[#MUI-33] Développer le composant Datepicker (#50)

| Numéro du ticket | Titre du ticket |
|------------------|-----------------|
|                  |                 |

## Description de la PR

## Modification du .env

## Check list

- [x] Pas de régression
- [x] TU/TI/TF rédigée
- [x] TU/TI/TF OK
- [x] CHANGELOG modifié

Reviewed-on: #50
Co-authored-by: tristan <tristan@yuno.malio.fr>
Co-committed-by: tristan <tristan@yuno.malio.fr>

app/components/malio/date/composables/useCalendarView.ts

@@ -0,0 +1,51 @@
+import {ref, type Ref} from 'vue'
+import {isValidIso} from './dateFormat'
+
+export function useCalendarView(viewMode: Ref<'days' | 'months'>) {
+  const today = new Date()
+  const currentMonth = ref(today.getMonth())
+  const currentYear = ref(today.getFullYear())
+
+  const goToPrev = () => {
+    if (viewMode.value === 'months') {
+      currentYear.value -= 1
+      return
+    }
+    if (currentMonth.value === 0) {
+      currentMonth.value = 11
+      currentYear.value -= 1
+    } else {
+      currentMonth.value -= 1
+    }
+  }
+
+  const goToNext = () => {
+    if (viewMode.value === 'months') {
+      currentYear.value += 1
+      return
+    }
+    if (currentMonth.value === 11) {
+      currentMonth.value = 0
+      currentYear.value += 1
+    } else {
+      currentMonth.value += 1
+    }
+  }
+
+  const selectMonth = (m: number) => {
+    currentMonth.value = m
+  }
+
+  const syncToIso = (iso: string | null) => {
+    if (iso && isValidIso(iso)) {
+      currentMonth.value = Number(iso.slice(5, 7)) - 1
+      currentYear.value = Number(iso.slice(0, 4))
+    } else {
+      const now = new Date()
+      currentMonth.value = now.getMonth()
+      currentYear.value = now.getFullYear()
+    }
+  }
+
+  return {currentMonth, currentYear, goToPrev, goToNext, selectMonth, syncToIso}
+}