Added i18n skeleton API for message_formatting

lib/i18n/message_format.dart

+/**
+ * Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+ * for details. All rights reserved. Use of this source code is governed by a
+ * BSD-style license that can be found in the LICENSE file.
+ *
+ * Message/plural format library with locale support.
+ *
+ * Message format grammar:
+ *
+ *    messageFormatPattern := string ( "{" messageFormatElement "}" string )*
+ *    messageFormatElement := argumentIndex [ "," elementFormat ]
+ *    elementFormat := "plural" "," pluralStyle
+ *                      | "select" "," selectStyle
+ *    pluralStyle :=  pluralFormatPattern
+ *    selectStyle :=  selectFormatPattern
+ *    pluralFormatPattern := \\[ "offset" ":" offsetIndex ] pluralForms*
+ *    selectFormatPattern := pluralForms*
+ *    pluralForms := stringKey "{" ( "{" messageFormatElement "}"|string )* "}"
+ *
+ *
+ * Message example:
+ *
+ * I see {NUM_PEOPLE, plural, offset:1
+ *         =0 {no one at all}
+ *         =1 {{WHO}}
+ *         one {{WHO} and one other person}
+ *         other {{WHO} and # other people}}
+ * in {PLACE}.
+ *
+ * Calling format({'NUM_PEOPLE': 2, 'WHO': 'Mark', 'PLACE': 'Athens'}) would
+ * produce "I see Mark and one other person in Athens." as output.
+ *
+ * See tests/message_format_test.dart for more examples.
+ */
+
+#library('MessageFormat');
+
+class MessageFormat {
+
+  /**
+   * Literal strings, including '', are replaced with \uFDDF_x_ for
+   * parsing purposes, and recovered during format phase.
+   * \uFDDF is a Unicode nonprinting character, not expected to be found in the
+   * typical message.
+   */
+  final String _LITERAL_PLACEHOLDER = '\uFDDF_';
+
+  /** String describing the use case for this message.*/
+  final String _messageDescription;
+
+  /**
+   * String that is used to determin the particular case and gender needed to be
+   * returned. The format of this string follows the same pattern as in Closure,
+   * Java, and C++. This pattern is described at the beginning of this class
+   * definition. See tests/message_format_test.dart for more examples.
+   */
+  final String _messageFunction;
+
+  /**
+   * Constructor. Accepts a String [_messageDescription] describing the use case
+   * for this string in the program, and a the String [_messageFunction] that is
+   * used to determine the particular case and gender for the given instance.
+   */
+  const MessageFormat(this._messageDescription, this._messageFunction);
+
+  /**
+   * Formats a message. By default, we treat '#' with special meaning
+   * representing the number (plural_variable - plural_offset). If [ignorePound]
+   * is true, then we do not treat '#' as a special character, and it is just
+   * treated literally. [namedParameters] is a map of String keys to String or
+   * int values to influence the formatting of the message or data in the
+   * message. For example, example, in the call to 
+   *     msg_formatter.format({'NUM_PEOPLE': 5, 'NAME': 'Angela'}),
+   * object \{'NUM_PEOPLE': 5, 'NAME': 'Angela'\} holds positional parameters.
+   * 1st parameter could mean 5 people, which could influence plural format,
+   * and 2nd parameter is just relevant data to be printed out in the proper
+   * position in the message.
+   * Returns the correctly formatted message in the desired language.
+   */
+  String format(Map<String, dynamic> messageParameters,
+                [bool ignorePound=false]) {
+    // TODO(efortuna): actually perform the translation here. For now, I'm just
+    // returning a description of the message to be returned.
+    return _messageDescription;
+  }
+}