use regex::Regex;
use std::sync::OnceLock;

#[derive(Debug, Clone, PartialEq, Eq)]
pub enum Confidence {
    /// Absolute path or path with explicit separator.
    High,
    /// Bare filename with extension; could be a word.
    Low,
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct PathCandidate {
    pub text: String,
    pub confidence: Confidence,
}

/// Heuristically extract path-like substrings from arbitrary text.
/// Confident matches (absolute paths, paths containing separators) → `High`.
/// Bare filenames with an extension → `Low` (advisory only).
pub fn extract_path_candidates(text: &str) -> Vec<PathCandidate> {
    static UNIX_ABS: OnceLock<Regex> = OnceLock::new();
    static WIN_ABS: OnceLock<Regex> = OnceLock::new();
    static REL_WITH_SEP: OnceLock<Regex> = OnceLock::new();
    static BARE_NAME: OnceLock<Regex> = OnceLock::new();

    let unix_abs = UNIX_ABS.get_or_init(|| Regex::new(r"(?m)(?:^|\s)(/[\w./~\-_]+)").unwrap());
    let win_abs = WIN_ABS.get_or_init(|| Regex::new(r#"(?m)(?:^|\s)([A-Za-z]:\\[\w.\\\-_]+)"#).unwrap());
    let rel = REL_WITH_SEP.get_or_init(|| Regex::new(r"(?m)(?:^|\s)((?:\./|\.\./|[\w\-_]+/)[\w./\-_]+)").unwrap());
    let bare = BARE_NAME.get_or_init(|| Regex::new(r"(?m)(?:^|\s)([\w\-_]+\.[A-Za-z]{1,8})(?:\s|[.,;:!?]|$)").unwrap());

    let mut out = Vec::new();
    let mut seen = std::collections::HashSet::new();

    for re in [unix_abs, win_abs, rel] {
        for cap in re.captures_iter(text) {
            let m = cap.get(1).unwrap().as_str().trim_end_matches(['.', ',', ';', ':', '!', '?']);
            if seen.insert(m.to_string()) {
                out.push(PathCandidate { text: m.to_string(), confidence: Confidence::High });
            }
        }
    }
    for cap in bare.captures_iter(text) {
        let m = cap.get(1).unwrap().as_str();
        if seen.insert(m.to_string()) {
            out.push(PathCandidate { text: m.to_string(), confidence: Confidence::Low });
        }
    }
    out
}