// Short chip labels for the panel: three characters by default, settable up.
//
// A chip per session only pays off if the label stays put. Two rules do that:
// labels are assigned oldest-session-first, so a session starting now takes the
// suffixed variant rather than pushing one off the label already on screen; and
// a label, once given, belongs to that session until it ends -- even after the
// session it was disambiguated against has closed. A label that moves under
// your hand is worse than one carrying a digit that no longer looks necessary.
//
// Imports nothing, so it runs under plain node or gjs.

// Both entry points take a width, and both default to this: the module is
// imported by tests and by the indicator alike, and a caller that forgets the
// setting should get the documented default rather than a stray one.
const DEFAULT_WIDTH = 3;

/** Widths arrive from GSettings and from tests. One character is the floor:
 *  at zero every label would be empty and the collision loop would not end. */
function usable(width) {
    const n = Math.trunc(Number(width));
    return Number.isFinite(n) && n >= 1 ? n : DEFAULT_WIDTH;
}

/** Split on separators and camelCase humps: "pet-project-server", "outlineMcp". */
function segments(name) {
    // Unicode-aware: splitting on [^a-zA-Z0-9] makes every Cyrillic letter a
    // separator, so "проект" reduces to nothing and every non-Latin project
    // ends up sharing the label "?".
    return name
        .replace(/(\p{Ll}|\p{N})(\p{Lu})/gu, '$1 $2')
        .split(/[^\p{L}\p{N}]+/u)
        .filter(Boolean);
}

/** Up to `width` characters for a project name.
 *
 *  Initials for multi-segment names, first letters for single words. Initials
 *  matter more than they look: a plain prefix collapses "dev-skills" and
 *  "dev-conventions" onto the same "dev", which is the exact case this has to
 *  keep apart. A wider label takes more initials, not a longer prefix, for the
 *  same reason.
 */
export function abbreviate(name, width = DEFAULT_WIDTH) {
    const parts = segments(String(name ?? ''));
    if (!parts.length)
        return '?';
    const raw = parts.length > 1
        ? parts.map(p => p[0]).join('')
        : parts[0];
    return raw.slice(0, usable(width)).toLowerCase();
}

/** Assign a label to every session, reusing the ones already handed out.
 *
 *  `previous` is the mapping from the last run; pass the returned map back in.
 *  Sessions absent from `sessions` drop out, which frees their label for reuse.
 *
 *  `width` applies to labels handed out now. Kept labels are kept whatever
 *  width they were cut at -- stickiness outranks it, and the caller that
 *  changes the width is the one that has to drop the old map.
 */
export function assignChips(sessions, previous = new Map(), width = DEFAULT_WIDTH) {
    const max = usable(width);
    const labels = new Map();
    const taken = new Set();

    for (const session of sessions) {
        const kept = previous.get(session.sessionId);
        if (kept !== undefined) {
            labels.set(session.sessionId, kept);
            taken.add(kept);
        }
    }

    const fresh = sessions
        .filter(s => !labels.has(s.sessionId))
        .sort((a, b) => (a.since || 0) - (b.since || 0));

    for (const session of fresh) {
        const base = abbreviate(session.base, max);
        let label = base;
        // Digits eat into the base rather than extending past the width, so
        // every chip stays the same size and the row does not ripple.
        for (let n = 2; taken.has(label); n++) {
            const suffix = String(n);
            label = base.slice(0, Math.max(1, max - suffix.length)) + suffix;
        }
        labels.set(session.sessionId, label);
        taken.add(label);
    }
    return labels;
}