saya-cli 0.3.1

//! The slash-command registry and typo suggestion. `KNOWN_COMMANDS` is the list
//! `parse_slash_command` dispatches over; [`closest_command`] picks the nearest
//! known name (Levenshtein distance ≤ 2) to suggest in an "unknown command"
//! error. Extracted from `slash.rs` to keep that file under the size cap.

/// Known slash command names handled by `parse_slash_command`.
pub(crate) const KNOWN_COMMANDS: &[&str] = &[
    "connect",
    "connections",
    "include",
    "exclude",
    "provider",
    "model",
    "privacy",
    "approvals",
    "schema",
    "sql",
    "export",
    "chart",
    "explain",
    "clear",
    "history",
    "sessions",
    "resume",
    "contracts",
    "contract",
    "remember",
    "forget",
    "queue",
    "confirm",
    "reject",
    "doctor",
    "help",
    "exit",
    "quit",
];

/// Calculates the Levenshtein edit distance between two strings using a single rolling row.
fn levenshtein(a: &str, b: &str) -> usize {
    let b_chars: Vec<char> = b.chars().collect();
    let mut row: Vec<usize> = (0..=b_chars.len()).collect();

    for (i, ca) in a.chars().enumerate() {
        let mut prev = row[0];
        row[0] = i + 1;
        for (j, &cb) in b_chars.iter().enumerate() {
            let old_row_j_plus_1 = row[j + 1];
            let cost = if ca == cb { 0 } else { 1 };
            row[j + 1] = (prev + cost).min(row[j] + 1).min(old_row_j_plus_1 + 1);
            prev = old_row_j_plus_1;
        }
    }

    row.last().copied().unwrap_or(0)
}

/// Returns the known command with the smallest Levenshtein distance to `input` if distance <= 2.
pub(crate) fn closest_command(input: &str) -> Option<&'static str> {
    let input_lower = input.to_lowercase();
    let mut best_cmd = None;
    let mut min_dist = usize::MAX;

    for &cmd in KNOWN_COMMANDS {
        let dist = levenshtein(&input_lower, cmd);
        if dist < min_dist {
            min_dist = dist;
            best_cmd = Some(cmd);
        }
    }

    if min_dist <= 2 { best_cmd } else { None }
}