import { formatRelativeTime } from './formatRelativeTime'

// Date strings deliberately omit the trailing 'Z' so they parse in the
// runner's local timezone — formatRelativeTime buckets by local calendar
// days, so this keeps assertions deterministic regardless of ambient TZ.
describe('formatRelativeTime', () => {
  let originalDate: typeof Date

  beforeEach(() => {
    // Save the original Date
    originalDate = global.Date
  })

  afterEach(() => {
    // Restore the original Date
    global.Date = originalDate
  })

  const mockDate = (isoString: string) => {
    const mockNow = new Date(isoString)
    // @ts-expect-error - need to override Date constructor for testing
    global.Date = class extends originalDate {
      // @ts-expect-error - need to override Date constructor for testing
      constructor(...args) {
        if (args.length === 0) {
          super(isoString)
        } else {
          // @ts-expect-error - need to override Date constructor for testing
          super(...args)
        }
      }

      static now() {
        return mockNow.getTime()
      }
    }
  }

  describe('Just now', () => {
    it('should return "Just now" for messages less than 1 minute ago', () => {
      mockDate('2024-01-15T12:00:00')
      const date = new Date('2024-01-15T11:59:30') // 30 seconds ago
      expect(formatRelativeTime(date)).toBe('Just now')
    })
  })

  describe('Today', () => {
    it('should return time in 12-hour format for messages from earlier today', () => {
      mockDate('2024-01-15T14:08:00')
      const date = new Date('2024-01-15T09:30:00')
      const result = formatRelativeTime(date)
      // Should be "9:30 AM" format
      expect(result).toMatch(/^\d{1,2}:\d{2} (AM|PM)$/i)
    })
  })

  describe('Yesterday', () => {
    it('should return "Yesterday" for messages from the previous calendar day', () => {
      mockDate('2024-01-15T12:00:00')
      const date = new Date('2024-01-14T12:00:00')
      expect(formatRelativeTime(date)).toBe('Yesterday')
    })

    it('should return "Yesterday" even if less than 24 hours ago but previous day', () => {
      mockDate('2024-01-15T01:00:00')
      const date = new Date('2024-01-14T23:00:00') // Only 2 hours ago
      expect(formatRelativeTime(date)).toBe('Yesterday')
    })

    it('should NOT return "Yesterday" for messages from 2 days ago', () => {
      mockDate('2024-01-15T12:00:00')
      const date = new Date('2024-01-13T12:00:00')
      expect(formatRelativeTime(date)).not.toBe('Yesterday')
    })
  })

  describe('2-6 days ago (short weekday)', () => {
    // The weekday branch uses the runtime locale
    // (toLocaleDateString(undefined, …)), so assertions compare against
    // the same locale-aware formatter rather than fixed English strings.
    it('should return a short weekday name for messages 2 days ago', () => {
      mockDate('2024-01-15T12:00:00')
      const date = new Date('2024-01-13T12:00:00') // Saturday
      expect(formatRelativeTime(date)).toBe(
        date.toLocaleDateString(undefined, { weekday: 'short' })
      )
    })

    it('should return a short weekday name for messages 6 days ago (boundary before dates)', () => {
      mockDate('2024-01-15T12:00:00')
      const date = new Date('2024-01-09T12:00:00') // Tuesday
      expect(formatRelativeTime(date)).toBe(
        date.toLocaleDateString(undefined, { weekday: 'short' })
      )
    })
  })

  describe('7+ days ago, same year (month and day)', () => {
    // Compare against the same locale-aware formatter rather than
    // hard-coded digits, which would fail under non-Latin numbering
    // systems (e.g. ar_EG renders "٨ يناير").
    it('should return month + day without year for messages 7 days ago', () => {
      mockDate('2024-01-15T12:00:00')
      const date = new Date('2024-01-08T12:00:00')
      expect(formatRelativeTime(date)).toBe(
        date.toLocaleDateString(undefined, { month: 'short', day: 'numeric' })
      )
    })

    it('should return month + day without year for messages more than 4 weeks ago in the same year', () => {
      mockDate('2024-02-15T12:00:00')
      const date = new Date('2024-01-01T12:00:00')
      expect(formatRelativeTime(date)).toBe(
        date.toLocaleDateString(undefined, { month: 'short', day: 'numeric' })
      )
    })
  })

  describe('Previous years (month, day and year)', () => {
    it('should include the year for messages from a previous year', () => {
      mockDate('2024-01-15T12:00:00')
      const date = new Date('2023-12-01T12:00:00')
      expect(formatRelativeTime(date)).toBe(
        date.toLocaleDateString(undefined, {
          month: 'short',
          day: 'numeric',
          year: 'numeric',
        })
      )
    })
  })

  describe('Edge cases', () => {
    it('should handle month boundaries correctly', () => {
      mockDate('2024-02-01T12:00:00')
      const date = new Date('2024-01-31T12:00:00')
      expect(formatRelativeTime(date)).toBe('Yesterday')
    })

    it('should handle year boundaries correctly', () => {
      mockDate('2024-01-01T12:00:00')
      const date = new Date('2023-12-31T12:00:00')
      expect(formatRelativeTime(date)).toBe('Yesterday')
    })

    it('should handle leap year correctly', () => {
      mockDate('2024-03-01T12:00:00')
      const date = new Date('2024-02-29T12:00:00')
      expect(formatRelativeTime(date)).toBe('Yesterday')
    })
  })
})