fix : wip

frontend/utils/date.ts

@@ -42,6 +42,46 @@ export const getWeekStartDate = (date: Date) => {
   return copy
 }
 
+export const getIsoWeekNumber = (date: Date) => {
+  const utc = new Date(Date.UTC(date.getFullYear(), date.getMonth(), date.getDate()))
+  const day = utc.getUTCDay() || 7
+  utc.setUTCDate(utc.getUTCDate() + 4 - day)
+  const yearStart = new Date(Date.UTC(utc.getUTCFullYear(), 0, 1))
+  return Math.ceil((((utc.getTime() - yearStart.getTime()) / 86400000) + 1) / 7)
+}
+
+export const getIsoWeekYear = (date: Date) => {
+  const utc = new Date(Date.UTC(date.getFullYear(), date.getMonth(), date.getDate()))
+  const day = utc.getUTCDay() || 7
+  utc.setUTCDate(utc.getUTCDate() + 4 - day)
+  return utc.getUTCFullYear()
+}
+
+export const ymdToWeekInputValue = (dateYmd: string) => {
+  const parsed = parseYmd(dateYmd)
+  if (!parsed) return ''
+  const weekDate = getWeekStartDate(parsed)
+  const weekNumber = getIsoWeekNumber(weekDate)
+  const weekYear = getIsoWeekYear(weekDate)
+  return `${weekYear}-W${String(weekNumber).padStart(2, '0')}`
+}
+
+export const weekInputValueToYmd = (weekValue: string) => {
+  const match = /^(\d{4})-W(\d{2})$/.exec(weekValue)
+  if (!match) return null
+
+  const year = Number(match[1])
+  const week = Number(match[2])
+  if (!Number.isInteger(year) || !Number.isInteger(week) || week < 1 || week > 53) return null
+
+  const jan4 = new Date(year, 0, 4)
+  const week1Monday = getWeekStartDate(jan4)
+  const monday = new Date(week1Monday)
+  monday.setDate(week1Monday.getDate() + ((week - 1) * 7))
+
+  return toYmd(monday.getFullYear(), monday.getMonth(), monday.getDate())
+}
+
 export const getTodayYmd = () => {
   const date = new Date()
   return toYmd(date.getFullYear(), date.getMonth(), date.getDate())
@@ -64,6 +104,7 @@ export const formatWeekRangeFr = (date: Date) => {
   const start = getWeekStartDate(date)
   const end = new Date(start)
   end.setDate(start.getDate() + 6)
+  const weekNumber = getIsoWeekNumber(start)
 
   const formatter = new Intl.DateTimeFormat('fr-FR', {
     day: '2-digit',
@@ -71,7 +112,7 @@ export const formatWeekRangeFr = (date: Date) => {
     year: 'numeric'
   })
 
-  return `Semaine du ${formatter.format(start)} au ${formatter.format(end)}`
+  return `S${weekNumber} du ${formatter.format(start)} au ${formatter.format(end)}`
 }
 
 export const getDaysInMonth = (year: number, month: number) => {