[ONOS-3906],[ONOS-3910] Implementation of YANG module and leaf/leaf-list translator.

Change-Id: If1a8a991ffafa14b51211f97c435176ee1bf856f
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/utils/io/impl/YangIoUtils.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/utils/io/impl/YangIoUtils.java
new file mode 100644
index 0000000..af83de4
--- /dev/null
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/utils/io/impl/YangIoUtils.java
@@ -0,0 +1,129 @@
+/*
+ * Copyright 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.utils.io.impl;
+
+import java.io.BufferedWriter;
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.util.List;
+
+import org.sonatype.plexus.build.incremental.BuildContext;
+import org.apache.maven.project.MavenProject;
+import org.apache.maven.model.Resource;
+
+import org.onosproject.yangutils.utils.UtilConstants;
+
+import static org.slf4j.LoggerFactory.getLogger;
+import org.slf4j.Logger;
+
+/**
+ * Provides common utility functionalities for code generation.
+ */
+public final class YangIoUtils {
+
+    private static final Logger log = getLogger(YangIoUtils.class);
+
+    /**
+     * Default constructor.
+     */
+    private YangIoUtils() {
+    }
+
+    /**
+     * Creates the directory structure.
+     *
+     * @param path directory path
+     * @return directory structure
+     */
+    public static File createDirectories(String path) {
+
+        File generatedDir = new File(UtilConstants.YANG_GEN_DIR + File.separator + path);
+        generatedDir.mkdirs();
+        return generatedDir;
+    }
+
+    /**
+     * Adds package info file for the created directory.
+     *
+     * @param path directory path
+     * @param classInfo class info for the package
+     * @param pack package of the directory
+     * @throws IOException when fails to create package info file.
+     */
+    public static void addPackageInfo(File path, String classInfo, String pack) throws IOException {
+
+        try {
+
+            File packageInfo = new File(path + File.separator + "package-info.java");
+            packageInfo.createNewFile();
+            if (packageInfo.exists()) {
+
+                FileWriter fileWriter = null;
+                BufferedWriter bufferedWriter = null;
+                fileWriter = new FileWriter(packageInfo);
+                bufferedWriter = new BufferedWriter(fileWriter);
+                bufferedWriter.write(CopyrightHeader.getCopyrightHeader());
+                bufferedWriter.write(JavaDocGen.getJavaDoc(JavaDocGen.JavaDocType.PACKAGE_INFO, classInfo));
+                bufferedWriter.write(UtilConstants.PACKAGE + UtilConstants.SPACE + pack + UtilConstants.SEMI_COLAN);
+                bufferedWriter.close();
+            }
+        } catch (IOException e) {
+            throw new IOException("Exception occured while creating package info file.");
+        }
+    }
+
+    /**
+     * Cleans the generated directory if already exist in source folder.
+     *
+     * @param baseDir generated directory in previous build.
+     */
+    public static void clean(String baseDir) {
+        File generatedDirectory = new File(baseDir + File.separator + UtilConstants.YANG_GEN_DIR);
+        if (generatedDirectory.exists()) {
+            List<String> javafiles;
+            try {
+                javafiles = YangFileScanner.getJavaFiles(generatedDirectory.toString());
+                for (String file : javafiles) {
+                    File currentFile = new File(file);
+                    currentFile.delete();
+                }
+            } catch (IOException e) {
+                log.info("Failed to delete the generated files in " + generatedDirectory + " directory");
+            }
+            generatedDirectory.delete();
+        }
+    }
+
+    /**
+     * Adds generated source directory to the compilation root.
+     *
+     * @param source directory
+     * @param project current maven project
+     * @param context current build context
+     */
+    public static void addToSource(String source, MavenProject project, BuildContext context) {
+
+        project.addCompileSourceRoot(source);
+        Resource rsc = new Resource();
+        rsc.setDirectory(source);
+        project.addResource(rsc);
+        context.refresh(project.getBasedir());
+        log.info("Source directory added to compilation root: " + source);
+    }
+
+}