import { describe, expect, it } from 'vitest'
import type { EntityObject } from '../../../../chrono_manager/src/models/entity'
import { daysVisibleRange } from '../../../src/utils/date'
import { expandEntityInstances } from '../../../src/utils/recurrence'

function localIso(year: number, month: number, day: number, hour = 0): string {
  return new Date(year, month, day, hour).toISOString()
}

function eventEntity(
  identifier: string,
  startsOn: string | null,
  endsOn: string | null,
  timeless = false,
): EntityObject {
  return {
    identifier,
    properties: {
      startsOn,
      endsOn,
      timeless,
    },
  } as unknown as EntityObject
}

describe('entity instance expansion', () => {
  it('normalizes timestamps and duration once', () => {
    const [instance] = expandEntityInstances(
      eventEntity('meeting', localIso(2026, 5, 15, 9), localIso(2026, 5, 15, 10)),
    )

    expect(instance.duration).toBe(60 * 60 * 1000)
    expect(new Date(instance.start).getHours()).toBe(9)
    expect(new Date(instance.dayStart).getHours()).toBe(0)
    expect(instance.instanceId).toBeNull()
    expect(instance.multiDay).toBe(false)
  })

  it('produces no instance for an invalid start timestamp', () => {
    expect(expandEntityInstances(eventEntity('invalid', 'not-a-date', null))).toEqual([])
  })

  it('marks an overnight event as multi-day', () => {
    const [instance] = expandEntityInstances(
      eventEntity('overnight', localIso(2026, 5, 15, 23), localIso(2026, 5, 16, 1)),
    )

    expect(instance.multiDay).toBe(true)
    expect(instance.timeless).toBe(true)
  })

  it('honors an exclusive midnight end', () => {
    const [instance] = expandEntityInstances(
      eventEntity('all-day', localIso(2026, 5, 20), localIso(2026, 5, 21), true),
    )

    const end = new Date(instance.end)
    expect([end.getDate(), end.getHours()]).toEqual([21, 0])
    expect(new Date(instance.dayStart).getDate()).toBe(20)
    expect(instance.multiDay).toBe(false)
  })

  it('treats UTC timestamps on timeless events as floating calendar dates', () => {
    const [instance] = expandEntityInstances(
      eventEntity('utc-all-day', '2025-03-27T00:00:00+00:00', '2025-03-28T00:00:00+00:00', true),
    )

    const start = new Date(instance.start)
    expect([start.getMonth(), start.getDate(), start.getHours()]).toEqual([2, 27, 0])
    expect(new Date(instance.end).getDate()).toBe(28)
  })

  it('gives a zero-duration event a queryable minimum duration', () => {
    const [instance] = expandEntityInstances(
      eventEntity('instant', localIso(2026, 5, 15, 9), null),
    )

    expect(instance.duration).toBe(1)
  })

  it('omits a non-recurring event outside the requested range', () => {
    const instances = expandEntityInstances(
      eventEntity('outside', localIso(2026, 6, 1, 9), localIso(2026, 6, 1, 10)),
      daysVisibleRange(new Date(2026, 5, 15), 2),
    )

    expect(instances).toEqual([])
  })
})