(*extension_id);
-    int page = GetPageIndex(*extension_id);
-    if (page == on_page && value > max_value)
-      max_value = value;
-  }
-  return max_value + 1;
+  if (page_ordinal_map_.empty())
+    return StringOrdinal::CreateInitialOrdinal();
+
+  return page_ordinal_map_.begin()->first;
 }
 
-int ExtensionPrefs::GetNaturalAppPageIndex() {
-  const DictionaryValue* extensions = prefs_->GetDictionary(kExtensionsPref);
-  if (!extensions)
-    return 0;
+StringOrdinal ExtensionPrefs::CreateFirstAppLaunchOrdinal(
+    const StringOrdinal& page_ordinal) const {
+  StringOrdinal max_ordinal;
+  StringOrdinal min_ordinal;
+  GetMaxAndMinAppLaunchOrdinalsOnPage(page_ordinal, &min_ordinal, &max_ordinal);
 
-  std::map<int, int> page_counts;
-  for (DictionaryValue::key_iterator extension_id = extensions->begin_keys();
-       extension_id != extensions->end_keys(); ++extension_id) {
-    int page_index = GetPageIndex(*extension_id);
-    if (page_index >= 0)
-      page_counts[page_index] = page_counts[page_index] + 1;
-  }
-  for (int i = 0; ; i++) {
-    std::map<int, int>::const_iterator it = page_counts.find(i);
-    if (it == page_counts.end() || it->second < kNaturalAppPageSize)
-      return i;
-  }
+  if (min_ordinal.IsValid())
+    return min_ordinal.CreateBefore();
+  else
+    return StringOrdinal::CreateInitialOrdinal();
 }
 
-void ExtensionPrefs::SetAppLauncherOrder(
-    const std::vector<std::string>& extension_ids) {
-  for (size_t i = 0; i < extension_ids.size(); ++i)
-    SetAppLaunchIndex(extension_ids.at(i), i);
+StringOrdinal ExtensionPrefs::GetAppLaunchOrdinal(
+    const std::string& extension_id) const {
+  std::string raw_value;
+  // If the preference read fails then raw_value will still be unset and we
+  // will return an invalid StringOrdinal to signal that no app launch ordinal
+  // was found.
+  ReadExtensionPrefString(extension_id, kPrefAppLaunchOrdinal, &raw_value);
+  return StringOrdinal(raw_value);
+}
+
+void ExtensionPrefs::SetAppLaunchOrdinal(const std::string& extension_id,
+                                         const StringOrdinal& ordinal) {
+  UpdateExtensionPref(extension_id, kPrefAppLaunchOrdinal,
+                      Value::CreateStringValue(ordinal.ToString()));
+}
+
+StringOrdinal ExtensionPrefs::GetNextAppLaunchOrdinal(
+    const StringOrdinal& page_ordinal) const {
+  StringOrdinal max_ordinal;
+  StringOrdinal min_ordinal;
+  GetMaxAndMinAppLaunchOrdinalsOnPage(page_ordinal, &min_ordinal, &max_ordinal);
+
+  if (max_ordinal.IsValid())
+    return max_ordinal.CreateAfter();
+  else
+    return StringOrdinal::CreateInitialOrdinal();
+}
+
+StringOrdinal ExtensionPrefs::GetNaturalAppPageOrdinal() const {
+  const DictionaryValue* extensions = prefs_->GetDictionary(kExtensionsPref);
+  CHECK(extensions);
+
+  if (page_ordinal_map_.empty())
+    return StringOrdinal::CreateInitialOrdinal();
+
+  std::map<StringOrdinal, int>::const_iterator it = page_ordinal_map_.begin();
+  for (; it != page_ordinal_map_.end(); ++it) {
+    if (it->second < kNaturalAppPageSize)
+      return it->first;
+  }
+
+  // Add a new page as all existing pages are full.
+  StringOrdinal last_element = page_ordinal_map_.rbegin()->first;
+  return last_element.CreateAfter();
+}
+
+void ExtensionPrefs::OnExtensionMoved(
+    const std::string& moved_extension_id,
+    const std::string& predecessor_extension_id,
+    const std::string& successor_extension_id) {
+  // We only need to update the ordinal if the app has at least 1 neighbor.
+  if (!predecessor_extension_id.empty() || !successor_extension_id.empty()) {
+    if (predecessor_extension_id.empty()) {
+      SetAppLaunchOrdinal(
+          moved_extension_id,
+          GetAppLaunchOrdinal(successor_extension_id).CreateBefore());
+    } else if (successor_extension_id.empty()) {
+      SetAppLaunchOrdinal(
+          moved_extension_id,
+          GetAppLaunchOrdinal(predecessor_extension_id).CreateAfter());
+    } else {
+      StringOrdinal predecessor_ordinal =
+          GetAppLaunchOrdinal(predecessor_extension_id);
+      StringOrdinal sucessor_ordinal =
+          GetAppLaunchOrdinal(successor_extension_id);
+      SetAppLaunchOrdinal(moved_extension_id,
+                          predecessor_ordinal.CreateBetween(sucessor_ordinal));
+    }
+  }
 
   content::NotificationService::current()->Notify(
       chrome::NOTIFICATION_EXTENSION_LAUNCHER_REORDERED,
@@ -1502,19 +1678,85 @@ void ExtensionPrefs::SetAppLauncherOrder(
       content::NotificationService::NoDetails());
 }
 
-int ExtensionPrefs::GetPageIndex(const std::string& extension_id) {
-  int value = -1;
-  ReadExtensionPrefInteger(extension_id, kPrefPageIndex, &value);
-  return value;
+StringOrdinal ExtensionPrefs::GetPageOrdinal(const std::string& extension_id)
+    const {
+  std::string raw_data;
+  // If the preference read fails then raw_data will still be unset and we will
+  // return an invalid StringOrdinal to signal that no page ordinal was found.
+  ReadExtensionPrefString(extension_id, kPrefPageOrdinal, &raw_data);
+  return StringOrdinal(raw_data);
+}
+
+void ExtensionPrefs::SetPageOrdinal(const std::string& extension_id,
+                                    const StringOrdinal& page_ordinal) {
+  UpdatePageOrdinalMap(GetPageOrdinal(extension_id), page_ordinal);
+  UpdateExtensionPref(extension_id, kPrefPageOrdinal,
+                      Value::CreateStringValue(page_ordinal.ToString()));
 }
 
-void ExtensionPrefs::SetPageIndex(const std::string& extension_id, int index) {
-  UpdateExtensionPref(extension_id, kPrefPageIndex,
-                      Value::CreateIntegerValue(index));
+void ExtensionPrefs::ClearPageOrdinal(const std::string& extension_id) {
+  UpdatePageOrdinalMap(GetPageOrdinal(extension_id), StringOrdinal());
+  UpdateExtensionPref(extension_id, kPrefPageOrdinal, NULL);
 }
 
-void ExtensionPrefs::ClearPageIndex(const std::string& extension_id) {
-  UpdateExtensionPref(extension_id, kPrefPageIndex, NULL);
+void ExtensionPrefs::InitializePageOrdinalMap(
+    const ExtensionIdSet& extension_ids) {
+  for (ExtensionIdSet::const_iterator ext_it = extension_ids.begin();
+       ext_it != extension_ids.end(); ++ext_it) {
+    UpdatePageOrdinalMap(StringOrdinal(), GetPageOrdinal(*ext_it));
+  }
+}
+
+void ExtensionPrefs::UpdatePageOrdinalMap(const StringOrdinal& old_value,
+                                          const StringOrdinal& new_value) {
+  if (new_value.IsValid())
+    ++page_ordinal_map_[new_value];
+
+  if (old_value.IsValid()) {
+    --page_ordinal_map_[old_value];
+
+    if (page_ordinal_map_[old_value] == 0)
+      page_ordinal_map_.erase(old_value);
+  }
+}
+
+int ExtensionPrefs::PageStringOrdinalAsInteger(
+    const StringOrdinal& page_ordinal)
+    const {
+  if (!page_ordinal.IsValid())
+    return -1;
+
+  std::map<StringOrdinal, int>::const_iterator it =
+      page_ordinal_map_.find(page_ordinal);
+  if (it != page_ordinal_map_.end()) {
+    return std::distance(page_ordinal_map_.begin(), it);
+  } else {
+    return -1;
+  }
+}
+
+StringOrdinal ExtensionPrefs::PageIntegerAsStringOrdinal(size_t page_index) {
+  const DictionaryValue* extensions = prefs_->GetDictionary(kExtensionsPref);
+  if (!extensions)
+    return StringOrdinal();
+
+  if (page_index < page_ordinal_map_.size()) {
+    std::map<StringOrdinal, int, StringOrdinalLessThan>::const_iterator it =
+        page_ordinal_map_.begin();
+    advance(it, page_index);
+
+    return it->first;
+  } else {
+    if (page_ordinal_map_.empty())
+      page_ordinal_map_[StringOrdinal::CreateInitialOrdinal()] = 0;
+
+    // Create new pages until we reach the desired index.
+    while (page_index >= page_ordinal_map_.size()) {
+      StringOrdinal new_page = page_ordinal_map_.rbegin()->first.CreateAfter();
+      page_ordinal_map_[new_page] = 0;
+    }
+    return page_ordinal_map_.rbegin()->first;
+  }
 }
 
 bool ExtensionPrefs::WasAppDraggedByUser(const std::string& extension_id) {
@@ -1661,7 +1903,9 @@ void ExtensionPrefs::InitPrefStore(bool extensions_disabled) {
   }
 
   FixMissingPrefs(extension_ids);
+  InitializePageOrdinalMap(extension_ids);
   MigratePermissions(extension_ids);
+  MigrateAppIndex(extension_ids);
 
   // Store extension controlled preference values in the
   // |extension_pref_value_map_|, which then informs the subscribers