/**
 * 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.math.stats.entropy;

import com.google.common.io.Closeables;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.util.ToolRunner;
import org.apache.mahout.common.MahoutTestCase;
import org.apache.mahout.common.iterator.sequencefile.PathFilters;
import org.apache.mahout.common.iterator.sequencefile.PathType;
import org.apache.mahout.common.iterator.sequencefile.SequenceFileDirValueIterator;
import org.junit.Test;

import java.util.Iterator;

public final class EntropyTest extends MahoutTestCase {

  @Test
  public void testLetters() throws Exception {
    String[] content = { "A", "A", "A", "A", "A", "B", "B", "C", "D", "E" };
    calculateEntropy(content, 1.96096405, "key");
  }

  @Test
  public void testYN() throws Exception {
    String[] content = { "Yes", "No", "Yes", "No", "No", "Yes", "No", "Yes" };
    calculateEntropy(content, 1.0, "value");
  }

  private void calculateEntropy(String[] content, double expected, String source) throws Exception {

    Configuration configuration = new Configuration();
    FileSystem fileSystem = FileSystem.get(configuration);
    Path input = getTestTempFilePath("input");
    Path output = getTestTempFilePath("output");

    // write content into test text file
    SequenceFile.Writer writer = new SequenceFile.Writer(fileSystem, configuration, input, Text.class, Text.class);
    Writable empty = new Text();
    try {
      for (String item : content) {
        if ("key".equals(source)) {
          writer.append(new Text(item), empty);
        } else {
          writer.append(empty, new Text(item));
        }

      }
    } finally {
      Closeables.closeQuietly(writer);
    }

    // run the job
    String[] args = { "-i", input.toString(), "-o", output.toString(), "-s", source };
    Entropy job = new Entropy();
    ToolRunner.run(job, args);

    assertEquals(content.length, job.getNumberItems());

    // check output
    Iterator<DoubleWritable> iteratorNodes =
        new SequenceFileDirValueIterator<DoubleWritable>(output,
                                                         PathType.LIST,
                                                         PathFilters.logsCRCFilter(),
                                                         null,
                                                         false,
                                                         new Configuration());
    assertTrue(iteratorNodes.hasNext());
    assertEquals(expected, iteratorNodes.next().get(), EPSILON);
  }

}