/*
    * 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 com.google.common.collect.Lists;
  import java.io.IOException;
  import java.util.List;
  import org.apache.giraph.edge.Edge;
  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.TaskAttemptContext;
  
  /**
   * VertexReader that readers lines of text with vertices encoded as adjacency
   * lists and converts each token to the correct type.  For example, a graph
   * with vertices as integers and values as doubles could be encoded as:
   *   1 0.1 2 0.2 3 0.3
   * to represent a vertex named 1, with 0.1 as its value and two edges, to
   * vertices 2 and 3, with edge values of 0.2 and 0.3, respectively.
   *
   * @param <I> Vertex index value
   * @param <V> Vertex value
   * @param <E> Edge value
   */
  @SuppressWarnings("rawtypes")
  public abstract class AdjacencyListTextVertexInputFormat<I extends
      WritableComparable, V extends Writable, E extends Writable> extends
      TextVertexInputFormat<I, V, E> {
    /** Delimiter for split */
    public static final String LINE_TOKENIZE_VALUE = "adj.list.input.delimiter";
    /** Default delimiter for split */
    public static final String LINE_TOKENIZE_VALUE_DEFAULT = "\t";
  
    /**
     * Utility for doing any cleaning of each line before it is tokenized.
     */
    public interface LineSanitizer {
      /**
       * Clean string s before attempting to tokenize it.
       *
       * @param s String to be cleaned.
       * @return Sanitized string.
       */
      String sanitize(String s);
    }
  
    @Override
    public abstract AdjacencyListTextVertexReader createVertexReader(
        InputSplit split, TaskAttemptContext context);
  
    /**
     * Vertex reader associated with {@link AdjacencyListTextVertexInputFormat}.
     */
    protected abstract class AdjacencyListTextVertexReader extends
      TextVertexReaderFromEachLineProcessed<String[]> {
      /** Cached delimiter used for split */
      private String splitValue = null;
      /** Sanitizer from constructor. */
      private final LineSanitizer sanitizer;
  
      /**
       * Constructor without line sanitizer.
       */
      public AdjacencyListTextVertexReader() {
        this(null);
      }
  
      /**
       * Constructor with line sanitizer.
       *
       * @param sanitizer Sanitizer to be used.
       */
      public AdjacencyListTextVertexReader(LineSanitizer sanitizer) {
        this.sanitizer = sanitizer;
      }
  
      @Override
      public void initialize(InputSplit inputSplit, TaskAttemptContext context)
        throws IOException, InterruptedException {
        super.initialize(inputSplit, context);
        splitValue =
            getConf().get(LINE_TOKENIZE_VALUE, LINE_TOKENIZE_VALUE_DEFAULT);
     }
 
     @Override
     protected String[] preprocessLine(Text line) throws IOException {
       String sanitizedLine;
       if (sanitizer != null) {
         sanitizedLine = sanitizer.sanitize(line.toString());
       } else {
         sanitizedLine = line.toString();
       }
       String [] values = sanitizedLine.split(splitValue);
       if ((values.length < 2) || (values.length % 2 != 0)) {
         throw new IllegalArgumentException(
           "Line did not split correctly: " + line);
       }
       return values;
     }
 
     @Override
     protected I getId(String[] values) throws IOException {
       return decodeId(values[0]);
     }
 
     /**
      * Decode the id for this line into an instance of its correct type.
      *
      * @param s Id of vertex from line
      * @return Vertex id
      */
     public abstract I decodeId(String s);
 
     @Override
     protected V getValue(String[] values) throws IOException {
       return decodeValue(values[1]);
     }
 
 
     /**
      * Decode the value for this line into an instance of its correct type.
      *
      * @param s Value from line
      * @return Vertex value
      */
     public abstract V decodeValue(String s);
 
     @Override
     protected Iterable<Edge<I, E>> getEdges(String[] values) throws
         IOException {
       int i = 2;
       List<Edge<I, E>> edges = Lists.newLinkedList();
       while (i < values.length) {
         edges.add(decodeEdge(values[i], values[i + 1]));
         i += 2;
       }
       return edges;
     }
 
     /**
      * Decode an edge from the line into an instance of a correctly typed Edge
      *
      * @param id The edge's id from the line
      * @param value The edge's value from the line
      * @return Edge with given target id and value
      */
     public abstract Edge<I, E> decodeEdge(String id, String value);
 
   }
 }