feat: add AI grading test endpoint and update connection logic

backend/src/routes/admin.ts

@@ -1,4 +1,5 @@
 import { Router } from 'express'
+import { z } from 'zod'
 import { validateBody, validateQuery, validateParams } from '../middleware/validate.js'
 import { asyncHandler } from '../utils/asyncHandler.js'
 import { requireAuth, requireAdmin } from '../middleware/auth.js'
@@ -7,6 +8,7 @@ import * as userRepo from '../repositories/userRepo.js'
 import * as resultRepo from '../repositories/resultRepo.js'
 import * as settingsRepo from '../repositories/settingsRepo.js'
 import { updateUserRoleSchema, updateSettingSchema, updateSettingsBatchSchema, listUsersQuerySchema, userIdParamSchema } from '../validators/adminSchemas.js'
+import { gradeQuestionWithAI } from '../services/aiGrading.js'
 import type { Request } from 'express'
 
 const router = Router()
@@ -140,4 +142,28 @@ router.put(
   })
 )
 
+// POST /api/admin/test-ai
+router.post(
+  '/test-ai',
+  validateBody(z.object({
+    provider: z.string().min(1),
+    apiKey: z.string().min(1),
+    model: z.string().min(1),
+    baseURL: z.string().optional(),
+  })),
+  asyncHandler(async (req: Request, res) => {
+    const { provider, apiKey, model, baseURL } = req.body
+    const result = await gradeQuestionWithAI(
+      {
+        type: 'short-answer',
+        question: { prompt: 'What is 2+2?', answer: '4' },
+        answer: '4',
+        language: 'en',
+      },
+      { provider, apiKey, model, baseURL },
+    )
+    res.json(result)
+  }),
+)
+
 export default router

backend/src/services/aiGrading.ts

@@ -14,12 +14,12 @@ interface GradeRequest {
   language: string
 }
 
-function getClient(): OpenAI | null {
-  const provider = getSetting('ai_provider')
-  const apiKey = getSetting('ai_api_key')
+function getClient(override?: { provider?: string; apiKey?: string; baseURL?: string }): OpenAI | null {
+  const provider = override?.provider ?? getSetting('ai_provider')
+  const apiKey = override?.apiKey ?? getSetting('ai_api_key')
   if (!provider || !apiKey) return null
 
-  const customBase = getSetting('ai_base_url')
+  const customBase = override?.baseURL ?? getSetting('ai_base_url')
   const baseURL = provider === 'openai' ? undefined : (customBase || undefined)
   return new OpenAI({ apiKey, baseURL })
 }
@@ -141,13 +141,16 @@ Use the human-readable text labels in the arrays.`
   }
 }
 
-export async function gradeQuestionWithAI(req: GradeRequest): Promise<GradingResult> {
-  const client = getClient()
+export async function gradeQuestionWithAI(
+  req: GradeRequest,
+  override?: { provider?: string; apiKey?: string; baseURL?: string; model?: string },
+): Promise<GradingResult> {
+  const client = getClient(override)
   if (!client) {
     throw new Error('AI grading is not configured. Please set provider and API key in admin settings.')
   }
 
-  const model = getSetting('ai_model') || 'gpt-4o-mini'
+  const model = (override?.model ?? getSetting('ai_model')) || 'gpt-4o-mini'
   const prompt = buildPrompt(req)
 
   const completion = await client.chat.completions.create({

frontend/src/api/adminApi.ts

@@ -96,14 +96,16 @@ export function sendTestEmail(to: string | undefined, smtp: SmtpConfig): Promise
   })
 }
 
-export function testAiConnection(): Promise<GradingResult> {
-  return apiFetch('/api/grade', {
+export interface AiTestPayload {
+  provider: string
+  apiKey: string
+  model: string
+  baseURL?: string
+}
+
+export function testAiConnection(payload: AiTestPayload): Promise<GradingResult> {
+  return apiFetch('/api/admin/test-ai', {
     method: 'POST',
-    body: JSON.stringify({
-      type: 'short-answer',
-      question: { prompt: 'What is 2+2?', answer: '4' },
-      answer: '4',
-      language: 'en',
-    }),
+    body: JSON.stringify(payload),
   })
 }

frontend/src/components/AdminDashboard.tsx

@@ -135,7 +135,12 @@ export default function AdminDashboard({ onExit }: Readonly<Props>) {
     setTestAiSending(true);
     setTestAiMsg(null);
     try {
-      await adminApi.testAiConnection();
+      await adminApi.testAiConnection({
+        provider: settingsDraft.ai_provider,
+        apiKey: settingsDraft.ai_api_key,
+        model: settingsDraft.ai_model || 'gpt-4o-mini',
+        baseURL: settingsDraft.ai_base_url || undefined,
+      });
       setTestAiMsg({ ok: true, text: t("admin.aiGrading.testSuccess") });
     } catch (e) {
       setTestAiMsg({ ok: false, text: (e as Error).message });