fix: harden upload resilience and contracts

lib/upload-request.ts

@@ -1,4 +1,5 @@
-import { isRecord } from './guards'
+import { NextResponse } from 'next/server'
+import { getErrorMessage, isRecord } from './guards'
 import type { DriveAction } from './types'
 
 interface StagingRequestBody {
@@ -9,6 +10,21 @@ interface DriveRequestBody extends StagingRequestBody {
   action: DriveAction
 }
 
+const UPLOAD_LOCK_ERROR = 'Un upload est deja en cours pour ce dossier. Patientez quelques secondes.'
+
+export function uploadErrorResponse(error: unknown, status: number, fallback?: string) {
+  const message = getErrorMessage(error, fallback)
+  return NextResponse.json({ success: false, error: message }, { status })
+}
+
+export function uploadErrorMessageResponse(message: string, status: number) {
+  return NextResponse.json({ success: false, error: message }, { status })
+}
+
+export function uploadLockConflictResponse() {
+  return uploadErrorMessageResponse(UPLOAD_LOCK_ERROR, 409)
+}
+
 export function parseStagingRequestBody(value: unknown): StagingRequestBody {
   if (!isRecord(value) || typeof value.stagingId !== 'string' || value.stagingId.trim() === '') {
     throw new Error('stagingId manquant')
@@ -17,9 +33,22 @@ export function parseStagingRequestBody(value: unknown): StagingRequestBody {
   return { stagingId: value.stagingId }
 }
 
+export async function readStagingRequestBody(req: Request): Promise<StagingRequestBody> {
+  const body: unknown = await req.json()
+  return parseStagingRequestBody(body)
+}
+
 export function parseDriveRequestBody(value: unknown): DriveRequestBody {
   const { stagingId } = parseStagingRequestBody(value)
-  const action = isRecord(value) && value.action === 'replace' ? 'replace' : 'new'
 
-  return { stagingId, action }
+  if (!isRecord(value) || (value.action !== 'new' && value.action !== 'replace')) {
+    throw new Error('Action Drive invalide')
+  }
+
+  return { stagingId, action: value.action }
+}
+
+export async function readDriveRequestBody(req: Request): Promise<DriveRequestBody> {
+  const body: unknown = await req.json()
+  return parseDriveRequestBody(body)
 }