refactor: migrate CasesPage and useInlineEdit to TanStack Query

Replace manual useEffect data fetching with useCases/usePendingIcdCases
query hooks. Replace direct API calls in useInlineEdit with useCaseUpdate
and useKvnrUpdate mutations. Use useIcdUpdate for ICD saving. Remove
onCaseSaved callback prop drilling — mutations auto-invalidate the cache.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/hooks/useCases.ts

@@ -0,0 +1,70 @@
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query'
+import api from '@/services/api'
+import type { Case, CaseListResponse } from '@/types'
+
+export interface CaseFilters {
+  page: number
+  per_page: number
+  search?: string
+  jahr?: number
+  fallgruppe?: string
+  has_icd?: string
+}
+
+export function useCases(filters: CaseFilters, options?: { enabled?: boolean }) {
+  return useQuery({
+    queryKey: ['cases', filters],
+    queryFn: () => {
+      const params: Record<string, string | number> = {
+        page: filters.page,
+        per_page: filters.per_page,
+      }
+      if (filters.search) params.search = filters.search
+      if (filters.jahr) params.jahr = filters.jahr
+      if (filters.fallgruppe) params.fallgruppe = filters.fallgruppe
+      if (filters.has_icd) params.has_icd = filters.has_icd
+      return api.get<CaseListResponse>('/cases/', { params }).then(r => r.data)
+    },
+    enabled: options?.enabled ?? true,
+  })
+}
+
+export function usePendingIcdCases(page: number, perPage: number, options?: { enabled?: boolean }) {
+  return useQuery({
+    queryKey: ['cases', 'pending-icd', { page, per_page: perPage }],
+    queryFn: () => api.get<CaseListResponse>('/cases/pending-icd', {
+      params: { page, per_page: perPage },
+    }).then(r => r.data),
+    enabled: options?.enabled ?? true,
+  })
+}
+
+export function useCaseUpdate() {
+  const queryClient = useQueryClient()
+  return useMutation({
+    mutationFn: ({ id, data }: { id: number; data: Record<string, unknown> }) =>
+      api.put<Case>(`/cases/${id}`, data).then(r => r.data),
+    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['cases'] }),
+  })
+}
+
+export function useKvnrUpdate() {
+  const queryClient = useQueryClient()
+  return useMutation({
+    mutationFn: ({ id, kvnr }: { id: number; kvnr: string | null }) =>
+      api.put<Case>(`/cases/${id}/kvnr`, { kvnr }).then(r => r.data),
+    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['cases'] }),
+  })
+}
+
+export function useIcdUpdate() {
+  const queryClient = useQueryClient()
+  return useMutation({
+    mutationFn: ({ id, icd }: { id: number; icd: string }) =>
+      api.put<Case>(`/cases/${id}/icd`, { icd }).then(r => r.data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['cases'] })
+      queryClient.invalidateQueries({ queryKey: ['dashboard'] })
+    },
+  })
+}

frontend/src/pages/CasesPage.tsx

@@ -2,9 +2,9 @@ import { useState, useEffect, useCallback, useRef } from 'react'
 import {
   Search, ChevronLeft, ChevronRight, Save, CheckCircle, XCircle, Pencil, X,
 } from 'lucide-react'
-import api from '@/services/api'
-import type { Case, CaseListResponse } from '@/types'
+import type { Case } from '@/types'
 import { useAuth } from '@/context/AuthContext'
+import { useCases, usePendingIcdCases, useIcdUpdate, type CaseFilters } from '@/hooks/useCases'
 import { Input } from '@/components/ui/input'
 import { Button } from '@/components/ui/button'
 import { Badge } from '@/components/ui/badge'
@@ -62,8 +62,6 @@ export function CasesPage({ pendingIcdOnly = false }: CasesPageProps) {
   const [hasIcd, setHasIcd] = useState<string>('__all__')
   const [page, setPage] = useState(1)
   const [perPage] = useState(50)
-  const [data, setData] = useState<CaseListResponse | null>(null)
-  const [loading, setLoading] = useState(true)
   const [selectedCase, setSelectedCase] = useState<Case | null>(null)
   const [sheetOpen, setSheetOpen] = useState(false)
 
@@ -84,30 +82,20 @@ export function CasesPage({ pendingIcdOnly = false }: CasesPageProps) {
     }
   }, [])
 
-  // Fetch cases
-  useEffect(() => {
-    setLoading(true)
+  // Fetch cases via TanStack Query
+  const filters: CaseFilters = {
+    page, per_page: perPage,
+    ...(debouncedSearch ? { search: debouncedSearch } : {}),
+    ...(jahr !== '__all__' ? { jahr: Number(jahr) } : {}),
+    ...(fallgruppe !== '__all__' ? { fallgruppe } : {}),
+    ...(hasIcd !== '__all__' ? { has_icd: hasIcd } : {}),
+  }
 
-    if (pendingIcdOnly) {
-      api.get<CaseListResponse>('/cases/pending-icd', {
-        params: { page, per_page: perPage },
-      })
-        .then((res) => setData(res.data))
-        .catch(() => setData(null))
-        .finally(() => setLoading(false))
-    } else {
-      const params: Record<string, string | number> = { page, per_page: perPage }
-      if (debouncedSearch) params.search = debouncedSearch
-      if (jahr !== '__all__') params.jahr = Number(jahr)
-      if (fallgruppe !== '__all__') params.fallgruppe = fallgruppe
-      if (hasIcd !== '__all__') params.has_icd = hasIcd
-
-      api.get<CaseListResponse>('/cases/', { params })
-        .then((res) => setData(res.data))
-        .catch(() => setData(null))
-        .finally(() => setLoading(false))
-    }
-  }, [page, perPage, debouncedSearch, jahr, fallgruppe, hasIcd, pendingIcdOnly])
+  const casesQuery = useCases(filters, { enabled: !pendingIcdOnly })
+  const pendingQuery = usePendingIcdCases(page, perPage, { enabled: pendingIcdOnly })
+  const activeQuery = pendingIcdOnly ? pendingQuery : casesQuery
+  const data = activeQuery.data ?? null
+  const loading = activeQuery.isLoading
 
   const totalPages = data ? Math.ceil(data.total / perPage) : 0
   const years = Array.from({ length: 5 }, (_, i) => currentYear - i)
@@ -117,19 +105,6 @@ export function CasesPage({ pendingIcdOnly = false }: CasesPageProps) {
     setSheetOpen(true)
   }
 
-  const handleCaseSaved = (updated: Case) => {
-    setSelectedCase(updated)
-    // Refresh list
-    setData((prev) =>
-      prev
-        ? {
-            ...prev,
-            items: prev.items.map((c) => (c.id === updated.id ? updated : c)),
-          }
-        : prev,
-    )
-  }
-
   return (
     <div className="p-6 space-y-4">
       <h1 className="text-2xl font-bold">
@@ -286,10 +261,7 @@ export function CasesPage({ pendingIcdOnly = false }: CasesPageProps) {
       <Sheet open={sheetOpen} onOpenChange={setSheetOpen}>
         <SheetContent className="w-full sm:max-w-lg overflow-y-auto">
           {selectedCase && (
-            <CaseDetail
-              caseData={selectedCase}
-              onCaseSaved={handleCaseSaved}
-            />
+            <CaseDetail caseData={selectedCase} />
           )}
         </SheetContent>
       </Sheet>
@@ -309,22 +281,16 @@ function StatusBadges({ c }: { c: Case }) {
   )
 }
 
-function CaseDetail({
-  caseData,
-  onCaseSaved,
-}: {
-  caseData: Case
-  onCaseSaved: (updated: Case) => void
-}) {
+function CaseDetail({ caseData }: { caseData: Case }) {
   const { isAdmin } = useAuth()
   const {
     editing, formValues, saving, error, success,
     startEditing, cancelEditing, saveAll, setFieldValue, canEditField, isDirty,
-  } = useInlineEdit(caseData, onCaseSaved)
+  } = useInlineEdit(caseData)
 
   // ICD has its own endpoint and state
+  const icdMutation = useIcdUpdate()
   const [icdValue, setIcdValue] = useState(caseData.icd || '')
-  const [icdSaving, setIcdSaving] = useState(false)
   const [icdError, setIcdError] = useState('')
   const [icdSuccess, setIcdSuccess] = useState(false)
 
@@ -336,17 +302,13 @@ function CaseDetail({
 
   const saveIcd = async () => {
     if (!icdValue.trim()) return
-    setIcdSaving(true)
     setIcdError('')
     setIcdSuccess(false)
     try {
-      const res = await api.put<Case>(`/cases/${caseData.id}/icd`, { icd: icdValue.trim() })
-      onCaseSaved(res.data)
+      await icdMutation.mutateAsync({ id: caseData.id, icd: icdValue.trim() })
       setIcdSuccess(true)
     } catch {
       setIcdError('Fehler beim Speichern des ICD-Codes.')
-    } finally {
-      setIcdSaving(false)
     }
   }
 
@@ -456,10 +418,10 @@ function CaseDetail({
             <Button
               size="sm"
               onClick={saveIcd}
-              disabled={icdSaving || !icdValue.trim()}
+              disabled={icdMutation.isPending || !icdValue.trim()}
             >
               <Save className="size-4 mr-1" />
-              {icdSaving ? 'Speichern...' : 'Speichern'}
+              {icdMutation.isPending ? 'Speichern...' : 'Speichern'}
             </Button>
           </div>
           {icdError && (

frontend/src/pages/cases/useInlineEdit.ts

@@ -1,6 +1,6 @@
 import { useState, useCallback, useEffect } from 'react'
-import api from '@/services/api'
 import type { Case } from '@/types'
+import { useCaseUpdate, useKvnrUpdate } from '@/hooks/useCases'
 import { CASE_SECTIONS, type FieldConfig } from './fieldConfig'
 
 type FormValues = Record<string, unknown>
@@ -43,8 +43,10 @@ function getDirtyFields(original: FormValues, current: FormValues): FormValues {
 
 export function useInlineEdit(
   caseData: Case,
-  onSaved: (updated: Case) => void,
 ): UseInlineEditReturn {
+  const caseUpdateMutation = useCaseUpdate()
+  const kvnrUpdateMutation = useKvnrUpdate()
+
   const [editing, setEditing] = useState(false)
   const [formValues, setFormValues] = useState<FormValues>(() => extractFormValues(caseData))
   const [originalValues, setOriginalValues] = useState<FormValues>(() => extractFormValues(caseData))
@@ -101,10 +103,11 @@ export function useInlineEdit(
       // Split: KVNR goes to its own endpoint (accessible by all users)
       if ('kvnr' in dirty) {
         const kvnrVal = dirty.kvnr as string | null
-        const res = await api.put<Case>(`/cases/${caseData.id}/kvnr`, {
+        const kvnrResult = await kvnrUpdateMutation.mutateAsync({
+          id: caseData.id,
           kvnr: kvnrVal?.trim() || null,
         })
-        lastResult = res.data
+        lastResult = kvnrResult
         delete dirty.kvnr
       }
 
@@ -119,12 +122,14 @@ export function useInlineEdit(
             payload[key] = value
           }
         }
-        const res = await api.put<Case>(`/cases/${caseData.id}`, payload)
-        lastResult = res.data
+        const updateResult = await caseUpdateMutation.mutateAsync({
+          id: caseData.id,
+          data: payload,
+        })
+        lastResult = updateResult
       }
 
       if (lastResult) {
-        onSaved(lastResult)
         setSuccess(true)
         setEditing(false)
       }
@@ -138,7 +143,7 @@ export function useInlineEdit(
     } finally {
       setSaving(false)
     }
-  }, [caseData.id, formValues, originalValues, onSaved])
+  }, [caseData.id, formValues, originalValues, caseUpdateMutation, kvnrUpdateMutation])
 
   const canEditField = useCallback(
     (field: FieldConfig, isAdmin: boolean): boolean => {