/*
 * 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.store.service;

import java.util.Iterator;

import org.onosproject.store.primitives.DocumentTreeNode;

/**
 * A hierarchical <a href="https://en.wikipedia.org/wiki/Document_Object_Model">document tree</a> data structure.
 *
 * @param V document tree value type
 */
public interface DocumentTree<V> {

    /**
     * Returns the {@link DocumentPath path} to root of the tree.
     *
     * @return path to root of the tree
     */
    DocumentPath root();

    /**
     * Returns an iterator for all the first order descendants of a node.
     *
     * @param path path to the node
     * @return an iterator for the child nodes of the specified node path
     * @throws NoSuchDocumentPathException if the path does not point to a valid node
     */
    Iterator<DocumentTreeNode<V>> getChildren(DocumentPath path);

    /**
     * Returns a document tree node.
     *
     * @param path path to node
     * @return node value or {@code null} if path does not point to a valid node
     */
    DocumentTreeNode<V> getNode(DocumentPath path);

    /**
     * Creates or updates a document tree node.
     *
     * @param path path for the node to create or update
     * @param value the non-null value to be associated with the key
     * @return the previous mapping or {@code null} if there was no previous mapping
     * @throws NoSuchDocumentPathException if the parent node (for the node to create/update) does not exist
     */
    V putNode(DocumentPath path, V value);

    /**
     * Creates a document tree node if one does not exist already.
     *
     * @param path path for the node to create
     * @param value the non-null value to be associated with the key
     * @return returns {@code true} if the mapping could be added successfully, {@code false} otherwise
     * @throws NoSuchDocumentPathException if the parent node (for the node to create) does not exist
     */
    boolean createNode(DocumentPath path, V value);

    /**
     * Removes the node with the specified path.
     *
     * is not a leaf node i.e has one or more children
     * @param path path for the node to remove
     * @return the previous value of the node or {@code null} if it did not exist
     * @throws IllegalDocumentModificationException if the remove to be removed
     */
    V removeNode(DocumentPath key);
}