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

//! Crate for changing case of Rust identifiers.
//!
//! # Features
//! * Supports `snake_case`, `lowercase`, `camelCase`, 
//!   `PascalCase`, `SCREAMING_SNAKE_CASE`, and `kebab-case`
//! * Rename variants, and fields
//! 
//! # Examples
//! ```rust
//! use ident_case::RenameRule;
//!
//! assert_eq!("helloWorld", RenameRule::CamelCase.apply_to_field("hello_world"));
//!
//! assert_eq!("i_love_serde", RenameRule::SnakeCase.apply_to_variant("ILoveSerde"));
//! ```

// Copyright 2017 Serde Developers
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use std::ascii::AsciiExt;
use std::str::FromStr;

use self::RenameRule::*;

/// A casing rule for renaming Rust identifiers.
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub enum RenameRule {
    /// No-op rename rule.
    None,
    /// Rename direct children to "lowercase" style.
    LowerCase,
    /// Rename direct children to "PascalCase" style, as typically used for enum variants.
    PascalCase,
    /// Rename direct children to "camelCase" style.
    CamelCase,
    /// Rename direct children to "snake_case" style, as commonly used for fields.
    SnakeCase,
    /// Rename direct children to "SCREAMING_SNAKE_CASE" style, as commonly used for constants.
    ScreamingSnakeCase,
    /// Rename direct children to "kebab-case" style.
    KebabCase,
}

impl RenameRule {
    /// Change case of a `PascalCase` variant.
    pub fn apply_to_variant<S: AsRef<str>>(&self, variant: S) -> String {
        
        let variant = variant.as_ref();
        match *self {
            None | PascalCase => variant.to_owned(),
            LowerCase => variant.to_ascii_lowercase(),
            CamelCase => variant[..1].to_ascii_lowercase() + &variant[1..],
            SnakeCase => {
                let mut snake = String::new();
                for (i, ch) in variant.char_indices() {
                    if i > 0 && ch.is_uppercase() {
                        snake.push('_');
                    }
                    snake.push(ch.to_ascii_lowercase());
                }
                snake
            }
            ScreamingSnakeCase => SnakeCase.apply_to_variant(variant).to_ascii_uppercase(),
            KebabCase => SnakeCase.apply_to_variant(variant).replace('_', "-"),
        }
    }

    /// Change case of a `snake_case` field.
    pub fn apply_to_field<S: AsRef<str>>(&self, field: S) -> String {
        
        let field = field.as_ref();
        match *self {
            None | LowerCase | SnakeCase => field.to_owned(),
            PascalCase => {
                let mut pascal = String::new();
                let mut capitalize = true;
                for ch in field.chars() {
                    if ch == '_' {
                        capitalize = true;
                    } else if capitalize {
                        pascal.push(ch.to_ascii_uppercase());
                        capitalize = false;
                    } else {
                        pascal.push(ch);
                    }
                }
                pascal
            }
            CamelCase => {
                let pascal = PascalCase.apply_to_field(field);
                pascal[..1].to_ascii_lowercase() + &pascal[1..]
            }
            ScreamingSnakeCase => field.to_ascii_uppercase(),
            KebabCase => field.replace('_', "-"),
        }
    }
}

impl FromStr for RenameRule {
    type Err = ();

    fn from_str(rename_all_str: &str) -> Result<Self, Self::Err> {
        match rename_all_str {
            "lowercase" => Ok(LowerCase),
            "PascalCase" => Ok(PascalCase),
            "camelCase" => Ok(CamelCase),
            "snake_case" => Ok(SnakeCase),
            "SCREAMING_SNAKE_CASE" => Ok(ScreamingSnakeCase),
            "kebab-case" => Ok(KebabCase),
            _ => Err(()),
        }
    }
}

impl Default for RenameRule {
    fn default() -> Self {
        RenameRule::None
    }
}

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

    #[test]
    fn rename_variants() {
        for &(original, lower, camel, snake, screaming, kebab) in
            &[
                ("Outcome", "outcome", "outcome", "outcome", "OUTCOME", "outcome"),
                ("VeryTasty", "verytasty", "veryTasty", "very_tasty", "VERY_TASTY", "very-tasty"),
                ("A", "a", "a", "a", "A", "a"),
                ("Z42", "z42", "z42", "z42", "Z42", "z42"),
            ] {
            assert_eq!(None.apply_to_variant(original), original);
            assert_eq!(LowerCase.apply_to_variant(original), lower);
            assert_eq!(PascalCase.apply_to_variant(original), original);
            assert_eq!(CamelCase.apply_to_variant(original), camel);
            assert_eq!(SnakeCase.apply_to_variant(original), snake);
            assert_eq!(ScreamingSnakeCase.apply_to_variant(original), screaming);
            assert_eq!(KebabCase.apply_to_variant(original), kebab);
        }
    }

    #[test]
    fn rename_fields() {
        for &(original, pascal, camel, screaming, kebab) in
            &[
                ("outcome", "Outcome", "outcome", "OUTCOME", "outcome"),
                ("very_tasty", "VeryTasty", "veryTasty", "VERY_TASTY", "very-tasty"),
                ("_leading_under", "LeadingUnder", "leadingUnder", "_LEADING_UNDER", "-leading-under"),
                ("double__under", "DoubleUnder", "doubleUnder", "DOUBLE__UNDER", "double--under"),
                ("a", "A", "a", "A", "a"),
                ("z42", "Z42", "z42", "Z42", "z42"),
            ] {
            assert_eq!(None.apply_to_field(original), original);
            assert_eq!(PascalCase.apply_to_field(original), pascal);
            assert_eq!(CamelCase.apply_to_field(original), camel);
            assert_eq!(SnakeCase.apply_to_field(original), original);
            assert_eq!(ScreamingSnakeCase.apply_to_field(original), screaming);
            assert_eq!(KebabCase.apply_to_field(original), kebab);
        }
    }
}