From c7fd8328d6e8f0aee65b5fb7014efc0413a48228 Mon Sep 17 00:00:00 2001
From: Matthieu <mtholot19@gmail.com>
Date: Wed, 4 Mar 2026 09:48:51 +0100
Subject: [PATCH] fix(errors) : humanize backend error messages for end users
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Add centralized error translation layer (humanizeError) that converts
raw Symfony/Doctrine/API Platform messages into user-friendly French.
Fix useApi to extract errors from all backend response formats
(violations, error, message, hydra:description, detail).
Add toast deduplication to prevent double display. Replace error toast
icon (X → CircleX) to distinguish from the dismiss button.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 app/components/ToastContainer.vue             |   3 +-
 app/components/model-types/ManagementView.vue |  25 ++-
 app/composables/useApi.ts                     |  14 +-
 app/composables/useEntityTypes.ts             |  20 ++-
 app/composables/useMachineCreatePage.ts       |   5 +-
 app/composables/useProducts.ts                |  17 +-
 app/composables/useSiteManagement.ts          |   5 +-
 app/composables/useToast.ts                   |  11 ++
 app/pages/component/create.vue                |   3 +-
 app/pages/index.vue                           |   5 +-
 app/pages/machine-skeleton/index.vue          |   5 +-
 app/pages/machines/index.vue                  |   5 +-
 app/pages/pieces/create.vue                   |   3 +-
 app/pages/product/[id]/edit.vue               |   3 +-
 app/shared/utils/errorMessages.ts             | 152 ++++++++++++++++++
 15 files changed, 227 insertions(+), 49 deletions(-)
 create mode 100644 app/shared/utils/errorMessages.ts

diff --git a/app/components/ToastContainer.vue b/app/components/ToastContainer.vue
index c66635c..cfa6837 100644
--- a/app/components/ToastContainer.vue
+++ b/app/components/ToastContainer.vue
@@ -24,7 +24,7 @@
                 class="w-4 h-4"
                 aria-hidden="true"
               />
-              <IconLucideX
+              <IconLucideCircleX
                 v-else-if="toast.type === 'error'"
                 class="w-4 h-4"
                 aria-hidden="true"
@@ -64,6 +64,7 @@
 import { useToast } from '~/composables/useToast'
 import IconLucideCheck from '~icons/lucide/check'
 import IconLucideX from '~icons/lucide/x'
+import IconLucideCircleX from '~icons/lucide/circle-x'
 import IconLucideAlertTriangle from '~icons/lucide/alert-triangle'
 import IconLucideInfo from '~icons/lucide/info'
 
diff --git a/app/components/model-types/ManagementView.vue b/app/components/model-types/ManagementView.vue
index 65788a7..f87f4e3 100644
--- a/app/components/model-types/ManagementView.vue
+++ b/app/components/model-types/ManagementView.vue
@@ -119,6 +119,7 @@ import {
   type ModelTypeListResponse,
 } from "~/services/modelTypes";
 import { useToast } from "~/composables/useToast";
+import { humanizeError } from "~/shared/utils/errorMessages";
 import { invalidateEntityTypeCache } from "~/composables/useEntityTypes";
 
 const DEFAULT_DESCRIPTION =
@@ -183,7 +184,8 @@ useHead(() => ({
   title: headingText.value,
 }));
 
-const extractErrorMessage = (error: unknown) => {
+const extractErrorMessage = (error: unknown): string => {
+  let raw: string | null = null;
   if (error && typeof error === "object") {
     const maybeFetchError = error as {
       data?: Record<string, unknown>;
@@ -192,21 +194,16 @@ const extractErrorMessage = (error: unknown) => {
     };
     if (maybeFetchError.data) {
       const data = maybeFetchError.data;
-      if (typeof data.message === "string") {
-        return data.message;
-      }
-      if (Array.isArray(data.message) && data.message.length > 0) {
-        return data.message[0];
-      }
-    }
-    if (typeof maybeFetchError.statusMessage === "string") {
-      return maybeFetchError.statusMessage;
-    }
-    if (typeof maybeFetchError.message === "string") {
-      return maybeFetchError.message;
+      if (typeof data['hydra:description'] === "string") raw = data['hydra:description'];
+      else if (typeof data.detail === "string") raw = data.detail;
+      else if (typeof data.message === "string") raw = data.message;
+      else if (Array.isArray(data.message) && data.message.length > 0) raw = data.message[0];
+      else if (typeof data.error === "string") raw = data.error;
     }
+    if (!raw && typeof maybeFetchError.statusMessage === "string") raw = maybeFetchError.statusMessage;
+    if (!raw && typeof maybeFetchError.message === "string") raw = maybeFetchError.message;
   }
-  return "Une erreur est survenue lors de la communication avec le serveur.";
+  return humanizeError(raw);
 };
 
 const refresh = async ({
diff --git a/app/composables/useApi.ts b/app/composables/useApi.ts
index 936e9f5..cecb7b3 100644
--- a/app/composables/useApi.ts
+++ b/app/composables/useApi.ts
@@ -1,4 +1,5 @@
 import { useToast } from './useToast'
+import { humanizeError, extractApiErrorMessage } from '~/shared/utils/errorMessages'
 
 export interface ApiResponse<T = any> {
   success: boolean
@@ -59,23 +60,26 @@ export function useApi() {
       } else {
         const contentType = response.headers.get('content-type') || ''
         let errorData: Record<string, unknown> = {}
-        if (contentType.includes('application/json')) {
+        if (contentType.includes('json')) {
           errorData = await response.json().catch(() => ({}))
         } else {
           const text = await response.text().catch(() => '')
           errorData = text ? { message: text } : {}
         }
-        const errorMessage = response.status === 403
+        const rawMessage = response.status === 403
           ? 'Permissions insuffisantes pour cette action.'
-          : (errorData.message as string) || `Erreur ${response.status}: ${response.statusText}`
+          : extractApiErrorMessage(errorData) || `Erreur ${response.status}: ${response.statusText}`
+        const errorMessage = humanizeError(rawMessage)
         showError(errorMessage)
         return { success: false, error: errorMessage, status: response.status }
       }
     } catch (error) {
       clearTimeout(timeoutId)
       const err = error as Error & { name?: string }
-      const errorMessage = err.name === 'AbortError' ? 'Timeout de la requête' : err.message || 'Erreur réseau'
-      showError(`Erreur réseau: ${errorMessage}`)
+      const errorMessage = err.name === 'AbortError'
+        ? 'La requête a pris trop de temps. Veuillez réessayer.'
+        : 'Impossible de contacter le serveur. Vérifiez votre connexion.'
+      showError(errorMessage)
       return { success: false, error: errorMessage }
     }
   }
diff --git a/app/composables/useEntityTypes.ts b/app/composables/useEntityTypes.ts
index b4d4e0b..54e447b 100644
--- a/app/composables/useEntityTypes.ts
+++ b/app/composables/useEntityTypes.ts
@@ -7,6 +7,7 @@
 
 import { ref, type Ref } from 'vue'
 import { useToast } from './useToast'
+import { humanizeError } from '~/shared/utils/errorMessages'
 import {
   listModelTypes,
   createModelType,
@@ -102,8 +103,8 @@ export function useEntityTypes(config: EntityTypeConfig) {
       return { success: true, data: state.types.value }
     } catch (error) {
       const err = error as Error & { message?: string }
-      const message = err?.message || 'Erreur inconnue'
-      showError(`Impossible de charger les types de ${label}: ${message}`)
+      const message = humanizeError(err?.message)
+      showError(`Impossible de charger les types de ${label}.`)
       return { success: false, error: message }
     } finally {
       state.loading.value = false
@@ -127,8 +128,9 @@ export function useEntityTypes(config: EntityTypeConfig) {
       return { success: true, data: normalized }
     } catch (error) {
       const err = error as Error & { data?: { message?: string }; message?: string }
-      const message = err?.data?.message || err?.message || 'Erreur inconnue'
-      showError(`Erreur lors de la création du type de ${label}: ${message}`)
+      const raw = err?.data?.message || err?.message
+      const message = humanizeError(raw)
+      showError(`Impossible de créer le type de ${label} : ${message}`)
       return { success: false, error: message }
     } finally {
       state.loading.value = false
@@ -152,8 +154,9 @@ export function useEntityTypes(config: EntityTypeConfig) {
       return { success: true, data: normalized }
     } catch (error) {
       const err = error as Error & { data?: { message?: string }; message?: string }
-      const message = err?.data?.message || err?.message || 'Erreur inconnue'
-      showError(`Erreur lors de la mise à jour du type de ${label}: ${message}`)
+      const raw = err?.data?.message || err?.message
+      const message = humanizeError(raw)
+      showError(`Impossible de mettre à jour le type de ${label} : ${message}`)
       return { success: false, error: message }
     } finally {
       state.loading.value = false
@@ -169,8 +172,9 @@ export function useEntityTypes(config: EntityTypeConfig) {
       return { success: true }
     } catch (error) {
       const err = error as Error & { data?: { message?: string }; message?: string }
-      const message = err?.data?.message || err?.message || 'Erreur inconnue'
-      showError(`Erreur lors de la suppression du type de ${label}: ${message}`)
+      const raw = err?.data?.message || err?.message
+      const message = humanizeError(raw)
+      showError(`Impossible de supprimer le type de ${label} : ${message}`)
       return { success: false, error: message }
     } finally {
       state.loading.value = false
diff --git a/app/composables/useMachineCreatePage.ts b/app/composables/useMachineCreatePage.ts
index 89af5af..6db7a74 100644
--- a/app/composables/useMachineCreatePage.ts
+++ b/app/composables/useMachineCreatePage.ts
@@ -15,6 +15,7 @@ import { usePieces } from '~/composables/usePieces'
 import { useProducts } from '~/composables/useProducts'
 import { useApi } from '~/composables/useApi'
 import { useToast } from '~/composables/useToast'
+import { humanizeError } from '~/shared/utils/errorMessages'
 import { useMachineCreateSelections } from '~/composables/useMachineCreateSelections'
 import {
   useMachineCreatePreview,
@@ -365,10 +366,10 @@ export function useMachineCreatePage() {
         clearRequirementSelections()
         await navigateTo('/machines')
       } else if (result.error) {
-        toast.showError(`Impossible de créer la machine: ${result.error}`)
+        toast.showError(`Impossible de créer la machine : ${humanizeError(result.error)}`)
       }
     } catch (error: any) {
-      toast.showError(`Erreur lors de la création: ${error.message}`)
+      toast.showError(`Impossible de créer la machine : ${humanizeError(error.message)}`)
     } finally {
       submitting.value = false
     }
diff --git a/app/composables/useProducts.ts b/app/composables/useProducts.ts
index 8ccd937..f295c94 100644
--- a/app/composables/useProducts.ts
+++ b/app/composables/useProducts.ts
@@ -1,6 +1,7 @@
 import { ref } from 'vue'
 import { useToast } from './useToast'
 import { useApi } from './useApi'
+import { humanizeError } from '~/shared/utils/errorMessages'
 import { buildConstructeurRequestPayload, uniqueConstructeurIds } from '~/shared/constructeurUtils'
 import { useConstructeurs, type Constructeur } from './useConstructeurs'
 import { extractRelationId, normalizeRelationIds } from '~/shared/apiRelations'
@@ -168,9 +169,9 @@ export function useProducts() {
       return result as ProductListResult
     } catch (err) {
       console.error('Erreur lors du chargement des produits:', err)
-      const message = (err as Error)?.message ?? 'Erreur inconnue'
+      const message = humanizeError((err as Error)?.message)
       error.value = message
-      showError(`Impossible de charger les produits: ${message}`)
+      showError(`Impossible de charger les produits.`)
       return { success: false, error: message }
     } finally {
       loading.value = false
@@ -197,9 +198,9 @@ export function useProducts() {
       return { success: false, error: result.error }
     } catch (err) {
       console.error('Erreur lors de la création du produit:', err)
-      const message = (err as Error)?.message ?? 'Erreur inconnue'
+      const message = humanizeError((err as Error)?.message)
       error.value = message
-      showError(message)
+      showError('Impossible de créer le produit.')
       return { success: false, error: message }
     } finally {
       loading.value = false
@@ -223,9 +224,9 @@ export function useProducts() {
       return { success: false, error: result.error }
     } catch (err) {
       console.error('Erreur lors de la mise à jour du produit:', err)
-      const message = (err as Error)?.message ?? 'Erreur inconnue'
+      const message = humanizeError((err as Error)?.message)
       error.value = message
-      showError(message)
+      showError('Impossible de mettre à jour le produit.')
       return { success: false, error: message }
     } finally {
       loading.value = false
@@ -248,9 +249,9 @@ export function useProducts() {
       return { success: false, error: result.error }
     } catch (err) {
       console.error('Erreur lors de la suppression du produit:', err)
-      const message = (err as Error)?.message ?? 'Erreur inconnue'
+      const message = humanizeError((err as Error)?.message)
       error.value = message
-      showError(message)
+      showError('Impossible de supprimer le produit.')
       return { success: false, error: message }
     } finally {
       loading.value = false
diff --git a/app/composables/useSiteManagement.ts b/app/composables/useSiteManagement.ts
index 54600ec..80f0f80 100644
--- a/app/composables/useSiteManagement.ts
+++ b/app/composables/useSiteManagement.ts
@@ -2,6 +2,7 @@ import { computed, onMounted, reactive, ref, watch } from 'vue'
 import { navigateTo, useRoute } from '#imports'
 import { useSites } from '~/composables/useSites'
 import { useToast } from '~/composables/useToast'
+import { humanizeError } from '~/shared/utils/errorMessages'
 import { useDocuments } from '~/composables/useDocuments'
 import { useConfirm } from '~/composables/useConfirm'
 import { getFileIcon } from '~/utils/fileIcons'
@@ -274,10 +275,10 @@ export function useSiteManagement() {
       if (result.success) {
         showSuccess(`Site "${site.name}" supprimé avec succès`)
       } else {
-        showError(`Erreur lors de la suppression: ${result.error}`)
+        showError(`Impossible de supprimer le site : ${humanizeError(result.error)}`)
       }
     } catch (error: any) {
-      showError(`Erreur lors de la suppression: ${error.message}`)
+      showError(`Impossible de supprimer le site : ${humanizeError(error.message)}`)
     }
   }
 
diff --git a/app/composables/useToast.ts b/app/composables/useToast.ts
index a27dcc5..0ff05a4 100644
--- a/app/composables/useToast.ts
+++ b/app/composables/useToast.ts
@@ -13,8 +13,19 @@ const toasts = ref<Toast[]>([])
 const MAX_TOASTS = 3
 let nextId = 1
 
+// Anti-doublon : ignore un toast identique affiché dans les 2 dernières secondes
+const recentMessages = new Map<string, number>()
+const DEDUP_WINDOW = 2000
+
 export function useToast() {
   const showToast = (message: string, type: ToastType = 'info', duration = 3500): number => {
+    const dedupKey = `${type}::${message}`
+    const lastShown = recentMessages.get(dedupKey)
+    if (lastShown && Date.now() - lastShown < DEDUP_WINDOW) {
+      return -1
+    }
+    recentMessages.set(dedupKey, Date.now())
+
     const id = nextId++
     const toast: Toast = {
       id,
diff --git a/app/pages/component/create.vue b/app/pages/component/create.vue
index 128ed6e..18a511b 100644
--- a/app/pages/component/create.vue
+++ b/app/pages/component/create.vue
@@ -370,6 +370,7 @@ import { useProducts } from '~/composables/useProducts'
 import { useProductTypes } from '~/composables/useProductTypes'
 import { useApi } from '~/composables/useApi'
 import { useToast } from '~/composables/useToast'
+import { humanizeError } from '~/shared/utils/errorMessages'
 import { useCustomFields } from '~/composables/useCustomFields'
 import { useDocuments } from '~/composables/useDocuments'
 import { formatStructurePreview, normalizeStructureForEditor } from '~/shared/modelUtils'
@@ -998,7 +999,7 @@ const submitCreation = async () => {
       toast.showError(result.error)
     }
   } catch (error: any) {
-    toast.showError(error?.message || 'Erreur lors de la création du composant')
+    toast.showError(humanizeError(error?.message) || 'Impossible de créer le composant')
   } finally {
     submitting.value = false
     uploadingDocuments.value = false
diff --git a/app/pages/index.vue b/app/pages/index.vue
index ba3b4bf..c390610 100644
--- a/app/pages/index.vue
+++ b/app/pages/index.vue
@@ -472,6 +472,7 @@ import { useSites } from '~/composables/useSites'
 import { useMachineTypesApi } from '~/composables/useMachineTypesApi'
 import { useMachines } from '~/composables/useMachines'
 import { useToast } from '~/composables/useToast'
+import { humanizeError } from '~/shared/utils/errorMessages'
 import IconLucideFactory from '~icons/lucide/factory'
 import IconLucideMapPin from '~icons/lucide/map-pin'
 import IconLucideUser from '~icons/lucide/user'
@@ -731,10 +732,10 @@ const confirmDeleteMachine = async (machine) => {
         showSuccess(`Machine "${machine.name}" supprimée avec succès`)
         await loadMachines()
       } else {
-        showError(`Erreur lors de la suppression: ${result.error}`)
+        showError(`Impossible de supprimer la machine : ${result.error}`)
       }
     } catch (error) {
-      showError(`Erreur lors de la suppression: ${error.message}`)
+      showError(`Impossible de supprimer la machine : ${humanizeError(error.message)}`)
     }
   }
 }
diff --git a/app/pages/machine-skeleton/index.vue b/app/pages/machine-skeleton/index.vue
index 7db315a..02ae0b9 100644
--- a/app/pages/machine-skeleton/index.vue
+++ b/app/pages/machine-skeleton/index.vue
@@ -104,6 +104,7 @@
 import { ref, computed, onMounted } from "vue";
 import { useMachineTypesApi } from "~/composables/useMachineTypesApi";
 import { useToast } from "~/composables/useToast";
+import { humanizeError } from "~/shared/utils/errorMessages";
 import IconLucidePlus from "~icons/lucide/plus";
 import IconLucidePackage from "~icons/lucide/package";
 import IconLucideLayoutGrid from "~icons/lucide/layout-grid";
@@ -148,10 +149,10 @@ const confirmDeleteType = async (type) => {
       if (result.success) {
         showSuccess(`Type "${type.name}" supprimé avec succès`);
       } else {
-        showError(`Erreur lors de la suppression: ${result.error}`);
+        showError(`Impossible de supprimer le type : ${result.error}`);
       }
     } catch (error) {
-      showError(`Erreur lors de la suppression: ${error.message}`);
+      showError(`Impossible de supprimer le type : ${humanizeError(error.message)}`);
     }
   }
 };
diff --git a/app/pages/machines/index.vue b/app/pages/machines/index.vue
index 7607d13..5402d28 100644
--- a/app/pages/machines/index.vue
+++ b/app/pages/machines/index.vue
@@ -138,6 +138,7 @@ import { useMachines } from '~/composables/useMachines'
 import { useSites } from '~/composables/useSites'
 import { useMachineTypesApi } from '~/composables/useMachineTypesApi'
 import { useToast } from '~/composables/useToast'
+import { humanizeError } from '~/shared/utils/errorMessages'
 import IconLucidePlus from '~icons/lucide/plus'
 import IconLucideFactory from '~icons/lucide/factory'
 import IconLucideMapPin from '~icons/lucide/map-pin'
@@ -214,10 +215,10 @@ const confirmDeleteMachine = async (machine) => {
       if (result.success) {
         showSuccess(`Machine "${machine.name}" supprimée avec succès`)
       } else {
-        showError(`Erreur lors de la suppression: ${result.error}`)
+        showError(`Impossible de supprimer la machine : ${result.error}`)
       }
     } catch (error) {
-      showError(`Erreur lors de la suppression: ${error.message}`)
+      showError(`Impossible de supprimer la machine : ${humanizeError(error.message)}`)
     }
   }
 }
diff --git a/app/pages/pieces/create.vue b/app/pages/pieces/create.vue
index 5b006da..ef60d6a 100644
--- a/app/pages/pieces/create.vue
+++ b/app/pages/pieces/create.vue
@@ -315,6 +315,7 @@ import SearchSelect from '~/components/common/SearchSelect.vue'
 import { usePieceTypes } from '~/composables/usePieceTypes'
 import { usePieces } from '~/composables/usePieces'
 import { useToast } from '~/composables/useToast'
+import { humanizeError } from '~/shared/utils/errorMessages'
 import { useCustomFields } from '~/composables/useCustomFields'
 import { useDocuments } from '~/composables/useDocuments'
 import { formatPieceStructurePreview } from '~/shared/modelUtils'
@@ -599,7 +600,7 @@ const submitCreation = async () => {
       toast.showError(result.error)
     }
   } catch (error: any) {
-    toast.showError(error?.message || 'Erreur lors de la création de la pièce')
+    toast.showError(humanizeError(error?.message) || 'Impossible de créer la pièce')
   } finally {
     submitting.value = false
     uploadingDocuments.value = false
diff --git a/app/pages/product/[id]/edit.vue b/app/pages/product/[id]/edit.vue
index 92fa521..2446f65 100644
--- a/app/pages/product/[id]/edit.vue
+++ b/app/pages/product/[id]/edit.vue
@@ -407,6 +407,7 @@ import DocumentPreviewModal from '~/components/DocumentPreviewModal.vue'
 import { useProducts } from '~/composables/useProducts'
 import { useCustomFields } from '~/composables/useCustomFields'
 import { useToast } from '~/composables/useToast'
+import { humanizeError } from '~/shared/utils/errorMessages'
 import { useDocuments } from '~/composables/useDocuments'
 import { useConstructeurs } from '~/composables/useConstructeurs'
 import { useProductHistory, type ProductHistoryEntry } from '~/composables/useProductHistory'
@@ -700,7 +701,7 @@ const submitEdition = async () => {
       await router.push('/product-catalog')
     }
   } catch (error: any) {
-    toast.showError(error?.message || 'Erreur lors de la mise à jour du produit')
+    toast.showError(humanizeError(error?.message) || 'Impossible de mettre à jour le produit')
   } finally {
     saving.value = false
   }
diff --git a/app/shared/utils/errorMessages.ts b/app/shared/utils/errorMessages.ts
new file mode 100644
index 0000000..c9da906
--- /dev/null
+++ b/app/shared/utils/errorMessages.ts
@@ -0,0 +1,152 @@
+/**
+ * Translates raw backend error messages (Symfony, Doctrine, API Platform)
+ * into user-friendly French messages for display in toasts/alerts.
+ */
+
+const EXACT_MATCHES: Record<string, string> = {
+  // UniqueConstraintSubscriber (HTTP 409)
+  'nom duplique': 'Un élément avec ce nom existe déjà.',
+
+  // English backend messages → French
+  'Machine not found.': 'Machine introuvable.',
+  'Composant not found.': 'Composant introuvable.',
+  'Piece not found.': 'Pièce introuvable.',
+  'Product not found.': 'Produit introuvable.',
+  'Site not found.': 'Site introuvable.',
+  'Custom field not found.': 'Champ personnalisé introuvable.',
+  'Custom field value not found.': 'Valeur du champ personnalisé introuvable.',
+  'Document not found.': 'Document introuvable.',
+  'File not found on disk.': 'Le fichier n\'a pas été trouvé sur le serveur.',
+  'Invalid document data.': 'Les données du document sont invalides.',
+  'Invalid JSON payload.': 'Les données envoyées sont invalides.',
+  'Unsupported entity type.': 'Type d\'entité non supporté.',
+  'Entity target is missing.': 'La cible de l\'entité est manquante.',
+  'customFieldId or customFieldName is required.': 'L\'identifiant du champ personnalisé est requis.',
+
+  // Symfony validator messages
+  'This value should not be blank.': 'Ce champ ne peut pas être vide.',
+  'This value is not a valid email address.': 'L\'adresse email n\'est pas valide.',
+  'This value is already used.': 'Cette valeur est déjà utilisée.',
+  'This field is missing.': 'Un champ obligatoire est manquant.',
+
+  // HTTP status texts (used in "Erreur XXX: StatusText" fallback)
+  'Internal Server Error': 'Erreur interne du serveur. Veuillez réessayer.',
+  'Bad Request': 'Requête invalide.',
+  'Not Found': 'Ressource introuvable.',
+  'Conflict': 'Un élément similaire existe déjà.',
+  'Unprocessable Entity': 'Données invalides.',
+  'Unprocessable Content': 'Données invalides.',
+  'Service Unavailable': 'Service temporairement indisponible. Veuillez réessayer.',
+  'Gateway Timeout': 'Le serveur met trop de temps à répondre. Veuillez réessayer.',
+}
+
+const TECHNICAL_PATTERNS: Array<[RegExp, string]> = [
+  // Database / Doctrine errors
+  [/SQLSTATE\[/i, 'Une erreur est survenue. Veuillez réessayer.'],
+  [/An exception occurred/i, 'Une erreur est survenue. Veuillez réessayer.'],
+  [/Duplicate entry/i, 'Un élément avec ces données existe déjà.'],
+  [/unique.*constraint.*violation/i, 'Un élément avec ces données existe déjà.'],
+  [/foreign key constraint/i, 'Impossible de supprimer cet élément car il est utilisé ailleurs.'],
+  [/violates not-null constraint/i, 'Un champ obligatoire n\'a pas été renseigné.'],
+  [/violates check constraint/i, 'Une valeur saisie est invalide.'],
+
+  // Symfony / API Platform internal messages
+  [/Expected argument of type/i, 'Les données envoyées sont invalides.'],
+  [/Could not denormalize/i, 'Les données envoyées sont invalides.'],
+  [/The JSON value could not be decoded/i, 'Les données envoyées sont invalides.'],
+  [/Syntax error.*JSON/i, 'Les données envoyées sont invalides.'],
+  [/No route found/i, 'Ressource introuvable.'],
+  [/Access Denied/i, 'Permissions insuffisantes pour cette action.'],
+]
+
+/**
+ * Detects if a message contains technical jargon that should not be shown to users.
+ */
+function containsTechnicalJargon(message: string): boolean {
+  const patterns = [
+    /stack trace/i,
+    /exception/i,
+    /\bat\s+[\w\\]+::/,
+    /vendor\//,
+    /\.php/,
+    /doctrine/i,
+    /symfony/i,
+    /SQLSTATE/i,
+    /PDOException/i,
+    /DBALException/i,
+    /RuntimeException/i,
+    /TypeError/i,
+    /LogicException/i,
+    /InvalidArgumentException/i,
+    /UnexpectedValueException/i,
+    /constraint.*violation/i,
+    /entity.*manager/i,
+    /Hydra error/i,
+  ]
+  return patterns.some((p) => p.test(message))
+}
+
+/**
+ * Translates a raw backend error message into a user-friendly French message.
+ *
+ * Usage:
+ *   import { humanizeError } from '~/shared/utils/errorMessages'
+ *   showError(humanizeError(rawMessage))
+ */
+export function humanizeError(rawMessage: string | undefined | null): string {
+  if (!rawMessage) return 'Une erreur est survenue.'
+
+  const trimmed = rawMessage.trim()
+  if (!trimmed) return 'Une erreur est survenue.'
+
+  // 1. Exact match
+  if (EXACT_MATCHES[trimmed]) return EXACT_MATCHES[trimmed]
+
+  // 2. "Erreur XXX: StatusText" pattern — translate the status text
+  const httpMatch = trimmed.match(/^Erreur (\d{3})\s*:\s*(.+)$/)
+  if (httpMatch) {
+    const statusText = httpMatch[2]!.trim()
+    if (EXACT_MATCHES[statusText]) return EXACT_MATCHES[statusText]
+    return `Erreur serveur (${httpMatch[1]}). Veuillez réessayer.`
+  }
+
+  // 3. Regex patterns for technical errors
+  for (const [pattern, replacement] of TECHNICAL_PATTERNS) {
+    if (pattern.test(trimmed)) return replacement
+  }
+
+  // 4. If it contains technical jargon, replace with generic message
+  if (containsTechnicalJargon(trimmed)) {
+    return 'Une erreur est survenue. Veuillez réessayer.'
+  }
+
+  // 5. Already user-friendly — return as-is
+  return trimmed
+}
+
+/**
+ * Extracts the best error message from various backend response formats.
+ * Handles: { message }, { error }, { detail }, { "hydra:description" }
+ */
+export function extractApiErrorMessage(errorData: Record<string, unknown>): string | null {
+  if (!errorData || typeof errorData !== 'object') return null
+
+  // Symfony validator violations — priorité max (message propre sans préfixe champ)
+  if (Array.isArray(errorData.violations) && errorData.violations.length > 0) {
+    const first = errorData.violations[0] as Record<string, unknown>
+    if (typeof first?.message === 'string') return first.message
+  }
+
+  // UniqueConstraintSubscriber format ({ success: false, error: "nom duplique" })
+  if (typeof errorData.error === 'string') return errorData.error
+
+  // Custom controllers format
+  if (typeof errorData.message === 'string') return errorData.message
+  if (Array.isArray(errorData.message) && typeof errorData.message[0] === 'string') return errorData.message[0]
+
+  // API Platform hydra format (fallback — peut contenir "propertyPath: message")
+  if (typeof errorData['hydra:description'] === 'string') return errorData['hydra:description']
+  if (typeof errorData.detail === 'string') return errorData.detail
+
+  return null
+}