bat/src/preprocessor.rs

use console::AnsiCodeIterator;

/// Expand tabs like an ANSI-enabled expand(1).
pub fn expand(line: &str, width: usize) -> String {
    let mut buffer = String::with_capacity(line.len() * 2);
    let mut cursor = 0;

    for chunk in AnsiCodeIterator::new(line) {
        match chunk {
            (text, true) => buffer.push_str(text),
            (mut text, false) => {
                while let Some(index) = text.find('\t') {
                    // Add previous text.
                    if index > 0 {
                        cursor += index;
                        buffer.push_str(&text[0..index]);
                    }

                    // Add tab.
                    let spaces = width - (cursor % width);
                    cursor += spaces;
                    buffer.push_str(&*" ".repeat(spaces));

                    // Next.
                    text = &text[index + 1..text.len()];
                }

                cursor += text.len();
                buffer.push_str(text);
            }
        }
    }

    buffer
}