/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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.apache.sling.servlets.get.impl.helpers;

import org.apache.sling.api.request.RecursionTooDeepException;
import org.apache.sling.api.resource.Resource;
import org.apache.sling.api.resource.ResourceUtil;
import org.apache.sling.commons.json.JSONException;
import org.apache.sling.commons.json.JSONObject;

import java.io.StringWriter;
import java.util.Iterator;
import java.util.LinkedList;

import javax.jcr.RepositoryException;

public class ResourceTraversor {

    private long count;

    private long maxResources;

    private int maxRecursionLevels;

    private JSONObject startObject;

    private String startingPath;

    private LinkedList<Resource> currentQueue;

    private LinkedList<Resource> nextQueue;

    private Resource startResource;

    private JsonResourceWriter jsResourceWriter;

    private boolean tidy;

    public ResourceTraversor(int levels, long maxNodes, Resource resource, boolean tidy) throws RepositoryException,
            JSONException {
        this.setMaxNodes(maxNodes);
        this.maxRecursionLevels = levels;
        this.startResource = resource;
        this.tidy = tidy;
        startingPath = resource.getPath();
        jsResourceWriter = new JsonResourceWriter(null);
        currentQueue = new LinkedList<Resource>();
        nextQueue = new LinkedList<Resource>();
        startObject = adapt(resource);
    }

    /**
     * Recursive descent from startResource, collecting JSONObjects into
     * startObject. Throws a RecursionTooDeepException if the maximum number of
     * nodes is reached on a "deep" traversal (where "deep" === level greateer
     * than 1).
     *
     * @throws RepositoryException
     * @throws RecursionTooDeepException When the resource has more child nodes
     *             then allowed.
     * @throws JSONException
     */
    public void collectResources() throws RepositoryException, RecursionTooDeepException, JSONException {
        collectChildren(startResource, 0);
    }

    /**
     * @param resource
     * @param currentLevel
     * @throws RecursionTooDeepException
     * @throws JSONException
     * @throws RepositoryException
     */
    private void collectChildren(Resource resource, int currentLevel) throws RecursionTooDeepException, JSONException,
            RepositoryException {

        if (maxRecursionLevels == -1 || currentLevel < maxRecursionLevels) {
            final Iterator<Resource> children = ResourceUtil.listChildren(resource);
            while (children.hasNext()) {
                count++;
                Resource res = children.next();
                // SLING-2320: always allow enumeration of one's children;
                // DOS-limitation is for deeper traversals.
                if (count > maxResources && maxRecursionLevels != 1) {
                    throw new RecursionTooDeepException(String.valueOf(currentLevel));
                }
                collectResource(res, currentLevel);
                nextQueue.addLast(res);
            }
        }

        while (!currentQueue.isEmpty() || !nextQueue.isEmpty()) {
            if (currentQueue.isEmpty()) {
                currentLevel++;
                currentQueue = nextQueue;
                nextQueue = new LinkedList<Resource>();
            }
            Resource nextResource = currentQueue.removeFirst();
            collectChildren(nextResource, currentLevel);
        }
    }

    /**
     * Adds a resource in the JSON tree.
     *
     * @param resource The resource to add
     * @param level The level where this resource is located.
     * @throws RepositoryException
     * @throws JSONException
     */
    protected void collectResource(Resource resource, int level) throws RepositoryException, JSONException {

        if (!resource.getPath().equals(startingPath)) {
            JSONObject o = adapt(resource);
            getParentJSONObject(resource, level).put(ResourceUtil.getName(resource), o);
        }
    }

    /**
     * Adapt a Resource to a JSON Object.
     *
     * @param resource The resource to adapt.
     * @return The JSON representation of the Resource
     * @throws JSONException
     */
    private JSONObject adapt(Resource resource) throws JSONException {
        // TODO Find a better way to adapt a Resource to a JSONObject.
        StringWriter writer = new StringWriter();
        jsResourceWriter.dump(resource, writer, 0, tidy);
        return new JSONObject(writer.getBuffer().toString());
    }

    /**
     * Get the JSON Object where this resource should be added in.
     *
     * @param resource
     * @param level
     * @return
     * @throws RepositoryException
     * @throws JSONException
     */
    private JSONObject getParentJSONObject(Resource resource, int level) throws RepositoryException, JSONException {
        String path = resource.getPath();
        // The root node.
        if (path.equals(startingPath)) {
            return startObject;
        }

        // Some level deeper
        String pathDiff = path.substring(startingPath.length());
        String[] names = pathDiff.split("/");
        JSONObject o = startObject;
        for (String name : names) {
            try {
                o = o.getJSONObject(name);
            } catch (JSONException e) {
            }
        }
        return o;

    }

    /**
     * @return The number of nodes this visitor found.
     */
    public long getCount() {
        return count;
    }

    /**
     * @param maxNodes the maxNodes to set
     */
    public void setMaxNodes(long maxNodes) {
        this.maxResources = maxNodes;
    }

    /**
     * @return the maxNodes
     */
    public long getMaxNodes() {
        return maxResources;
    }

    public JSONObject getJSONObject() {
        return startObject;
    }

}