/*
    * 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.io;
  
  import org.apache.giraph.conf.DefaultImmutableClassesGiraphConfigurable;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.io.Text;
  import org.apache.hadoop.io.Writable;
  import org.apache.hadoop.io.WritableComparable;
  import org.apache.hadoop.mapreduce.InputSplit;
  import org.apache.hadoop.mapreduce.JobContext;
  import org.apache.hadoop.util.ReflectionUtils;
  
  import java.io.DataInput;
  import java.io.DataOutput;
  import java.io.IOException;
  import java.util.List;
  
  /**
   * Common interface for {@link VertexInputFormat} and {@link EdgeInputFormat}.
   *
   * @param <I> Vertex id
   * @param <V> Vertex data
   * @param <E> Edge data
   */
  public abstract class GiraphInputFormat<I extends WritableComparable,
      V extends Writable, E extends Writable> extends
      DefaultImmutableClassesGiraphConfigurable<I, V, E> {
    /**
     * Check that input is valid.
     *
     * @param conf Configuration
     */
    public abstract void checkInputSpecs(Configuration conf);
  
    /**
     * Get the list of input splits for the format.
     *
     * @param context The job context
     * @param minSplitCountHint Minimum number of splits to create (hint)
     * @return The list of input splits
     * @throws IOException
     * @throws InterruptedException
     */
    public abstract List<InputSplit> getSplits(JobContext context,
        int minSplitCountHint) throws IOException, InterruptedException;
  
    /**
     * Write input split info to DataOutput.
     *
     * @param inputSplit InputSplit
     * @param dataOutput DataOutput
     */
    public void writeInputSplit(InputSplit inputSplit,
        DataOutput dataOutput) throws IOException {
      Text.writeString(dataOutput, inputSplit.getClass().getName());
      ((Writable) inputSplit).write(dataOutput);
    }
  
    /**
     * Read input split info from DataInput.
     *
     * @param dataInput DataInput
     * @return InputSplit
     */
    public InputSplit readInputSplit(DataInput dataInput) throws IOException,
        ClassNotFoundException {
      String inputSplitClass = Text.readString(dataInput);
      InputSplit inputSplit = (InputSplit) ReflectionUtils.newInstance(
              getConf().getClassByName(inputSplitClass), getConf());
      ((Writable) inputSplit).readFields(dataInput);
      return inputSplit;
    }
  }