/**
 * 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.mahout.fpm.pfpgrowth;

import java.io.IOException;
import java.util.Collection;
import java.util.HashSet;
import java.util.List;
import java.util.Map.Entry;

import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.mahout.common.Pair;
import org.apache.mahout.math.map.OpenIntLongHashMap;
import org.apache.mahout.math.map.OpenObjectIntHashMap;

/**
 *  maps each transaction to all unique items groups in the transaction. mapper
 * outputs the group id as key and the transaction as value
 * 
 */
public class ParallelFPGrowthMapper extends Mapper<LongWritable,TransactionTree,LongWritable,TransactionTree> {
  
  private final OpenIntLongHashMap gListInt = new OpenIntLongHashMap();
  
  @Override
  protected void map(LongWritable offset, TransactionTree input, Context context)
    throws IOException, InterruptedException {

    for (Pair<List<Integer>,Long> pattern : input) {
      Integer[] prunedItems = pattern.getFirst().toArray(new Integer[pattern.getFirst().size()]);

      Collection<Long> groups = new HashSet<Long>();
      for (int j = prunedItems.length - 1; j >= 0; j--) {
        // generate group dependent shards
        Integer item = prunedItems[j];
        Long groupID = gListInt.get(item);

        if (!groups.contains(groupID)) {
          Integer[] tempItems = new Integer[j + 1];
          System.arraycopy(prunedItems, 0, tempItems, 0, j + 1);
          context.setStatus("Parallel FPGrowth: Generating Group Dependent transactions for: " + item);
          context.write(new LongWritable(groupID), new TransactionTree(tempItems, pattern.getSecond()));
        }
        groups.add(groupID);
      }
    }
    
  }
  
  @Override
  protected void setup(Context context) throws IOException, InterruptedException {
    super.setup(context);
    OpenObjectIntHashMap<String> fMap = new OpenObjectIntHashMap<String>();
    int i = 0;
    for (Pair<String,Long> e : PFPGrowth.readFList(context.getConfiguration())) {
      fMap.put(e.getFirst(), i++);
    }
    
    for (Entry<String,Long> e : PFPGrowth.readGList(context.getConfiguration()).entrySet()) {
      gListInt.put(fMap.get(e.getKey()), e.getValue());
    }
    
  }
}