YANG Derived Data Type Support + Change in YANG Parser Grammar to 
Support String values which are not in double quotes with UT case + 
Addition of Revision Date Validation with UT case + Removal of 
String.valueOf

Change-Id: Ic152265a35c0d2b0f84473a94ca67681cf8efca8
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeDefListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeDefListener.java
new file mode 100644
index 0000000..9d41253
--- /dev/null
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeDefListener.java
@@ -0,0 +1,203 @@
+/*
+ * Copyright 2014-2016 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.yangutils.parser.impl.listeners;
+
+/*
+ * Reference: RFC6020 and YANG ANTLR Grammar
+ *
+ * body-stmts          = *((extension-stmt /
+ *                          feature-stmt /
+ *                          identity-stmt /
+ *                          typedef-stmt /
+ *                          grouping-stmt /
+ *                          data-def-stmt /
+ *                          augment-stmt /
+ *                          rpc-stmt /
+ *                          notification-stmt /
+ *                          deviation-stmt) stmtsep)
+ *
+ * typedef-stmt        = typedef-keyword sep identifier-arg-str optsep
+ *                       "{" stmtsep
+ *                           ;; these stmts can appear in any order
+ *                           type-stmt stmtsep
+ *                          [units-stmt stmtsep]
+ *                           [default-stmt stmtsep]
+ *                           [status-stmt stmtsep]
+ *                           [description-stmt stmtsep]
+ *                           [reference-stmt stmtsep]
+ *                         "}"
+ *
+ * ANTLR grammar rule
+ * typedefStatement : TYPEDEF_KEYWORD IDENTIFIER LEFT_CURLY_BRACE
+ *                (typeStatement | unitsStatement | defaultStatement | statusStatement
+ *                | descriptionStatement | referenceStatement)* RIGHT_CURLY_BRACE;
+ */
+
+import org.onosproject.yangutils.datamodel.YangContainer;
+import org.onosproject.yangutils.datamodel.YangList;
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangNode;
+import org.onosproject.yangutils.datamodel.YangSubModule;
+import org.onosproject.yangutils.datamodel.YangTypeDef;
+import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
+import static org.onosproject.yangutils.parser.ParsableDataType.TYPEDEF_DATA;
+import static org.onosproject.yangutils.parser.ParsableDataType.UNITS_DATA;
+import static org.onosproject.yangutils.parser.ParsableDataType.DEFAULT_DATA;
+import static org.onosproject.yangutils.parser.ParsableDataType.TYPE_DATA;
+import static org.onosproject.yangutils.parser.ParsableDataType.DESCRIPTION_DATA;
+import static org.onosproject.yangutils.parser.ParsableDataType.REFERENCE_DATA;
+import static org.onosproject.yangutils.parser.ParsableDataType.STATUS_DATA;
+import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
+import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+import org.onosproject.yangutils.parser.impl.YangUtilsParserManager;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.EXIT;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructExtendedListenerErrorMessage;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorMessageConstruction.constructListenerErrorMessage;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_CARDINALITY;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.UNHANDLED_PARSED_DATA;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_CURRENT_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
+
+/**
+ * Implements listener based call back function corresponding to the "typedef"
+ * rule defined in ANTLR grammar file for corresponding ABNF rule in RFC 6020.
+ */
+public final class TypeDefListener {
+
+    private static ParsableDataType yangConstruct;
+
+    /**
+     * Creates a new typedef listener.
+     */
+    private TypeDefListener() {
+    }
+
+    /**
+     * It is called when parser enters grammar rule (typedef), it perform
+     * validations and updates the data model tree.
+     *
+     * @param listener listener's object.
+     * @param ctx context object of the grammar rule.
+     */
+    public static void processTypeDefEntry(TreeWalkListener listener,
+            GeneratedYangParser.TypedefStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, TYPEDEF_DATA, ctx.IDENTIFIER().getText(), ENTRY);
+
+        boolean result = validateSubStatementsCardinality(ctx);
+        if (!result) {
+            throw new ParserException(constructListenerErrorMessage(INVALID_CARDINALITY, yangConstruct, "", ENTRY));
+        }
+
+        YangTypeDef typeDefNode = new YangTypeDef();
+        typeDefNode.setDerivedName(ctx.IDENTIFIER().getText());
+
+        Parsable curData = listener.getParsedDataStack().peek();
+
+        if (curData instanceof YangModule | curData instanceof YangSubModule | curData instanceof YangContainer
+                | curData instanceof YangList) {
+            /*
+             * TODO YangGrouping, YangRpc, YangInput, YangOutput, Notification.
+             */
+            YangNode curNode = (YangNode) curData;
+            try {
+                curNode.addChild(typeDefNode);
+            } catch (DataModelException e) {
+                throw new ParserException(constructExtendedListenerErrorMessage(UNHANDLED_PARSED_DATA,
+                        TYPEDEF_DATA, ctx.IDENTIFIER().getText(), ENTRY, e.getMessage()));
+            }
+            listener.getParsedDataStack().push(typeDefNode);
+        } else {
+            throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER,
+                    TYPEDEF_DATA, ctx.IDENTIFIER().getText(), ENTRY));
+        }
+    }
+
+    /**
+     * It is called when parser exits from grammar rule (typedef), it perform
+     * validations and updates the data model tree.
+     *
+     * @param listener listener's object.
+     * @param ctx context object of the grammar rule.
+     */
+    public static void processTypeDefExit(TreeWalkListener listener,
+            GeneratedYangParser.TypedefStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, TYPEDEF_DATA, ctx.IDENTIFIER().getText(), EXIT);
+
+        if (listener.getParsedDataStack().peek() instanceof YangTypeDef) {
+            listener.getParsedDataStack().pop();
+        } else {
+            listener.getErrorInformation().setErrorFlag(true);
+            throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, TYPEDEF_DATA,
+                    ctx.IDENTIFIER().getText(), EXIT));
+        }
+    }
+
+    /**
+     * Validates the cardinality of typedef sub-statements as per grammar.
+     *
+     * @param ctx context object of the grammar rule.
+     * @return true/false validation success or failure.
+     */
+    private static boolean validateSubStatementsCardinality(GeneratedYangParser.TypedefStatementContext ctx) {
+
+        if ((!ctx.unitsStatement().isEmpty())
+                && (ctx.unitsStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = UNITS_DATA;
+            return false;
+        }
+
+        if ((!ctx.defaultStatement().isEmpty())
+                && (ctx.defaultStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = DEFAULT_DATA;
+            return false;
+        }
+
+        if (ctx.typeStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY) {
+            yangConstruct = TYPE_DATA;
+            return false;
+        }
+
+        if ((!ctx.descriptionStatement().isEmpty())
+                && (ctx.descriptionStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = DESCRIPTION_DATA;
+            return false;
+        }
+
+        if ((!ctx.referenceStatement().isEmpty())
+                && (ctx.referenceStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = REFERENCE_DATA;
+            return false;
+        }
+
+        if ((!ctx.statusStatement().isEmpty())
+                && (ctx.statusStatement().size() != YangUtilsParserManager.SUB_STATEMENT_CARDINALITY)) {
+            yangConstruct = STATUS_DATA;
+            return false;
+        }
+        return true;
+    }
+}