/*
 * 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.accumulo.examples.shard;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Map.Entry;
import java.util.Random;

import org.apache.accumulo.core.client.Accumulo;
import org.apache.accumulo.core.client.AccumuloClient;
import org.apache.accumulo.core.client.BatchScanner;
import org.apache.accumulo.core.client.IteratorSetting;
import org.apache.accumulo.core.client.Scanner;
import org.apache.accumulo.core.data.Key;
import org.apache.accumulo.core.data.Range;
import org.apache.accumulo.core.data.Value;
import org.apache.accumulo.core.iterators.user.IntersectingIterator;
import org.apache.accumulo.core.security.Authorizations;
import org.apache.accumulo.examples.cli.ClientOpts;
import org.apache.hadoop.io.Text;

import com.beust.jcommander.Parameter;
import com.google.common.collect.Iterators;

/**
 * Using the doc2word table created by Reverse.java, this program randomly selects N words per
 * document. Then it continually queries a random set of words in the shard table (created by
 * {@link Index}) using the {@link IntersectingIterator}.
 */
public class ContinuousQuery {

  static class Opts extends ClientOpts {

    @Parameter(names = "--shardTable", required = true, description = "name of the shard table")
    String tableName = null;

    @Parameter(names = "--doc2Term", required = true, description = "name of the doc2Term table")
    String doc2Term;

    @Parameter(names = "--terms", required = true, description = "the number of terms in the query")
    int numTerms;

    @Parameter(names = "--count", description = "the number of queries to run")
    long iterations = Long.MAX_VALUE;
  }

  public static void main(String[] args) throws Exception {
    Opts opts = new Opts();
    opts.parseArgs(ContinuousQuery.class.getName(), args);

    try (AccumuloClient client = Accumulo.newClient().from(opts.getClientPropsPath()).build()) {
      ArrayList<Text[]> randTerms;
      try (Scanner scanner = client.createScanner(opts.doc2Term, Authorizations.EMPTY)) {
        randTerms = findRandomTerms(scanner, opts.numTerms);
      }

      Random rand = new Random();

      try (BatchScanner bs = client.createBatchScanner(opts.tableName, Authorizations.EMPTY, 5)) {
        for (long i = 0; i < opts.iterations; i += 1) {
          Text[] columns = randTerms.get(rand.nextInt(randTerms.size()));

          bs.clearScanIterators();
          bs.clearColumns();

          IteratorSetting ii = new IteratorSetting(20, "ii", IntersectingIterator.class);
          IntersectingIterator.setColumnFamilies(ii, columns);
          bs.addScanIterator(ii);
          bs.setRanges(Collections.singleton(new Range()));

          long t1 = System.currentTimeMillis();
          int count = Iterators.size(bs.iterator());
          long t2 = System.currentTimeMillis();

          System.out.printf("  %s %,d %6.3f%n", Arrays.asList(columns), count, (t2 - t1) / 1000.0);
        }
      }
    }
  }

  private static ArrayList<Text[]> findRandomTerms(Scanner scanner, int numTerms) {

    Text currentRow = null;

    ArrayList<Text> words = new ArrayList<>();
    ArrayList<Text[]> ret = new ArrayList<>();

    Random rand = new Random();

    for (Entry<Key,Value> entry : scanner) {
      Key key = entry.getKey();

      if (currentRow == null)
        currentRow = key.getRow();

      if (!currentRow.equals(key.getRow())) {
        selectRandomWords(words, ret, rand, numTerms);
        words.clear();
        currentRow = key.getRow();
      }

      words.add(key.getColumnFamily());
    }

    selectRandomWords(words, ret, rand, numTerms);

    return ret;
  }

  private static void selectRandomWords(ArrayList<Text> words, ArrayList<Text[]> ret, Random rand,
      int numTerms) {
    if (words.size() >= numTerms) {
      Collections.shuffle(words, rand);
      Text[] docWords = new Text[numTerms];
      for (int i = 0; i < docWords.length; i++) {
        docWords[i] = words.get(i);
      }

      ret.add(docWords);
    }
  }
}