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

use nom::{
    character::complete::{char, digit1},
    combinator::{map_res, verify},
    sequence::preceded,
};

use crate::{IResult, Span};

/// A date
///
/// The parser has some sanity check to make sure the date remotely makes sense
/// but it doesn't verify it is an actual real date valid date.
///
/// If that is important, you should use a date-time library to verify the validity.
#[derive(Debug, Copy, Clone, Eq, PartialEq)]
pub struct Date {
    year: u16,
    month_of_year: u8,
    day_of_month: u8,
}

impl Date {
    /// Create a new date
    #[must_use]
    pub fn new(year: u16, month_of_year: u8, day_of_month: u8) -> Self {
        Self {
            year,
            month_of_year,
            day_of_month,
        }
    }

    /// Returns the year
    #[must_use]
    pub fn year(&self) -> u16 {
        self.year
    }

    /// Returns the number of the month in the year
    ///
    /// The result is between `1` (january) and `12` (december) inclusive.
    #[must_use]
    pub fn month_of_year(&self) -> u8 {
        self.month_of_year
    }

    /// Returns the number of the day in the month
    ///
    /// The result is between `1` and `31` inclusive
    #[must_use]
    pub fn day_of_month(&self) -> u8 {
        self.day_of_month
    }
}

impl PartialOrd for Date {
    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
        Some(self.cmp(other))
    }
}

impl Ord for Date {
    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
        self.year
            .cmp(&other.year)
            .then_with(|| self.month_of_year.cmp(&other.month_of_year))
            .then_with(|| self.day_of_month.cmp(&other.day_of_month))
    }
}

pub(super) fn date(input: Span<'_>) -> IResult<'_, Date> {
    let (input, year) = year(input)?;
    let (input, month_of_year) = preceded(char('-'), month)(input)?;
    let (input, day_of_month) = preceded(char('-'), day)(input)?;
    Ok((
        input,
        Date {
            year,
            month_of_year,
            day_of_month,
        },
    ))
}

fn year(input: Span<'_>) -> IResult<'_, u16> {
    verify(map_res(digit1, |s: Span<'_>| s.fragment().parse()), |y| {
        *y > 0
    })(input)
}

fn month(input: Span<'_>) -> IResult<'_, u8> {
    verify(map_res(digit1, |s: Span<'_>| s.fragment().parse()), |m| {
        *m > 0 && *m <= 12
    })(input)
}

fn day(input: Span<'_>) -> IResult<'_, u8> {
    verify(map_res(digit1, |s: Span<'_>| s.fragment().parse()), |d| {
        *d > 0 && *d <= 31
    })(input)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn valid_date() {
        assert_eq!(
            date(Span::new("2022-08-15")).unwrap().1,
            Date {
                year: 2022,
                month_of_year: 8,
                day_of_month: 15
            }
        );
    }

    #[rstest]
    fn invalid_date(
        #[values(
            "hello",
            "0-1-1",
            "2000-00-12",
            "2000-13-12",
            "2000-11-00",
            "2000-11-32"
        )]
        input: &str,
    ) {
        assert!(date(Span::new(input)).is_err());
    }

    #[rstest]
    #[case(Date::new(2018, 11, 7), Date::new(2018, 11, 8))]
    #[case(Date::new(2018, 11, 8), Date::new(2018, 12, 7))]
    #[case(Date::new(2017, 11, 8), Date::new(2018, 11, 7))]
    fn date_comparison(#[case] before: Date, #[case] after: Date) {
        assert!(before < after);
        assert!(after > before);
    }
}