/**
 * BUG A regression — write-path timezone serialization.
 *
 * Verifies that timed events are serialized to an unambiguous UTC instant
 * (so the operator's wall-clock time round-trips correctly regardless of the
 * API container's timezone), while all-day events keep their DATE strings.
 *
 * The PWA vitest harness runs with TZ=UTC, so the assertions are computed
 * relative to the local zone (whatever it is) rather than hard-coding an offset.
 * The core guarantee under test: the serialized timed value is a UTC instant
 * (ends in 'Z') derived from the LOCAL wall clock — never the naive wall-clock
 * string passed through verbatim, and never an instant that loses the local hour.
 */

import { describe, it, expect } from 'vitest'
import { serializeEventDateTime, localWallClockToUtcIso } from './eventDateTime.js'

describe('serializeEventDateTime (BUG A — write-path TZ)', () => {
  it('serializes a timed start to a UTC instant (ends in Z)', () => {
    const { start } = serializeEventDateTime(false, '2026-06-07', '09:00', '2026-06-07', '10:00')
    expect(start.endsWith('Z')).toBe(true)
    // It must NOT be the naive wall-clock string (the original bug shape).
    expect(start).not.toBe('2026-06-07T09:00:00')
  })

  it('the serialized instant round-trips back to the SAME local wall clock', () => {
    // This is the heart of BUG A: 09:00 in → 09:00 back out in the operator's zone.
    const { start, end } = serializeEventDateTime(false, '2026-06-07', '09:00', '2026-06-07', '10:30')
    const startBack = new Date(start)
    expect(startBack.getHours()).toBe(9)
    expect(startBack.getMinutes()).toBe(0)
    const endBack = new Date(end)
    expect(endBack.getHours()).toBe(10)
    expect(endBack.getMinutes()).toBe(30)
  })

  it('equals the instant new Date(local parts) produces — not a passthrough', () => {
    const { start } = serializeEventDateTime(false, '2026-06-07', '09:00', '2026-06-07', '10:00')
    expect(start).toBe(new Date('2026-06-07T09:00:00').toISOString())
  })

  it('leaves all-day events as DATE strings (no time, no Z) — D-13 contract', () => {
    const { start, end } = serializeEventDateTime(true, '2026-06-07', '09:00', '2026-06-09', '10:00')
    expect(start).toBe('2026-06-07')
    expect(end).toBe('2026-06-09')
  })

  it('localWallClockToUtcIso round-trips a local wall clock to a UTC instant', () => {
    const iso = localWallClockToUtcIso('2026-06-07', '09:00')
    expect(iso.endsWith('Z')).toBe(true)
    expect(new Date(iso).getHours()).toBe(9)
  })
})