arvo 0.9.0

Validated, immutable value objects for common domain types (email, money, identifiers, …)
Documentation 
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
147
148
149

use crate::errors::ValidationError;
use crate::traits::ValueObject;

/// Unit of weight/mass.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum WeightUnit {
    Mg,
    G,
    Kg,
    T,
    Oz,
    Lb,
}

impl std::fmt::Display for WeightUnit {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            WeightUnit::Mg => write!(f, "mg"),
            WeightUnit::G => write!(f, "g"),
            WeightUnit::Kg => write!(f, "kg"),
            WeightUnit::T => write!(f, "t"),
            WeightUnit::Oz => write!(f, "oz"),
            WeightUnit::Lb => write!(f, "lb"),
        }
    }
}

/// Input for [`Weight`].
#[derive(Debug, Clone, PartialEq)]
pub struct WeightInput {
    pub value: f64,
    pub unit: WeightUnit,
}

/// A validated weight/mass measurement.
///
/// **Validation:** value must be finite and non-negative.
///
/// # Example
///
/// ```rust,ignore
/// use arvo::measurement::{Weight, WeightInput, WeightUnit};
/// use arvo::traits::ValueObject;
///
/// let w = Weight::new(WeightInput { value: 75.0, unit: WeightUnit::Kg })?;
/// assert_eq!(w.value(), "75 kg");
/// ```
#[derive(Debug, Clone, PartialEq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct Weight {
    value: f64,
    unit: WeightUnit,
    #[cfg_attr(feature = "serde", serde(skip))]
    canonical: String,
}

impl ValueObject for Weight {
    type Input = WeightInput;
    type Output = str;
    type Error = ValidationError;

    fn new(input: Self::Input) -> Result<Self, Self::Error> {
        if !input.value.is_finite() || input.value < 0.0 {
            return Err(ValidationError::invalid("Weight", &input.value.to_string()));
        }
        let canonical = format!("{} {}", input.value, input.unit);
        Ok(Self {
            value: input.value,
            unit: input.unit,
            canonical,
        })
    }

    fn value(&self) -> &Self::Output {
        &self.canonical
    }

    fn into_inner(self) -> Self::Input {
        WeightInput {
            value: self.value,
            unit: self.unit,
        }
    }
}

impl Weight {
    pub fn amount(&self) -> f64 {
        self.value
    }
    pub fn unit(&self) -> &WeightUnit {
        &self.unit
    }
}

impl std::fmt::Display for Weight {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.canonical)
    }
}

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

    #[test]
    fn accepts_valid() {
        let w = Weight::new(WeightInput {
            value: 75.0,
            unit: WeightUnit::Kg,
        })
        .unwrap();
        assert_eq!(w.value(), "75 kg");
        assert_eq!(w.amount(), 75.0);
    }

    #[test]
    fn accepts_zero() {
        assert!(
            Weight::new(WeightInput {
                value: 0.0,
                unit: WeightUnit::G
            })
            .is_ok()
        );
    }

    #[test]
    fn rejects_negative() {
        assert!(
            Weight::new(WeightInput {
                value: -1.0,
                unit: WeightUnit::Kg
            })
            .is_err()
        );
    }

    #[test]
    fn rejects_nan() {
        assert!(
            Weight::new(WeightInput {
                value: f64::NAN,
                unit: WeightUnit::Kg
            })
            .is_err()
        );
    }
}