/*
 * 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.drill.exec.store.mock;

import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Random;

import org.apache.drill.exec.vector.ValueVector;
import org.apache.drill.exec.vector.VarCharVector;

/**
 * Very simple date value generator that produces ISO dates
 * uniformly distributed over the last year. ISO format
 * is: 2016-12-07.
 * <p>
 * There are many possible date formats; this class does not
 * attempt to generate all of them. Drill provides a date
 * type, but we use a string format because example cases from
 * people using the product often read text files. Finally, we
 * (reluctantly) use the old-style date formats instead of the
 * new Java 8 classes because Drill prefers to build with Java 7.
 */

public class DateGen implements FieldGen {

  private final int ONE_DAY = 24 * 60 * 60 * 1000;
  private final int ONE_YEAR = ONE_DAY * 365;

  private final Random rand = new Random();
  private long baseTime;
  private SimpleDateFormat fmt;

  public DateGen() {
    // Start a year ago.
    baseTime = System.currentTimeMillis() - ONE_YEAR;
    fmt = new SimpleDateFormat("yyyy-mm-DD");
  }

  @Override
  public void setup(ColumnDef colDef) { }

  private long value() {
    return baseTime + rand.nextInt(365) * ONE_DAY;
  }

  @Override
  public void setValue(ValueVector v, int index) {
    VarCharVector vector = (VarCharVector) v;
    long randTime = baseTime + value();
    String str = fmt.format(new Date(randTime));
    vector.getMutator().setSafe(index, str.getBytes());
  }
}