package com.github.triceo.splitlog;
   
   import java.io.BufferedWriter;
   import java.io.IOException;
   import java.io.OutputStream;
   import java.io.OutputStreamWriter;
   import java.util.Collections;
   import java.util.HashSet;
   import java.util.LinkedHashSet;
  import java.util.List;
  import java.util.Set;
  import java.util.SortedSet;
  import java.util.TreeSet;
  
  import org.apache.commons.io.IOUtils;
  import org.apache.commons.lang3.tuple.Pair;
  import org.slf4j.Logger;
  
  import com.github.triceo.splitlog.api.Follower;
  import com.github.triceo.splitlog.api.LogWatch;
  import com.github.triceo.splitlog.api.MergingFollower;
  import com.github.triceo.splitlog.api.Message;
  import com.github.triceo.splitlog.api.MessageComparator;
  import com.github.triceo.splitlog.api.MessageDeliveryStatus;
  import com.github.triceo.splitlog.api.MessageFormatter;
  import com.github.triceo.splitlog.api.MessageMeasure;
  import com.github.triceo.splitlog.api.SimpleMessageCondition;
  import com.github.triceo.splitlog.formatters.NoopMessageFormatter;
  import com.github.triceo.splitlog.logging.SplitlogLoggerFactory;
  
  /**
   * This is a log follower that holds no message data, just the tags. For message
   * data, it will always turn to the underlying {@link LogWatch}.
   *
   * This class assumes that LogWatch and user code are the only two threads that
   * use it. Never use one instance of this class from two or more user threads.
   * Otherwise, unpredictable behavior from waitFor() methods is possible.
   *
   * Metrics within will never be terminated (and thus removed) unless done by the
   * user. Not even when no longer {@link #isFollowing()}.
   *
   * FIXME maybe we should do something about that ^^^^
   *
   * Will use {@link NoopMessageFormatter} as default message formatter.
   */
  final class DefaultFollower extends AbstractCommonFollower<Follower, LogWatch> implements Follower {
  
      private static final Logger LOGGER = SplitlogLoggerFactory.getLogger(DefaultFollower.class);
  
      private final ConsumerManager<Follower> consumers = new ConsumerManager<Follower>(this);
      private final Set<Message> tags = new LinkedHashSet<Message>();
      private final DefaultLogWatch watch;
  
      public DefaultFollower(final DefaultLogWatch watch,
              final List<Pair<String, MessageMeasure<? extends Number, Follower>>> measuresHandedDown) {
          for (final Pair<String, MessageMeasure<? extends Number, Follower>> pair : measuresHandedDown) {
              this.startMeasuring(pair.getValue(), pair.getKey(), false);
          }
          this.watch = watch;
      }
  
      @Override
      protected ConsumerManager<Follower> getConsumerManager() {
          return this.consumers;
      }
  
      @Override
      protected MessageFormatter getDefaultFormatter() {
          return NoopMessageFormatter.INSTANCE;
      }
  
      @Override
      public LogWatch getFollowed() {
          return this.getWatch();
      }
  
      // FIXME should be synchronized; but then the tests hang weirdly
      @Override
      public SortedSet<Message> getMessages(final SimpleMessageCondition condition, final MessageComparator order) {
          final SortedSet<Message> messages = new TreeSet<Message>(order);
          for (final Message msg : this.getWatch().getAllMessages(this)) {
              if (!condition.accept(msg)) {
                  continue;
              }
              messages.add(msg);
          }
          messages.addAll(this.getTags());
          return Collections.unmodifiableSortedSet(messages);
      }
  
      protected Set<Message> getTags() {
          return this.tags;
      }
  
      protected DefaultLogWatch getWatch() {
          return this.watch;
      }
  
      @Override
     public boolean isStopped() {
         return !this.getFollowed().isFollowedBy(this);
     }
 
     @Override
     public MergingFollower mergeWith(final Follower f) {
         if (f == null) {
             throw new IllegalArgumentException("Cannot merge with null.");
         } else if (f == this) {
             throw new IllegalArgumentException("Cannot merge with self.");
         }
         return new DefaultMergingFollower(this, f);
     }
 
     @Override
     public MergingFollower mergeWith(final MergingFollower f) {
         if (f == null) {
             throw new IllegalArgumentException("Cannot merge with null.");
         }
         final Set<Follower> followers = new HashSet<Follower>(f.getMerged());
         followers.add(this);
         return new DefaultMergingFollower(followers.toArray(new Follower[followers.size()]));
     }
 
     @Override
     public synchronized void messageReceived(final Message msg, final MessageDeliveryStatus status,
         final LogWatch source) {
         if (this.isStopped()) {
             throw new IllegalStateException("Follower already stopped.");
         } else if (source != this.getWatch()) {
             throw new IllegalArgumentException("Forbidden notification source: " + source);
         }
         DefaultFollower.LOGGER.info("{} notified of '{}' with status {}.", this, msg, status);
         this.getExchange().messageReceived(msg, status, source);
         this.getConsumerManager().messageReceived(msg, status, this);
     }
 
     @Override
     public synchronized boolean stop() {
         if (this.isStopped()) {
             return false;
         }
         DefaultFollower.LOGGER.info("Stopping {}.", this);
         this.getFollowed().stopFollowing(this);
         this.getConsumerManager().stop();
         this.getExchange().stop();
         DefaultFollower.LOGGER.info("Stopped {}.", this);
         return true;
     }
 
     @Override
     public Message tag(final String tagLine) {
         final Message message = new MessageBuilder(tagLine).buildTag();
         this.tags.add(message);
         return message;
     }
 
     @Override
     public String toString() {
         final StringBuilder builder = new StringBuilder();
         builder.append("DefaultFollower [getUniqueId()=").append(this.getUniqueId()).append(", ");
         if (this.getFollowed() != null) {
             builder.append("getFollowed()=").append(this.getFollowed()).append(", ");
         }
         builder.append("isStopped()=").append(this.isStopped()).append("]");
         return builder.toString();
     }
 
     @Override
     public boolean write(final OutputStream stream, final SimpleMessageCondition condition,
         final MessageComparator order, final MessageFormatter formatter) {
         if (stream == null) {
             throw new IllegalArgumentException("Stream may not be null.");
         } else if (condition == null) {
             throw new IllegalArgumentException("Condition may not be null.");
         } else if (order == null) {
             throw new IllegalArgumentException("Comparator may not be null.");
         }
         BufferedWriter w = null;
         try {
             w = new BufferedWriter(new OutputStreamWriter(stream, "UTF-8"));
             for (final Message msg : this.getMessages(condition, order)) {
                 w.write(formatter.format(msg, this.getFollowed().getWatchedFile()));
                 w.newLine();
             }
             return true;
         } catch (final IOException ex) {
             return false;
         } finally {
             IOUtils.closeQuietly(w);
         }
     }
 
 }