claux 20260705.0.0

Terminal AI coding assistant with tool execution
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//! Utility modules for claux.

pub mod diff;

/// Largest prefix of `s` that fits in `max_bytes`, cut on a char boundary.
/// Byte-indexed slicing (`&s[..n]`) panics mid-codepoint; tool output,
/// commands, and git status all carry arbitrary UTF-8, so every truncation
/// must go through here or `tail_str`.
pub fn truncate_str(s: &str, max_bytes: usize) -> &str {
    if s.len() <= max_bytes {
        return s;
    }
    let mut end = max_bytes;
    while !s.is_char_boundary(end) {
        end -= 1;
    }
    &s[..end]
}

/// Largest suffix of `s` that fits in `max_bytes`, cut on a char boundary.
pub fn tail_str(s: &str, max_bytes: usize) -> &str {
    if s.len() <= max_bytes {
        return s;
    }
    let mut start = s.len() - max_bytes;
    while !s.is_char_boundary(start) {
        start += 1;
    }
    &s[start..]
}

/// Double-press confirmation for Ctrl+C, so one stray keypress can't kill
/// a live session. The first press arms; a second within the window
/// confirms. Any other activity should call `disarm`.
#[derive(Default)]
pub struct CtrlCArm {
    armed_at: Option<std::time::Instant>,
}

impl CtrlCArm {
    const WINDOW: std::time::Duration = std::time::Duration::from_secs(2);

    /// Register a Ctrl+C press. Returns true when this press confirms an
    /// exit (a prior press armed it within the window); otherwise arms.
    pub fn press(&mut self) -> bool {
        if self.armed_at.is_some_and(|t| t.elapsed() < Self::WINDOW) {
            true
        } else {
            self.armed_at = Some(std::time::Instant::now());
            false
        }
    }

    pub fn is_armed(&self) -> bool {
        self.armed_at.is_some_and(|t| t.elapsed() < Self::WINDOW)
    }

    pub fn disarm(&mut self) {
        self.armed_at = None;
    }
}

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

    #[test]
    fn truncate_ascii() {
        assert_eq!(truncate_str("hello", 3), "hel");
        assert_eq!(truncate_str("hello", 5), "hello");
        assert_eq!(truncate_str("hello", 10), "hello");
    }

    #[test]
    fn truncate_multibyte_boundary() {
        // "é" is 2 bytes; cutting at byte 1 must back off to 0
        assert_eq!(truncate_str("é", 1), "");
        // cutting "aéb" at byte 2 lands mid-'é', backs off to "a"
        assert_eq!(truncate_str("aéb", 2), "a");
        // 4-byte emoji
        assert_eq!(truncate_str("🦀🦀", 5), "🦀");
        assert_eq!(truncate_str("🦀🦀", 4), "🦀");
        assert_eq!(truncate_str("🦀🦀", 3), "");
    }

    #[test]
    fn tail_ascii() {
        assert_eq!(tail_str("hello", 3), "llo");
        assert_eq!(tail_str("hello", 5), "hello");
        assert_eq!(tail_str("hello", 10), "hello");
    }

    #[test]
    fn tail_multibyte_boundary() {
        // a suffix cut landing mid-'é' must move forward past it
        assert_eq!(tail_str("aéb", 2), "b");
        assert_eq!(tail_str("🦀🦀", 5), "🦀");
        assert_eq!(tail_str("🦀🦀", 3), "");
    }

    #[test]
    fn empty_string() {
        assert_eq!(truncate_str("", 5), "");
        assert_eq!(tail_str("", 5), "");
    }

    #[test]
    fn ctrl_c_first_press_arms_second_confirms() {
        let mut arm = CtrlCArm::default();
        assert!(!arm.press(), "first press must not exit");
        assert!(arm.is_armed());
        assert!(arm.press(), "second press within window must exit");
    }

    #[test]
    fn ctrl_c_disarm_resets() {
        let mut arm = CtrlCArm::default();
        assert!(!arm.press());
        arm.disarm();
        assert!(!arm.is_armed());
        assert!(!arm.press(), "press after disarm must re-arm, not exit");
    }
}