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ai-routes.js

@@ -0,0 +1,606 @@
+
+const express = require('express');
+const router = express.Router();
+const OpenAI = require('openai');
+const { User, ConfigModel } = require('./models');
+
+// --- AI Client Initialization ---
+
+let openAIClient = null;
+function getOpenRouter() {
+    if (openAIClient) return openAIClient;
+    if (!process.env.OPENROUTER_API_KEY) return null;
+    
+    openAIClient = new OpenAI({
+        baseURL: "https://openrouter.ai/api/v1",
+        apiKey: process.env.OPENROUTER_API_KEY,
+        defaultHeaders: {
+            "HTTP-Referer": "https://smart-school-ai.com", // Placeholder
+            "X-Title": "Smart School System", 
+        },
+    });
+    return openAIClient;
+}
+
+let genAIContext = null;
+async function getGenAI() {
+    if (genAIContext) return genAIContext;
+    const { GoogleGenAI, Type, Modality } = await import("@google/genai");
+    const ai = new GoogleGenAI({ apiKey: process.env.API_KEY });
+    genAIContext = { ai, Type, Modality };
+    return genAIContext;
+}
+
+// --- Helpers ---
+
+const wait = (ms) => new Promise(resolve => setTimeout(resolve, ms));
+
+async function callAIWithRetry(aiModel, params, retries = 1) {
+    for (let i = 0; i < retries; i++) {
+        try {
+            return await aiModel.generateContent(params);
+        } catch (e) {
+            if (e.status === 400 || e.status === 401 || e.status === 403) throw e;
+            if (i < retries - 1) {
+                await wait(1000 * Math.pow(2, i));
+                continue;
+            }
+            throw e;
+        }
+    }
+}
+
+function convertGeminiToOpenAI(baseParams) {
+    const messages = [];
+    if (baseParams.config?.systemInstruction) {
+        messages.push({ role: 'system', content: baseParams.config.systemInstruction });
+    }
+    if (baseParams.contents && Array.isArray(baseParams.contents)) {
+        baseParams.contents.forEach(content => {
+            let role = 'user';
+            if (content.role === 'model') role = 'assistant';
+            
+            const messageContent = [];
+            if (content.parts && Array.isArray(content.parts)) {
+                content.parts.forEach(p => {
+                    if (p.text) {
+                        messageContent.push({ type: 'text', text: p.text });
+                    } else if (p.inlineData && p.inlineData.mimeType.startsWith('image/')) {
+                        messageContent.push({
+                            type: 'image_url',
+                            image_url: {
+                                url: `data:${p.inlineData.mimeType};base64,${p.inlineData.data}`
+                            }
+                        });
+                    }
+                });
+            }
+            if (messageContent.length > 0) {
+                if (messageContent.length === 1 && messageContent[0].type === 'text') {
+                    messages.push({ role: role, content: messageContent[0].text });
+                } else {
+                    messages.push({ role: role, content: messageContent });
+                }
+            }
+        });
+    }
+    return messages;
+}
+
+// --- Dynamic Provider Management ---
+
+const PROVIDERS = {
+    GEMINI: 'GEMINI',
+    OPENROUTER: 'OPENROUTER',
+    GEMMA: 'GEMMA'
+};
+
+let activeProviderOrder = [PROVIDERS.GEMINI, PROVIDERS.OPENROUTER, PROVIDERS.GEMMA];
+
+function deprioritizeProvider(providerName) {
+    if (activeProviderOrder[activeProviderOrder.length - 1] === providerName) return;
+    console.log(`📉 [AI Debug] Performance Opt: Deprioritizing ${providerName} due to quota limits.`);
+    activeProviderOrder = activeProviderOrder.filter(p => p !== providerName).concat(providerName);
+    console.log(`🔄 [AI Debug] New Provider Order: ${activeProviderOrder.join(' -> ')}`);
+}
+
+function isQuotaError(e) {
+    const msg = e.message || '';
+    return e.status === 429 || e.status === 503 || 
+           msg.includes('Quota') || 
+           msg.includes('overloaded') || 
+           msg.includes('RESOURCE_EXHAUSTED') ||
+           msg.includes('Rate limit') ||
+           msg.includes('credits');
+}
+
+// --- Provider Callers ---
+
+async function callGeminiProvider(aiModelObj, baseParams) {
+    const primaryModels = ['gemini-2.5-flash', 'gemini-2.5-flash-lite'];
+    let lastError = null;
+    for (const modelName of primaryModels) {
+        try {
+            console.log(`🚀 [AI Debug] Calling Gemini non-stream: ${modelName}`);
+            const currentParams = { ...baseParams, model: modelName };
+            return await callAIWithRetry(aiModelObj, currentParams, 1);
+        } catch (e) {
+            lastError = e;
+            console.error(`⚠️ [AI Debug] Gemini ${modelName} Error:`, e.status, e.message);
+            if (isQuotaError(e)) {
+                console.warn(`⚠️ [AI Debug] Gemini ${modelName} exhausted. Trying next internal model...`);
+                continue; 
+            }
+            throw e; 
+        }
+    }
+    throw lastError; 
+}
+
+async function callOpenRouterProvider(baseParams) {
+    const openRouter = getOpenRouter();
+    if (!openRouter) throw new Error("OpenRouter not configured");
+
+    const openRouterModels = [
+        'qwen/qwen3-coder:free',
+        'openai/gpt-oss-120b:free',
+        'qwen/qwen3-235b-a22b:free',
+        'tngtech/deepseek-r1t-chimera:free'
+    ];
+
+    const openAIMessages = convertGeminiToOpenAI(baseParams);
+    let lastError = null;
+
+    for (const modelName of openRouterModels) {
+        try {
+            console.log(`🛡️ [AI Debug] Switching to OpenRouter Model: ${modelName}`);
+            const completion = await openRouter.chat.completions.create({
+                model: modelName,
+                messages: openAIMessages,
+            });
+            if (!completion || !completion.choices || !completion.choices[0]) {
+                throw new Error(`Invalid response structure from ${modelName}`);
+            }
+            const content = completion.choices[0].message.content || "";
+            return { text: content };
+        } catch (e) {
+            lastError = e;
+            console.warn(`⚠️ [AI Debug] OpenRouter Model ${modelName} failed.`, e.message);
+        }
+    }
+    throw lastError || new Error("OpenRouter failed");
+}
+
+async function callGemmaProvider(aiModelObj, baseParams) {
+    const fallbackModels = ['gemma-3-27b-it', 'gemma-3-12b-it', 'gemma-3-4b-it'];
+    const gemmaConfig = { ...baseParams.config };
+    if (gemmaConfig.systemInstruction) delete gemmaConfig.systemInstruction;
+    
+    let lastError = null;
+    for (const modelName of fallbackModels) {
+        try {
+            console.log(`🛡️ [AI Debug] Switching to Final Backup (Gemma 3): ${modelName}`);
+            const currentParams = { 
+                ...baseParams, 
+                model: modelName,
+                config: gemmaConfig 
+            };
+            return await callAIWithRetry(aiModelObj, currentParams, 1);
+        } catch (e) {
+            lastError = e;
+            console.warn(`⚠️ [AI Debug] Backup Model ${modelName} failed.`, e.message);
+        }
+    }
+    throw lastError || new Error("Gemma failed");
+}
+
+// --- Streaming Helpers ---
+
+async function streamGemini(aiModelObj, baseParams, res) {
+    const models = ['gemini-2.5-flash', 'gemini-2.5-flash-lite'];
+    let lastError = null;
+    for (const modelName of models) {
+        try {
+            console.log(`🌊 [AI Debug] STREAMING Gemini model: ${modelName}`);
+            const currentParams = { ...baseParams, model: modelName };
+            const streamResult = await aiModelObj.generateContentStream(currentParams);
+            let fullText = '';
+            for await (const chunk of streamResult) {
+                const text = chunk.text;
+                if (text) {
+                    fullText += text;
+                    res.write(`data: ${JSON.stringify({ text: text })}\n\n`);
+                }
+            }
+            console.log(`✅ [AI Debug] Gemini ${modelName} stream complete.`);
+            return fullText; 
+        } catch (e) {
+            lastError = e;
+            console.error(`❌ [AI Debug] Gemini Stream Error (${modelName}):`, e.status, e.message);
+            if (isQuotaError(e)) {
+                console.warn(`[AI Debug] Stream Gemini ${modelName} quota exhausted. Switching to next internal model...`);
+                continue; 
+            }
+            throw e; 
+        }
+    }
+    throw lastError || new Error("Gemini streaming failed after retrying internal models");
+}
+
+async function streamGemma(aiModelObj, baseParams, res) {
+    const models = ['gemma-3-27b-it', 'gemma-3-12b-it', 'gemma-3-4b-it'];
+    const gemmaConfig = { ...baseParams.config };
+    if (gemmaConfig.systemInstruction) delete gemmaConfig.systemInstruction;
+
+    let lastError = null;
+    for (const modelName of models) {
+        try {
+            console.log(`🛡️ [AI Debug] Streaming Fallback to Gemma: ${modelName}`);
+            const currentParams = { ...baseParams, model: modelName, config: gemmaConfig };
+            const streamResult = await aiModelObj.generateContentStream(currentParams);
+            let fullText = '';
+            for await (const chunk of streamResult) {
+                const text = chunk.text;
+                if (text) {
+                    fullText += text;
+                    res.write(`data: ${JSON.stringify({ text: text })}\n\n`);
+                }
+            }
+            return fullText;
+        } catch (e) {
+            lastError = e;
+            console.warn(`Stream Gemma ${modelName} failed: ${e.message}`);
+        }
+    }
+    throw lastError || new Error("Gemma streaming failed");
+}
+
+async function streamOpenRouter(baseParams, res) {
+    const openRouter = getOpenRouter();
+    if (!openRouter) throw new Error("OpenRouter not configured");
+    
+    const openRouterModels = [
+        'qwen/qwen3-coder:free',
+        'openai/gpt-oss-120b:free', 
+        'qwen/qwen3-235b-a22b:free',
+        'tngtech/deepseek-r1t-chimera:free'
+    ];
+    const messages = convertGeminiToOpenAI(baseParams);
+    
+    let lastError = null;
+    for (const modelName of openRouterModels) {
+        try {
+            console.log(`🛡️ [AI Debug] Streaming via OpenRouter: ${modelName}`);
+            const stream = await openRouter.chat.completions.create({
+                model: modelName,
+                messages: messages,
+                stream: true
+            });
+            let fullText = '';
+            for await (const chunk of stream) {
+                const text = chunk.choices[0]?.delta?.content || '';
+                if (text) {
+                    fullText += text;
+                    res.write(`data: ${JSON.stringify({ text: text })}\n\n`);
+                }
+            }
+            return fullText;
+        } catch (e) {
+            lastError = e;
+            console.warn(`[AI Debug] Stream OpenRouter ${modelName} failed`, e.message);
+        }
+    }
+    throw lastError || new Error("All OpenRouter streams failed");
+}
+
+// --- Main Generation Functions ---
+
+async function generateContentWithSmartFallback(aiModelObj, baseParams) {
+    let hasAudio = false;
+    if (baseParams.contents && Array.isArray(baseParams.contents)) {
+        for (const c of baseParams.contents) {
+            if (c.parts) {
+                for (const p of c.parts) {
+                    if (p.inlineData && p.inlineData.mimeType.startsWith('audio/')) {
+                        hasAudio = true;
+                    }
+                }
+            }
+        }
+    }
+
+    if (hasAudio) {
+        console.log("🎤 [AI Debug] Audio detected, forcing Gemini.");
+        try {
+            return await callGeminiProvider(aiModelObj, baseParams);
+        } catch (e) {
+            console.error("❌ [AI Debug] Audio Gemini Failed:", e.message);
+            if (isQuotaError(e)) {
+                deprioritizeProvider(PROVIDERS.GEMINI);
+                throw new Error('QUOTA_EXCEEDED_AUDIO: 语音服务繁忙，请稍后再试或使用纯文本/图片提问。');
+            }
+            throw e;
+        }
+    }
+
+    let finalError = null;
+    for (const provider of activeProviderOrder) {
+        try {
+            if (provider === PROVIDERS.GEMINI) {
+                return await callGeminiProvider(aiModelObj, baseParams);
+            } else if (provider === PROVIDERS.OPENROUTER) {
+                return await callOpenRouterProvider(baseParams);
+            } else if (provider === PROVIDERS.GEMMA) {
+                return await callGemmaProvider(aiModelObj, baseParams);
+            }
+        } catch (e) {
+            finalError = e;
+            if (isQuotaError(e)) {
+                deprioritizeProvider(provider);
+                continue; 
+            }
+            console.warn(`⚠️ [AI Debug] ${provider} failed with non-quota error:`, e.message);
+        }
+    }
+    throw new Error('All AI models (Gemini, OpenRouter, Gemma) are currently unavailable.');
+}
+
+async function streamContentWithSmartFallback(aiModelObj, baseParams, res) {
+    let hasAudio = false;
+    if (baseParams.contents && Array.isArray(baseParams.contents)) {
+        for (const c of baseParams.contents) {
+            if (c.parts) {
+                for (const p of c.parts) {
+                    if (p.inlineData && p.inlineData.mimeType.startsWith('audio/')) {
+                        hasAudio = true;
+                    }
+                }
+            }
+        }
+    }
+
+    if (hasAudio) {
+        try {
+            return await streamGemini(aiModelObj, baseParams, res);
+        } catch(e) {
+            deprioritizeProvider(PROVIDERS.GEMINI);
+            throw new Error('QUOTA_EXCEEDED_AUDIO: 语音服务繁忙，请稍后再试或使用纯文本/图片提问。');
+        }
+    }
+
+    let finalError = null;
+    console.log(`🚦 [AI Debug] Starting stream with order: ${activeProviderOrder.join(' -> ')}`);
+
+    for (const provider of activeProviderOrder) {
+        try {
+            if (provider === PROVIDERS.GEMINI) {
+                return await streamGemini(aiModelObj, baseParams, res);
+            } else if (provider === PROVIDERS.OPENROUTER) {
+                return await streamOpenRouter(baseParams, res);
+            } else if (provider === PROVIDERS.GEMMA) {
+                return await streamGemma(aiModelObj, baseParams, res);
+            }
+        } catch (e) {
+            finalError = e;
+            if (isQuotaError(e)) {
+                deprioritizeProvider(provider);
+                continue;
+            }
+            console.warn(`Streaming ${provider} failed:`, e.message);
+        }
+    }
+    throw finalError || new Error('All streaming models unavailable.');
+}
+
+// --- Middleware ---
+
+const checkAIAccess = async (req, res, next) => {
+    const username = req.headers['x-user-username'];
+    const role = req.headers['x-user-role'];
+    if (!username) return res.status(401).json({ error: 'Unauthorized' });
+    
+    const config = await ConfigModel.findOne({ key: 'main' });
+    
+    if (config && config.enableAI === false && role !== 'ADMIN') {
+        return res.status(503).json({ error: 'MAINTENANCE', message: 'AI 功能正在维护中，请联系管理员。' });
+    }
+
+    if (role === 'ADMIN') return next();
+
+    const user = await User.findOne({ username });
+    if (!user) return res.status(404).json({ error: 'User not found' });
+    
+    if (user.role === 'STUDENT' || user.role === 'PRINCIPAL') return res.status(403).json({ error: 'Permission denied' });
+    if (!user.aiAccess) return res.status(403).json({ error: 'AI Access not enabled for this user' });
+    
+    next();
+};
+
+// --- Routes ---
+
+// POST /api/ai/chat
+router.post('/chat', checkAIAccess, async (req, res) => {
+    const { text, audio, history } = req.body; 
+    
+    res.setHeader('Content-Type', 'text/event-stream');
+    res.setHeader('Cache-Control', 'no-cache');
+    res.setHeader('Connection', 'keep-alive');
+    res.flushHeaders();
+
+    try {
+        const { ai, Modality } = await getGenAI();
+
+        const currentParts = [];
+        if (audio) {
+            currentParts.push({ inlineData: { mimeType: 'audio/wav', data: audio } });
+        }
+        if (text) {
+            currentParts.push({ text: text });
+        }
+        if (currentParts.length === 0) {
+            res.write(`data: ${JSON.stringify({ error: 'No input' })}\n\n`);
+            res.end();
+            return;
+        }
+
+        const fullContents = [];
+        if (history && Array.isArray(history)) {
+            history.forEach(msg => {
+                const role = msg.role === 'user' ? 'user' : 'model';
+                if (msg.text) {
+                    fullContents.push({ role: role, parts: [{ text: msg.text }] });
+                }
+            });
+        }
+        fullContents.push({ role: 'user', parts: currentParts });
+
+        // Step 1: Thinking
+        const answerText = await streamContentWithSmartFallback(ai.models, {
+            contents: fullContents, 
+            config: {
+                systemInstruction: "你是一位友善、耐心且知识渊博的中小学AI助教。请用简洁、鼓励性的语言回答学生的问题。如果学生使用语音，你也应当在回答中体现出自然的口语风格。回复支持 Markdown 格式。",
+            }
+        }, res);
+        
+        const finalAnswer = answerText || "抱歉，我没有听清，请再说一遍。";
+
+        // Step 2: Speaking
+        try {
+            const ttsResponse = await ai.models.generateContent({
+                model: "gemini-2.5-flash-preview-tts", 
+                contents: [{ parts: [{ text: finalAnswer }] }],
+                config: {
+                    responseModalities: [Modality.AUDIO],
+                    speechConfig: {
+                        voiceConfig: {
+                            prebuiltVoiceConfig: { voiceName: 'Kore' },
+                        },
+                    },
+                },
+            });
+            const audioBytes = ttsResponse.candidates?.[0]?.content?.parts?.[0]?.inlineData?.data;
+            if (audioBytes) {
+                res.write(`data: ${JSON.stringify({ audio: audioBytes })}\n\n`);
+            }
+        } catch (ttsError) {
+            console.warn("⚠️ TTS Generation skipped (Quota or Error). Returning text only.");
+        }
+
+        await ConfigModel.findOneAndUpdate({ key: 'main' }, { $inc: { aiTotalCalls: 1 } }, { upsert: true });
+
+        res.write('data: [DONE]\n\n');
+        res.end();
+
+    } catch (e) {
+        console.error("AI Chat Error:", e);
+        const errPayload = { error: 'Unknown Error' };
+        if (e.message?.includes('QUOTA_EXCEEDED_MEDIA') || e.message?.includes('QUOTA_EXCEEDED_AUDIO')) {
+             errPayload.error = 'QUOTA_EXCEEDED_MEDIA';
+             errPayload.message = e.message;
+        } else if (e.status === 429 || e.message?.includes('QUOTA_EXCEEDED') || e.message?.includes('RESOURCE_EXHAUSTED')) {
+             errPayload.error = 'QUOTA_EXCEEDED';
+             errPayload.message = '所有AI模型（包括备用线路）的免费额度均已耗尽，请明天再试。';
+        } else {
+             errPayload.error = 'SERVER_ERROR';
+             errPayload.message = e.message || 'AI Service Unavailable';
+        }
+        res.write(`data: ${JSON.stringify(errPayload)}\n\n`);
+        res.end();
+    }
+});
+
+// POST /api/ai/evaluate
+router.post('/evaluate', checkAIAccess, async (req, res) => {
+    const { question, audio, image } = req.body; 
+
+    if (!question || (!audio && !image)) return res.status(400).json({ error: 'Missing question or input (audio/image)' });
+
+    try {
+        const { ai, Type, Modality } = await getGenAI();
+
+        const evalParts = [{ text: `请作为一名严谨的老师，对学生的回答进行评分。题目是：${question}。` }];
+        if (audio) {
+            evalParts.push({ text: "学生的回答在音频中。" });
+            evalParts.push({ inlineData: { mimeType: 'audio/wav', data: audio } });
+        }
+        if (image) {
+            evalParts.push({ text: "学生的回答写在图片中，请识别图片中的文字内容并进行批改。" });
+            evalParts.push({ inlineData: { mimeType: 'image/jpeg', data: image } });
+        }
+        evalParts.push({ text: `请分析：1. 内容准确性 2. 表达/书写规范。返回 JSON: {score(0-100), feedback(简短评语), transcription(识别内容)}` });
+
+        // 1. Analyze
+        const response = await generateContentWithSmartFallback(ai.models, {
+            contents: { parts: evalParts },
+            config: {
+                responseMimeType: "application/json",
+                responseSchema: {
+                    type: Type.OBJECT,
+                    properties: {
+                        score: { type: Type.NUMBER },
+                        feedback: { type: Type.STRING },
+                        transcription: { type: Type.STRING }
+                    },
+                    required: ["score", "feedback", "transcription"]
+                }
+            }
+        });
+
+        let resultJson;
+        let rawText = response.text || "{}";
+        if (rawText.includes('```json')) {
+            rawText = rawText.replace(/```json/g, '').replace(/```/g, '').trim();
+        } else if (rawText.includes('```')) {
+            rawText = rawText.replace(/```/g, '').trim();
+        }
+
+        try {
+            resultJson = JSON.parse(rawText);
+        } catch (jsonErr) {
+            resultJson = {
+                score: 0,
+                feedback: rawText,
+                transcription: "（解析 JSON 失败，显示原始回复）"
+            };
+        }
+
+        // 2. TTS
+        let feedbackAudio = null;
+        if (resultJson.feedback) {
+            try {
+                const ttsResponse = await ai.models.generateContent({
+                    model: "gemini-2.5-flash-preview-tts",
+                    contents: [{ parts: [{ text: resultJson.feedback }] }],
+                    config: {
+                        responseModalities: [Modality.AUDIO],
+                        speechConfig: {
+                            voiceConfig: { prebuiltVoiceConfig: { voiceName: 'Kore' } },
+                        },
+                    },
+                });
+                feedbackAudio = ttsResponse.candidates?.[0]?.content?.parts?.[0]?.inlineData?.data;
+            } catch (ttsErr) {
+                console.warn("⚠️ TTS Generation failed:", ttsErr.message);
+            }
+        }
+
+        await ConfigModel.findOneAndUpdate({ key: 'main' }, { $inc: { aiTotalCalls: 1 } }, { upsert: true });
+
+        res.json({
+            ...resultJson,
+            audio: feedbackAudio
+        });
+
+    } catch (e) {
+        console.error("AI Eval Error:", e);
+        if (e.message?.includes('QUOTA_EXCEEDED_MEDIA') || e.message?.includes('QUOTA_EXCEEDED_AUDIO')) {
+             return res.status(429).json({ error: 'QUOTA_EXCEEDED', message: e.message });
+        }
+        if (e.status === 429 || e.message?.includes('QUOTA_EXCEEDED') || e.message?.includes('RESOURCE_EXHAUSTED')) {
+             return res.status(429).json({ error: 'QUOTA_EXCEEDED', message: '所有AI模型的免费额度均已耗尽，请明天再试。' });
+        }
+        res.status(500).json({ error: e.message || 'AI Service Unavailable' });
+    }
+});
+
+module.exports = router;

pages/AIAssistant.tsx

@@ -224,15 +224,22 @@ export const AIAssistant: React.FC = () => {
             const reader = response.body.getReader();
             const decoder = new TextDecoder();
             let aiTextAccumulated = '';
+            let buffer = ''; // Buffer for handling split chunks
 
             while (true) {
                 const { done, value } = await reader.read();
                 if (done) break;
                 
-                const chunk = decoder.decode(value, { stream: true });
-                const lines = chunk.split('\n\n');
+                // Append new data to buffer
+                buffer += decoder.decode(value, { stream: true });
                 
-                for (const line of lines) {
+                // Split by double newline (SSE event separator)
+                const parts = buffer.split('\n\n');
+                
+                // Keep the last part in buffer as it might be incomplete
+                buffer = parts.pop() || ''; 
+                
+                for (const line of parts) {
                     if (line.startsWith('data: ')) {
                         const jsonStr = line.replace('data: ', '').trim();
                         if (jsonStr === '[DONE]') break;

server.js

@@ -6,35 +6,8 @@ const {
     WishModel, FeedbackModel
 } = require('./models');
 
-// Initialize OpenAI (OpenRouter) Client
-const OpenAI = require('openai');
-let openAIClient = null;
-
-function getOpenRouter() {
-    if (openAIClient) return openAIClient;
-    if (!process.env.OPENROUTER_API_KEY) return null;
-    
-    openAIClient = new OpenAI({
-        baseURL: "https://openrouter.ai/api/v1",
-        apiKey: process.env.OPENROUTER_API_KEY,
-        defaultHeaders: {
-            "HTTP-Referer": "https://smart-school-ai.com", // Placeholder
-            "X-Title": "Smart School System", 
-        },
-    });
-    return openAIClient;
-}
-
-// Initialize Gemini via Dynamic Import (Helper)
-// @google/genai is an ESM-only package, so we cannot use require() in this CommonJS file.
-let genAIContext = null;
-async function getGenAI() {
-    if (genAIContext) return genAIContext;
-    const { GoogleGenAI, Type, Modality } = await import("@google/genai");
-    const ai = new GoogleGenAI({ apiKey: process.env.API_KEY });
-    genAIContext = { ai, Type, Modality };
-    return genAIContext;
-}
+// Import AI Routes
+const aiRoutes = require('./ai-routes');
 
 const express = require('express');
 const mongoose = require('mongoose');
@@ -48,7 +21,18 @@ const PORT = 7860;
 const MONGO_URI = 'mongodb+srv://dv890a:db8822723@chatpro.gw3v0v7.mongodb.net/chatpro?retryWrites=true&w=majority&appName=chatpro&authSource=admin';
 
 const app = express();
-app.use(compression());
+
+// FIX: Disable compression for AI Chat SSE endpoint to allow real-time streaming
+app.use(compression({
+  filter: (req, res) => {
+    // Note: The route is now mounted at /api/ai, so the full path contains /api/ai/chat
+    if (req.path.includes('/api/ai/chat')) {
+        return false; // Don't compress SSE streams
+    }
+    return compression.filter(req, res);
+  }
+}));
+
 app.use(cors());
 app.use(bodyParser.json({ limit: '50mb' })); // Increased limit for audio
 app.use(express.static(path.join(__dirname, 'dist'), {
@@ -122,682 +106,8 @@ const generateStudentNo = async () => {
     return `${year}${random}`;
 };
 
-// --- Helper: Basic Retry Logic (Network blips) ---
-const wait = (ms) => new Promise(resolve => setTimeout(resolve, ms));
-
-async function callAIWithRetry(aiModel, params, retries = 1) {
-    for (let i = 0; i < retries; i++) {
-        try {
-            return await aiModel.generateContent(params);
-        } catch (e) {
-            // If it's a critical auth error or bad request, don't retry locally
-            if (e.status === 400 || e.status === 401 || e.status === 403) throw e;
-            if (i < retries - 1) {
-                await wait(1000 * Math.pow(2, i));
-                continue;
-            }
-            throw e;
-        }
-    }
-}
-
-// --- Adapter: Google Gemini Params -> OpenAI Messages ---
-function convertGeminiToOpenAI(baseParams) {
-    const messages = [];
-    
-    // 1. System Instruction
-    if (baseParams.config?.systemInstruction) {
-        messages.push({ role: 'system', content: baseParams.config.systemInstruction });
-    }
-
-    // 2. Chat History & User Input
-    if (baseParams.contents && Array.isArray(baseParams.contents)) {
-        baseParams.contents.forEach(content => {
-            let role = 'user';
-            if (content.role === 'model') role = 'assistant';
-            
-            const messageContent = [];
-            
-            if (content.parts && Array.isArray(content.parts)) {
-                content.parts.forEach(p => {
-                    if (p.text) {
-                        messageContent.push({ type: 'text', text: p.text });
-                    } else if (p.inlineData && p.inlineData.mimeType.startsWith('image/')) {
-                        // Support Image for OpenRouter models that support vision
-                        // Convert inline base64 to data URL
-                        messageContent.push({
-                            type: 'image_url',
-                            image_url: {
-                                url: `data:${p.inlineData.mimeType};base64,${p.inlineData.data}`
-                            }
-                        });
-                    }
-                    // Audio is intentionally ignored for OpenRouter as we handle audio constraint separately
-                });
-            }
-            
-            if (messageContent.length > 0) {
-                // Optimization: If simple text, send as string (better compatibility with some models)
-                if (messageContent.length === 1 && messageContent[0].type === 'text') {
-                    messages.push({ role: role, content: messageContent[0].text });
-                } else {
-                    messages.push({ role: role, content: messageContent });
-                }
-            }
-        });
-    }
-    
-    return messages;
-}
-
-// --- DYNAMIC PROVIDER MANAGEMENT ---
-const PROVIDERS = {
-    GEMINI: 'GEMINI',
-    OPENROUTER: 'OPENROUTER',
-    GEMMA: 'GEMMA'
-};
-
-// Initial Order. When a provider fails due to Quota, it gets moved to the back.
-let activeProviderOrder = [PROVIDERS.GEMINI, PROVIDERS.OPENROUTER, PROVIDERS.GEMMA];
-
-function deprioritizeProvider(providerName) {
-    // If it's already at the end, do nothing
-    if (activeProviderOrder[activeProviderOrder.length - 1] === providerName) return;
-    
-    console.log(`📉 [AI Debug] Performance Opt: Deprioritizing ${providerName} due to quota limits.`);
-    // Move to end
-    activeProviderOrder = activeProviderOrder.filter(p => p !== providerName).concat(providerName);
-    console.log(`🔄 [AI Debug] New Provider Order: ${activeProviderOrder.join(' -> ')}`);
-}
-
-function isQuotaError(e) {
-    const msg = e.message || '';
-    return e.status === 429 || e.status === 503 || 
-           msg.includes('Quota') || 
-           msg.includes('overloaded') || 
-           msg.includes('RESOURCE_EXHAUSTED') ||
-           msg.includes('Rate limit') ||
-           msg.includes('credits');
-}
-
-// --- INDIVIDUAL PROVIDER CALLERS ---
-
-async function callGeminiProvider(aiModelObj, baseParams) {
-    const primaryModels = [
-        'gemini-2.5-flash',       // Standard (20 RPD) - Try first
-        'gemini-2.5-flash-lite'   // Lite (20 RPD) - Separate quota bucket
-    ];
-
-    let lastError = null;
-    for (const modelName of primaryModels) {
-        try {
-            console.log(`🚀 [AI Debug] Calling Gemini non-stream: ${modelName}`);
-            const currentParams = { ...baseParams, model: modelName };
-            return await callAIWithRetry(aiModelObj, currentParams, 1);
-        } catch (e) {
-            lastError = e;
-            console.error(`⚠️ [AI Debug] Gemini ${modelName} Error:`, e.status, e.message);
-            if (isQuotaError(e)) {
-                // IMPORTANT: Continue to next internal model, do not throw yet
-                console.warn(`⚠️ [AI Debug] Gemini ${modelName} exhausted. Trying next internal model...`);
-                continue; 
-            }
-            throw e; // Fail fast on non-quota errors
-        }
-    }
-    throw lastError; // All internal models failed
-}
-
-async function callOpenRouterProvider(baseParams) {
-    const openRouter = getOpenRouter();
-    if (!openRouter) throw new Error("OpenRouter not configured");
-
-    const openRouterModels = [
-        'qwen/qwen3-coder:free',
-        'openai/gpt-oss-120b:free',
-        'qwen/qwen3-235b-a22b:free',
-        'tngtech/deepseek-r1t-chimera:free'
-    ];
-
-    const openAIMessages = convertGeminiToOpenAI(baseParams);
-    let lastError = null;
-
-    for (const modelName of openRouterModels) {
-        try {
-            console.log(`🛡️ [AI Debug] Switching to OpenRouter Model: ${modelName}`);
-            const completion = await openRouter.chat.completions.create({
-                model: modelName,
-                messages: openAIMessages,
-            });
-
-            // Defensive Check
-            if (!completion || !completion.choices || !completion.choices[0] || !completion.choices[0].message) {
-                throw new Error(`Invalid response structure from ${modelName}`);
-            }
-
-            const content = completion.choices[0].message.content || "";
-            return { text: content };
-
-        } catch (e) {
-            lastError = e;
-            console.warn(`⚠️ [AI Debug] OpenRouter Model ${modelName} failed.`, e.message);
-            // Continue to next OpenRouter model
-        }
-    }
-    throw lastError || new Error("OpenRouter failed");
-}
-
-async function callGemmaProvider(aiModelObj, baseParams) {
-    const fallbackModels = [
-        'gemma-3-27b-it',
-        'gemma-3-12b-it',
-        'gemma-3-4b-it'
-    ];
-    
-    // Strip system instruction for Gemma compatibility
-    const gemmaConfig = { ...baseParams.config };
-    if (gemmaConfig.systemInstruction) delete gemmaConfig.systemInstruction;
-    
-    let lastError = null;
-    for (const modelName of fallbackModels) {
-        try {
-            console.log(`🛡️ [AI Debug] Switching to Final Backup (Gemma 3): ${modelName}`);
-            const currentParams = { 
-                ...baseParams, 
-                model: modelName,
-                config: gemmaConfig 
-            };
-            return await callAIWithRetry(aiModelObj, currentParams, 1);
-        } catch (e) {
-            lastError = e;
-            console.warn(`⚠️ [AI Debug] Backup Model ${modelName} failed.`, e.message);
-        }
-    }
-    throw lastError || new Error("Gemma failed");
-}
-
-// --- STREAMING PROVIDER HELPERS ---
-
-async function streamGemini(aiModelObj, baseParams, res) {
-    // Try multiple Flash models internally for quota resilience
-    const models = ['gemini-2.5-flash', 'gemini-2.5-flash-lite'];
-    
-    let lastError = null;
-    for (const modelName of models) {
-        try {
-            console.log(`🌊 [AI Debug] STREAMING Gemini model: ${modelName}`);
-            const currentParams = { ...baseParams, model: modelName };
-            const streamResult = await aiModelObj.generateContentStream(currentParams);
-            
-            let fullText = '';
-            for await (const chunk of streamResult) {
-                const text = chunk.text;
-                if (text) {
-                    fullText += text;
-                    res.write(`data: ${JSON.stringify({ text: text })}\n\n`);
-                }
-            }
-            console.log(`✅ [AI Debug] Gemini ${modelName} stream complete.`);
-            return fullText; // Success
-        } catch (e) {
-            lastError = e;
-            console.error(`❌ [AI Debug] Gemini Stream Error (${modelName}):`, e.status, e.message);
-            
-            if (isQuotaError(e)) {
-                // IMPORTANT: Continue to next internal model
-                console.warn(`[AI Debug] Stream Gemini ${modelName} quota exhausted. Switching to next internal model...`);
-                continue; 
-            }
-            throw e; // Non-quota error, fail fast
-        }
-    }
-    throw lastError || new Error("Gemini streaming failed after retrying internal models");
-}
-
-async function streamGemma(aiModelObj, baseParams, res) {
-    const models = ['gemma-3-27b-it', 'gemma-3-12b-it', 'gemma-3-4b-it'];
-    const gemmaConfig = { ...baseParams.config };
-    if (gemmaConfig.systemInstruction) delete gemmaConfig.systemInstruction;
-
-    let lastError = null;
-    for (const modelName of models) {
-        try {
-            console.log(`🛡️ [AI Debug] Streaming Fallback to Gemma: ${modelName}`);
-            const currentParams = { ...baseParams, model: modelName, config: gemmaConfig };
-            const streamResult = await aiModelObj.generateContentStream(currentParams);
-            
-            let fullText = '';
-            for await (const chunk of streamResult) {
-                const text = chunk.text;
-                if (text) {
-                    fullText += text;
-                    res.write(`data: ${JSON.stringify({ text: text })}\n\n`);
-                }
-            }
-            return fullText;
-        } catch (e) {
-            lastError = e;
-            console.warn(`Stream Gemma ${modelName} failed: ${e.message}`);
-            // Continue to next gemma model
-        }
-    }
-    throw lastError || new Error("Gemma streaming failed");
-}
-
-async function streamOpenRouter(baseParams, res) {
-    const openRouter = getOpenRouter();
-    if (!openRouter) throw new Error("OpenRouter not configured");
-    
-    // Updated free model list
-    const openRouterModels = [
-        'qwen/qwen3-coder:free',
-        'openai/gpt-oss-120b:free', 
-        'qwen/qwen3-235b-a22b:free',
-        'tngtech/deepseek-r1t-chimera:free'
-    ];
-    const messages = convertGeminiToOpenAI(baseParams);
-    
-    let lastError = null;
-    for (const modelName of openRouterModels) {
-        try {
-            console.log(`🛡️ [AI Debug] Streaming via OpenRouter: ${modelName}`);
-            const stream = await openRouter.chat.completions.create({
-                model: modelName,
-                messages: messages,
-                stream: true
-            });
-            
-            let fullText = '';
-            for await (const chunk of stream) {
-                const text = chunk.choices[0]?.delta?.content || '';
-                if (text) {
-                    fullText += text;
-                    res.write(`data: ${JSON.stringify({ text: text })}\n\n`);
-                }
-            }
-            return fullText;
-        } catch (e) {
-            lastError = e;
-            console.warn(`[AI Debug] Stream OpenRouter ${modelName} failed`, e.message);
-            // CRITICAL FIX: Do NOT throw here. Continue loop to try next OpenRouter model.
-            // Only throw if loop finishes.
-        }
-    }
-    throw lastError || new Error("All OpenRouter streams failed");
-}
-
-// --- MAIN GENERATION FUNCTIONS ---
-
-async function generateContentWithSmartFallback(aiModelObj, baseParams) {
-    // Check specifically for Audio (Gemini Only)
-    let hasAudio = false;
-    if (baseParams.contents && Array.isArray(baseParams.contents)) {
-        for (const c of baseParams.contents) {
-            if (c.parts) {
-                for (const p of c.parts) {
-                    if (p.inlineData && p.inlineData.mimeType.startsWith('audio/')) {
-                        hasAudio = true;
-                    }
-                }
-            }
-        }
-    }
-
-    // Constraint: Audio MUST use Gemini.
-    if (hasAudio) {
-        console.log("🎤 [AI Debug] Audio detected, forcing Gemini.");
-        try {
-            return await callGeminiProvider(aiModelObj, baseParams);
-        } catch (e) {
-            console.error("❌ [AI Debug] Audio Gemini Failed:", e.message);
-            if (isQuotaError(e)) {
-                // Critical: Even if we fail this request, deprioritize Gemini for future TEXT requests
-                deprioritizeProvider(PROVIDERS.GEMINI);
-                throw new Error('QUOTA_EXCEEDED_AUDIO: 语音服务繁忙，请稍后再试或使用纯文本/图片提问。');
-            }
-            throw e;
-        }
-    }
-
-    // Text OR Image Requests: Iterate through dynamic order
-    let finalError = null;
-
-    for (const provider of activeProviderOrder) {
-        try {
-            if (provider === PROVIDERS.GEMINI) {
-                return await callGeminiProvider(aiModelObj, baseParams);
-            } else if (provider === PROVIDERS.OPENROUTER) {
-                return await callOpenRouterProvider(baseParams);
-            } else if (provider === PROVIDERS.GEMMA) {
-                return await callGemmaProvider(aiModelObj, baseParams);
-            }
-        } catch (e) {
-            finalError = e;
-            if (isQuotaError(e)) {
-                // Optimize: Move this provider to the back so next requests don't wait
-                deprioritizeProvider(provider);
-                continue; // Try next provider immediately
-            }
-            // If it's not a quota error (e.g. invalid input, 400 Bad Request due to image not supported by specific model),
-            // we typically continue to the next provider to see if they can handle it.
-            console.warn(`⚠️ [AI Debug] ${provider} failed with non-quota error:`, e.message);
-        }
-    }
-
-    throw new Error('All AI models (Gemini, OpenRouter, Gemma) are currently unavailable.');
-}
-
-async function streamContentWithSmartFallback(aiModelObj, baseParams, res) {
-    // Check for Audio Input (Gemini Only)
-    let hasAudio = false;
-    if (baseParams.contents && Array.isArray(baseParams.contents)) {
-        for (const c of baseParams.contents) {
-            if (c.parts) {
-                for (const p of c.parts) {
-                    if (p.inlineData && p.inlineData.mimeType.startsWith('audio/')) {
-                        hasAudio = true;
-                    }
-                }
-            }
-        }
-    }
-
-    if (hasAudio) {
-        try {
-            return await streamGemini(aiModelObj, baseParams, res);
-        } catch(e) {
-            deprioritizeProvider(PROVIDERS.GEMINI);
-            throw new Error('QUOTA_EXCEEDED_AUDIO: 语音服务繁忙，请稍后再试或使用纯文本/图片提问。');
-        }
-    }
-
-    let finalError = null;
-    console.log(`🚦 [AI Debug] Starting stream with order: ${activeProviderOrder.join(' -> ')}`);
-
-    for (const provider of activeProviderOrder) {
-        try {
-            if (provider === PROVIDERS.GEMINI) {
-                return await streamGemini(aiModelObj, baseParams, res);
-            } else if (provider === PROVIDERS.OPENROUTER) {
-                return await streamOpenRouter(baseParams, res);
-            } else if (provider === PROVIDERS.GEMMA) {
-                // Now supports streaming fallback to Gemma
-                return await streamGemma(aiModelObj, baseParams, res);
-            }
-        } catch (e) {
-            finalError = e;
-            if (isQuotaError(e)) {
-                deprioritizeProvider(provider);
-                continue;
-            }
-            console.warn(`Streaming ${provider} failed:`, e.message);
-        }
-    }
-    throw finalError || new Error('All streaming models unavailable.');
-}
-
-// --- Middleware: Check AI Access ---
-const checkAIAccess = async (req, res, next) => {
-    const username = req.headers['x-user-username'];
-    const role = req.headers['x-user-role'];
-    if (!username) return res.status(401).json({ error: 'Unauthorized' });
-    
-    // 1. Check Global Switch (Admins can bypass for management, but for calling AI endpoints we still check)
-    // Actually, Admin dashboard does NOT call /chat, so this middleware is fine to block /chat for everyone if disabled.
-    const config = await ConfigModel.findOne({ key: 'main' });
-    
-    // If Admin, they are always allowed to access these endpoints (e.g. for testing) unless they explicitly disabled it and we want to enforce it.
-    // But usually Admins want to test. However, user said "if not open, ai is in maintenance".
-    // Let's enforce Maintenance Mode for *Teachers*, but Admin might be exempt? 
-    // Requirement: "if enabled, teacher can use. if not, maintenance". 
-    // It implies Admin controls it. Let's block *Teachers* if disabled.
-    
-    if (config && config.enableAI === false && role !== 'ADMIN') {
-        return res.status(503).json({ error: 'MAINTENANCE', message: 'AI 功能正在维护中，请联系管理员。' });
-    }
-
-    // Admins always have access to endpoint
-    if (role === 'ADMIN') return next();
-
-    const user = await User.findOne({ username });
-    if (!user) return res.status(404).json({ error: 'User not found' });
-    
-    // Students/Principals NO ACCESS to chat endpoint (Double check)
-    if (user.role === 'STUDENT' || user.role === 'PRINCIPAL') return res.status(403).json({ error: 'Permission denied' });
-    
-    // Teachers need enabled flag
-    if (!user.aiAccess) return res.status(403).json({ error: 'AI Access not enabled for this user' });
-    
-    next();
-};
-
-// --- NEW AI ROUTES ---
-
-// Scenario 1: AI Chat (Audio/Text In -> AI Think -> Text + Audio Out)
-// Now Supports History for Context AND STREAMING
-app.post('/api/ai/chat', checkAIAccess, async (req, res) => {
-    const { text, audio, history } = req.body; 
-    
-    // Set headers for SSE
-    res.setHeader('Content-Type', 'text/event-stream');
-    res.setHeader('Cache-Control', 'no-cache');
-    res.setHeader('Connection', 'keep-alive');
-    res.flushHeaders();
-
-    try {
-        const { ai, Modality } = await getGenAI();
-
-        // 1. Build Content parts for Current Turn
-        const currentParts = [];
-        if (audio) {
-            currentParts.push({
-                inlineData: {
-                    mimeType: 'audio/wav',
-                    data: audio
-                }
-            });
-        }
-        if (text) {
-            currentParts.push({ text: text });
-        }
-        if (currentParts.length === 0) {
-            res.write(`data: ${JSON.stringify({ error: 'No input' })}\n\n`);
-            res.end();
-            return;
-        }
-
-        // 2. Build Full Context (History + Current)
-        const fullContents = [];
-        
-        // Add previous history if exists
-        if (history && Array.isArray(history)) {
-            history.forEach(msg => {
-                const role = msg.role === 'user' ? 'user' : 'model';
-                if (msg.text) {
-                    fullContents.push({
-                        role: role,
-                        parts: [{ text: msg.text }]
-                    });
-                }
-            });
-        }
-
-        // Add current message
-        fullContents.push({
-            role: 'user',
-            parts: currentParts
-        });
-
-        // Step 1: Thinking (Streaming)
-        // Use streamContentWithSmartFallback instead of generate...
-        const answerText = await streamContentWithSmartFallback(ai.models, {
-            contents: fullContents, 
-            config: {
-                systemInstruction: "你是一位友善、耐心且知识渊博的中小学AI助教。请用简洁、鼓励性的语言回答学生的问题。如果学生使用语音，你也应当在回答中体现出自然的口语风格。回复支持 Markdown 格式。",
-            }
-        }, res);
-        
-        // Ensure we got some text back
-        const finalAnswer = answerText || "抱歉，我没有听清，请再说一遍。";
-
-        // Step 2: Speaking (Gemini TTS) - Sent as final chunk
-        // CRITICAL FIX: Wrap TTS in try-catch to allow graceful degradation.
-        // If TTS fails (quota exceeded), we simply return text without audio.
-        try {
-            // Note: TTS does NOT support streaming response in this context easily via SSE for binary.
-            // We wait for full audio and send as base64 in a data event.
-            const ttsResponse = await ai.models.generateContent({
-                model: "gemini-2.5-flash-preview-tts", 
-                contents: [{ parts: [{ text: finalAnswer }] }],
-                config: {
-                    responseModalities: [Modality.AUDIO],
-                    speechConfig: {
-                        voiceConfig: {
-                            prebuiltVoiceConfig: { voiceName: 'Kore' },
-                        },
-                    },
-                },
-            });
-            const audioBytes = ttsResponse.candidates?.[0]?.content?.parts?.[0]?.inlineData?.data;
-            if (audioBytes) {
-                res.write(`data: ${JSON.stringify({ audio: audioBytes })}\n\n`);
-            }
-        } catch (ttsError) {
-            console.warn("⚠️ TTS Generation skipped (Quota or Error). Returning text only.");
-        }
-
-        // Increment Counter
-        await ConfigModel.findOneAndUpdate({ key: 'main' }, { $inc: { aiTotalCalls: 1 } }, { upsert: true });
-
-        // End stream
-        res.write('data: [DONE]\n\n');
-        res.end();
-
-    } catch (e) {
-        console.error("AI Chat Error:", e);
-        // If headers already sent, we must send error as event
-        const errPayload = { error: 'Unknown Error' };
-        
-        if (e.message?.includes('QUOTA_EXCEEDED_MEDIA') || e.message?.includes('QUOTA_EXCEEDED_AUDIO')) {
-             errPayload.error = 'QUOTA_EXCEEDED_MEDIA';
-             errPayload.message = e.message;
-        } else if (e.status === 429 || e.message?.includes('QUOTA_EXCEEDED') || e.message?.includes('RESOURCE_EXHAUSTED')) {
-             errPayload.error = 'QUOTA_EXCEEDED';
-             errPayload.message = '所有AI模型（包括备用线路）的免费额度均已耗尽，请明天再试。';
-        } else {
-             errPayload.error = 'SERVER_ERROR';
-             errPayload.message = e.message || 'AI Service Unavailable';
-        }
-        
-        res.write(`data: ${JSON.stringify(errPayload)}\n\n`);
-        res.end();
-    }
-});
-
-// Scenario 2: Evaluation (Question + Audio/Image Answer -> AI Score + Feedback + Audio)
-app.post('/api/ai/evaluate', checkAIAccess, async (req, res) => {
-    const { question, audio, image } = req.body; // Image is base64
-
-    if (!question || (!audio && !image)) return res.status(400).json({ error: 'Missing question or input (audio/image)' });
-
-    try {
-        const { ai, Type, Modality } = await getGenAI();
-
-        const evalParts = [{ text: `请作为一名严谨的老师，对学生的回答进行评分。题目是：${question}。` }];
-        
-        if (audio) {
-            evalParts.push({ text: "学生的回答在音频中。" });
-            evalParts.push({ inlineData: { mimeType: 'audio/wav', data: audio } });
-        }
-        if (image) {
-            evalParts.push({ text: "学生的回答写在图片中，请识别图片中的文字内容并进行批改。" });
-            evalParts.push({ inlineData: { mimeType: 'image/jpeg', data: image } });
-        }
-
-        evalParts.push({ text: `请分析：1. 内容准确性 2. 表达/书写规范。返回 JSON: {score(0-100), feedback(简短评语), transcription(识别内容)}` });
-
-        // 1. Analyze (Using Multi-Stage Smart Fallback)
-        // Note: Evaluation usually outputs JSON. Gemma might struggle with strict JSON schemas without system instruction.
-        // We hope Primary Tier handles this. If falling back to Gemma, it might return raw text.
-        // For stability, Evaluation heavily relies on Gemini.
-        const response = await generateContentWithSmartFallback(ai.models, {
-            contents: { parts: evalParts },
-            config: {
-                responseMimeType: "application/json",
-                responseSchema: {
-                    type: Type.OBJECT,
-                    properties: {
-                        score: { type: Type.NUMBER },
-                        feedback: { type: Type.STRING },
-                        transcription: { type: Type.STRING }
-                    },
-                    required: ["score", "feedback", "transcription"]
-                }
-            }
-        });
-
-        let resultJson;
-        // Attempt to parse JSON. OpenRouter models might wrap JSON in Markdown code blocks (```json ... ```).
-        let rawText = response.text || "{}";
-        if (rawText.includes('```json')) {
-            rawText = rawText.replace(/```json/g, '').replace(/```/g, '').trim();
-        } else if (rawText.includes('```')) {
-            rawText = rawText.replace(/```/g, '').trim();
-        }
-
-        try {
-            resultJson = JSON.parse(rawText);
-        } catch (jsonErr) {
-            // Fallback for models that return unstructured text
-            resultJson = {
-                score: 0,
-                feedback: rawText,
-                transcription: "（解析 JSON 失败，显示原始回复）"
-            };
-        }
-
-        // 2. Generate Audio for the Feedback (TTS) - Graceful Degradation
-        let feedbackAudio = null;
-        if (resultJson.feedback) {
-            try {
-                const ttsResponse = await ai.models.generateContent({
-                    model: "gemini-2.5-flash-preview-tts",
-                    contents: [{ parts: [{ text: resultJson.feedback }] }],
-                    config: {
-                        responseModalities: [Modality.AUDIO],
-                        speechConfig: {
-                            voiceConfig: {
-                                prebuiltVoiceConfig: { voiceName: 'Kore' },
-                            },
-                },
-            },
-                });
-                feedbackAudio = ttsResponse.candidates?.[0]?.content?.parts?.[0]?.inlineData?.data;
-            } catch (ttsErr) {
-                console.warn("⚠️ TTS Generation failed:", ttsErr.message);
-            }
-        }
-
-        // Increment Counter
-        await ConfigModel.findOneAndUpdate({ key: 'main' }, { $inc: { aiTotalCalls: 1 } }, { upsert: true });
-
-        res.json({
-            ...resultJson,
-            audio: feedbackAudio
-        });
-
-    } catch (e) {
-        console.error("AI Eval Error:", e);
-        if (e.message?.includes('QUOTA_EXCEEDED_MEDIA') || e.message?.includes('QUOTA_EXCEEDED_AUDIO')) {
-             return res.status(429).json({ error: 'QUOTA_EXCEEDED', message: e.message });
-        }
-        if (e.status === 429 || e.message?.includes('QUOTA_EXCEEDED') || e.message?.includes('RESOURCE_EXHAUSTED')) {
-             return res.status(429).json({ error: 'QUOTA_EXCEEDED', message: '所有AI模型的免费额度均已耗尽，请明天再试。' });
-        }
-        res.status(500).json({ error: e.message || 'AI Service Unavailable' });
-    }
-});
-
+// MOUNT AI ROUTES
+app.use('/api/ai', aiRoutes);
 
 // ... (Rest of Existing Routes) ...
 app.get('/api/classes/:className/teachers', async (req, res) => {