Implementing better fallback algorithm....

chrome/common/extensions/extension_message_bundle.h

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_COMMON_EXTENSIONS_EXTENSION_MESSAGE_BUNDLE_H_
 #define CHROME_COMMON_EXTENSIONS_EXTENSION_MESSAGE_BUNDLE_H_
 
 #include <map>
 #include <string>
+#include <vector>
 
+#include "base/linked_ptr.h"
 #include "base/values.h"
 
 // Contains localized extension messages for one locale. Any messages that the
 // locale does not provide are pulled from the default locale.
 class ExtensionMessageBundle {
  public:
   typedef std::map<std::string, std::string> SubstitutionMap;
+  typedef std::vector<linked_ptr<DictionaryValue> > CatalogVector;
 
   // JSON keys of interest for messages file.
   static const wchar_t* kContentKey;
   static const wchar_t* kMessageKey;
   static const wchar_t* kPlaceholdersKey;
 
   // Begin/end markers for placeholders and messages
   static const char* kPlaceholderBegin;
   static const char* kPlaceholderEnd;
   static const char* kMessageBegin;
   static const char* kMessageEnd;
 
   // Extension name and description message names
   static const char* kExtensionName;
   static const char* kExtensionDescription;
 
   // Creates ExtensionMessageBundle or returns NULL if there was an error.
-  static ExtensionMessageBundle* Create(
-      const DictionaryValue& default_locale_catalog,
-      const DictionaryValue& current_locale_catalog,
-      std::string* error);
+  // Expects locale_catalogs to be sorted from more specific to less specific,
+  // with default catalog at the end.
+  static ExtensionMessageBundle* Create(const CatalogVector& locale_catalogs,
+                                        std::string* error);
 
   // Get message from the catalog with given key.
   // Returned message has all of the internal placeholders resolved to their
   // value (content).
   // Returns empty string if it can't find a message.
   // We don't use simple GetMessage name, since there is a global
   // #define GetMessage GetMessageW override in Chrome code.
   std::string GetL10nMessage(const std::string& name) const;
 
   // Get message from the given catalog with given key.
@@ skipping 26 matching lines @@
   template<typename str>
   static bool IsValidName(const str& name);
 
   // Getter for dictionary_.
   const SubstitutionMap* dictionary() const { return &dictionary_; }
 
  private:
   // Use Create to create ExtensionMessageBundle instance.
    ExtensionMessageBundle();
 
-  // Initializes the instance from the contents of two catalogs. If a key is not
-  // present in current_locale_catalog, the value from default_local_catalog is
-  // used instead.
+  // Initializes the instance from the contents of vector of catalogs.
+  // If the key is not present in more specific catalog we fall back to next one
+  // (less specific).
   // Returns false on error.
-  bool Init(const DictionaryValue& default_locale_catalog,
-            const DictionaryValue& current_locale_catalog,
-            std::string* error);
+  bool Init(const CatalogVector& locale_catalogs, std::string* error);
 
   // Helper methods that navigate JSON tree and return simplified message.
   // They replace all $PLACEHOLDERS$ with their value, and return just key/value
   // of the message.
   bool GetMessageValue(const std::wstring& wkey,
                        const DictionaryValue& catalog,
                        std::string* value,
                        std::string* error) const;
 
   // Get all placeholders for a given message from JSON subtree.
   bool GetPlaceholders(const DictionaryValue& name_tree,
                        const std::string& name_key,
                        SubstitutionMap* placeholders,
                        std::string* error) const;
 
   // For a given message, replaces all placeholders with their actual value.
   // Returns false if replacement failed (see ReplaceVariables).
   bool ReplacePlaceholders(const SubstitutionMap& placeholders,
                            std::string* message,
                            std::string* error) const;
 
   // Holds all messages for application locale.
   SubstitutionMap dictionary_;
 };
 
 #endif  // CHROME_COMMON_EXTENSIONS_EXTENSION_MESSAGE_BUNDLE_H_