import { describe, expect, test } from 'bun:test';
import { type SchedulableMonitor, selectDueMonitors } from './sweep';

const NOW = new Date('2026-07-28T12:00:00Z');
const minutesAgo = (n: number) => new Date(NOW.getTime() - n * 60_000);

function monitor(over: Partial<SchedulableMonitor> = {}): SchedulableMonitor {
  return { id: 'm1', intervalMinutes: 15, enabled: true, lastRunAt: minutesAgo(20), ...over };
}

describe('selectDueMonitors', () => {
  test('a monitor past its interval is due', () => {
    expect(selectDueMonitors([monitor()], NOW)).toHaveLength(1);
  });

  test('a monitor within its interval is not due', () => {
    expect(selectDueMonitors([monitor({ lastRunAt: minutesAgo(5) })], NOW)).toEqual([]);
  });

  // Otherwise a newly created monitor stays silent for a full interval, which
  // reads as "monitoring is broken" exactly when someone just switched it on.
  test('a monitor that has never run is due immediately', () => {
    expect(selectDueMonitors([monitor({ lastRunAt: null })], NOW)).toHaveLength(1);
  });

  test('a disabled monitor is never due, even when overdue', () => {
    expect(
      selectDueMonitors([monitor({ enabled: false, lastRunAt: minutesAgo(999) })], NOW),
    ).toEqual([]);
  });

  test('a disabled monitor that has never run is still not due', () => {
    expect(selectDueMonitors([monitor({ enabled: false, lastRunAt: null })], NOW)).toEqual([]);
  });

  test('exactly at the interval boundary is due', () => {
    expect(selectDueMonitors([monitor({ lastRunAt: minutesAgo(15) })], NOW)).toHaveLength(1);
  });

  test('selects only the due subset, preserving order', () => {
    const due = selectDueMonitors(
      [
        monitor({ id: 'a', lastRunAt: minutesAgo(20) }),
        monitor({ id: 'b', lastRunAt: minutesAgo(1) }),
        monitor({ id: 'c', lastRunAt: null }),
        monitor({ id: 'd', enabled: false, lastRunAt: null }),
      ],
      NOW,
    );
    expect(due.map((m) => m.id)).toEqual(['a', 'c']);
  });

  // A 1h monitor swept on a 5m grid: not due at 55m, due at 60m. The grid
  // rounds a period UP, it never fires one early.
  test('a long interval is not fired early by a frequent sweep', () => {
    const hourly = monitor({ intervalMinutes: 60, lastRunAt: minutesAgo(55) });
    expect(selectDueMonitors([hourly], NOW)).toEqual([]);
    const later = new Date(NOW.getTime() + 5 * 60_000);
    expect(selectDueMonitors([hourly], later)).toHaveLength(1);
  });
});