content: /**
   * 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
   * <p/>
   * http://www.apache.org/licenses/LICENSE-2.0
   * <p/>
   * 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.alibaba.jstorm.hdfs.spout;
  
  import java.io.PrintStream;
  import java.util.TreeSet;
  
  public class ProgressTracker {
  
    TreeSet<FileOffset> offsets = new TreeSet<>();
  
    public synchronized void recordAckedOffset(FileOffset newOffset) {
      if(newOffset==null) {
        return;
      }
      offsets.add(newOffset);
  
      FileOffset currHead = offsets.first();
  
      if( currHead.isNextOffset(newOffset) ) { // check is a minor optimization
        trimHead();
      }
    }
  
    // remove contiguous elements from the head of the heap
    // e.g.:  1,2,3,4,10,11,12,15  =>  4,10,11,12,15
    private synchronized void trimHead() {
      if(offsets.size()<=1) {
        return;
      }
      FileOffset head = offsets.first();
      FileOffset head2 = offsets.higher(head);
      if( head.isNextOffset(head2) ) {
        offsets.pollFirst();
        trimHead();
      }
      return;
    }
  
    public synchronized FileOffset getCommitPosition() {
      if(!offsets.isEmpty()) {
        return offsets.first().clone();
      }
      return null;
    }
  
    public synchronized void dumpState(PrintStream stream) {
      stream.println(offsets);
    }
  
    public synchronized int size() {
      return offsets.size();
    }
  }
  