packages/charted/lib/core/scales/time_scale.dart

//
// Copyright 2014 Google Inc. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd
//

part of charted.core.scales;

/// TimeScale is a linear scale that operates on time.
class TimeScale extends BaseLinearScale {
  static const _scaleSteps = const [
    1e3, // 1-second
    5e3, // 5-second
    15e3, // 15-second
    3e4, // 30-second
    6e4, // 1-minute
    3e5, // 5-minute
    9e5, // 15-minute
    18e5, // 30-minute
    36e5, // 1-hour
    108e5, // 3-hour
    216e5, // 6-hour
    432e5, // 12-hour
    864e5, // 1-day
    1728e5, // 2-day
    6048e5, // 1-week
    2592e6, // 1-month
    7776e6, // 3-month
    31536e6 // 1-year
  ];

  static final _scaleLocalMethods = [
    [TimeInterval.second, 1],
    [TimeInterval.second, 5],
    [TimeInterval.second, 15],
    [TimeInterval.second, 30],
    [TimeInterval.minute, 1],
    [TimeInterval.minute, 5],
    [TimeInterval.minute, 15],
    [TimeInterval.minute, 30],
    [TimeInterval.hour, 1],
    [TimeInterval.hour, 3],
    [TimeInterval.hour, 6],
    [TimeInterval.hour, 12],
    [TimeInterval.day, 1],
    [TimeInterval.day, 2],
    [TimeInterval.week, 1],
    [TimeInterval.month, 1],
    [TimeInterval.month, 3],
    [TimeInterval.year, 1]
  ];

  static final FormatFunction _scaleLocalFormat = new TimeFormat().multi([
    [".%L", (DateTime d) => d.millisecond > 0],
    [":%S", (DateTime d) => d.second > 0],
    ["%I:%M", (DateTime d) => d.minute > 0],
    ["%I %p", (DateTime d) => d.hour > 0],
    ["%a %d", (DateTime d) => (d.weekday % 7) > 0 && d.day != 1],
    ["%b %d", (DateTime d) => d.day != 1],
    ["%B", (DateTime d) => d.month > 1],
    ["%Y", (d) => true]
  ]);

  TimeScale();
  TimeScale._clone(TimeScale source) : super._clone(source);

  @override
  num scale(Object val) =>
      super.scale(val is DateTime ? val.millisecondsSinceEpoch : val);

  @override
  set domain(Iterable<dynamic> value) {
    super.domain = value
        .map<num>((d) => d is DateTime ? d.millisecondsSinceEpoch : d as num)
        .toList();
  }

  @override
  FormatFunction createTickFormatter([String format]) => _scaleLocalFormat;

  @override
  TimeScale clone() => new TimeScale._clone(this);

  List<dynamic> _getTickMethod(Extent<num> extent, int count) {
    num target = (extent.max - extent.min) / count;
    int i = ScaleUtils.bisect(_scaleSteps, target);

    return i == _scaleSteps.length
        ? [
            TimeInterval.year,
            _linearTickRange(
                    new Extent<num>(extent.min / 31536e6, extent.max / 31536e6))
                .step
          ]
        : i == 0
            ? [new ScaleMilliSeconds(), _linearTickRange(extent).step]
            : _scaleLocalMethods[
                target / _scaleSteps[i - 1] < _scaleSteps[i] / target
                    ? i - 1
                    : i];
  }

  List<num> niceInterval(int ticksCount) {
    var extent = ScaleUtils.extent(domain);
    var method = _getTickMethod(extent, ticksCount);
    TimeInterval interval = method[0];
    int skip = method[1];

    bool skipped(DateTime date) {
      var seconds = date.millisecondsSinceEpoch;
      return interval.range(seconds, seconds + 1, skip).length == 0;
    }

    if (skip > 1) {
      domain = ScaleUtils.nice(
          domain as List<num>,
          new RoundingFunctions((dateMillis) {
            var date =
                new DateTime.fromMillisecondsSinceEpoch(dateMillis.round());
            while (skipped(date = interval.floor(date))) {
              date = new DateTime.fromMillisecondsSinceEpoch(
                  date.millisecondsSinceEpoch - 1);
            }
            return date.millisecondsSinceEpoch;
          }, (dateMillis) {
            var date =
                new DateTime.fromMillisecondsSinceEpoch(dateMillis.round());
            while (skipped(date = interval.ceil(date))) {
              date = new DateTime.fromMillisecondsSinceEpoch(
                  date.millisecondsSinceEpoch + 1);
            }
            return date.millisecondsSinceEpoch;
          }));
    } else {
      domain = ScaleUtils.nice(
          domain as List<num>,
          new RoundingFunctions(
              (date) => interval.floor(date).millisecondsSinceEpoch,
              (date) => interval.ceil(date).millisecondsSinceEpoch));
    }
    return domain;
  }

  @override
  set nice(bool value) {
    assert(value != null);
    if (value != null && _nice != value) {
      _nice = value;
      domain = niceInterval(_ticksCount);
    }
  }

  List<DateTime> ticksInterval(int ticksCount) {
    var extent = ScaleUtils.extent(domain);
    var method = _getTickMethod(extent, ticksCount);
    TimeInterval interval = method[0];
    int skip = method[1];
    return interval
        .range(extent.min, extent.max + 1, skip < 1 ? 1 : skip)
        .toList();
  }

  @override
  List<DateTime> get ticks => ticksInterval(ticksCount);
}

class ScaleMilliSeconds implements TimeInterval {
  DateTime floor(dynamic val) => _toDateTime(val);
  DateTime ceil(dynamic val) => _toDateTime(val);
  DateTime round(dynamic val) => _toDateTime(val);

  DateTime offset(Object val, int dt) {
    return new DateTime.fromMillisecondsSinceEpoch(_toMilliseconds(val) + dt);
  }

  List<DateTime> range(dynamic t0, dynamic t1, int step) {
    int start = _toMilliseconds(t0);
    int stop = _toMilliseconds(t1);
    return new Range((start / step).ceil() * step, stop, step)
        .map((d) => new DateTime.fromMillisecondsSinceEpoch(d as int))
        .toList();
  }

  static DateTime _toDateTime(/* int | DateTime */ dynamic x) {
    return x is int
        ? new DateTime.fromMillisecondsSinceEpoch(x)
        : x as DateTime;
  }

  static int _toMilliseconds(/* int | DateTime */ dynamic val) {
    return val is int ? val : (val as DateTime).millisecondsSinceEpoch;
  }
}