CQSPeekMessageAction.java

/**
 * Copyright 2012 Comcast Corporation
 * 
 * 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 com.comcast.cqs.controller;

import java.io.IOException;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Random;

import javax.servlet.AsyncContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.json.JSONException;

import com.comcast.cmb.common.model.User;
import com.comcast.cmb.common.persistence.PersistenceFactory;
import com.comcast.cmb.common.util.CMBErrorCodes;
import com.comcast.cmb.common.util.CMBException;
import com.comcast.cmb.common.util.CMBProperties;
import com.comcast.cmb.common.util.PersistenceException;
import com.comcast.cqs.io.CQSMessagePopulator;
import com.comcast.cqs.model.CQSMessage;
import com.comcast.cqs.model.CQSQueue;
import com.comcast.cqs.util.CQSConstants;
import com.comcast.cqs.util.Util;

/**
 * Peek message in queue
 * @author bwolf
 *
 */
public class CQSPeekMessageAction extends CQSAction {
	
	private static final Random rand = new Random();
	
	public CQSPeekMessageAction() {
		super("PeekMessage");
	}

	@Override
	public boolean doAction(User user, AsyncContext asyncContext) throws Exception {
		
        HttpServletRequest request = (HttpServletRequest)asyncContext.getRequest();
        HttpServletResponse response = (HttpServletResponse)asyncContext.getResponse();

	    CQSQueue queue = CQSCache.getCachedQueue(user, request);
		List<CQSMessage> messageList = getMessages(request, true, queue);
        
        Map<String, String[]> requestParams = request.getParameterMap();
        List<String> filterAttributes = new ArrayList<String>();
        List<String> filterMessageAttributes = new ArrayList<String>();
        
        for (String k: requestParams.keySet()) {
        	if (k.contains(CQSConstants.MESSAGE_ATTRIBUTE_NAME)) {
        		filterMessageAttributes.add(requestParams.get(k)[0]);
        	} else if (k.contains(CQSConstants.ATTRIBUTE_NAME)) {
        		filterAttributes.add(requestParams.get(k)[0]);
        	}
        }
        
        String out = CQSMessagePopulator.getReceiveMessageResponseAfterSerializing(messageList, filterAttributes, filterMessageAttributes);
        writeResponse(out, response);
        
        return messageList == null ? false : true;
	}
	
	protected List<CQSMessage> getMessages(HttpServletRequest request, boolean useParams, CQSQueue queue) throws PersistenceException, CMBException, IOException, NoSuchAlgorithmException, InterruptedException, JSONException {
		
		String previousReceiptHandle = request.getParameter("PreviousReceiptHandle");
		String nextReceiptHandle = request.getParameter("NextReceiptHandle");
		String shardNumber = request.getParameter("Shard");
		
	    int shard = 0;
	    
		if (previousReceiptHandle != null) {
			shard = Util.getShardFromReceiptHandle(previousReceiptHandle);
		} else if (nextReceiptHandle != null) {
			shard = Util.getShardFromReceiptHandle(nextReceiptHandle);
		} else if (shardNumber != null) {
			shard = Integer.parseInt(shardNumber);
		} else if (queue.getNumberOfShards() > 1) {
	    	shard = rand.nextInt(queue.getNumberOfShards());
		}
		
		if (shard < 0 || shard >= queue.getNumberOfShards()) {
            throw new CMBException(CMBErrorCodes.InvalidParameterValue, "Shard number " + shard +" exceeds number of available shards in queue (" + queue.getNumberOfShards() + ").");
		}
		
		int maxNumberOfMessages = CMBProperties.getInstance().getCQSMaxReceiveMessageCount();
		        
        if (useParams && request.getParameter(CQSConstants.MAX_NUMBER_OF_MESSAGES) != null) {
            
        	maxNumberOfMessages = Integer.parseInt(request.getParameter(CQSConstants.MAX_NUMBER_OF_MESSAGES));
            
        	if (maxNumberOfMessages < 1 || maxNumberOfMessages > CMBProperties.getInstance().getCQSMaxReceiveMessageCount()) {
                throw new CMBException(CMBErrorCodes.InvalidParameterValue, "The value for MaxNumberOfMessages is not valid (must be from 1 to " + CMBProperties.getInstance().getCQSMaxReceiveMessageCount() + ").");
            }
        }

        List<CQSMessage> messageList = PersistenceFactory.getCQSMessagePersistence().peekQueue(queue.getRelativeUrl(), shard, previousReceiptHandle, nextReceiptHandle, maxNumberOfMessages);
        
        return messageList;
	}
}