/*
 * 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.calcite.avatica.util;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Objects;

/** A range of time units. The first is more significant than the
 * other (e.g. year-to-day) or the same as the other (e.g. month). */
public enum TimeUnitRange {
  YEAR(TimeUnit.YEAR, null),
  YEAR_TO_MONTH(TimeUnit.YEAR, TimeUnit.MONTH),
  MONTH(TimeUnit.MONTH, null),
  DAY(TimeUnit.DAY, null),
  DAY_TO_HOUR(TimeUnit.DAY, TimeUnit.HOUR),
  DAY_TO_MINUTE(TimeUnit.DAY, TimeUnit.MINUTE),
  DAY_TO_SECOND(TimeUnit.DAY, TimeUnit.SECOND),
  HOUR(TimeUnit.HOUR, null),
  HOUR_TO_MINUTE(TimeUnit.HOUR, TimeUnit.MINUTE),
  HOUR_TO_SECOND(TimeUnit.HOUR, TimeUnit.SECOND),
  MINUTE(TimeUnit.MINUTE, null),
  MINUTE_TO_SECOND(TimeUnit.MINUTE, TimeUnit.SECOND),
  SECOND(TimeUnit.SECOND, null),

  // non-standard time units cannot participate in ranges
  ISOYEAR(TimeUnit.ISOYEAR, null),
  QUARTER(TimeUnit.QUARTER, null),
  WEEK(TimeUnit.WEEK, null),
  MILLISECOND(TimeUnit.MILLISECOND, null),
  MICROSECOND(TimeUnit.MICROSECOND, null),
  NANOSECOND(TimeUnit.NANOSECOND, null),
  DOW(TimeUnit.DOW, null),
  ISODOW(TimeUnit.ISODOW, null),
  DOY(TimeUnit.DOY, null),
  EPOCH(TimeUnit.EPOCH, null),
  DECADE(TimeUnit.DECADE, null),
  CENTURY(TimeUnit.CENTURY, null),
  MILLENNIUM(TimeUnit.MILLENNIUM, null),
  SECOND_TO_MICROSECOND(TimeUnit.SECOND, TimeUnit.MICROSECOND)
  ;

  public final TimeUnit startUnit;
  public final TimeUnit endUnit;

  private static final Map<Pair<TimeUnit>, TimeUnitRange> MAP = createMap();

  /**
   * Creates a TimeUnitRange.
   *
   * @param startUnit Start time unit
   * @param endUnit   End time unit
   */
  TimeUnitRange(TimeUnit startUnit, TimeUnit endUnit) {
    assert startUnit != null;
    this.startUnit = startUnit;
    this.endUnit = endUnit;
  }

  /**
   * Returns a {@code TimeUnitRange} with a given start and end unit.
   *
   * @param startUnit Start unit
   * @param endUnit   End unit
   * @return Time unit range, or null if not valid
   */
  public static TimeUnitRange of(TimeUnit startUnit, TimeUnit endUnit) {
    return MAP.get(new Pair<>(startUnit, endUnit));
  }

  private static Map<Pair<TimeUnit>, TimeUnitRange> createMap() {
    Map<Pair<TimeUnit>, TimeUnitRange> map = new HashMap<>();
    for (TimeUnitRange value : values()) {
      map.put(new Pair<>(value.startUnit, value.endUnit), value);
    }
    return Collections.unmodifiableMap(map);
  }

  /** Whether this is in the YEAR-TO-MONTH family of intervals. */
  public boolean monthly() {
    return ordinal() <= MONTH.ordinal();
  }

  /** Immutable pair of values of the same type.
   * @param <E> the element type */
  private static class Pair<E> {
    final E left;
    final E right;

    private Pair(E left, E right) {
      this.left = left;
      this.right = right;
    }

    @Override public int hashCode() {
      int k = (left == null) ? 0 : left.hashCode();
      int k1 = (right == null) ? 0 : right.hashCode();
      return ((k << 4) | k) ^ k1;
    }

    @Override public boolean equals(Object obj) {
      return obj == this
          || obj instanceof Pair
          && Objects.equals(left, ((Pair) obj).left)
          && Objects.equals(right, ((Pair) obj).right);
    }
  }
}

// End TimeUnitRange.java
