1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146

// This file is part of ICU4X. For terms of use, please see the file
// called LICENSE at the top level of the ICU4X source tree
// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).

use crate::Calendar;
use core::fmt;
use core::marker::PhantomData;

/// A duration between two dates
///
/// Can be used to perform date arithmetic
///
/// # Example
///
/// ```rust
/// use icu_calendar::{
///     types::IsoWeekday, Date, DateDuration, DateDurationUnit,
/// };
///
/// // Creating ISO date: 1992-09-02.
/// let mut date_iso = Date::try_new_iso_date(1992, 9, 2)
///     .expect("Failed to initialize ISO Date instance.");
///
/// assert_eq!(date_iso.day_of_week(), IsoWeekday::Wednesday);
/// assert_eq!(date_iso.year().number, 1992);
/// assert_eq!(date_iso.month().ordinal, 9);
/// assert_eq!(date_iso.day_of_month().0, 2);
///
/// // Answering questions about days in month and year.
/// assert_eq!(date_iso.days_in_year(), 366);
/// assert_eq!(date_iso.days_in_month(), 30);
///
/// // Advancing date in-place by 1 year, 2 months, 3 weeks, 4 days.
/// date_iso.add(DateDuration::new(1, 2, 3, 4));
/// assert_eq!(date_iso.year().number, 1993);
/// assert_eq!(date_iso.month().ordinal, 11);
/// assert_eq!(date_iso.day_of_month().0, 27);
///
/// // Reverse date advancement.
/// date_iso.add(DateDuration::new(-1, -2, -3, -4));
/// assert_eq!(date_iso.year().number, 1992);
/// assert_eq!(date_iso.month().ordinal, 9);
/// assert_eq!(date_iso.day_of_month().0, 2);
///
/// // Creating ISO date: 2022-01-30.
/// let newer_date_iso = Date::try_new_iso_date(2022, 1, 30)
///     .expect("Failed to initialize ISO Date instance.");
///
/// // Comparing dates: 2022-01-30 and 1992-09-02.
/// let duration = newer_date_iso.until(
///     &date_iso,
///     DateDurationUnit::Years,
///     DateDurationUnit::Days,
/// );
/// assert_eq!(duration.years, 30);
/// assert_eq!(duration.months, -8);
/// assert_eq!(duration.days, 28);
///
/// // Create new date with date advancement. Reassign to new variable.
/// let mutated_date_iso = date_iso.added(DateDuration::new(1, 2, 3, 4));
/// assert_eq!(mutated_date_iso.year().number, 1993);
/// assert_eq!(mutated_date_iso.month().ordinal, 11);
/// assert_eq!(mutated_date_iso.day_of_month().0, 27);
/// ```
#[derive(Copy, Clone, Eq, PartialEq)]
#[allow(clippy::exhaustive_structs)] // this type should be stable (and is intended to be constructed manually)
pub struct DateDuration<C: Calendar + ?Sized> {
    /// The number of years
    pub years: i32,
    /// The number of months
    pub months: i32,
    /// The number of weeks
    pub weeks: i32,
    /// The number of days
    pub days: i32,
    /// A marker for the calendar
    pub marker: PhantomData<C>,
}

/// A "duration unit" used to specify the minimum or maximum duration of time to
/// care about
#[derive(Copy, Clone, Eq, PartialEq, Debug)]
#[allow(clippy::exhaustive_enums)] // this type should be stable
pub enum DateDurationUnit {
    /// Duration in years
    Years,
    /// Duration in months
    Months,
    /// Duration in weeks
    Weeks,
    /// Duration in days
    Days,
}

impl<C: Calendar + ?Sized> Default for DateDuration<C> {
    fn default() -> Self {
        Self {
            years: 0,
            months: 0,
            weeks: 0,
            days: 0,
            marker: PhantomData,
        }
    }
}

impl<C: Calendar + ?Sized> DateDuration<C> {
    /// Construct a DateDuration
    ///
    /// ```rust
    /// # use icu_calendar::*;
    /// // two years, three months, and five days
    /// let duration: DateDuration<Iso> = DateDuration::new(2, 3, 0, 5);
    /// ```
    pub fn new(years: i32, months: i32, weeks: i32, days: i32) -> Self {
        DateDuration {
            years,
            months,
            weeks,
            days,
            marker: PhantomData,
        }
    }

    /// Explicitly cast duration to one for a different calendar
    pub fn cast_unit<C2: Calendar + ?Sized>(self) -> DateDuration<C2> {
        DateDuration {
            years: self.years,
            months: self.months,
            days: self.days,
            weeks: self.weeks,
            marker: PhantomData,
        }
    }
}

impl<C: Calendar> fmt::Debug for DateDuration<C> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
        f.debug_struct("DateDuration")
            .field("years", &self.years)
            .field("months", &self.months)
            .field("weeks", &self.weeks)
            .field("days", &self.days)
            .finish()
    }
}