Added seperate permission tree class

components/device-mgt/org.wso2.carbon.device.mgt.core/src/main/java/org/wso2/carbon/device/mgt/core/config/permission/PermissionTree.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright (c) 2015, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
+ *
+ * WSO2 Inc. licenses this file to you 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.wso2.carbon.device.mgt.core.config.permission;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import java.util.StringTokenizer;
+
+/**
+ * This class represents a tree data structure which will be used for adding and retrieving permissions.
+ */
+public class PermissionTree {
+
+    private PermissionNode rootNode;
+    private static final String DYNAMIC_PATH_NOTATION = "*";
+    private static final Log log = LogFactory.getLog(PermissionTree.class);
+
+    public PermissionTree() {
+        rootNode = new PermissionNode("/"); // initializing the root node.
+    }
+
+    /**
+     * This method is used to add permissions to the tree. Once it receives the permission
+     * it will traverse through the given request path with respect to the permission and place
+     * the permission in the appropriate place in the tree.
+     *
+     * @param permission Permission object.
+     */
+    public void addPermission(Permission permission) {
+        StringTokenizer st = new StringTokenizer(permission.getUrl(), "/");
+        PermissionNode tempRoot = rootNode;
+        PermissionNode tempChild;
+        while (st.hasMoreTokens()) {
+            tempChild = new PermissionNode(st.nextToken());
+            tempRoot = addPermissionNode(tempRoot, tempChild);
+        }
+        tempRoot.addPermission(permission.getMethod(), permission); //setting permission to the vertex
+        if (log.isDebugEnabled()) {
+            log.debug("Added permission '" + permission.getName() + "'");
+        }
+    }
+
+    /**
+     * This method is used to add vertex to the graph. The method will check for the given child
+     * whether exists within the list of children of the given parent.
+     *
+     * @param parent Parent PermissionNode.
+     * @param child  Child PermissionNode.
+     * @return returns the newly created child or the existing child.
+     */
+    private PermissionNode addPermissionNode(PermissionNode parent, PermissionNode child) {
+        PermissionNode existChild = parent.getChild(child.getPathName());
+        if (existChild == null) {
+            parent.addChild(child);
+            return child;
+        }
+        return existChild;
+    }
+
+    /**
+     * This method is used to retrieve the permission for a given url and http method.
+     * Breath First Search (BFS) is used to traverse the tree.
+     *
+     * @param url        Request URL.
+     * @param httpMethod HTTP method of the request.
+     * @return returns the permission with related to the request path or null if there is
+     * no any permission that is stored with respected to the given request path.
+     */
+    public Permission getPermission(String url, String httpMethod) {
+        StringTokenizer st = new StringTokenizer(url, "/");
+        PermissionNode tempRoot = rootNode;
+        while (st.hasMoreTokens()) {
+            String currentToken = st.nextToken();
+
+            // returns the child node which matches with the 'currentToken' path.
+            tempRoot = tempRoot.getChild(currentToken);
+
+            // if tempRoot is null, that means 'currentToken' is not matched with the child's path.
+            // It means that it is at a point where the request must have dynamic path variables.
+            // Therefor it looks for '*' in the request path. ('*' denotes dynamic path variable).
+            if (tempRoot == null) {
+                tempRoot = tempRoot.getChild(DYNAMIC_PATH_NOTATION);
+                // if tempRoot is null, that means there is no any permission which matches with the
+                // given path
+                if (tempRoot == null) {
+                    if (log.isDebugEnabled()) {
+                        log.debug("Permission for request path '" + url + "' does not exist");
+                    }
+                    return null;
+                }
+            }
+        }
+        return tempRoot.getPermission(httpMethod);
+    }
+}