[ONOS-4744] Leafref implementation and UT
Change-Id: I151797185e0bb1695c0640b667ae76ef87c4d4b0
diff --git a/utils/yangutils/plugin/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PathListener.java b/utils/yangutils/plugin/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PathListener.java
new file mode 100644
index 0000000..b02c6f4
--- /dev/null
+++ b/utils/yangutils/plugin/src/main/java/org/onosproject/yangutils/parser/impl/listeners/PathListener.java
@@ -0,0 +1,89 @@
+/*
+ * Copyright 2016-present 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;
+
+import org.onosproject.yangutils.datamodel.YangLeafRef;
+import org.onosproject.yangutils.datamodel.utils.Parsable;
+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.ListenerErrorMessageConstruction.constructListenerErrorMessage;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerUtil.validatePathArgument;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
+import static org.onosproject.yangutils.datamodel.utils.YangConstructType.PATH_DATA;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.MISSING_HOLDER;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorLocation.ENTRY;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerErrorType.INVALID_HOLDER;
+
+/*
+ * Reference: RFC6020 and YANG ANTLR Grammar
+ *
+ * ABNF grammar as per RFC6020
+ * leafref-specification =
+ * ;; these stmts can appear in any order
+ * path-stmt stmtsep
+ * [require-instance-stmt stmtsep]
+ *
+ * path-stmt = path-keyword sep path-arg-str stmtend
+ *
+ * ANTLR grammar rule
+ *
+ * leafrefSpecification : (pathStatement (requireInstanceStatement)?) | ((requireInstanceStatement)? pathStatement);
+ *
+ * pathStatement : PATH_KEYWORD path STMTEND;
+ */
+
+/**
+ * Represents listener based call back function corresponding to the
+ * "path" rule defined in ANTLR grammar file for corresponding ABNF rule
+ * in RFC 6020.
+ */
+public final class PathListener {
+
+ /**
+ * Creates a new path listener.
+ */
+ private PathListener() {
+ }
+
+ /**
+ * It is called when parser receives an input matching the grammar rule
+ * (path), performs validation and updates the data model tree.
+ *
+ * @param listener listener's object
+ * @param ctx context object of the grammar rule
+ */
+ public static void processPathEntry(TreeWalkListener listener,
+ GeneratedYangParser.PathStatementContext ctx) {
+
+ // Check for stack to be non empty.
+ checkStackIsNotEmpty(listener, MISSING_HOLDER, PATH_DATA, ctx.path().getText(), ENTRY);
+
+ Parsable curData = listener.getParsedDataStack().peek();
+
+ // Checks the holder of path as leafref, else throws error.
+ if (curData instanceof YangLeafRef) {
+
+ // Splitting the path argument and updating it in the datamodel tree.
+ validatePathArgument(ctx.path().getText(), PATH_DATA, ctx, (YangLeafRef) curData);
+ } else {
+ throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, PATH_DATA,
+ ctx.path().getText(), ENTRY));
+ }
+ }
+}