[ONOS-3897] Yang Listener for Enumeration Data Type

Change-Id: If257c73da8fe2dcc2f4111f103967cfcdd7fa273
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/EnumListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/EnumListener.java
new file mode 100644
index 0000000..e255441
--- /dev/null
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/EnumListener.java
@@ -0,0 +1,168 @@
+/*
+ * 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
+ *
+ * ABNF grammar as per RFC6020
+ *  enum-stmt           = enum-keyword sep string optsep
+ *                        (";" /
+ *                         "{" stmtsep
+ *                             ;; these stmts can appear in any order
+ *                             [value-stmt stmtsep]
+ *                             [status-stmt stmtsep]
+ *                             [description-stmt stmtsep]
+ *                             [reference-stmt stmtsep]
+ *                          "}")
+ *
+ * ANTLR grammar rule
+ * enumStatement : ENUM_KEYWORD string (STMTEND | LEFT_CURLY_BRACE enumStatementBody RIGHT_CURLY_BRACE);
+ *
+ *         enumStatementBody : valueStatement? statusStatement? descriptionStatement? referenceStatement?
+ *         | valueStatement? statusStatement? referenceStatement? descriptionStatement?
+ *         | valueStatement? descriptionStatement? statusStatement? referenceStatement?
+ *         | valueStatement? descriptionStatement? referenceStatement? statusStatement?
+ *         | valueStatement? referenceStatement? statusStatement? descriptionStatement?
+ *         | valueStatement? referenceStatement? descriptionStatement? statusStatement?
+ *         | statusStatement? valueStatement? descriptionStatement? referenceStatement?
+ *         | statusStatement? valueStatement? referenceStatement? descriptionStatement?
+ *         | statusStatement? descriptionStatement? descriptionStatement? valueStatement?
+ *         | statusStatement? descriptionStatement? valueStatement? descriptionStatement?
+ *         | statusStatement? referenceStatement? valueStatement? descriptionStatement?
+ *         | statusStatement? referenceStatement? descriptionStatement? valueStatement?
+ *         | descriptionStatement? valueStatement? statusStatement? referenceStatement?
+ *         | descriptionStatement? valueStatement? referenceStatement? statusStatement?
+ *         | descriptionStatement? statusStatement? valueStatement? referenceStatement?
+ *         | descriptionStatement? statusStatement? referenceStatement? valueStatement?
+ *         | descriptionStatement? referenceStatement? valueStatement? statusStatement?
+ *         | descriptionStatement? referenceStatement? statusStatement? valueStatement?
+ *         | referenceStatement? valueStatement? descriptionStatement? statusStatement?
+ *         | referenceStatement? valueStatement? statusStatement? descriptionStatement?
+ *         | referenceStatement? statusStatement? descriptionStatement? valueStatement?
+ *         | referenceStatement? statusStatement? valueStatement? descriptionStatement?
+ *         | referenceStatement? descriptionStatement? valueStatement? statusStatement?
+ *         | referenceStatement? descriptionStatement? statusStatement? valueStatement?
+ *         ;
+ */
+
+import org.onosproject.yangutils.datamodel.YangEnum;
+import org.onosproject.yangutils.datamodel.YangEnumeration;
+import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
+import org.onosproject.yangutils.parser.Parsable;
+import static org.onosproject.yangutils.parser.ParsableDataType.ENUM_DATA;
+import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
+import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+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.DUPLICATE_ENTRY;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_CURRENT_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
+
+/**
+ * Implements listener based call back function corresponding to the "enum" rule
+ * defined in ANTLR grammar file for corresponding ABNF rule in RFC 6020.
+ */
+public final class EnumListener {
+
+    /**
+     * Creates a new enum listener.
+     */
+    private EnumListener() {
+    }
+
+    /**
+     * It is called when parser enters grammar rule (enum), 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 processEnumEntry(TreeWalkListener listener, GeneratedYangParser.EnumStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, ENUM_DATA, ctx.string().getText(), ENTRY);
+
+        YangEnum enumNode = new YangEnum();
+        enumNode.setNamedValue(ctx.string().getText());
+        listener.getParsedDataStack().push(enumNode);
+    }
+
+    /**
+     * It is called when parser exits from grammar rule (enum), it perform
+     * validations and update the data model tree.
+     *
+     * @param listener Listener's object.
+     * @param ctx context object of the grammar rule.
+     */
+    public static void processEnumExit(TreeWalkListener listener, GeneratedYangParser.EnumStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, ENUM_DATA, ctx.string().getText(), EXIT);
+
+        Parsable tmpEnumNode = listener.getParsedDataStack().peek();
+        if (tmpEnumNode instanceof YangEnum) {
+            listener.getParsedDataStack().pop();
+
+            // Check for stack to be non empty.
+            checkStackIsNotEmpty(listener, MISSING_HOLDER, ENUM_DATA, ctx.string().getText(), EXIT);
+
+            Parsable tmpNode = listener.getParsedDataStack().peek();
+            switch (tmpNode.getParsableDataType()) {
+                case ENUMERATION_DATA: {
+                    YangEnumeration yangEnumeration = (YangEnumeration) tmpNode;
+                    if ((ctx.enumStatementBody() == null) || (ctx.enumStatementBody().valueStatement() == null)) {
+                        int maxValue = 0;
+                        boolean isValuePresent = false;
+
+                        for (YangEnum curEnum : yangEnumeration.getEnumSet()) {
+                            if (maxValue <= curEnum.getValue()) {
+                                maxValue = curEnum.getValue();
+                                isValuePresent = true;
+                            }
+                        }
+                        if (isValuePresent) {
+                            maxValue++;
+                        }
+                        ((YangEnum) tmpEnumNode).setValue(maxValue);
+                    }
+                    try {
+                        yangEnumeration.addEnumInfo((YangEnum) tmpEnumNode);
+                    } catch (DataModelException e) {
+                        ParserException parserException = new ParserException(constructExtendedListenerErrorMessage(
+                                DUPLICATE_ENTRY, ENUM_DATA, ctx.string().getText(), EXIT, e.getMessage()));
+                        parserException.setLine(ctx.string().STRING(0).getSymbol().getLine());
+                        parserException.setCharPosition(ctx.string().STRING(0).getSymbol().getCharPositionInLine());
+                        throw parserException;
+                    }
+                    break;
+                }
+                default:
+                    throw new ParserException(
+                            constructListenerErrorMessage(INVALID_HOLDER, ENUM_DATA, ctx.string().getText(), EXIT));
+            }
+        } else {
+            throw new ParserException(
+                    constructListenerErrorMessage(MISSING_CURRENT_HOLDER, ENUM_DATA, ctx.string().getText(), EXIT));
+        }
+    }
+}
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/EnumerationListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/EnumerationListener.java
new file mode 100644
index 0000000..f83c49c
--- /dev/null
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/EnumerationListener.java
@@ -0,0 +1,152 @@
+/*
+ * 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
+ *
+ * ABNF grammar as per RFC6020
+ * type-body-stmts     = numerical-restrictions /
+ *                       decimal64-specification /
+ *                      string-restrictions /
+ *                       enum-specification /
+ *                       leafref-specification /
+ *                       identityref-specification /
+ *                       instance-identifier-specification /
+ *                       bits-specification /
+ *                       union-specification
+ *
+ * enum-specification  = 1*(enum-stmt stmtsep)
+ *
+ * ANTLR grammar rule
+ *
+ * typeBodyStatements : numericalRestrictions | stringRestrictions | enumSpecification
+ *                 | leafrefSpecification | identityrefSpecification | instanceIdentifierSpecification
+ *                 | bitsSpecification | unionSpecification;
+ *
+ * enumSpecification : enumStatement+;
+ */
+
+import org.onosproject.yangutils.datamodel.YangEnumeration;
+import org.onosproject.yangutils.datamodel.YangLeaf;
+import org.onosproject.yangutils.datamodel.YangLeafList;
+import org.onosproject.yangutils.datamodel.YangType;
+import org.onosproject.yangutils.parser.Parsable;
+import static org.onosproject.yangutils.parser.ParsableDataType.ENUMERATION_DATA;
+import static org.onosproject.yangutils.parser.ParsableDataType.TYPE_DATA;
+import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
+import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+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.constructListenerErrorMessage;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_CURRENT_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
+
+/**
+ * Implements listener based call back function corresponding to the
+ * "enumeration" rule defined in ANTLR grammar file for corresponding ABNF rule
+ * in RFC 6020.
+ */
+public final class EnumerationListener {
+
+    /**
+     * Creates a new enumeration listener.
+     */
+    private EnumerationListener() {
+    }
+
+    /**
+     * It is called when parser enters grammar rule (enumeration), 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 processEnumerationEntry(TreeWalkListener listener,
+            GeneratedYangParser.EnumSpecificationContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, ENUMERATION_DATA, "", ENTRY);
+
+        if (listener.getParsedDataStack().peek() instanceof YangType) {
+            YangEnumeration enumerationNode = new YangEnumeration();
+            Parsable typeData = listener.getParsedDataStack().pop();
+
+            // Check for stack to be non empty.
+            checkStackIsNotEmpty(listener, MISSING_HOLDER, ENUMERATION_DATA, "", ENTRY);
+
+            Parsable tmpData = listener.getParsedDataStack().peek();
+
+            switch (tmpData.getParsableDataType()) {
+                case LEAF_DATA:
+                    enumerationNode.setEnumerationName(((YangLeaf) tmpData).getLeafName());
+                    break;
+                case LEAF_LIST_DATA:
+                    enumerationNode.setEnumerationName(((YangLeafList) tmpData).getLeafName());
+                    break;
+                // TODO typedef, union, deviate.
+                default:
+                    throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, TYPE_DATA,
+                            ((YangType) typeData).getDataTypeName(), ENTRY));
+            }
+            listener.getParsedDataStack().push(typeData);
+            listener.getParsedDataStack().push(enumerationNode);
+        } else {
+            throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, ENUMERATION_DATA, "", ENTRY));
+        }
+    }
+
+    /**
+     * It is called when parser exits from grammar rule (enumeration), it
+     * perform validations and update the data model tree.
+     *
+     * @param listener Listener's object.
+     * @param ctx context object of the grammar rule.
+     */
+    public static void processEnumerationExit(TreeWalkListener listener,
+            GeneratedYangParser.EnumSpecificationContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, ENUMERATION_DATA, "", EXIT);
+
+        Parsable tmpEnumerationNode = listener.getParsedDataStack().peek();
+        if (tmpEnumerationNode instanceof YangEnumeration) {
+            listener.getParsedDataStack().pop();
+
+            // Check for stack to be non empty.
+            checkStackIsNotEmpty(listener, MISSING_HOLDER, ENUMERATION_DATA, "", EXIT);
+
+            Parsable tmpNode = listener.getParsedDataStack().peek();
+            switch (tmpNode.getParsableDataType()) {
+                case TYPE_DATA: {
+                    YangType typeNode = (YangType) tmpNode;
+                    typeNode.setDataTypeExtendedInfo((YangEnumeration) tmpEnumerationNode);
+                    break;
+                }
+                default:
+                    throw new ParserException(
+                            constructListenerErrorMessage(INVALID_HOLDER, ENUMERATION_DATA, "", EXIT));
+            }
+        } else {
+            throw new ParserException(
+                    constructListenerErrorMessage(MISSING_CURRENT_HOLDER, ENUMERATION_DATA, "", EXIT));
+        }
+    }
+}
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeListener.java
index e5ebf36..de595f5 100644
--- a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeListener.java
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/TypeListener.java
@@ -21,18 +21,18 @@
 import org.onosproject.yangutils.datamodel.YangLeafList;
 import org.onosproject.yangutils.datamodel.YangType;
 import org.onosproject.yangutils.parser.Parsable;
+import static org.onosproject.yangutils.parser.ParsableDataType.TYPE_DATA;
 import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
 import org.onosproject.yangutils.parser.exceptions.ParserException;
 import org.onosproject.yangutils.parser.impl.TreeWalkListener;
-
-import static org.onosproject.yangutils.parser.ParsableDataType.TYPE_DATA;
 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.constructListenerErrorMessage;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_CURRENT_HOLDER;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
 import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
 
-
 /*
  * Reference: RFC6020 and YANG ANTLR Grammar
  *
@@ -48,8 +48,8 @@
  */
 
 /**
- * Implements listener based call back function corresponding to the "type"
- * rule defined in ANTLR grammar file for corresponding ABNF rule in RFC 6020.
+ * Implements listener based call back function corresponding to the "type" rule
+ * defined in ANTLR grammar file for corresponding ABNF rule in RFC 6020.
  */
 public final class TypeListener {
 
@@ -60,15 +60,14 @@
     }
 
     /**
-     * It is called when parser receives an input matching the grammar
-     * rule (type), performs validation and updates the data model
-     * tree.
+     * It is called when parser receives an input matching the grammar rule
+     * (type), performs validation and updates the data model tree.
      *
      * @param listener listener's object.
      * @param ctx context object of the grammar rule.
      */
     public static void processTypeEntry(TreeWalkListener listener,
-                                        GeneratedYangParser.TypeStatementContext ctx) {
+            GeneratedYangParser.TypeStatementContext ctx) {
 
         // Check for stack to be non empty.
         checkStackIsNotEmpty(listener, MISSING_HOLDER, TYPE_DATA, ctx.string().getText(), ENTRY);
@@ -78,21 +77,46 @@
         type.setDataTypeName(ctx.string().getText());
         type.setDataType(yangDataTypes);
 
+        listener.getParsedDataStack().push(type);
+    }
+
+    /**
+     * It is called when parser exits from grammar rule (type), it perform
+     * validations and update the data model tree.
+     *
+     * @param listener Listener's object.
+     * @param ctx context object of the grammar rule.
+     */
+    public static void processTypeExit(TreeWalkListener listener,
+            GeneratedYangParser.TypeStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_CURRENT_HOLDER, TYPE_DATA, ctx.string().getText(), EXIT);
+
+        Parsable type = listener.getParsedDataStack().pop();
+        if (!(type instanceof YangType)) {
+            throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, TYPE_DATA,
+                    ctx.string().getText(), EXIT));
+        }
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, TYPE_DATA, ctx.string().getText(), EXIT);
+
         Parsable tmpData = listener.getParsedDataStack().peek();
         switch (tmpData.getParsableDataType()) {
             case LEAF_DATA:
                 YangLeaf leaf = (YangLeaf) tmpData;
-                leaf.setDataType(type);
+                leaf.setDataType((YangType) type);
                 break;
             case LEAF_LIST_DATA:
                 YangLeafList leafList = (YangLeafList) tmpData;
-                leafList.setDataType(type);
+                leafList.setDataType((YangType) type);
                 break;
             case TYPEDEF_DATA: //TODO
                 break;
             default:
                 throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, TYPE_DATA,
-                        ctx.string().getText(), ENTRY));
+                        ctx.string().getText(), EXIT));
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ValueListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ValueListener.java
new file mode 100644
index 0000000..07ada45
--- /dev/null
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ValueListener.java
@@ -0,0 +1,115 @@
+/*
+ * 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
+ *
+ * ABNF grammar as per RFC6020
+ * value-stmt = value-keyword sep integer-value stmtend
+ *
+ * ANTLR grammar rule
+ * valueStatement : VALUE_KEYWORD ((MINUS INTEGER) | INTEGER) STMTEND;
+ */
+
+import org.onosproject.yangutils.datamodel.YangEnum;
+import org.onosproject.yangutils.datamodel.YangEnumeration;
+import org.onosproject.yangutils.parser.Parsable;
+import static org.onosproject.yangutils.parser.ParsableDataType.VALUE_DATA;
+import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.exceptions.ParserException;
+import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+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.constructListenerErrorMessage;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
+
+/**
+ * Implements listener based call back function corresponding to the "value"
+ * rule defined in ANTLR grammar file for corresponding ABNF rule in RFC 6020.
+ */
+public final class ValueListener {
+
+    /**
+     * Creates a new value listener.
+     */
+    private ValueListener() {
+    }
+
+    /**
+     * It is called when parser receives an input matching the grammar rule
+     * (value), perform validations and update the data model tree.
+     *
+     * @param listener Listener's object.
+     * @param ctx context object of the grammar rule.
+     */
+    public static void processValueEntry(TreeWalkListener listener, GeneratedYangParser.ValueStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, VALUE_DATA, ctx.INTEGER().getText(), ENTRY);
+
+        // Obtain the node of the stack.
+        Parsable tmpNode = listener.getParsedDataStack().peek();
+        switch (tmpNode.getParsableDataType()) {
+            case ENUM_DATA: {
+                YangEnum enumNode = (YangEnum) tmpNode;
+                if (!isEnumValueValid(listener, ctx)) {
+                    ParserException parserException = new ParserException("Input version not supported");
+                    parserException.setLine(ctx.INTEGER().getSymbol().getLine());
+                    parserException.setCharPosition(ctx.INTEGER().getSymbol().getCharPositionInLine());
+                    throw parserException;
+                }
+                enumNode.setValue(Integer.valueOf(ctx.INTEGER().getText()));
+                break;
+            }
+            default:
+                throw new ParserException(
+                        constructListenerErrorMessage(INVALID_HOLDER, VALUE_DATA, ctx.INTEGER().getText(), ENTRY));
+        }
+    }
+
+    /**
+     * Validates ENUM value uniqueness.
+     *
+     * @param listener Listener's object.
+     * @param ctx context object of the grammar rule.
+     * @return validation result
+     */
+    private static boolean isEnumValueValid(TreeWalkListener listener, GeneratedYangParser.ValueStatementContext ctx) {
+        Parsable enumNode = listener.getParsedDataStack().pop();
+        Parsable tmpNode = listener.getParsedDataStack().peek();
+        switch (tmpNode.getParsableDataType()) {
+            case ENUMERATION_DATA: {
+                YangEnumeration yangEnumeration = (YangEnumeration) tmpNode;
+                for (YangEnum curEnum : yangEnumeration.getEnumSet()) {
+                    if (Integer.valueOf(ctx.INTEGER().getText()) == curEnum.getValue()) {
+                        listener.getParsedDataStack().push(enumNode);
+                        return false;
+                    }
+                }
+                listener.getParsedDataStack().push(enumNode);
+                return true;
+            }
+            default:
+                listener.getParsedDataStack().push(enumNode);
+                throw new ParserException(
+                        constructListenerErrorMessage(INVALID_HOLDER, VALUE_DATA, ctx.INTEGER().getText(), EXIT));
+        }
+    }
+}