1use std::fmt;
2
3use crate::{capitalize, lowercase, transform};
4
5/// This trait defines a lower camel case conversion.
6///
7/// In lowerCamelCase, word boundaries are indicated by capital letters,
8/// excepting the first word.
9///
10/// ## Example:
11///
12/// ```rust
13/// use heck::ToLowerCamelCase;
14///
15/// let sentence = "It is we who built these palaces and cities.";
16/// assert_eq!(sentence.to_lower_camel_case(), "itIsWeWhoBuiltThesePalacesAndCities");
17/// ```
18pub trait ToLowerCamelCase: ToOwned {
19    /// Convert this type to lower camel case.
20    fn to_lower_camel_case(&self) -> Self::Owned;
21}
22
23impl ToLowerCamelCase for str {
24    fn to_lower_camel_case(&self) -> String {
25        AsLowerCamelCase(self).to_string()
26    }
27}
28
29/// This wrapper performs a lower camel case conversion in [`fmt::Display`].
30///
31/// ## Example:
32///
33/// ```
34/// use heck::AsLowerCamelCase;
35///
36/// let sentence = "It is we who built these palaces and cities.";
37/// assert_eq!(format!("{}", AsLowerCamelCase(sentence)), "itIsWeWhoBuiltThesePalacesAndCities");
38/// ```
39pub struct AsLowerCamelCase<T: AsRef<str>>(pub T);
40
41impl<T: AsRef<str>> fmt::Display for AsLowerCamelCase<T> {
42    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
43        let mut first = true;
44        transform(
45            self.0.as_ref(),
46            |s, f| {
47                if first {
48                    first = false;
49                    lowercase(s, f)
50                } else {
51                    capitalize(s, f)
52                }
53            },
54            |_| Ok(()),
55            f,
56        )
57    }
58}
59
60#[cfg(test)]
61mod tests {
62    use super::ToLowerCamelCase;
63
64    macro_rules! t {
65        ($t:ident : $s1:expr => $s2:expr) => {
66            #[test]
67            fn $t() {
68                assert_eq!($s1.to_lower_camel_case(), $s2)
69            }
70        };
71    }
72
73    t!(test1: "CamelCase" => "camelCase");
74    t!(test2: "This is Human case." => "thisIsHumanCase");
75    t!(test3: "MixedUP CamelCase, with some Spaces" => "mixedUpCamelCaseWithSomeSpaces");
76    t!(test4: "mixed_up_ snake_case, with some _spaces" => "mixedUpSnakeCaseWithSomeSpaces");
77    t!(test5: "kebab-case" => "kebabCase");
78    t!(test6: "SHOUTY_SNAKE_CASE" => "shoutySnakeCase");
79    t!(test7: "snake_case" => "snakeCase");
80    t!(test8: "this-contains_ ALLKinds OfWord_Boundaries" => "thisContainsAllKindsOfWordBoundaries");
81    #[cfg(feature = "unicode")]
82    t!(test9: "XΣXΣ baffle" => "xσxςBaffle");
83    t!(test10: "XMLHttpRequest" => "xmlHttpRequest");
84    // TODO unicode tests
85}
86