/**
 * DC-161: ICS parser unit tests.
 * Covers: basic VEVENT extraction, all-day events, RRULE expansion
 * (DAILY/WEEKLY-BYDAY/MONTHLY + COUNT/UNTIL/INTERVAL), EXDATE,
 * RECURRENCE-ID overrides, event cap, malformed DTSTART.
 */

const { parseIcs, parseIcsDate, unfoldLines } = require('../../src/calendar/ics-parser');

const RANGE = { start: new Date('2026-10-01T00:00:00Z'), end: new Date('2026-11-01T00:00:00Z') };

function ics(body) {
  return `BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//Test//EN\r\n${body}\r\nEND:VCALENDAR`;
}

describe('DC-161 ics-parser', () => {
  test('parses a simple timed event', () => {
    const { events, errors } = parseIcs(ics(
      'BEGIN:VEVENT\r\nUID:1\r\nDTSTART:20261007T140000Z\r\nDTEND:20261007T150000Z\r\nSUMMARY:Dentist\\, cleaning\r\nLOCATION:Main St\r\nEND:VEVENT'
    ), RANGE);
    expect(errors).toEqual([]);
    expect(events).toHaveLength(1);
    expect(events[0].title).toBe('Dentist, cleaning');
    expect(events[0].start.toISOString()).toBe('2026-10-07T14:00:00.000Z');
    expect(events[0].allDay).toBe(false);
    expect(events[0].location).toBe('Main St');
  });

  test('parses an all-day event (DATE value)', () => {
    const { events } = parseIcs(ics(
      'BEGIN:VEVENT\r\nUID:2\r\nDTSTART;VALUE=DATE:20261010\r\nSUMMARY:Conference\r\nEND:VEVENT'
    ), RANGE);
    expect(events[0].allDay).toBe(true);
    expect(events[0].start.getFullYear()).toBe(2026);
    expect(events[0].start.getMonth()).toBe(9);
    expect(events[0].start.getDate()).toBe(10);
  });

  test('daily recurrence with COUNT expands within window', () => {
    const { events } = parseIcs(ics(
      'BEGIN:VEVENT\r\nUID:3\r\nDTSTART:20261001T090000Z\r\nDTEND:20261001T093000Z\r\nRRULE:FREQ=DAILY;COUNT=5\r\nSUMMARY:Standup\r\nEND:VEVENT'
    ), RANGE);
    expect(events).toHaveLength(5);
    expect(events[0].start.getUTCDate()).toBe(1);
    expect(events[4].start.getUTCDate()).toBe(5);
    expect(events.every(e => e.recurring)).toBe(true);
  });

  test('weekly BYDAY expansion lands on correct weekdays', () => {
    const { events } = parseIcs(ics(
      'BEGIN:VEVENT\r\nUID:4\r\nDTSTART:20261005T100000Z\r\nDTEND:20261005T110000Z\r\nRRULE:FREQ=WEEKLY;BYDAY=MO,WE,FR\r\nSUMMARY:Gym\r\nEND:VEVENT'
    ), RANGE);
    // Oct 5 2026 is a Monday. Expect 3/wk for the 4 weeks in October window.
    expect(events.length).toBeGreaterThanOrEqual(11);
    for (const ev of events) {
      expect([1, 3, 5]).toContain(ev.start.getUTCDay());
    }
  });

  test('EXDATE excludes occurrences', () => {
    const { events } = parseIcs(ics(
      'BEGIN:VEVENT\r\nUID:5\r\nDTSTART:20261001T090000Z\r\nRRULE:FREQ=DAILY;COUNT=4\r\nEXDATE:20261003T090000Z\r\nSUMMARY:Except Wednesday\r\nEND:VEVENT'
    ), RANGE);
    expect(events).toHaveLength(3);
    expect(events.some(e => e.start.getUTCDate() === 3)).toBe(false);
  });

  test('UNTIL bounds recurrence', () => {
    const { events } = parseIcs(ics(
      'BEGIN:VEVENT\r\nUID:6\r\nDTSTART:20261001T090000Z\r\nRRULE:FREQ=DAILY;UNTIL=20261004T090000Z\r\nSUMMARY:Bounded\r\nEND:VEVENT'
    ), RANGE);
    expect(events).toHaveLength(4);
  });

  test('events outside window are excluded; window straddles inclusion', () => {
    const { events } = parseIcs(ics(
      'BEGIN:VEVENT\r\nUID:7\r\nDTSTART:20260901T090000Z\r\nDTEND:20260901T100000Z\r\nSUMMARY:September only\r\nEND:VEVENT'
    ), RANGE);
    expect(events).toHaveLength(0);
  });

  test('RECURRENCE-ID override replaces instance title', () => {
    const { events } = parseIcs(ics(
      'BEGIN:VEVENT\r\nUID:8\r\nDTSTART:20261001T090000Z\r\nRRULE:FREQ=DAILY;COUNT=3\r\nSUMMARY:Original\r\nEND:VEVENT\r\n' +
      'BEGIN:VEVENT\r\nUID:8\r\nRECURRENCE-ID:20261002T090000Z\r\nDTSTART:20261002T130000Z\r\nSUMMARY:Moved to 1pm\r\nEND:VEVENT'
    ), RANGE);
    const moved = events.find(e => e.start.getUTCDate() === 2);
    expect(moved.title).toBe('Moved to 1pm');
    expect(moved.start.getUTCHours()).toBe(13);
  });

  test('malformed DTSTART is reported as an error, not thrown', () => {
    const { events, errors } = parseIcs(ics(
      'BEGIN:VEVENT\r\nUID:9\r\nDTSTART:notadate\r\nSUMMARY:Broken\r\nEND:VEVENT'
    ), RANGE);
    expect(events).toHaveLength(0);
    expect(errors.length).toBeGreaterThanOrEqual(1);
  });

  test('event count is capped at 500', () => {
    let body = '';
    for (let i = 0; i < 600; i++) {
      body += `BEGIN:VEVENT\r\nUID:x${i}\r\nDTSTART:20261001T${String(i % 24).padStart(2, '0')}0000Z\r\nSUMMARY:E${i}\r\nEND:VEVENT\r\n`;
    }
    const { events } = parseIcs(ics(body), RANGE);
    expect(events).toHaveLength(500);
  });

  test('unfoldLines joins folded lines (RFC: CRLF + one WSP removed)', () => {
    // Two leading spaces: fold char removed, second space is content
    expect(unfoldLines('SUMMARY:hello\r\n  world')).toEqual(['SUMMARY:hello world']);
    // Exactly one space: fully joined
    expect(unfoldLines('SUMMARY:hello\r\n world')).toEqual(['SUMMARY:helloworld']);
  });

  test('parseIcsDate handles UTC, floating, and date forms', () => {
    expect(parseIcsDate('20261007T140000Z').toISOString()).toBe('2026-10-07T14:00:00.000Z');
    expect(parseIcsDate('20261007')).toEqual(new Date(2026, 9, 7));
    expect(parseIcsDate('20261007T140000')).toEqual(new Date(2026, 9, 7, 14, 0, 0));
    expect(parseIcsDate('garbage')).toBeNull();
  });
});