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use std::fmt;
pub struct Indented<'a, D> {
inner: &'a mut D,
ind: Option<usize>,
started: bool,
}
impl<'a, D> Indented<'a, D> {
pub fn numbered(inner: &'a mut D, ind: usize) -> Self {
Self {
inner,
ind: Some(ind),
started: false,
}
}
pub fn new(inner: &'a mut D) -> Self {
Self {
inner,
ind: None,
started: false,
}
}
}
impl<T> fmt::Write for Indented<'_, T>
where
T: fmt::Write,
{
fn write_str(&mut self, s: &str) -> fmt::Result {
for (ind, mut line) in s.split('\n').enumerate() {
if !self.started {
line = line.trim_start();
if line.is_empty() {
continue;
}
self.started = true;
match self.ind {
Some(ind) => self.inner.write_fmt(format_args!("{: >4}: ", ind))?,
None => self.inner.write_fmt(format_args!(" "))?,
}
} else if ind > 0 {
self.inner.write_char('\n')?;
if self.ind.is_some() {
self.inner.write_fmt(format_args!(" "))?;
} else {
self.inner.write_fmt(format_args!(" "))?;
}
}
self.inner.write_fmt(format_args!("{}", line))?;
}
Ok(())
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::fmt::Write as _;
#[test]
fn one_digit() {
let input = "verify\nthis";
let expected = " 2: verify\n this";
let mut output = String::new();
Indented {
inner: &mut output,
ind: Some(2),
started: false,
}
.write_str(input)
.unwrap();
assert_eq!(expected, output);
}
#[test]
fn two_digits() {
let input = "verify\nthis";
let expected = " 12: verify\n this";
let mut output = String::new();
Indented {
inner: &mut output,
ind: Some(12),
started: false,
}
.write_str(input)
.unwrap();
assert_eq!(expected, output);
}
#[test]
fn no_digits() {
let input = "verify\nthis";
let expected = " verify\n this";
let mut output = String::new();
Indented {
inner: &mut output,
ind: None,
started: false,
}
.write_str(input)
.unwrap();
assert_eq!(expected, output);
}
}