/*
    * 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.hadoop.chukwa.datacollection;
  
  
  import java.io.File;
  import java.io.IOException;
  import java.lang.reflect.Constructor;
  import java.util.Iterator;
  
  import org.apache.hadoop.conf.*;
  import org.apache.hadoop.chukwa.datacollection.agent.ChukwaAgent;
  import org.apache.hadoop.chukwa.datacollection.agent.MemLimitQueue;
  import org.apache.hadoop.chukwa.datacollection.sender.RetryListOfCollectors;
  import org.apache.log4j.Logger;
  
  public class DataFactory {
    static Logger log = Logger.getLogger(DataFactory.class);
    static final String COLLECTORS_FILENAME = "collectors";
    static final String CHUNK_QUEUE = "chukwaAgent.chunk.queue";
    
    private static DataFactory dataFactory = null;
    private ChunkQueue chunkQueue = null;
  
    private String defaultTags = "";
    
    static {
      dataFactory = new DataFactory();
    }
  
    private DataFactory() {
    }
  
    public static DataFactory getInstance() {
      return dataFactory;
    }
  
    public synchronized ChunkQueue getEventQueue() {
      if (chunkQueue == null) {
        chunkQueue = createEventQueue();
      }
      return chunkQueue;
    }
    
    public synchronized ChunkQueue createEventQueue() {
      Configuration conf = ChukwaAgent.getStaticConfiguration();
      if(conf == null){
      //Must be a unit test, use default queue with default configuration
        return new MemLimitQueue(null);
      }
      String receiver = conf.get(CHUNK_QUEUE);
      ChunkQueue queue = null;
      if(receiver == null){
        log.warn("Empty configuration for " + CHUNK_QUEUE + ". Defaulting to MemLimitQueue");
        queue = new MemLimitQueue(conf);
        return queue;
      }
      
      try {
        Class<?> clazz = Class.forName(receiver);
        log.info(clazz);
        if(!ChunkQueue.class.isAssignableFrom(clazz)){
          throw new Exception(receiver + " is not an instance of ChunkQueue");
        }
        try {
          Constructor<?> ctor = clazz.getConstructor(new Class[]{Configuration.class});
          queue = (ChunkQueue) ctor.newInstance(conf);
        } catch(NoSuchMethodException nsme){
          //Queue implementations which take no configuration parameter
          queue = (ChunkQueue) clazz.newInstance();
        }
      } catch(Exception e) {
        log.error("Could not instantiate configured ChunkQueue due to: " + e);
        log.error("Defaulting to MemLimitQueue");
        queue = new MemLimitQueue(conf);
      }
      return queue;
    }
  
    public String getDefaultTags() {
      return defaultTags;
    }
    
   public void addDefaultTag(String tag) {
     this.defaultTags += " " + tag.trim();
   }
   
   /**
    * @return empty list if file does not exist
    * @throws IOException on other error
    */
   public Iterator<String> getCollectorURLs(Configuration conf, String filename) throws IOException {
     String chukwaHome = System.getenv("CHUKWA_HOME");
     if (chukwaHome == null) {
       chukwaHome = ".";
     }
 
     if (!chukwaHome.endsWith("/")) {
       chukwaHome = chukwaHome + File.separator;
     }
     log.info("Config - System.getenv(\"CHUKWA_HOME\"): [" + chukwaHome + "]");
 
     String chukwaConf = System.getenv("CHUKWA_CONF_DIR");
     if (chukwaConf == null) {
       chukwaConf = chukwaHome + "conf" + File.separator;
     }
 
     log.info("Config - System.getenv(\"chukwaConf\"): [" + chukwaConf + "]");
 
     log.info("setting up collectors file: " + chukwaConf + File.separator
         + COLLECTORS_FILENAME);
     File collectors = new File(chukwaConf + File.separator + filename);
     try {
       return new RetryListOfCollectors(collectors, conf);
     } catch (java.io.IOException e) {
       log.error("failed to read collectors file: ", e);
       throw e;
     }
   }
   public Iterator<String> getCollectorURLs(Configuration conf) throws IOException {
     return getCollectorURLs(conf, "collectors");
   }
 
 }