/*
    * 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.giraph.bsp;
  
  import java.io.IOException;
  
  import org.apache.hadoop.mapreduce.InputSplit;
  import org.apache.hadoop.mapreduce.RecordReader;
  import org.apache.hadoop.mapreduce.TaskAttemptContext;
  import org.apache.hadoop.io.Text;
  
  /**
   * Only returns a single key-value pair so that the map() can run.
   */
  class BspRecordReader extends RecordReader<Text, Text> {
    /** Singular key object */
    private static final Text ONLY_KEY = new Text("only key");
    /** Single value object */
    private static final Text ONLY_VALUE = new Text("only value");
  
    /** Has the one record been seen? */
    private boolean seenRecord = false;
  
    @Override
    public void close() throws IOException {
      return;
    }
  
    @Override
    public float getProgress() throws IOException {
      return seenRecord ? 1f : 0f;
    }
  
    @Override
    public Text getCurrentKey() throws IOException, InterruptedException {
      return ONLY_KEY;
    }
  
    @Override
    public Text getCurrentValue() throws IOException, InterruptedException {
      return ONLY_VALUE;
    }
  
    @Override
    public void initialize(InputSplit inputSplit, TaskAttemptContext context)
      throws IOException, InterruptedException {
    }
  
    @Override
    public boolean nextKeyValue() throws IOException, InterruptedException {
      if (!seenRecord) {
        seenRecord = true;
        return true;
      }
      return false;
    }
  }