//! Shared text utilities for parsing and matching.

/// Case-insensitive prefix check without allocation.
///
/// Returns the remaining part of the string if `s` starts with `prefix`
/// (case-insensitive), otherwise returns `None`. Safe for multi-byte UTF-8.
pub fn strip_prefix_ci<'a>(s: &'a str, prefix: &str) -> Option<&'a str> {
    if s.len() < prefix.len() || !s.is_char_boundary(prefix.len()) {
        return None;
    }
    let s_prefix = &s[..prefix.len()];
    if s_prefix.eq_ignore_ascii_case(prefix) {
        Some(&s[prefix.len()..])
    } else {
        None
    }
}

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

    #[test]
    fn test_basic_match() {
        assert_eq!(strip_prefix_ci("PROJECT:test", "project:"), Some("test"));
        assert_eq!(strip_prefix_ci("Project:test", "project:"), Some("test"));
    }

    #[test]
    fn test_no_match() {
        assert_eq!(strip_prefix_ci("proj:test", "project:"), None);
        assert_eq!(strip_prefix_ci("pr", "project:"), None);
    }

    #[test]
    fn test_multibyte_utf8_safe() {
        // Ensure no panic on multi-byte characters near prefix boundary
        assert_eq!(strip_prefix_ci("pr😀:H", "pri:"), None);
        assert_eq!(strip_prefix_ci("düe:tom", "due:"), None);
    }
}