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
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
use crate::errors::{Error, Result};
use serde::{Deserialize, Serialize};
use std::{
fmt::{self, Debug, Display, Formatter},
str::FromStr,
};
const MONEY_TO_RAW_POWER_OF_10_CONVERSION: u32 = 9;
const MONEY_TO_RAW_CONVERSION: u64 = 1_000_000_000;
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
pub struct Money(u64);
impl Money {
pub const fn zero() -> Self {
Self(0)
}
pub const fn from_nano(value: u64) -> Self {
Self(value)
}
pub const fn as_nano(self) -> u64 {
self.0
}
pub fn checked_add(self, rhs: Money) -> Option<Money> {
self.0.checked_add(rhs.0).map(Self::from_nano)
}
pub fn checked_sub(self, rhs: Money) -> Option<Money> {
self.0.checked_sub(rhs.0).map(Self::from_nano)
}
}
impl FromStr for Money {
type Err = Error;
fn from_str(value_str: &str) -> Result<Self> {
let mut itr = value_str.splitn(2, '.');
let converted_units = {
let units = itr
.next()
.and_then(|s| s.parse::<u64>().ok())
.ok_or_else(|| Error::FailedToParse("Can't parse Money units".to_string()))?;
units
.checked_mul(MONEY_TO_RAW_CONVERSION)
.ok_or_else(|| Error::ExcessiveValue)?
};
let remainder = {
let remainder_str = itr.next().unwrap_or_default().trim_end_matches('0');
if remainder_str.is_empty() {
0
} else {
let parsed_remainder = remainder_str
.parse::<u64>()
.map_err(|_| Error::FailedToParse("Can't parse Money remainder".to_string()))?;
let remainder_conversion = MONEY_TO_RAW_POWER_OF_10_CONVERSION
.checked_sub(remainder_str.len() as u32)
.ok_or_else(|| Error::LossOfPrecision)?;
parsed_remainder * 10_u64.pow(remainder_conversion)
}
};
Ok(Self::from_nano(converted_units + remainder))
}
}
impl Debug for Money {
fn fmt(&self, formatter: &mut Formatter) -> fmt::Result {
Display::fmt(self, formatter)
}
}
impl Display for Money {
fn fmt(&self, formatter: &mut Formatter) -> fmt::Result {
let unit = self.0 / MONEY_TO_RAW_CONVERSION;
let remainder = self.0 % MONEY_TO_RAW_CONVERSION;
write!(formatter, "{}.{}", unit, format!("{:09}", remainder))
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::u64;
use unwrap::unwrap;
#[test]
fn from_str() {
assert_eq!(Money(0), unwrap!(Money::from_str("0")));
assert_eq!(Money(0), unwrap!(Money::from_str("0.")));
assert_eq!(Money(0), unwrap!(Money::from_str("0.0")));
assert_eq!(Money(1), unwrap!(Money::from_str("0.000000001")));
assert_eq!(Money(1_000_000_000), unwrap!(Money::from_str("1")));
assert_eq!(Money(1_000_000_000), unwrap!(Money::from_str("1.")));
assert_eq!(Money(1_000_000_000), unwrap!(Money::from_str("1.0")));
assert_eq!(
Money(1_000_000_001),
unwrap!(Money::from_str("1.000000001"))
);
assert_eq!(Money(1_100_000_000), unwrap!(Money::from_str("1.1")));
assert_eq!(
Money(1_100_000_001),
unwrap!(Money::from_str("1.100000001"))
);
assert_eq!(
Money(4_294_967_295_000_000_000),
unwrap!(Money::from_str("4294967295"))
);
assert_eq!(
Money(4_294_967_295_999_999_999),
unwrap!(Money::from_str("4294967295.999999999")),
);
assert_eq!(
Money(4_294_967_295_999_999_999),
unwrap!(Money::from_str("4294967295.9999999990000")),
);
assert_eq!(
Err(Error::FailedToParse("Can't parse Money units".to_string())),
Money::from_str("a")
);
assert_eq!(
Err(Error::FailedToParse(
"Can't parse Money remainder".to_string()
)),
Money::from_str("0.a")
);
assert_eq!(
Err(Error::FailedToParse(
"Can't parse Money remainder".to_string()
)),
Money::from_str("0.0.0")
);
assert_eq!(Err(Error::LossOfPrecision), Money::from_str("0.0000000009"));
assert_eq!(Err(Error::ExcessiveValue), Money::from_str("18446744074"));
}
#[test]
fn display() {
assert_eq!("0.000000000", format!("{}", Money(0)));
assert_eq!("0.000000001", format!("{}", Money(1)));
assert_eq!("0.000000010", format!("{}", Money(10)));
assert_eq!("1.000000000", format!("{}", Money(1_000_000_000)));
assert_eq!("1.000000001", format!("{}", Money(1_000_000_001)));
assert_eq!(
"4294967295.000000000",
format!("{}", Money(4_294_967_295_000_000_000))
);
}
#[test]
fn checked_add_sub() {
assert_eq!(Some(Money(3)), Money(1).checked_add(Money(2)));
assert_eq!(None, Money(u64::MAX).checked_add(Money(1)));
assert_eq!(None, Money(u64::MAX).checked_add(Money(u64::MAX)));
assert_eq!(Some(Money(0)), Money(u64::MAX).checked_sub(Money(u64::MAX)));
assert_eq!(None, Money(0).checked_sub(Money(u64::MAX)));
assert_eq!(None, Money(10).checked_sub(Money(11)));
}
}