/*
    * 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.formats;
  
  import org.apache.giraph.edge.Edge;
  import org.apache.giraph.edge.EdgeFactory;
  import org.apache.hadoop.io.LongWritable;
  import org.apache.hadoop.io.NullWritable;
  import org.apache.hadoop.io.Text;
  import org.apache.hadoop.mapreduce.InputSplit;
  import org.apache.hadoop.mapreduce.TaskAttemptContext;
  
  import com.google.common.collect.Lists;
  
  import java.io.IOException;
  import java.util.List;
  import java.util.regex.Pattern;
  
  /**
   * Simple text-based {@link org.apache.giraph.io.VertexInputFormat} for
   * unweighted graphs with long ids.
   *
   * Each line consists of: vertex neighbor1 neighbor2 ...
   */
  public class LongLongNullTextInputFormat extends
      TextVertexInputFormat<LongWritable, LongWritable, NullWritable> {
    /** Separator of the vertex and neighbors */
    private static final Pattern SEPARATOR = Pattern.compile("[\t ]");
  
    @Override
    public TextVertexReader createVertexReader(InputSplit split,
                                               TaskAttemptContext context)
      throws IOException {
      return new LongLongNullVertexReader();
    }
  
    /**
     * Vertex reader associated with {@link LongLongNullTextInputFormat}.
     */
    public class LongLongNullVertexReader extends
        TextVertexReaderFromEachLineProcessed<String[]> {
      /** Cached vertex id for the current line */
      private LongWritable id;
  
      @Override
      protected String[] preprocessLine(Text line) throws IOException {
        String[] tokens = SEPARATOR.split(line.toString());
        id = new LongWritable(Long.parseLong(tokens[0]));
        return tokens;
      }
  
      @Override
      protected LongWritable getId(String[] tokens) throws IOException {
        return id;
      }
  
      @Override
      protected LongWritable getValue(String[] tokens) throws IOException {
        return id;
      }
  
      @Override
      protected Iterable<Edge<LongWritable, NullWritable>> getEdges(
          String[] tokens) throws IOException {
        List<Edge<LongWritable, NullWritable>> edges =
            Lists.newArrayListWithCapacity(tokens.length - 1);
        for (int n = 1; n < tokens.length; n++) {
          edges.add(EdgeFactory.create(
              new LongWritable(Long.parseLong(tokens[n]))));
        }
        return edges;
      }
    }
  }