import { describe, it, expect } from 'vitest'
import {
  formatDateForDisplay,
  formatDateForInput,
  parseInputDate,
  isValidDate,
  getDayName,
  getMonthName,
} from '@/utils/dates'

describe('dates.ts utilities', () => {
  describe('formatDateForDisplay', () => {
    it('formats ISO string to Swedish display format', () => {
      const result = formatDateForDisplay('2026-06-15')
      expect(result).toBe('15 juni 2026')
    })

    it('formats Date object to Swedish display format', () => {
      const date = new Date('2026-06-15T00:00:00Z')
      const result = formatDateForDisplay(date)
      expect(result).toBe('15 juni 2026')
    })

    it('handles January correctly', () => {
      const result = formatDateForDisplay('2026-01-01')
      expect(result).toBe('1 januari 2026')
    })

    it('handles December correctly', () => {
      const result = formatDateForDisplay('2026-12-25')
      expect(result).toBe('25 december 2026')
    })

    it('returns empty string for invalid date', () => {
      const result = formatDateForDisplay('invalid')
      expect(result).toBe('')
    })
  })

  describe('formatDateForInput', () => {
    it('formats ISO string to input format', () => {
      const result = formatDateForInput('2026-06-15')
      expect(result).toBe('2026-06-15')
    })

    it('formats Date object to input format', () => {
      const date = new Date('2026-06-15T00:00:00Z')
      const result = formatDateForInput(date)
      expect(result).toBe('2026-06-15')
    })

    it('pads month and day with zeros', () => {
      const result = formatDateForInput('2026-01-05')
      expect(result).toBe('2026-01-05')
    })

    it('returns empty string for invalid date', () => {
      const result = formatDateForInput('invalid')
      expect(result).toBe('')
    })
  })

  describe('parseInputDate', () => {
    it('parses ISO date string to Date object', () => {
      const result = parseInputDate('2026-06-15')
      expect(result).toBeInstanceOf(Date)
      expect(result.toISOString()).toContain('2026-06-15')
    })

    it('creates valid Date for valid input', () => {
      const result = parseInputDate('2026-06-15')
      expect(isValidDate(result)).toBe(true)
    })
  })

  describe('isValidDate', () => {
    it('returns true for valid Date object', () => {
      const date = new Date('2026-06-15')
      expect(isValidDate(date)).toBe(true)
    })

    it('returns false for invalid Date', () => {
      const date = new Date('invalid')
      expect(isValidDate(date)).toBe(false)
    })

    it('returns false for non-Date values', () => {
      expect(isValidDate('2026-06-15')).toBe(false)
      expect(isValidDate(20260615)).toBe(false)
      expect(isValidDate(null)).toBe(false)
      expect(isValidDate(undefined)).toBe(false)
    })
  })

  describe('getDayName', () => {
    it('returns Swedish day name', () => {
      const date = new Date('2026-06-15T00:00:00Z') // Monday
      const result = getDayName(date)
      expect(result.toLowerCase()).toBe('måndag')
    })

    it('returns empty string for invalid date', () => {
      const result = getDayName(new Date('invalid'))
      expect(result).toBe('')
    })
  })

  describe('getMonthName', () => {
    it('returns Swedish month name', () => {
      const date = new Date('2026-06-15T00:00:00Z')
      const result = getMonthName(date)
      expect(result).toBe('juni')
    })

    it('returns correct month names for all months', () => {
      const monthNames = [
        'januari',
        'februari',
        'mars',
        'april',
        'maj',
        'juni',
        'juli',
        'augusti',
        'september',
        'oktober',
        'november',
        'december',
      ]

      monthNames.forEach((monthName, index) => {
        const date = new Date(`2026-${String(index + 1).padStart(2, '0')}-15T00:00:00Z`)
        const result = getMonthName(date)
        expect(result).toBe(monthName)
      })
    })

    it('returns empty string for invalid date', () => {
      const result = getMonthName(new Date('invalid'))
      expect(result).toBe('')
    })
  })
})