import { describe, expect, it } from 'vitest'
import { useCalendar } from '../use-calendar'

describe('useCalendar', () => {
  describe('initialization', () => {
    it('initializes with null date by default', () => {
      const { selectedDate } = useCalendar()
      expect(selectedDate.value).toBeNull()
    })

    it('initializes with provided date', () => {
      const date = new Date(2025, 5, 15) // June 15, 2025
      const { selectedDate } = useCalendar(date)
      expect(selectedDate.value?.getFullYear()).toBe(2025)
      expect(selectedDate.value?.getMonth()).toBe(5)
      expect(selectedDate.value?.getDate()).toBe(15)
    })

    it('sets viewDate to today when no initial date provided', () => {
      const { viewDate } = useCalendar()
      const today = new Date()
      expect(viewDate.value.getFullYear()).toBe(today.getFullYear())
      expect(viewDate.value.getMonth()).toBe(today.getMonth())
    })

    it('sets viewDate to initial date when provided', () => {
      const date = new Date(2025, 5, 15)
      const { viewDate } = useCalendar(date)
      expect(viewDate.value.getFullYear()).toBe(2025)
      expect(viewDate.value.getMonth()).toBe(5)
    })
  })

  describe('weekday headers', () => {
    it('returns weekday headers starting with Sunday by default', () => {
      const { weekdayHeaders } = useCalendar()
      expect(weekdayHeaders.value).toEqual(['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'])
    })

    it('returns weekday headers starting with Monday when firstDay is 1', () => {
      const { weekdayHeaders } = useCalendar(null, { firstDay: 1 })
      expect(weekdayHeaders.value).toEqual(['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'])
    })

    it('returns full weekday names for accessibility', () => {
      const { weekdayHeadersFull } = useCalendar()
      expect(weekdayHeadersFull.value).toEqual([
        'Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday',
      ])
    })
  })

  describe('month display', () => {
    it('returns correct month name', () => {
      const date = new Date(2025, 5, 15) // June
      const { monthName } = useCalendar(date)
      expect(monthName.value).toBe('June')
    })

    it('returns correct short month name', () => {
      const date = new Date(2025, 11, 25) // December
      const { monthNameShort } = useCalendar(date)
      expect(monthNameShort.value).toBe('Dec')
    })
  })

  describe('calendar days', () => {
    it('generates 42 days (6 weeks)', () => {
      const { calendarDays } = useCalendar(new Date(2025, 5, 15))
      expect(calendarDays.value).toHaveLength(42)
    })

    it('marks days outside current month', () => {
      const { calendarDays } = useCalendar(new Date(2025, 5, 15)) // June 2025
      const outsideDays = calendarDays.value.filter(d => d.isOutsideMonth)
      expect(outsideDays.length).toBeGreaterThan(0)
    })

    it('marks the selected date', () => {
      const date = new Date(2025, 5, 15)
      const { calendarDays } = useCalendar(date)
      const selectedDays = calendarDays.value.filter(d => d.isSelected)
      expect(selectedDays).toHaveLength(1)
      expect(selectedDays[0]?.day).toBe(15)
    })

    it('marks today correctly', () => {
      const today = new Date()
      const { calendarDays, goToDate } = useCalendar()
      goToDate(today)
      const todayDays = calendarDays.value.filter(d => d.isToday && !d.isOutsideMonth)
      expect(todayDays).toHaveLength(1)
      expect(todayDays[0]?.day).toBe(today.getDate())
    })
  })

  describe('navigation', () => {
    it('navigates to next month', () => {
      const { viewMonth, viewYear, nextMonth } = useCalendar(new Date(2025, 5, 15))
      expect(viewMonth.value).toBe(5)
      nextMonth()
      expect(viewMonth.value).toBe(6)
      expect(viewYear.value).toBe(2025)
    })

    it('navigates to previous month', () => {
      const { viewMonth, viewYear, prevMonth } = useCalendar(new Date(2025, 5, 15))
      expect(viewMonth.value).toBe(5)
      prevMonth()
      expect(viewMonth.value).toBe(4)
      expect(viewYear.value).toBe(2025)
    })

    it('handles year rollover when navigating forward', () => {
      const { viewMonth, viewYear, nextMonth } = useCalendar(new Date(2025, 11, 15))
      expect(viewMonth.value).toBe(11)
      nextMonth()
      expect(viewMonth.value).toBe(0)
      expect(viewYear.value).toBe(2026)
    })

    it('handles year rollover when navigating backward', () => {
      const { viewMonth, viewYear, prevMonth } = useCalendar(new Date(2025, 0, 15))
      expect(viewMonth.value).toBe(0)
      prevMonth()
      expect(viewMonth.value).toBe(11)
      expect(viewYear.value).toBe(2024)
    })

    it('goes to specific month', () => {
      const { viewMonth, goToMonth } = useCalendar(new Date(2025, 5, 15))
      goToMonth(10)
      expect(viewMonth.value).toBe(10)
    })

    it('goes to specific year', () => {
      const { viewYear, goToYear } = useCalendar(new Date(2025, 5, 15))
      goToYear(2030)
      expect(viewYear.value).toBe(2030)
    })

    it('goes to today', () => {
      const { viewMonth, viewYear, goToToday } = useCalendar(new Date(2020, 0, 1))
      const today = new Date()
      goToToday()
      expect(viewMonth.value).toBe(today.getMonth())
      expect(viewYear.value).toBe(today.getFullYear())
    })
  })

  describe('selection', () => {
    it('selects a date', () => {
      const { selectedDate, selectDate } = useCalendar()
      const date = new Date(2025, 5, 20)
      selectDate(date)
      expect(selectedDate.value?.getDate()).toBe(20)
      expect(selectedDate.value?.getMonth()).toBe(5)
    })

    it('clears selection', () => {
      const { selectedDate, clearSelection } = useCalendar(new Date(2025, 5, 15))
      expect(selectedDate.value).not.toBeNull()
      clearSelection()
      expect(selectedDate.value).toBeNull()
    })

    it('does not select disabled dates', () => {
      const minDate = new Date(2025, 5, 10)
      const { selectedDate, selectDate } = useCalendar(null, { minDate })
      selectDate(new Date(2025, 5, 5)) // Before minDate
      expect(selectedDate.value).toBeNull()
    })
  })

  describe('date constraints', () => {
    it('marks dates before minDate as disabled', () => {
      const minDate = new Date(2025, 5, 15)
      const { calendarDays } = useCalendar(new Date(2025, 5, 20), { minDate })
      const june14 = calendarDays.value.find(d => d.day === 14 && d.month === 5)
      const june15 = calendarDays.value.find(d => d.day === 15 && d.month === 5)
      expect(june14?.isDisabled).toBe(true)
      expect(june15?.isDisabled).toBe(false)
    })

    it('marks dates after maxDate as disabled', () => {
      const maxDate = new Date(2025, 5, 15)
      const { calendarDays } = useCalendar(new Date(2025, 5, 10), { maxDate })
      const june15 = calendarDays.value.find(d => d.day === 15 && d.month === 5)
      const june16 = calendarDays.value.find(d => d.day === 16 && d.month === 5)
      expect(june15?.isDisabled).toBe(false)
      expect(june16?.isDisabled).toBe(true)
    })
  })

  describe('formatting', () => {
    it('formats date with default format', () => {
      const { formatDate } = useCalendar(new Date(2025, 5, 15))
      expect(formatDate()).toBe('15 Jun 2025')
    })

    it('formats date with custom format', () => {
      const { formatDate } = useCalendar(new Date(2025, 5, 15))
      expect(formatDate('YYYY-MM-DD')).toBe('2025-06-15')
    })

    it('formats date with full month name', () => {
      const { formatDate } = useCalendar(new Date(2025, 5, 15))
      expect(formatDate('MMMM D, YYYY')).toBe('June 15, 2025')
    })

    it('returns empty string when no date selected', () => {
      const { formatDate } = useCalendar()
      expect(formatDate()).toBe('')
    })
  })

  describe('utility functions', () => {
    it('isSameDay returns true for same day', () => {
      const { isSameDay } = useCalendar()
      const a = new Date(2025, 5, 15, 10, 30)
      const b = new Date(2025, 5, 15, 20, 45)
      expect(isSameDay(a, b)).toBe(true)
    })

    it('isSameDay returns false for different days', () => {
      const { isSameDay } = useCalendar()
      const a = new Date(2025, 5, 15)
      const b = new Date(2025, 5, 16)
      expect(isSameDay(a, b)).toBe(false)
    })

    it('isSameDay handles null values', () => {
      const { isSameDay } = useCalendar()
      expect(isSameDay(null, new Date())).toBe(false)
      expect(isSameDay(new Date(), null)).toBe(false)
      expect(isSameDay(null, null)).toBe(false)
    })
  })
})