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

use std::{error, fmt, num, str::FromStr};

/// A VCF number describing the cardinality of a field.
#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
pub enum Number {
    /// An explicit size.
    Count(usize),
    /// The number of alternate bases (`A`).
    AlternateBases,
    /// The number of reference and alternate bases (`R`).
    ReferenceAlternateBases,
    /// The number of samples (`G`).
    Samples,
    /// The size is unknown.
    Unknown,
}

impl Number {
    /// The number of alternate bases (`A`).
    pub const A: Self = Self::AlternateBases;

    /// The number of reference and alternate bases (`R`).
    pub const R: Self = Self::ReferenceAlternateBases;

    /// The number of samples (`G`).
    pub const G: Self = Self::Samples;
}

impl Default for Number {
    fn default() -> Self {
        Self::Count(1)
    }
}

impl fmt::Display for Number {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Count(n) => write!(f, "{n}"),
            Self::AlternateBases => f.write_str("A"),
            Self::ReferenceAlternateBases => f.write_str("R"),
            Self::Samples => f.write_str("G"),
            Self::Unknown => f.write_str("."),
        }
    }
}

/// An error returned when a VCF number fails to parse.
#[derive(Clone, Debug, Eq, PartialEq)]
pub enum ParseError {
    /// The input is empty.
    Empty,
    /// The input is invalid.
    Invalid(num::ParseIntError),
}

impl error::Error for ParseError {
    fn source(&self) -> Option<&(dyn error::Error + 'static)> {
        match self {
            Self::Empty => None,
            Self::Invalid(e) => Some(e),
        }
    }
}

impl fmt::Display for ParseError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Empty => f.write_str("empty input"),
            Self::Invalid(_) => f.write_str("invalid input"),
        }
    }
}

impl FromStr for Number {
    type Err = ParseError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match s {
            "" => Err(ParseError::Empty),
            "A" => Ok(Self::AlternateBases),
            "R" => Ok(Self::ReferenceAlternateBases),
            "G" => Ok(Self::Samples),
            "." => Ok(Self::Unknown),
            _ => s.parse().map(Self::Count).map_err(ParseError::Invalid),
        }
    }
}

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

    #[test]
    fn test_default() {
        assert_eq!(Number::default(), Number::Count(1));
    }

    #[test]
    fn test_fmt() {
        assert_eq!(Number::Count(1).to_string(), "1");
        assert_eq!(Number::AlternateBases.to_string(), "A");
        assert_eq!(Number::ReferenceAlternateBases.to_string(), "R");
        assert_eq!(Number::Samples.to_string(), "G");
        assert_eq!(Number::Unknown.to_string(), ".");
    }

    #[test]
    fn test_from_str() {
        assert_eq!("1".parse(), Ok(Number::Count(1)));
        assert_eq!("A".parse(), Ok(Number::AlternateBases));
        assert_eq!("R".parse(), Ok(Number::ReferenceAlternateBases));
        assert_eq!("G".parse(), Ok(Number::Samples));
        assert_eq!(".".parse(), Ok(Number::Unknown));

        assert_eq!("".parse::<Number>(), Err(ParseError::Empty));
        assert!(matches!(
            "Noodles".parse::<Number>(),
            Err(ParseError::Invalid(_))
        ));
    }
}