summaryrefslogtreecommitdiffstats
path: root/vendor/heck/src/lib.rs
blob: 49bfb0efdec8d9e58d3e25596c0643214ba56e07 (plain)
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
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
//! **heck** is a case conversion library.
//!
//! This library exists to provide case conversion between common cases like
//! CamelCase and snake_case. It is intended to be unicode aware, internally
//! consistent, and reasonably well performing.
//!
//! ## Definition of a word boundary
//!
//! Word boundaries are defined as the "unicode words" defined in the
//! `unicode_segmentation` library, as well as within those words in this
//! manner:
//!
//! 1. All underscore characters are considered word boundaries.
//! 2. If an uppercase character is followed by lowercase letters, a word
//! boundary is considered to be just prior to that uppercase character.
//! 3. If multiple uppercase characters are consecutive, they are considered to
//! be within a single word, except that the last will be part of the next word
//! if it is followed by lowercase characters (see rule 2).
//!
//! That is, "HelloWorld" is segmented `Hello|World` whereas "XMLHttpRequest" is
//! segmented `XML|Http|Request`.
//!
//! Characters not within words (such as spaces, punctuations, and underscores)
//! are not included in the output string except as they are a part of the case
//! being converted to. Multiple adjacent word boundaries (such as a series of
//! underscores) are folded into one. ("hello__world" in snake case is therefore
//! "hello_world", not the exact same string). Leading or trailing word boundary
//! indicators are dropped, except insofar as CamelCase capitalizes the first
//! word.
//!
//! ### Cases contained in this library:
//!
//! 1. UpperCamelCase
//! 2. lowerCamelCase
//! 3. snake_case
//! 4. kebab-case
//! 5. SHOUTY_SNAKE_CASE
//! 6. Title Case
//! 7. SHOUTY-KEBAB-CASE
//! 8. Train-Case
#![deny(missing_docs)]
#![forbid(unsafe_code)]

mod kebab;
mod lower_camel;
mod shouty_kebab;
mod shouty_snake;
mod snake;
mod title;
mod train;
mod upper_camel;

pub use kebab::{AsKebabCase, ToKebabCase};
pub use lower_camel::{AsLowerCamelCase, ToLowerCamelCase};
pub use shouty_kebab::{AsShoutyKebabCase, ToShoutyKebabCase};
pub use shouty_snake::{
    AsShoutySnakeCase, AsShoutySnakeCase as AsShoutySnekCase, ToShoutySnakeCase, ToShoutySnekCase,
};
pub use snake::{AsSnakeCase, AsSnakeCase as AsSnekCase, ToSnakeCase, ToSnekCase};
pub use title::{AsTitleCase, ToTitleCase};
pub use train::{AsTrainCase, ToTrainCase};
pub use upper_camel::{
    AsUpperCamelCase, AsUpperCamelCase as AsPascalCase, ToPascalCase, ToUpperCamelCase,
};

use std::fmt;

#[cfg(feature = "unicode")]
fn get_iterator(s: &str) -> unicode_segmentation::UnicodeWords {
    use unicode_segmentation::UnicodeSegmentation;
    s.unicode_words()
}
#[cfg(not(feature = "unicode"))]
fn get_iterator(s: &str) -> impl Iterator<Item = &str> {
    s.split(|letter: char| !letter.is_ascii_alphanumeric())
}

fn transform<F, G>(
    s: &str,
    mut with_word: F,
    mut boundary: G,
    f: &mut fmt::Formatter,
) -> fmt::Result
where
    F: FnMut(&str, &mut fmt::Formatter) -> fmt::Result,
    G: FnMut(&mut fmt::Formatter) -> fmt::Result,
{
    /// Tracks the current 'mode' of the transformation algorithm as it scans
    /// the input string.
    ///
    /// The mode is a tri-state which tracks the case of the last cased
    /// character of the current word. If there is no cased character
    /// (either lowercase or uppercase) since the previous word boundary,
    /// than the mode is `Boundary`. If the last cased character is lowercase,
    /// then the mode is `Lowercase`. Othertherwise, the mode is
    /// `Uppercase`.
    #[derive(Clone, Copy, PartialEq)]
    enum WordMode {
        /// There have been no lowercase or uppercase characters in the current
        /// word.
        Boundary,
        /// The previous cased character in the current word is lowercase.
        Lowercase,
        /// The previous cased character in the current word is uppercase.
        Uppercase,
    }

    let mut first_word = true;

    for word in get_iterator(s) {
        let mut char_indices = word.char_indices().peekable();
        let mut init = 0;
        let mut mode = WordMode::Boundary;

        while let Some((i, c)) = char_indices.next() {
            // Skip underscore characters
            if c == '_' {
                if init == i {
                    init += 1;
                }
                continue;
            }

            if let Some(&(next_i, next)) = char_indices.peek() {
                // The mode including the current character, assuming the
                // current character does not result in a word boundary.
                let next_mode = if c.is_lowercase() {
                    WordMode::Lowercase
                } else if c.is_uppercase() {
                    WordMode::Uppercase
                } else {
                    mode
                };

                // Word boundary after if next is underscore or current is
                // not uppercase and next is uppercase
                if next == '_' || (next_mode == WordMode::Lowercase && next.is_uppercase()) {
                    if !first_word {
                        boundary(f)?;
                    }
                    with_word(&word[init..next_i], f)?;
                    first_word = false;
                    init = next_i;
                    mode = WordMode::Boundary;

                // Otherwise if current and previous are uppercase and next
                // is lowercase, word boundary before
                } else if mode == WordMode::Uppercase && c.is_uppercase() && next.is_lowercase() {
                    if !first_word {
                        boundary(f)?;
                    } else {
                        first_word = false;
                    }
                    with_word(&word[init..i], f)?;
                    init = i;
                    mode = WordMode::Boundary;

                // Otherwise no word boundary, just update the mode
                } else {
                    mode = next_mode;
                }
            } else {
                // Collect trailing characters as a word
                if !first_word {
                    boundary(f)?;
                } else {
                    first_word = false;
                }
                with_word(&word[init..], f)?;
                break;
            }
        }
    }

    Ok(())
}

fn lowercase(s: &str, f: &mut fmt::Formatter) -> fmt::Result {
    let mut chars = s.chars().peekable();
    while let Some(c) = chars.next() {
        if c == 'Σ' && chars.peek().is_none() {
            write!(f, "ς")?;
        } else {
            write!(f, "{}", c.to_lowercase())?;
        }
    }

    Ok(())
}

fn uppercase(s: &str, f: &mut fmt::Formatter) -> fmt::Result {
    for c in s.chars() {
        write!(f, "{}", c.to_uppercase())?;
    }

    Ok(())
}

fn capitalize(s: &str, f: &mut fmt::Formatter) -> fmt::Result {
    let mut char_indices = s.char_indices();
    if let Some((_, c)) = char_indices.next() {
        write!(f, "{}", c.to_uppercase())?;
        if let Some((i, _)) = char_indices.next() {
            lowercase(&s[i..], f)?;
        }
    }

    Ok(())
}