max / pter

1.4 KB · 57 lines History Blame Raw

1	/// Normalize whitespace in the final markdown output.
2	///
3	/// - Collapse runs of 3+ newlines into 2 (one blank line)
4	/// - Trim leading/trailing whitespace
5	/// - Remove trailing whitespace from each line
6	pub fn normalize(input: &str) -> String {
7	let mut result = String::with_capacity(input.len());
8	let mut consecutive_newlines = 0u32;
9
10	for ch in input.chars() {
11	if ch == '\n' {
12	consecutive_newlines += 1;
13	if consecutive_newlines <= 2 {
14	result.push('\n');
15	}
16	} else {
17	consecutive_newlines = 0;
18	result.push(ch);
19	}
20	}
21
22	// Trim trailing whitespace from each line
23	let lines: Vec<&str> = result.lines().map(\|l\| l.trim_end()).collect();
24	let joined = lines.join("\n");
25	joined.trim().to_string()
26	}
27
28	#[cfg(test)]
29	mod tests {
30	use super::*;
31
32	#[test]
33	fn collapse_excessive_newlines() {
34	assert_eq!(normalize("a\n\n\n\nb"), "a\n\nb");
35	}
36
37	#[test]
38	fn preserve_single_blank_line() {
39	assert_eq!(normalize("a\n\nb"), "a\n\nb");
40	}
41
42	#[test]
43	fn trim_trailing_whitespace() {
44	assert_eq!(normalize("hello \nworld "), "hello\nworld");
45	}
46
47	#[test]
48	fn trim_outer_whitespace() {
49	assert_eq!(normalize("\n\nhello\n\n"), "hello");
50	}
51
52	#[test]
53	fn empty_input() {
54	assert_eq!(normalize(""), "");
55	}
56	}
57