/*
    * 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.sender;
  
  import java.io.IOException;
  import org.apache.hadoop.chukwa.datacollection.DataFactory;
  import org.apache.hadoop.chukwa.datacollection.agent.*;
  import org.apache.hadoop.chukwa.datacollection.adaptor.Adaptor;
  import org.apache.hadoop.chukwa.datacollection.collector.servlet.CommitCheckServlet;
  import org.apache.hadoop.chukwa.datacollection.collector.servlet.ServletCollector;
  import org.apache.hadoop.chukwa.datacollection.sender.ChukwaHttpSender.CommitListEntry;
  import java.util.*;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  import org.apache.hadoop.conf.*;
  import org.apache.commons.httpclient.*;
  import org.apache.commons.httpclient.methods.GetMethod;
  import org.apache.commons.httpclient.methods.PostMethod;
  //import com.google.common.collect.SortedSetMultimap;
  //import com.google.common.collect.TreeMultimap;
  
  import org.apache.log4j.Logger;
  
  /**
   * An enhancement to ChukwaHttpSender that handles asynchronous acknowledgment.
   * 
   * This class will periodically poll the collectors to find out how much data
   * has been committed to HDFS, and will then pass those acks on to the Agent.
   */
  public class AsyncAckSender extends ChukwaHttpSender{
    
    protected static Logger log = Logger.getLogger(AsyncAckSender.class);
    /*
     * Represents the state required for an asynchronous ack.
     * 
     * Supplements CommitListEntry with a filename and offset;
     * the data commits when that file reaches that length.
     */
    public static class DelayedCommit extends CommitListEntry implements Comparable<DelayedCommit> {
      final String fname;
      long fOffset;
      final String aName;
      public DelayedCommit(Adaptor a, long uuid, long len, String fname, 
          long offset, String aName) {
        super(a, uuid, len);
        this.fname = fname;
        this.fOffset = offset;
        this.aName = aName;
      }
  
      @Override
      public int hashCode() {
        return super.hashCode() ^ fname.hashCode() ^ (int)(fOffset) ^ (int) (fOffset >> 32);
      }
      
      //sort by adaptor name first, then by start offset
      //note that returning 1 means this is "greater" than RHS
      public int compareTo(DelayedCommit o) {
        int c = o.aName.compareTo(this.aName);
        if(c != 0)
          return c;
        c = fname.compareTo(this.fname);
        if(c != 0)
          return c;
        if(o.start < start)
          return 1;
        else if(o.start > start)
          return -1;
        else return 0;
      }
      
      public String toString() {
        return adaptor +" commits from" + start + " to " + uuid + " when " + fname + " hits " + fOffset;
      }
    }
    
    public static final String POLLPERIOD_OPT = "connector.commitpoll.period";
    public static final String POLLHOSTS_OPT = "connector.commitpoll.hostfile";
    final ChukwaAgent agent;
    
    /*
     * The list of commits that we're expecting.
     * This is the structure used to pass the list to the CommitPollThread.  
     * Adjacent commits to the same file will be coalesced.
    * 
    */
   final List<DelayedCommit> mergedList;
   
   /**
    * Periodically scans a subset of the collectors, looking for committed files.
    * This way, not every collector is pestering the namenode with periodic lses.
    */
   final class CommitPollThread extends Thread {
     private ChukwaHttpSender scanPath;
     private int pollPeriod = 1000 * 30;
 
 
     private final Map<String, PriorityQueue<DelayedCommit>> pendingCommits;
 
     CommitPollThread(Configuration conf, Iterator<String> tryList) {
       pollPeriod = conf.getInt(POLLPERIOD_OPT, pollPeriod);
       scanPath = new ChukwaHttpSender(conf);
       scanPath.setCollectors(tryList);
       pendingCommits = new HashMap<String, PriorityQueue<DelayedCommit>>();
     }
 
     private volatile boolean running = true;
     public void shutdown() {
       running = false;
       this.interrupt();
     }
     
     public void run() {
       try {
         while(running) {
           Thread.sleep(pollPeriod);
           //update table using list of pending delayed commits, in this thread
           checkForCommits();
           mergePendingTable();
         }
       } catch(InterruptedException e) {}
       catch(IOException e) {
         log.error(e);
       }
     } 
     
     /*
      * Note that this method is NOT threadsafe, and should only be called
      * from the same thread that will later check for commits
      */
     private void mergePendingTable() {
       synchronized(mergedList) {
         for(DelayedCommit dc:mergedList) {
           
           PriorityQueue<DelayedCommit> pendList = pendingCommits.get(dc.fname);
           if(pendList == null) {
             pendList = new PriorityQueue<DelayedCommit>();
             pendingCommits.put(dc.fname, pendList);
           }
           pendList.add(dc);
         }
         mergedList.clear();
       } //end synchronized
     }
     
     Pattern respLine = Pattern.compile("<li>(.*) ([0-9]+)</li>");
     private void checkForCommits() throws IOException, InterruptedException {
       
       log.info("checking for commited chunks");
       GetMethod method = new GetMethod();
       List<String> parsedFStatuses = scanPath.reliablySend(method, CommitCheckServlet.DEFAULT_PATH); 
 
       //do an http get
       for(String stat: parsedFStatuses) {
         Matcher m = respLine.matcher(stat);
         if(!m.matches())
           continue;
         String path = m.group(1);
         Long committedOffset = Long.parseLong(m.group(2));
 
         PriorityQueue<DelayedCommit> delayedOnFile = pendingCommits.get(path);
         if(delayedOnFile == null)
           continue;
        
         HashSet<Adaptor> committed = new HashSet<Adaptor>();
         while(!delayedOnFile.isEmpty()) {
           DelayedCommit fired = delayedOnFile.element();
           if(fired.fOffset > committedOffset)
             break;
           else {
             ChukwaAgent.Offset o = agent.offset(fired.adaptor);
             if(o != null && fired.start > o.offset()) {
               log.error("can't commit "+ o.adaptorID() +  "  without ordering assumption");
               break; //don't commit
             }
             delayedOnFile.remove();
             String s = agent.reportCommit(fired.adaptor, fired.uuid);
             committed.add(fired.adaptor);
             //TODO: if s == null, then the adaptor has been stopped.
             //should we stop sending acks?
             log.info("COMMIT to "+ committedOffset+ " on "+ path+ ", updating " +s);
           }
         }
         adaptorReset.reportCommits(committed);
       }
     }
 
   } 
   
   CommitPollThread pollThread;
   
   //note that at present we don't actually run this thread; we just use its methods.
   public AdaptorResetThread adaptorReset;
   Configuration conf;
   
   public AsyncAckSender(Configuration conf, ChukwaAgent a) throws IOException {
     super(conf);
     log.info("delayed-commit processing enabled");
     agent = a;
     
     mergedList = new ArrayList<DelayedCommit>();
     this.conf = conf;
     adaptorReset = new AdaptorResetThread(conf, a);
     adaptorReset.start();
     //initialize the commitpoll later, once we have the list of collectors
   }
   
   
   @Override
   public void setCollectors(Iterator<String> collectors) {
    Iterator<String> tryList = null;
    String scanHostsFilename = conf.get(POLLHOSTS_OPT, "collectors");
    try {
      tryList = DataFactory.getInstance().getCollectorURLs(conf, scanHostsFilename);
    } catch(IOException e) {
      log.warn("couldn't read " + scanHostsFilename+ " falling back on collectors list");
    }
 
    if(collectors instanceof RetryListOfCollectors) {
      super.setCollectors(collectors);
      if(tryList == null)
        tryList = ((RetryListOfCollectors) collectors).clone();
    } 
    else {
      ArrayList<String> l = new ArrayList<String>();
      while(collectors.hasNext())
        l.add(collectors.next());
      super.setCollectors(l.iterator());
      if(tryList == null)
        tryList = l.iterator();
    }
 
    pollThread = new CommitPollThread(conf, tryList);
    pollThread.setDaemon(true);
    pollThread.start();
   }
   
   /*
    * This method is the interface from AsyncAckSender to the CommitPollThread --
    * it gets a lock on the merge table, and then updates it with a batch of pending acks
    *
    *  This method is called from the thread doing a post; the merge table is
    *  read by the CommitPollThread when it figures out what commits are expected.
    */
   private void delayCommits(List<DelayedCommit> delayed) {
     Collections.sort(delayed);
     
     synchronized(mergedList) {
       DelayedCommit region =null;
       for(DelayedCommit cur: delayed) {
         if(region == null)
           region = cur;
         else if((cur.adaptor == region.adaptor) &&
             cur.fname.equals(region.fname) && (cur.start <= region.uuid)) {
           //since the list is sorted, region.start < cur.start
           region.uuid = Math.max(region.uuid, cur.uuid); //merge
           region.fOffset = Math.max(region.fOffset, cur.fOffset);
         } else {
           mergedList.add(region);
           region= cur;
         }
       }
       mergedList.add(region);
     }
   }
   
   
   Pattern partialCommitPat = Pattern.compile("(.*) ([0-9]+)");
   @Override
   public List<CommitListEntry> postAndParseResponse(PostMethod method, 
       List<CommitListEntry> expectedCommitResults)
   throws IOException, InterruptedException {
     adaptorReset.reportPending(expectedCommitResults);
     List<String> resp = reliablySend(method, ServletCollector.PATH);
       //expect most of 'em to be delayed
     List<DelayedCommit> toDelay = new ArrayList<DelayedCommit>(resp.size());
     ArrayList<CommitListEntry> result =  new ArrayList<CommitListEntry>();
     
     for(int i = 0; i < resp.size(); ++i)  {
       if(resp.get(i).startsWith(ServletCollector.ACK_PREFIX))
         result.add(expectedCommitResults.get(i));
       else {
         CommitListEntry cle = expectedCommitResults.get(i);
         Matcher m = partialCommitPat.matcher(resp.get(i));
         if(!m.matches())
           log.warn("unexpected response: "+ resp.get(i));
         else
           log.info("waiting for " + m.group(1) + " to hit " + m.group(2) + 
               " before committing "+ agent.getAdaptorName(cle.adaptor));
         
         String name = agent.getAdaptorName(cle.adaptor);
         if(name != null)//null name implies adaptor no longer running
           toDelay.add(new DelayedCommit(cle.adaptor, cle.uuid, cle.start, m.group(1), 
                 Long.parseLong(m.group(2)), name));
       }
     }
     delayCommits(toDelay);
     return result;
   }
   
   @Override
   protected boolean failedCollector(String downed) {
     log.info("collector "+ downed + " down; resetting adaptors");
     adaptorReset.resetTimedOutAdaptors(0); //reset all adaptors with outstanding data.
     return false;
   }
   
   @Override
   public void stop() {
     pollThread.shutdown();
   }
 
 }