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

//! Performs validation and correction of GTIN-8 codes.

use utils;

/// Errors that make GTIN-8 correction impossible.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum FixError {
    /// The provided string contains non-ASCII characters.
    NonAsciiString,
    /// The provided code was too long to be valid.
    TooLong,
    /// The calculated check-digit did not match the code's check-digit.
    CheckDigitIncorrect,
}

/// Check that a GTIN-8 code is valid by confirming that it is exactly
/// 8 digits in length and that the check-digit is correct.
///
/// # Examples
/// ```
/// use gtin_validate::gtin8;
///
/// assert_eq!(gtin8::check("14567810"), true);  // Valid GTIN-8
/// assert_eq!(gtin8::check("1456781"), false);  // too short
/// assert_eq!(gtin8::check("14567811"), false); // Bad check digit
/// ```
pub fn check(code: &str) -> bool {
    if code.len() != 8 {
        return false;
    }
    if !utils::is_ascii_numeric(code) {
        return false;
    }

    // Calculate and compare check digit
    let bytes = code.as_bytes();
    let check = utils::compute_check_digit(bytes);
    if check != bytes[7] - 48 {
        return false;
    }

    true
}

/// Attempt to fix an invalid GTIN-8 code by stripping whitespace from
/// the left and right sides and zero-padding the code if it is less
/// than 8 digits in length.
///
/// These corrections fix many common errors introduced by manual data
/// entry and software that treats GTINs as integers rather than
/// strings, thus truncating the leading zeros.
///
/// # Examples
/// ```
/// use gtin_validate::gtin8;
///
/// // Add missing zero, fixing length
/// let result1 = gtin8::fix("5766796");
/// assert!(result1.is_ok());
/// assert_eq!(result1.unwrap(), "05766796");
///
/// // Remove extra whitespace
/// let result2 = gtin8::fix("05766796 ");
/// assert!(result2.is_ok());
/// assert_eq!(result2.unwrap(), "05766796");
/// ```
///
/// Here is how you catch errors:
///
/// ```
/// # use gtin_validate::gtin8;
/// match gtin8::fix("14567811") {
///   Ok(fixed) => {println!("Fixed GTIN-14: {}", fixed);}
///   Err(_) => {println!("Could not fix GTIN-14");}
/// }
/// ```
pub fn fix(code: &str) -> Result<String, FixError> {
    let mut fixed = code.trim_left().trim_right().to_string();

    if !fixed.is_ascii() {
        return Err(FixError::NonAsciiString);
    }
    if fixed.len() > 8 {
        return Err(FixError::TooLong);
    }
    fixed = utils::zero_pad(fixed, 8);
    if !check(&fixed) {
        return Err(FixError::CheckDigitIncorrect);
    }

    Ok(fixed)
}

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

    #[test]
    fn check_valid() {
        assert_eq!(check("00000000"), true);
        assert_eq!(check("49137712"), true);
        assert_eq!(check("44196318"), true);
    }

    #[test]
    fn check_invalid_length() {
        assert_eq!(check("0000000"), false); // too short
        assert_eq!(check("734289412"), false); // too long
    }

    #[test]
    fn check_non_ascii() {
        assert_eq!(check("❤"), false);
    }

    #[test]
    fn check_non_numeric() {
        assert_eq!(check("a"), false);
        assert_eq!(check("abcdabcd"), false); // length 8
        assert_eq!(check("0000000a"), false); // invalid check digit
    }

    #[test]
    fn check_invalid_check_digit() {
        assert_eq!(check("00000001"), false);
        assert_eq!(check("00000002"), false);
        assert_eq!(check("00000003"), false);
        assert_eq!(check("00000004"), false);
        assert_eq!(check("00000005"), false);
        assert_eq!(check("00000006"), false);
        assert_eq!(check("00000007"), false);
        assert_eq!(check("00000008"), false);
        assert_eq!(check("00000009"), false);
    }

    #[test]
    fn check_static_data() {
        assert_eq!(check("14567810"), true); // Valid GTIN-8
        assert_eq!(check("1456781"), false); // too short
        assert_eq!(check("14567811"), false); // Bad check digit
    }

    #[test]
    fn fix_non_ascii() {
        assert!(fix("❤").is_err());
    }

    #[test]
    fn fix_needs_zero_padding() {
        assert!(fix("0").is_ok());
        assert_eq!(fix("0").unwrap(), "00000000");
        assert_eq!(fix("9944220").unwrap(), "09944220");
    }

    proptest! {
        #[test]
        fn doesnt_crash(ref s in ".*") {
            check(s);
        }
    }
}