// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

part of dart.core;

/**
 * A span of time, such as 27 days, 4 hours, 12 minutes, and 3 seconds.
 *
 * To create a new Duration object, use this class's single constructor
 * giving the appropriate arguments:
 *
 *     Duration fastestMarathon = new Duration(hours:2, minutes:3, seconds:2);
 *
 * The Duration is the sum of all individual parts.
 * This means that individual parts can be larger than the next-bigger unit.
 * For example, [minutes] can be greater than 59.
 *
 *     assert(fastestMarathon.inMinutes == 123);
 *
 * All individual parts are allowed to be negative.
 *
 * Use one of the properties, such as [inDays],
 * to retrieve the integer value of the Duration in the specified time unit.
 * Note that the returned value is rounded down.
 * For example, 
 *
 *     Duration aLongWeekend = new Duration(hours:88);
 *     assert(aLongWeekend.inDays == 3);
 *
 * This class provides a collection of arithmetic
 * and comparison operators,
 * plus a set of constants useful for converting time units.
 *
 * See [DateTime] to represent a point in time.
 * See [Stopwatch] to measure time-spans.
 *
 */
class Duration implements Comparable<Duration> {
  static const int MICROSECONDS_PER_MILLISECOND = 1000;
  static const int MILLISECONDS_PER_SECOND = 1000;
  static const int SECONDS_PER_MINUTE = 60;
  static const int MINUTES_PER_HOUR = 60;
  static const int HOURS_PER_DAY = 24;

  static const int MICROSECONDS_PER_SECOND =
      MICROSECONDS_PER_MILLISECOND * MILLISECONDS_PER_SECOND;
  static const int MICROSECONDS_PER_MINUTE =
      MICROSECONDS_PER_SECOND * SECONDS_PER_MINUTE;
  static const int MICROSECONDS_PER_HOUR =
      MICROSECONDS_PER_MINUTE * MINUTES_PER_HOUR;
  static const int MICROSECONDS_PER_DAY =
      MICROSECONDS_PER_HOUR * HOURS_PER_DAY;


  static const int MILLISECONDS_PER_MINUTE =
      MILLISECONDS_PER_SECOND * SECONDS_PER_MINUTE;
  static const int MILLISECONDS_PER_HOUR =
      MILLISECONDS_PER_MINUTE * MINUTES_PER_HOUR;
  static const int MILLISECONDS_PER_DAY =
      MILLISECONDS_PER_HOUR * HOURS_PER_DAY;

  static const int SECONDS_PER_HOUR = SECONDS_PER_MINUTE * MINUTES_PER_HOUR;
  static const int SECONDS_PER_DAY = SECONDS_PER_HOUR * HOURS_PER_DAY;

  static const int MINUTES_PER_DAY = MINUTES_PER_HOUR * HOURS_PER_DAY;

  static const Duration ZERO = const Duration(seconds: 0);

  /*
   * The value of this Duration object in microseconds.
   */
  final int _duration;

  /**
   * Creates a new Duration object whose value
   * is the sum of all individual parts.
   *
   * Individual parts can be larger than the next-bigger unit.
   * For example, [hours] can be greater than 23.
   *
   * All individual parts are allowed to be negative.
   * All arguments are 0 by default.
   */
  const Duration({int days: 0,
                  int hours: 0,
                  int minutes: 0,
                  int seconds: 0,
                  int milliseconds: 0,
                  int microseconds: 0})
      : _duration = days * MICROSECONDS_PER_DAY +
                    hours * MICROSECONDS_PER_HOUR +
                    minutes * MICROSECONDS_PER_MINUTE +
                    seconds * MICROSECONDS_PER_SECOND +
                    milliseconds * MICROSECONDS_PER_MILLISECOND +
                    microseconds;

  /**
   * Adds this Duration and [other] and
   * returns the sum as a new Duration object.
   */
  Duration operator +(Duration other) {
    return new Duration(microseconds: _duration + other._duration);
  }

  /**
   * Subtracts [other] from this Duration and
   * returns the difference as a new Duration object.
   */
  Duration operator -(Duration other) {
    return new Duration(microseconds: _duration - other._duration);
  }

  /**
   * Multiplies this Duration by the given [factor] and returns the result
   * as a new Duration object.
   *
   * Note that when [factor] is a double, and the duration is greater than
   * 53 bits, precision is lost because of double-precision arithmetic.
   */
  Duration operator *(num factor) {
    return new Duration(microseconds: (_duration * factor).round());
  }

  /**
   * Divides this Duration by the given [quotient] and returns the truncated
   * result as a new Duration object.
   *
   * Throws an [IntegerDivisionByZeroException] if [quotient] is `0`.
   */
  Duration operator ~/(int quotient) {
    // By doing the check here instead of relying on "~/" below we get the
    // exception even with dart2js.
    if (quotient == 0) throw new IntegerDivisionByZeroException();
    return new Duration(microseconds: _duration ~/ quotient);
  }

  /**
   * Returns `true` if the value of this Duration
   * is less than the value of [other].
   */
  bool operator <(Duration other) => this._duration < other._duration;

  /**
   * Returns `true` if the value of this Duration
   * is greater than the value of [other].
   */
  bool operator >(Duration other) => this._duration > other._duration;

  /**
   * Returns `true` if the value of this Duration
   * is less than or equal to the value of [other].
   */
  bool operator <=(Duration other) => this._duration <= other._duration;

  /**
   * Returns `true` if the value of this Duration
   * is greater than or equal to the value of [other].
   */
  bool operator >=(Duration other) => this._duration >= other._duration;

  /**
   * Returns the number of whole days spanned by this Duration.
   */
  int get inDays => _duration ~/ Duration.MICROSECONDS_PER_DAY;

  /**
   * Returns the number of whole hours spanned by this Duration.
   *
   * The returned value can be greater than 23.
   */
  int get inHours => _duration ~/ Duration.MICROSECONDS_PER_HOUR;

  /**
   * Returns the number of whole minutes spanned by this Duration.
   *
   * The returned value can be greater than 59.
   */
  int get inMinutes => _duration ~/ Duration.MICROSECONDS_PER_MINUTE;

  /**
   * Returns the number of whole seconds spanned by this Duration.
   *
   * The returned value can be greater than 59.
   */
  int get inSeconds => _duration ~/ Duration.MICROSECONDS_PER_SECOND;

  /**
   * Returns number of whole milliseconds spanned by this Duration.
   *
   * The returned value can be greater than 999.
   */
  int get inMilliseconds => _duration ~/ Duration.MICROSECONDS_PER_MILLISECOND;

  /**
   * Returns number of whole microseconds spanned by this Duration.
   */
  int get inMicroseconds => _duration;

  /**
   * Returns `true` if this Duration is the same object as [other].
   */
  bool operator ==(other) {
    if (other is !Duration) return false;
    return _duration == other._duration;
  }

  int get hashCode => _duration.hashCode;

  /**
   * Compares this Duration to [other],
   * returning zero if the values are equal.
   *
   * This function returns a negative integer
   * if this Duration is smaller than [other],
   * or a positive integer if it is greater.
   */
  int compareTo(Duration other) => _duration.compareTo(other._duration);

  String toString() {
    String sixDigits(int n) {
      if (n >= 100000) return "$n";
      if (n >= 10000) return "0$n";
      if (n >= 1000) return "00$n";
      if (n >= 100) return "000$n";
      if (n > 10) return "0000$n";
      return "00000$n";
    }
    String twoDigits(int n) {
      if (n >= 10) return "$n";
      return "0$n";
    }

    if (inMicroseconds < 0) {
      Duration duration =
          new Duration(microseconds: -inMicroseconds);
      return "-$duration";
    }
    String twoDigitMinutes = twoDigits(inMinutes.remainder(MINUTES_PER_HOUR));
    String twoDigitSeconds = twoDigits(inSeconds.remainder(SECONDS_PER_MINUTE));
    String sixDigitUs =
        sixDigits(inMicroseconds.remainder(MICROSECONDS_PER_SECOND));
    return "$inHours:$twoDigitMinutes:$twoDigitSeconds.$sixDigitUs";
  }
}