Ulas Kalayci
4a050e92a8
Fix recurring events with FREQ=WEEKLY;INTERVAL=N;BYDAY ignoring the interval when crossing a week boundary (e.g. Friday → Monday). Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
115 lines
4.1 KiB
JavaScript
115 lines
4.1 KiB
JavaScript
/**
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* Modul: Wiederholungsregeln (Recurrence)
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* Zweck: RRULE-Subset-Parser (FREQ=DAILY/WEEKLY/MONTHLY, BYDAY, INTERVAL, UNTIL)
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* + Berechnung des nächsten Fälligkeitsdatums für wiederkehrende Aufgaben
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* Abhängigkeiten: keine
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*/
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const DAY_MAP = { MO: 1, TU: 2, WE: 3, TH: 4, FR: 5, SA: 6, SU: 0 };
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/**
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* Parsed einen RRULE-String in ein Objekt.
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* Beispiel: "FREQ=WEEKLY;BYDAY=MO,TH;INTERVAL=1"
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* @param {string} rule
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* @returns {{ freq, interval, byday, until }|null}
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*/
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function parseRRule(rule) {
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if (!rule) return null;
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// Strip "RRULE:" prefix if present (ICS stores rules as "RRULE:FREQ=...")
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const raw = rule.startsWith('RRULE:') ? rule.slice(6) : rule;
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const parts = {};
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for (const segment of raw.split(';')) {
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const eq = segment.indexOf('=');
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if (eq === -1) continue;
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parts[segment.slice(0, eq).toUpperCase()] = segment.slice(eq + 1);
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}
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const freq = parts.FREQ ?? null;
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const interval = parseInt(parts.INTERVAL ?? '1', 10) || 1;
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const byday = (parts.BYDAY ?? '').split(',')
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.map((d) => DAY_MAP[d.trim().toUpperCase()])
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.filter((d) => d !== undefined);
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const until = parts.UNTIL ? parseUntilDate(parts.UNTIL) : null;
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if (!['DAILY', 'WEEKLY', 'MONTHLY', 'YEARLY'].includes(freq)) return null;
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return { freq, interval, byday, until };
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}
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function parseUntilDate(str) {
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// Akzeptiert YYYYMMDD oder YYYYMMDDTHHmmssZ
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const clean = str.replace(/[TZ]/g, '');
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const y = parseInt(clean.slice(0, 4), 10);
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const m = parseInt(clean.slice(4, 6), 10) - 1;
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const d = parseInt(clean.slice(6, 8), 10);
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return new Date(Date.UTC(y, m, d));
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}
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/**
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* Berechnet das nächste Fälligkeitsdatum nach dem gegebenen Basisdatum.
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* @param {string} baseDateStr - ISO-Datums-String (YYYY-MM-DD)
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* @param {string} rrule - RRULE-String
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* @returns {string|null} - Nächstes Datum als YYYY-MM-DD oder null (Ende der Serie)
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*/
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function nextOccurrence(baseDateStr, rrule) {
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const parsed = parseRRule(rrule);
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if (!parsed || !baseDateStr) return null;
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const base = new Date(baseDateStr + 'T00:00:00Z');
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if (isNaN(base.getTime())) return null;
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const { freq, interval, byday, until } = parsed;
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const next = new Date(base);
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if (freq === 'DAILY') {
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next.setUTCDate(next.getUTCDate() + interval);
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} else if (freq === 'WEEKLY') {
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if (byday.length === 0) {
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// Kein BYDAY → selber Wochentag, nächste Woche
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next.setUTCDate(next.getUTCDate() + 7 * interval);
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} else {
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// Finde den nächsten passenden Wochentag (nach heute)
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const currentDay = base.getUTCDay();
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const sorted = [...byday].sort((a, b) => {
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const da = (a - currentDay + 7) % 7 || 7;
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const db = (b - currentDay + 7) % 7 || 7;
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return da - db;
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});
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// Tage bis zum nächsten Vorkommen (mind. 1, damit nicht derselbe Tag)
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let daysUntil = (sorted[0] - currentDay + 7) % 7;
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if (daysUntil === 0) {
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// Selber Wochentag → ganzes Intervall überspringen
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daysUntil = 7 * interval;
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} else if ((sorted[0] + 6) % 7 < (currentDay + 6) % 7) {
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// Wochengrenze überschritten (ISO-Woche MO–SO) → interval-1 Wochen extra überspringen
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daysUntil += 7 * (interval - 1);
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}
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next.setUTCDate(next.getUTCDate() + daysUntil);
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}
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} else if (freq === 'MONTHLY') {
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const targetDay = base.getUTCDate();
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next.setUTCMonth(next.getUTCMonth() + interval);
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// Monatsüberlauf korrigieren (z.B. 31. März + 1 Monat → 30. April)
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const lastDay = new Date(Date.UTC(next.getUTCFullYear(), next.getUTCMonth() + 1, 0)).getUTCDate();
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next.setUTCDate(Math.min(targetDay, lastDay));
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} else if (freq === 'YEARLY') {
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const targetMonth = base.getUTCMonth();
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const targetDay = base.getUTCDate();
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next.setUTCFullYear(next.getUTCFullYear() + interval);
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// Feb 29 in non-leap year → Feb 28
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next.setUTCMonth(targetMonth);
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const lastDay = new Date(Date.UTC(next.getUTCFullYear(), targetMonth + 1, 0)).getUTCDate();
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next.setUTCDate(Math.min(targetDay, lastDay));
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}
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// UNTIL-Grenze prüfen
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if (until && next > until) return null;
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return next.toISOString().slice(0, 10); // YYYY-MM-DD
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}
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export { parseRRule, nextOccurrence };
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