import {describe, expect, it} from 'vitest'
import {
  formatWeekDisplay,
  isValidIsoWeek,
  isoWeekToMonday,
  mondayOf,
  sundayOf,
  toIsoWeek,
} from './dateWeek'

describe('dateWeek', () => {
  describe('mondayOf / sundayOf', () => {
    it('returns Monday and Sunday of a midweek date', () => {
      expect(mondayOf('2026-05-20')).toBe('2026-05-18') // mercredi
      expect(sundayOf('2026-05-20')).toBe('2026-05-24')
    })
    it('keeps Monday on a Monday', () => {
      expect(mondayOf('2026-05-18')).toBe('2026-05-18')
    })
    it('returns the preceding Monday for a Sunday', () => {
      expect(mondayOf('2026-05-24')).toBe('2026-05-18')
    })
  })

  describe('toIsoWeek', () => {
    it('returns the ISO week of a date', () => {
      expect(toIsoWeek('2026-05-20')).toBe('2026-W21')
    })
    it('handles year boundaries', () => {
      expect(toIsoWeek('2026-01-01')).toBe('2026-W01')
      expect(toIsoWeek('2025-12-31')).toBe('2026-W01')
      expect(toIsoWeek('2027-01-01')).toBe('2026-W53')
    })
  })

  describe('isoWeekToMonday', () => {
    it('returns the Monday of a week string', () => {
      expect(isoWeekToMonday('2026-W21')).toBe('2026-05-18')
    })
    it('round-trips with toIsoWeek', () => {
      for (const w of ['2026-W01', '2026-W21', '2026-W53', '2024-W09']) {
        const monday = isoWeekToMonday(w)
        expect(monday).not.toBeNull()
        expect(toIsoWeek(monday as string)).toBe(w)
      }
    })
    it('returns null for invalid input', () => {
      expect(isoWeekToMonday('2026-21')).toBeNull()
      expect(isoWeekToMonday('2026-W00')).toBeNull()
      expect(isoWeekToMonday('2026-W54')).toBeNull()
      expect(isoWeekToMonday('2025-W53')).toBeNull() // 2025 n'a que 52 semaines ISO
    })
  })

  describe('isValidIsoWeek', () => {
    it('accepts a real ISO week', () => {
      expect(isValidIsoWeek('2026-W21')).toBe(true)
    })
    it('rejects malformed or impossible weeks', () => {
      expect(isValidIsoWeek('2026-21')).toBe(false)
      expect(isValidIsoWeek('2026-W00')).toBe(false)
      expect(isValidIsoWeek('2026-W54')).toBe(false)
    })
  })

  describe('formatWeekDisplay', () => {
    it('formats a week as a human label', () => {
      expect(formatWeekDisplay('2026-W21')).toBe('Semaine 21 (18/05 → 24/05/2026)')
    })
    it('returns empty string for invalid input', () => {
      expect(formatWeekDisplay('2026-W54')).toBe('')
    })
  })
})