feat: exam actions and data safety fixes

src/app/(dashboard)/teacher/exams/[id]/build/page.tsx

@@ -16,38 +16,93 @@ export default async function BuildExamPage({ params }: { params: Promise<{ id:
   // In a real app, this might be paginated or filtered by exam subject/grade
   const { data: questionsData } = await getQuestions({ pageSize: 100 })
   
-  const questionOptions: Question[] = questionsData.map((q) => ({
-    id: q.id,
-    content: q.content as any,
-    type: q.type as any,
-    difficulty: q.difficulty ?? 1,
-    createdAt: new Date(q.createdAt),
-    updatedAt: new Date(q.updatedAt),
-    author: q.author ? {
-      id: q.author.id,
-      name: q.author.name || "Unknown",
-      image: q.author.image || null
-    } : null,
-    knowledgePoints: (q.questionsToKnowledgePoints || []).map((kp) => ({
-      id: kp.knowledgePoint.id,
-      name: kp.knowledgePoint.name
-    }))
-  }))
-
   const initialSelected = (exam.questions || []).map(q => ({
     id: q.id,
     score: q.score || 0
   }))
 
-  // Prepare initialStructure on server side to avoid hydration mismatch with random IDs
-  let initialStructure: ExamNode[] = exam.structure as ExamNode[] || []
+  const selectedQuestionIds = initialSelected.map((s) => s.id)
+  const { data: selectedQuestionsData } = selectedQuestionIds.length
+    ? await getQuestions({ ids: selectedQuestionIds, pageSize: Math.max(10, selectedQuestionIds.length) })
+    : { data: [] as typeof questionsData }
+
+  type RawQuestion = (typeof questionsData)[number]
+
+  const toQuestionOption = (q: RawQuestion): Question => ({
+    id: q.id,
+    content: q.content as Question["content"],
+    type: q.type as Question["type"],
+    difficulty: q.difficulty ?? 1,
+    createdAt: new Date(q.createdAt),
+    updatedAt: new Date(q.updatedAt),
+    author: q.author
+      ? {
+          id: q.author.id,
+          name: q.author.name || "Unknown",
+          image: q.author.image || null,
+        }
+      : null,
+    knowledgePoints:
+      q.questionsToKnowledgePoints?.map((kp) => ({
+        id: kp.knowledgePoint.id,
+        name: kp.knowledgePoint.name,
+      })) ?? [],
+  })
+
+  const questionOptionsById = new Map<string, Question>()
+  for (const q of questionsData) questionOptionsById.set(q.id, toQuestionOption(q))
+  for (const q of selectedQuestionsData) questionOptionsById.set(q.id, toQuestionOption(q))
+  const questionOptions = Array.from(questionOptionsById.values())
+
+  const normalizeStructure = (nodes: unknown): ExamNode[] => {
+    const seen = new Set<string>()
+    const isRecord = (v: unknown): v is Record<string, unknown> =>
+      typeof v === "object" && v !== null
+
+    const normalize = (raw: unknown[]): ExamNode[] => {
+      return raw
+        .map((n) => {
+          if (!isRecord(n)) return null
+          const type = n.type
+          if (type !== "group" && type !== "question") return null
+
+          let id = typeof n.id === "string" && n.id.length > 0 ? n.id : createId()
+          while (seen.has(id)) id = createId()
+          seen.add(id)
+
+          if (type === "group") {
+            return {
+              id,
+              type: "group",
+              title: typeof n.title === "string" ? n.title : undefined,
+              children: normalize(Array.isArray(n.children) ? n.children : []),
+            } satisfies ExamNode
+          }
+
+          if (typeof n.questionId !== "string" || n.questionId.length === 0) return null
+
+          return {
+            id,
+            type: "question",
+            questionId: n.questionId,
+            score: typeof n.score === "number" ? n.score : undefined,
+          } satisfies ExamNode
+        })
+        .filter(Boolean) as ExamNode[]
+    }
+
+    if (!Array.isArray(nodes)) return []
+    return normalize(nodes)
+  }
+
+  let initialStructure: ExamNode[] = normalizeStructure(exam.structure)
   
   if (initialStructure.length === 0 && initialSelected.length > 0) {
-    initialStructure = initialSelected.map(s => ({
-      id: createId(), // Generate stable ID on server
-      type: 'question',
+    initialStructure = initialSelected.map((s) => ({
+      id: createId(),
+      type: "question",
       questionId: s.id,
-      score: s.score
+      score: s.score,
     }))
   }