[ONOS-4350] Inter Jar dependency implementation and code restructuring.

Change-Id: Iacac75e4187aed93ce1754c170a9c19707e5b8c3
diff --git a/utils/yangutils/plugin/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ImportListener.java b/utils/yangutils/plugin/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ImportListener.java
new file mode 100644
index 0000000..76a2e30
--- /dev/null
+++ b/utils/yangutils/plugin/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ImportListener.java
@@ -0,0 +1,140 @@
+/*
+ * 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.YangImport;
+import org.onosproject.yangutils.datamodel.YangModule;
+import org.onosproject.yangutils.datamodel.YangSubModule;
+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.datamodel.utils.YangConstructType.IMPORT_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.ListenerUtil.getValidIdentifier;
+import static org.onosproject.yangutils.parser.impl.parserutils.ListenerValidation.checkStackIsNotEmpty;
+
+/*
+ * Reference: RFC6020 and YANG ANTLR Grammar
+ *
+ * ABNF grammar as per RFC6020
+ * linkage-stmts       = ;; these stmts can appear in any order
+ *                       *(import-stmt stmtsep)
+ *                       *(include-stmt stmtsep)
+ *
+ * import-stmt         = import-keyword sep identifier-arg-str optsep
+ *                       "{" stmtsep
+ *                           prefix-stmt stmtsep
+ *                           [revision-date-stmt stmtsep]
+ *                        "}"
+ *
+ * ANTLR grammar rule
+ * linkage_stmts : (import_stmt
+ *               | include_stmt)*;
+ * import_stmt : IMPORT_KEYWORD identifier LEFT_CURLY_BRACE import_stmt_body
+ *               RIGHT_CURLY_BRACE;
+ * import_stmt_body : prefix_stmt revision_date_stmt?;
+ */
+
+/**
+ * Represents listener based call back function corresponding to the "import"
+ * rule defined in ANTLR grammar file for corresponding ABNF rule in RFC 6020.
+ */
+public final class ImportListener {
+
+    /**
+     * Creates a new import listener.
+     */
+    private ImportListener() {
+    }
+
+    /**
+     * It is called when parser receives an input matching the grammar rule
+     * (import), perform validations and update the data model tree.
+     *
+     * @param listener Listener's object
+     * @param ctx      context object of the grammar rule
+     */
+    public static void processImportEntry(TreeWalkListener listener, GeneratedYangParser.ImportStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, IMPORT_DATA, ctx.identifier().getText(), ENTRY);
+
+        String identifier = getValidIdentifier(ctx.identifier().getText(), IMPORT_DATA, ctx);
+
+        YangImport importNode = new YangImport();
+        importNode.setModuleName(identifier);
+
+        // Set the line number and character position in line for the belongs to.
+        int errorLine = ctx.getStart().getLine();
+        int errorPosition = ctx.getStart().getCharPositionInLine();
+        importNode.setLineNumber(errorLine);
+        importNode.setCharPosition(errorPosition);
+
+        // Push import node to the stack.
+        listener.getParsedDataStack().push(importNode);
+    }
+
+    /**
+     * It is called when parser exits from grammar rule (import), 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 processImportExit(TreeWalkListener listener, GeneratedYangParser.ImportStatementContext ctx) {
+
+        // Check for stack to be non empty.
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, IMPORT_DATA, ctx.identifier().getText(), EXIT);
+
+        Parsable tmpImportNode = listener.getParsedDataStack().peek();
+        if (tmpImportNode instanceof YangImport) {
+            listener.getParsedDataStack().pop();
+
+            // Check for stack to be non empty.
+            checkStackIsNotEmpty(listener, MISSING_HOLDER, IMPORT_DATA, ctx.identifier().getText(),
+                    EXIT);
+
+            Parsable tmpNode = listener.getParsedDataStack().peek();
+            switch (tmpNode.getYangConstructType()) {
+                case MODULE_DATA: {
+                    YangModule module = (YangModule) tmpNode;
+                    module.addToImportList((YangImport) tmpImportNode);
+                    break;
+                }
+                case SUB_MODULE_DATA: {
+                    YangSubModule subModule = (YangSubModule) tmpNode;
+                    subModule.addToImportList((YangImport) tmpImportNode);
+                    break;
+                }
+                default:
+                    throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, IMPORT_DATA,
+                            ctx.identifier().getText(),
+                            EXIT));
+            }
+        } else {
+            throw new ParserException(constructListenerErrorMessage(MISSING_CURRENT_HOLDER, IMPORT_DATA,
+                    ctx.identifier().getText(), EXIT));
+        }
+    }
+}