/**
 * 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.hadoop.mrunit.mapreduce;


import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.mapreduce.Counters;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.reduce.WrappedReducer;
import org.apache.hadoop.mrunit.ReduceDriverBase;
import org.apache.hadoop.mrunit.mapreduce.mock.MockReduceContext;
import org.apache.hadoop.mrunit.types.Pair;

/**
 * Harness that allows you to test a Reducer instance. You provide a key and a
 * set of intermediate values for that key that represent inputs that should
 * be sent to the Reducer (as if they came from a Mapper), and outputs you
 * expect to be sent by the Reducer to the collector. By calling runTest(),
 * the harness will deliver the input to the Reducer and will check its
 * outputs against the expected results. This is designed to handle a single
 * (k, v*) -> (k, v)* case from the Reducer, representing a single unit test.
 * Multiple input (k, v*) sets should go in separate unit tests.
 */
public class ReduceDriver<K1, V1, K2, V2> extends ReduceDriverBase<K1, V1, K2, V2> {

  public static final Log LOG = LogFactory.getLog(ReduceDriver.class);

  private Reducer<K1, V1, K2, V2> myReducer;
  private Counters counters;

  public ReduceDriver(final Reducer<K1, V1, K2, V2> r) {
    myReducer = r;
    counters = new Counters();
  }

  public ReduceDriver() {
    counters = new Counters();
  }

  /**
   * Sets the reducer object to use for this test
   *
   * @param r
   *          The reducer object to use
   */
  public void setReducer(Reducer<K1, V1, K2, V2> r) {
    myReducer = r;
  }

  /**
   * Identical to setReducer(), but with fluent programming style
   *
   * @param r
   *          The Reducer to use
   * @return this
   */
  public ReduceDriver<K1, V1, K2, V2> withReducer(Reducer<K1, V1, K2, V2> r) {
    setReducer(r);
    return this;
  }

  public Reducer<K1, V1, K2, V2> getReducer() {
    return myReducer;
  }

  /** @return the counters used in this test */
  public Counters getCounters() {
    return counters;
  }

  /** Sets the counters object to use for this test.
   * @param ctrs The counters object to use.
   */
  public void setCounters(final Counters ctrs) {
    this.counters = ctrs;
  }

  /** Sets the counters to use and returns self for fluent style */
  public ReduceDriver<K1, V1, K2, V2> withCounters(final Counters ctrs) {
    setCounters(ctrs);
    return this;
  }

  /**
   * Identical to setInputKey() but with fluent programming style
   *
   * @return this
   */
  public ReduceDriver<K1, V1, K2, V2> withInputKey(K1 key) {
    setInputKey(key);
    return this;
  }

  /**
   * Identical to addInputValue() but with fluent programming style
   *
   * @param val
   * @return this
   */
  public ReduceDriver<K1, V1, K2, V2> withInputValue(V1 val) {
    addInputValue(val);
    return this;
  }

  /**
   * Identical to addInputValues() but with fluent programming style
   *
   * @param values
   * @return this
   */
  public ReduceDriver<K1, V1, K2, V2> withInputValues(List<V1> values) {
    addInputValues(values);
    return this;
  }

  /**
   * Identical to setInput() but returns self for fluent programming style
   *
   * @return this
   */
  public ReduceDriver<K1, V1, K2, V2> withInput(K1 key, List<V1> values) {
    setInput(key, values);
    return this;
  }

  /**
   * Works like addOutput(), but returns self for fluent style
   *
   * @param outputRecord
   * @return this
   */
  public ReduceDriver<K1, V1, K2, V2> withOutput(Pair<K2, V2> outputRecord) {
    addOutput(outputRecord);
    return this;
  }

  /**
   * Works like addOutput(), but returns self for fluent style
   *
   * @param key The key part of a (k, v) pair to add
   * @param val The val part of a (k, v) pair to add
   * @return this
   */
  public ReduceDriver<K1, V1, K2, V2> withOutput(K2 key, V2 val) {
    addOutput(key, val);
    return this;
  }

  /**
   * Identical to setInput, but with a fluent programming style
   *
   * @param input
   *          A string of the form "key \t val". Trims any whitespace.
   * @return this
   */
  public ReduceDriver<K1, V1, K2, V2> withInputFromString(String input) {
    setInputFromString(input);
    return this;
  }

  /**
   * Identical to addOutput, but with a fluent programming style
   *
   * @param output
   *          A string of the form "key \t val". Trims any whitespace.
   * @return this
   */
  public ReduceDriver<K1, V1, K2, V2> withOutputFromString(String output) {
    addOutputFromString(output);
    return this;
  }

  @Override
  public List<Pair<K2, V2>> run() throws IOException {
    List<Pair<K1, List<V1>>> inputs = new ArrayList<Pair<K1, List<V1>>>();
    inputs.add(new Pair<K1, List<V1>>(inputKey, inputValues));

    try {
      MockReduceContext<K1, V1, K2, V2> context = 
        new MockReduceContext<K1, V1, K2, V2>(inputs, getCounters());
      myReducer.run(new WrappedReducer<K1, V1, K2, V2>().getReducerContext(context));
      return context.getOutputs();
    } catch (InterruptedException ie) {
      throw new IOException(ie);
    }
  }

  @Override
  public String toString() {
    return "ReduceDriver (0.20+) (" + myReducer + ")";
  }
}