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use {
super::TAB_REPLACEMENT,
unicode_width::UnicodeWidthChar,
};
#[derive(Debug, Clone, Copy)]
pub struct StrFit {
bytes_count: usize,
cols_count: usize,
has_tab: bool,
}
impl StrFit {
pub fn from(s: &str, cols_max: usize) -> Self {
let mut bytes_count = 0;
let mut cols_count = 0;
let mut has_tab = false;
for (idx, c) in s.char_indices() {
let char_width = if '\t' == c {
has_tab = true;
TAB_REPLACEMENT.len()
} else {
UnicodeWidthChar::width(c).unwrap_or(0)
};
let next_str_width = cols_count + char_width;
if next_str_width > cols_max {
break;
}
cols_count = next_str_width;
bytes_count = idx + c.len_utf8();
}
Self {
bytes_count,
cols_count,
has_tab,
}
}
}
/// return the counts in bytes and columns of the longest substring
/// fitting the given number of columns
pub fn count_fitting(s: &str, cols_max: usize) -> (usize, usize) {
let fit = StrFit::from(s, cols_max);
(fit.bytes_count, fit.cols_count)
}
/// return both the longest fitting string and the number of cols
/// it takes on screen.
/// We don't build a string around the whole str, which could be costly
/// if it's very big
pub fn make_string(s: &str, cols_max: usize) -> (String, usize) {
let fit = StrFit::from(s, cols_max);
if fit.has_tab {
let string = (&s[0..fit.bytes_count]).replace('\t', TAB_REPLACEMENT);
(string, fit.cols_count)
} else {
(s[0..fit.bytes_count].to_string(), fit.cols_count)
}
}
#[cfg(test)]
mod fitting_count_tests {
use super::*;
#[test]
fn test_count_fitting() {
assert_eq!(count_fitting("test", 3), (3, 3));
assert_eq!(count_fitting("test", 5), (4, 4));
let c12 = "Comunicações"; // normalized string (12 characters, 14 bytes)
assert_eq!(c12.len(), 14);
assert_eq!(c12.chars().count(), 12);
assert_eq!(count_fitting(c12, 12), (14, 12));
assert_eq!(count_fitting(c12, 10), (12, 10));
assert_eq!(count_fitting(c12, 11), (13, 11));
let c14 = "Comunicações"; // unnormalized string (14 characters, 16 bytes)
assert_eq!(c14.len(), 16);
assert_eq!(c14.chars().count(), 14);
assert_eq!(count_fitting(c14, 12), (16, 12));
let ja = "概要"; // each char takes 3 bytes and 2 columns
assert_eq!(ja.len(), 6);
assert_eq!(ja.chars().count(), 2);
assert_eq!(count_fitting(ja, 1), (0, 0));
assert_eq!(count_fitting(ja, 2), (3, 2));
assert_eq!(count_fitting(ja, 3), (3, 2));
assert_eq!(count_fitting(ja, 4), (6, 4));
assert_eq!(count_fitting(ja, 5), (6, 4));
}
}
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