// DC-168: calendar event-cache semantics (shared by widget + tests).
// Keyed by uid+start (recurring instances differ per occurrence); a fetched
// window is authoritative for entries starting inside it (deletions and
// reschedules propagate), entries outside it survive.
'use strict';
(function () {
  function eventKey(ev) {
    // Audit 2026-10-27: a null/invalid start threw RangeError out of merge()
    // and flipped the whole widget offline — degrade to a string key instead.
    const d = new Date(ev.start);
    const startIso = isNaN(d.getTime())
      ? `invalid:${ev.start == null ? 'null' : String(ev.start)}`
      : d.toISOString();
    return ev.uid ? `${ev.uid}@${startIso}` : `${startIso}|${ev.title || ''}`;
  }

  function createCache() {
    const map = new Map();
    return {
      size: () => map.size,
      merge(body, range) {
        if (range) {
          for (const [k, ev] of map) {
            const t = new Date(ev.start).getTime();
            if (t >= range.start.getTime() && t <= range.end.getTime()) map.delete(k);
          }
        }
        for (const ev of ((body && Array.isArray(body.events)) ? body.events : [])) {
          map.set(eventKey(ev), ev);
        }
        return { events: [...map.values()].sort((a, b) => new Date(a.start) - new Date(b.start)) };
      },
    };
  }

  const api = { eventKey, createCache };
  if (typeof module !== 'undefined' && module.exports) module.exports = api;
  if (typeof window !== 'undefined') window.CalendarCache = api;
})();