dynfmt/
curly.rs

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
//! Implementation for simple format strings using curly braces.
//!
//! See [`SimpleCurlyFormat`] for more information.
//!
//! [`SimpleCurlyFormat`]: struct.SimpleCurlyFormat.html

use regex::{CaptureMatches, Captures, Regex};

use crate::{ArgumentResult, ArgumentSpec, Error, Format, Position};

lazy_static::lazy_static! {
/// The regular expression used for parsing simple curly format strings.
    static ref PYTHON_RE: Regex = Regex::new(r"\{(?P<key>\w+)?\}").unwrap();
}

fn parse_position(key: &str) -> Position<'_> {
    key.parse()
        .map(Position::Index)
        .unwrap_or_else(|_| Position::Key(key))
}

fn parse_next(captures: Captures<'_>) -> ArgumentSpec<'_> {
    let position = captures
        .name("key")
        .map(|m| parse_position(m.as_str()))
        .unwrap_or_else(|| Position::Auto);

    let group = captures.get(0).unwrap();
    ArgumentSpec::new(group.start(), group.end()).with_position(position)
}

/// Format argument iterator for [`SimpleCurlyFormat`].
///
/// [`SimpleCurlyFormat`]: struct.SimpleCurlyFormat.html
#[derive(Debug)]
pub struct SimpleCurlyIter<'f> {
    captures: CaptureMatches<'static, 'f>,
}

impl<'f> SimpleCurlyIter<'f> {
    fn new(format: &'f str) -> Self {
        SimpleCurlyIter {
            captures: PYTHON_RE.captures_iter(format),
        }
    }
}

impl<'f> Iterator for SimpleCurlyIter<'f> {
    type Item = ArgumentResult<'f>;

    fn next(&mut self) -> Option<Self::Item> {
        self.captures.next().map(|capture| Ok(parse_next(capture)))
    }
}

/// Format implementation for simple curly brace based format strings.
///
/// This syntax is a subset of what Python 3, Rust, .NET and many logging libraries use. Each
/// argument is formated in display mode.
///
///   1. `{}`: Refers to the next positional argument.
///   2. `{0}`: Refers to the argument at index `0`.
///   3. `{name}`: Refers to the named argument with key `"name"`.
///
/// # Example
///
/// ```rust
/// use dynfmt::{Format, SimpleCurlyFormat};
///
/// let formatted = SimpleCurlyFormat.format("hello, {}", &["world"]);
/// assert_eq!("hello, world", formatted.expect("formatting failed"));
/// ```
#[derive(Debug)]
pub struct SimpleCurlyFormat;

impl<'f> Format<'f> for SimpleCurlyFormat {
    type Iter = SimpleCurlyIter<'f>;

    fn iter_args(&self, format: &'f str) -> Result<Self::Iter, Error<'f>> {
        Ok(SimpleCurlyIter::new(format))
    }
}