import { runInNewContext } from 'node:vm';
import { BACKUP_SCHEDULE_TIME_ZONE, isBackupDue } from './backup-due';

describe('isBackupDue', () => {
  it('reads the schedule in Europe/Berlin by default', () => {
    expect(BACKUP_SCHEDULE_TIME_ZONE).toBe('Europe/Berlin');
  });

  it('is due when there is no backup yet', () => {
    expect(
      isBackupDue('0 3 * * *', null, new Date('2026-10-13T00:30:00Z')),
    ).toBe(true);
  });

  it('is not due again on the same day for "0 3 * * *"', () =>
    expect(
      isBackupDue(
        '0 3 * * *',
        new Date('2026-10-12T01:00:00Z'),
        new Date('2026-10-13T00:30:00Z'),
      ),
    ).toBe(false));

  it('is due after the next 03:00 Europe/Berlin', () =>
    expect(
      isBackupDue(
        '0 3 * * *',
        new Date('2026-10-12T01:00:00Z'),
        new Date('2026-10-13T01:05:00Z'),
      ),
    ).toBe(true));

  it('is due exactly at the next scheduled time', () =>
    expect(
      isBackupDue(
        '0 3 * * *',
        new Date('2026-10-12T01:00:00Z'),
        new Date('2026-10-13T01:00:00Z'),
      ),
    ).toBe(true));

  it('counts a backup written after the scheduled time (e.g. "Jetzt sichern") as covering it', () =>
    expect(
      isBackupDue(
        '0 3 * * *',
        new Date('2026-10-13T01:10:00Z'),
        new Date('2026-10-13T02:00:00Z'),
      ),
    ).toBe(false));

  it('stays due after a missed run until a backup exists', () =>
    expect(
      isBackupDue(
        '0 3 * * *',
        new Date('2026-10-10T01:00:00Z'),
        new Date('2026-10-13T05:00:00Z'),
      ),
    ).toBe(true));

  it('uses the given time zone', () => {
    const lastBackupAt = new Date('2026-10-12T03:00:00Z');
    const now = new Date('2026-10-13T02:00:00Z');

    // Next 03:00 UTC is 03:00Z, next 03:00 Berlin was 01:00Z.
    expect(isBackupDue('0 3 * * *', lastBackupAt, now, 'UTC')).toBe(false);
    expect(isBackupDue('0 3 * * *', lastBackupAt, now)).toBe(true);
  });

  // fs.Stats.mtime is created by Node's core; under Jest it is not an
  // instance of the test's Date (cron checks `instanceof Date`).
  it('accepts a Date from another realm', () => {
    const foreign = runInNewContext('new Date("2026-10-12T01:00:00Z")') as Date;

    expect(
      isBackupDue('0 3 * * *', foreign, new Date('2026-10-13T00:30:00Z')),
    ).toBe(false);
  });

  it('rejects an invalid schedule even without a backup', () => {
    expect(() => isBackupDue('every night', null, new Date())).toThrow();
  });
});