/// Strip mIRC-style formatting control codes from a string.
///
/// Removes CTCP delimiter (\x01), bold (\x02), color (\x03 + optional fg[,bg]
/// digits), reset (\x0F), monospace (\x11), reverse (\x16), italic (\x1D),
/// strikethrough (\x1E), and underline (\x1F).
pub fn strip_formatting(input: &str) -> String {
    let bytes = input.as_bytes();
    let len = bytes.len();
    let mut out: Vec<u8> = Vec::with_capacity(len);
    let mut i = 0;

    while i < len {
        match bytes[i] {
            b'\x01' | b'\x02' | b'\x0F' | b'\x11' | b'\x16' | b'\x1D' | b'\x1E' | b'\x1F' => {
                i += 1;
            }
            b'\x03' => {
                i += 1;
                let mut digits = 0;
                while i < len && digits < 2 && bytes[i].is_ascii_digit() {
                    i += 1;
                    digits += 1;
                }
                if i < len && bytes[i] == b',' && i + 1 < len && bytes[i + 1].is_ascii_digit() {
                    i += 1;
                    digits = 0;
                    while i < len && digits < 2 && bytes[i].is_ascii_digit() {
                        i += 1;
                        digits += 1;
                    }
                }
            }
            b => {
                out.push(b);
                i += 1;
            }
        }
    }

    // IRC control codes are single-byte ASCII (< 0x80) so removing them from
    // valid UTF-8 always yields valid UTF-8.
    String::from_utf8(out).expect("stripping ASCII control codes preserves UTF-8")
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn clean_text_unchanged() {
        assert_eq!(strip_formatting("hello world"), "hello world");
    }

    #[test]
    fn strips_bold() {
        assert_eq!(strip_formatting("\x02bold\x02"), "bold");
    }

    #[test]
    fn strips_italic() {
        assert_eq!(strip_formatting("\x1Ditalic\x1D"), "italic");
    }

    #[test]
    fn strips_underline() {
        assert_eq!(strip_formatting("\x1Funderline\x1F"), "underline");
    }

    #[test]
    fn strips_reset() {
        assert_eq!(strip_formatting("styled\x0F plain"), "styled plain");
    }

    #[test]
    fn strips_color_no_params() {
        assert_eq!(strip_formatting("\x03hello"), "hello");
    }

    #[test]
    fn strips_color_fg_only() {
        assert_eq!(strip_formatting("\x034red text"), "red text");
    }

    #[test]
    fn strips_color_two_digit_fg() {
        assert_eq!(strip_formatting("\x0312blue text"), "blue text");
    }

    #[test]
    fn strips_color_fg_and_bg() {
        assert_eq!(strip_formatting("\x034,2red on blue"), "red on blue");
    }

    #[test]
    fn strips_color_two_digit_fg_and_bg() {
        assert_eq!(strip_formatting("\x0304,12colored"), "colored");
    }

    #[test]
    fn color_comma_without_bg_digit_preserves_comma() {
        // \x03 followed by digit then comma but no bg digit — comma is kept
        assert_eq!(strip_formatting("\x034,text"), ",text");
    }

    #[test]
    fn mixed_codes() {
        assert_eq!(
            strip_formatting("\x02\x034,5bold color\x0F normal"),
            "bold color normal"
        );
    }

    #[test]
    fn color_at_end_of_string() {
        assert_eq!(strip_formatting("text\x03"), "text");
        assert_eq!(strip_formatting("text\x034"), "text");
        assert_eq!(strip_formatting("text\x0304,"), "text,");
        assert_eq!(strip_formatting("text\x0304,1"), "text");
    }

    #[test]
    fn strips_monospace() {
        assert_eq!(strip_formatting("\x11code\x11"), "code");
    }

    #[test]
    fn strips_reverse() {
        assert_eq!(strip_formatting("\x16reversed\x16"), "reversed");
    }

    #[test]
    fn strips_strikethrough() {
        assert_eq!(strip_formatting("\x1Estruck\x1E"), "struck");
    }

    #[test]
    fn empty_input() {
        assert_eq!(strip_formatting(""), "");
    }

    #[test]
    fn preserves_multibyte_utf8() {
        assert_eq!(strip_formatting("✨ hello ⚡"), "✨ hello ⚡");
    }

    #[test]
    fn strips_codes_around_emoji() {
        // \x034 = color fg 4; \x0333 = color fg 33, leaving trailing "3"
        assert_eq!(
            strip_formatting("\x02✨\x02 boosted \x034⚡\x03333 sats"),
            "✨ boosted ⚡3 sats"
        );
    }

    #[test]
    fn preserves_cjk_and_accented_chars() {
        assert_eq!(strip_formatting("\x02café\x02 日本語"), "café 日本語");
    }

    #[test]
    fn strips_ctcp_delimiter() {
        assert_eq!(strip_formatting("\x01ACTION sniffs\x01"), "ACTION sniffs");
    }

    #[test]
    fn strips_ctcp_delimiter_mixed_with_formatting() {
        assert_eq!(
            strip_formatting("\x01\x02ACTION bold\x02\x01"),
            "ACTION bold"
        );
    }
}