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import { documentHasRecurrence, parseProperty, recurrenceBase } from "@/worker/caldav/ical/core";
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import { parseCalendarDocument } from "@/worker/caldav/ical/parse";
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import { calendarOccurrences, occurrenceOverlaps } from "@/worker/caldav/ical/recurrence";
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import type { CalendarOccurrence, CalendarTimeRange, RecurrenceBounds } from "@/worker/caldav/ical/types";
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function formatUtcDate(ms: number): string {
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  const date = new Date(ms);
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  const pad = (value: number) => String(value).padStart(2, "0");
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  return `${date.getUTCFullYear()}${pad(date.getUTCMonth() + 1)}${pad(date.getUTCDate())}`;
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}
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function formatUtcDateTime(ms: number): string {
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  const date = new Date(ms);
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  const pad = (value: number) => String(value).padStart(2, "0");
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  return `${formatUtcDate(ms)}T${pad(date.getUTCHours())}${pad(date.getUTCMinutes())}${pad(date.getUTCSeconds())}Z`;
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}
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function datePropertyLine(name: string, ms: number, valueType: "date" | "date-time"): string {
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  return valueType === "date" ? `${name};VALUE=DATE:${formatUtcDate(ms)}` : `${name}:${formatUtcDateTime(ms)}`;
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}
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function expandedComponent(occurrence: CalendarOccurrence, forceRecurrenceId: boolean): string[] {
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  const excluded = new Set(["DTSTART", "DTEND", "DUE", "DURATION", "RRULE", "RDATE", "EXDATE", "RECURRENCE-ID"]);
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  const preserved = occurrence.component.lines.filter((line) => {
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    const prop = parseProperty(line);
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    return prop && !excluded.has(prop.name);
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  });
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  const lines = [`BEGIN:${occurrence.component.componentType}`, ...preserved];
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  const recurrenceValueType =
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    occurrence.component.recurrenceId?.valueType ?? recurrenceBase(occurrence.component)?.valueType ?? "date-time";
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  const startValueType =
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    occurrence.component.dtstart?.valueType ?? recurrenceBase(occurrence.component)?.valueType ?? "date-time";
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  if (forceRecurrenceId || !occurrence.isInitial || occurrence.component.recurrenceId) {
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    lines.push(datePropertyLine("RECURRENCE-ID", occurrence.originalStartMs, recurrenceValueType));
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  }
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  lines.push(datePropertyLine("DTSTART", occurrence.startMs, startValueType));
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  if (occurrence.component.componentType === "VEVENT") {
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    if (occurrence.endMs !== occurrence.startMs)
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      lines.push(datePropertyLine("DTEND", occurrence.endMs, startValueType));
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  } else if (occurrence.component.componentType === "VTODO") {
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    lines.push(datePropertyLine("DUE", occurrence.endMs, startValueType));
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  }
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  lines.push(`END:${occurrence.component.componentType}`);
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  return lines;
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}
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export function expandCalendarData(body: string, range: CalendarTimeRange, bounds: RecurrenceBounds): string {
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  const document = parseCalendarDocument(body);
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  const lines = ["BEGIN:VCALENDAR", "VERSION:2.0", "PRODID:-//dab//CalDAV//EN"];
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  const forceRecurrenceId = documentHasRecurrence(document.components) && document.overrides.length === 0;
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  for (const occurrence of calendarOccurrences(document, bounds, range)) {
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    if (occurrenceOverlaps(document, occurrence, range)) {
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      lines.push(...expandedComponent(occurrence, forceRecurrenceId));
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    }
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  }
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  lines.push("END:VCALENDAR", "");
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  return lines.join("\r\n");
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}