// Date/time helpers for the mentions box. Kept framework-free and pure so they
// are unit-testable. Timestamps are unix SECONDS (as carried on the wire).

export type MentionDateGroup = 'today' | 'yesterday' | 'older';

const DAY_MS = 86_400_000;

const startOfDay = (d: Date): number => new Date(d.getFullYear(), d.getMonth(), d.getDate()).getTime();

const pad = (n: number): string => (n < 10 ? `0${n}` : `${n}`);

/**
 * Bucket a mention timestamp into today / yesterday / older relative to `now`.
 */
export const getMentionDateGroup = (timestampSeconds: number, now: Date = new Date()): MentionDateGroup => {
    if (!timestampSeconds || timestampSeconds <= 0) return 'older';

    const ts = timestampSeconds * 1000;
    const todayStart = startOfDay(now);

    if (ts >= todayStart) return 'today';
    if (ts >= todayStart - DAY_MS) return 'yesterday';

    return 'older';
};

/**
 * Compact per-row time label: HH:MM for today/yesterday (the section header
 * disambiguates the day), DD-MM for older entries. Empty string when unknown.
 */
export const formatMentionTime = (timestampSeconds: number, now: Date = new Date()): string => {
    if (!timestampSeconds || timestampSeconds <= 0) return '';

    const d = new Date(timestampSeconds * 1000);

    if (getMentionDateGroup(timestampSeconds, now) === 'older') return `${pad(d.getDate())}-${pad(d.getMonth() + 1)}`;

    return `${pad(d.getHours())}:${pad(d.getMinutes())}`;
};