import { describe, it, expect, afterEach } from 'vitest'
import {
  DEFAULT_TIMEZONE,
  COMMON_TIMEZONES,
  detectTimezone,
  listTimezones,
  isValidTimezone,
} from '../src/lib/timezone.js'
import { createEvent } from '../src/lib/event-factory.js'

describe('DEFAULT_TIMEZONE', () => {
  it('is Australia/Melbourne per requirement', () => {
    expect(DEFAULT_TIMEZONE).toBe('Australia/Melbourne')
  })
})

describe('isValidTimezone', () => {
  it('accepts valid IANA zone ids', () => {
    expect(isValidTimezone('Australia/Melbourne')).toBe(true)
    expect(isValidTimezone('Asia/Shanghai')).toBe(true)
    expect(isValidTimezone('America/New_York')).toBe(true)
    expect(isValidTimezone('Europe/London')).toBe(true)
  })

  it('rejects empty / non-string / malformed', () => {
    expect(isValidTimezone('')).toBe(false)
    expect(isValidTimezone(null)).toBe(false)
    expect(isValidTimezone(undefined)).toBe(false)
    expect(isValidTimezone(123)).toBe(false)
    expect(isValidTimezone('UTC')).toBe(false) // 单段, 本应用要求至少一段 '/'
    expect(isValidTimezone('Not A Zone')).toBe(false)
    expect(isValidTimezone('Bogus/Zone/With Space')).toBe(false)
  })
})

describe('detectTimezone', () => {
  // 保存原始 Intl 引用以便恢复
  const origDateTimeFormat = Intl.DateTimeFormat
  afterEach(() => {
    Intl.DateTimeFormat = origDateTimeFormat
  })

  it('returns a valid IANA zone in a normal environment', () => {
    // Node 环境总能解析出系统时区
    const tz = detectTimezone()
    expect(isValidTimezone(tz)).toBe(true)
  })

  it('falls back to Melbourne when Intl.DateTimeFormat throws', () => {
    Intl.DateTimeFormat = function () {
      throw new Error('unsupported')
    }
    expect(detectTimezone()).toBe(DEFAULT_TIMEZONE)
  })

  it('falls back to Melbourne when resolved timeZone is empty', () => {
    Intl.DateTimeFormat = function () {
      return { resolvedOptions: () => ({ timeZone: '' }) }
    }
    expect(detectTimezone()).toBe(DEFAULT_TIMEZONE)
  })

  it('falls back to Melbourne when resolved timeZone is malformed', () => {
    Intl.DateTimeFormat = function () {
      return { resolvedOptions: () => ({ timeZone: 'Not A Zone' }) }
    }
    expect(detectTimezone()).toBe(DEFAULT_TIMEZONE)
  })

  it('returns the detected zone when it is valid', () => {
    Intl.DateTimeFormat = function () {
      return { resolvedOptions: () => ({ timeZone: 'Asia/Shanghai' }) }
    }
    expect(detectTimezone()).toBe('Asia/Shanghai')
  })
})

describe('listTimezones', () => {
  it('always includes Melbourne, Shanghai, UTC', () => {
    const list = listTimezones()
    expect(list).toContain('Australia/Melbourne')
    expect(list).toContain('Asia/Shanghai')
    expect(list).toContain('UTC')
  })

  it('has no duplicates', () => {
    const list = listTimezones()
    expect(new Set(list).size).toBe(list.length)
  })

  it('places UTC first, rest sorted', () => {
    const list = listTimezones()
    expect(list[0]).toBe('UTC')
    const rest = list.slice(1)
    const sorted = [...rest].sort((a, b) => a.localeCompare(b))
    expect(rest).toEqual(sorted)
  })

  it('every entry is a valid IANA zone (UTC excepted)', () => {
    const list = listTimezones()
    for (const tz of list) {
      if (tz === 'UTC') continue
      expect(isValidTimezone(tz)).toBe(true)
    }
  })

  it('includes all COMMON_TIMEZONES entries', () => {
    const list = listTimezones()
    for (const tz of COMMON_TIMEZONES) {
      expect(list).toContain(tz)
    }
  })
})

describe('createEvent timezone override', () => {
  // 确认 useCalendar.addEvent 依赖的覆盖路径：传入 { tzid } 后新建事件的
  // tzid 即为该值（而非 event-factory 的独立默认 'UTC'）。
  it('honors the tzid passed via overrides', () => {
    const ev = createEvent({ tzid: 'Asia/Shanghai' })
    expect(ev.tzid).toBe('Asia/Shanghai')
  })

  it('falls back to UTC when no tzid override is given (standalone default)', () => {
    const ev = createEvent()
    expect(ev.tzid).toBe('UTC')
  })
})