⚡ [performance] Precalculate chat history mapping in fallback chain

lib/chat.ts

@@ -22,6 +22,17 @@ export async function generateTutorResponse(
     // Prepare history: filters system messages and removes redundant user message if any
     const validHistory = prepareHistory(history, message);
 
+    // Pre-calculate mapped history for different providers to avoid redundant allocations in fallbacks
+    const geminiHistory = validHistory.map(msg => ({
+        role: msg.role === "user" ? "user" : "model",
+        parts: [{ text: msg.content }],
+    }));
+
+    const groqHistory = validHistory.map(h => ({
+        role: h.role === "ai" ? "assistant" : "user" as any, // eslint-disable-line @typescript-eslint/no-explicit-any
+        content: h.content
+    }));
+
     // 1. Try Gemini 2.5 Flash (Best balance of speed and smarts)
     try {
         const model = genAI.getGenerativeModel({
@@ -30,10 +41,7 @@ export async function generateTutorResponse(
         });
 
         const chat = model.startChat({
-            history: validHistory.map(msg => ({
-                role: msg.role === "user" ? "user" : "model",
-                parts: [{ text: msg.content }],
-            })),
+            history: geminiHistory,
         });
 
         const result = await chat.sendMessage(message);
@@ -51,10 +59,7 @@ export async function generateTutorResponse(
         });
 
         const chat = model.startChat({
-            history: validHistory.map(msg => ({
-                role: msg.role === "user" ? "user" : "model",
-                parts: [{ text: msg.content }],
-            })),
+            history: geminiHistory,
         });
 
         const result = await chat.sendMessage(message);
@@ -69,10 +74,7 @@ export async function generateTutorResponse(
         const completion = await groq.chat.completions.create({
             messages: [
                 { role: "system", content: systemPrompt },
-                ...validHistory.map(h => ({
-                    role: h.role === "ai" ? "assistant" : "user" as any ,// eslint-disable-line @typescript-eslint/no-explicit-any
-                    content: h.content
-                })),
+                ...groqHistory,
                 { role: "user", content: message }
             ],
             model: TEXT_MODELS.LLAMA_70B.model,
@@ -90,10 +92,7 @@ export async function generateTutorResponse(
         const completion = await groq.chat.completions.create({
             messages: [
                 { role: "system", content: systemPrompt },
-                ...validHistory.map(h => ({
-                    role: h.role === "ai" ? "assistant" : "user" as any ,// eslint-disable-line @typescript-eslint/no-explicit-any
-                    content: h.content
-                })),
+                ...groqHistory,
                 { role: "user", content: message }
             ],
             model: TEXT_MODELS.LLAMA_8B.model,

lib/chat_optimization.bench.ts

@@ -0,0 +1,74 @@
+
+export interface ChatMessage {
+  role: "user" | "ai" | "system";
+  content: string;
+}
+
+const history: ChatMessage[] = Array.from({ length: 20 }, (_, i) => ({
+    role: i % 2 === 0 ? "user" : "ai",
+    content: "This is some content for the chat message " + i
+}));
+
+const ITERATIONS = 100_000;
+
+function benchmarkRepeatedMapping() {
+    const start = performance.now();
+    for (let i = 0; i < ITERATIONS; i++) {
+        // Simulating the 4 blocks in generateTutorResponse
+        const h1 = history.map(msg => ({
+            role: msg.role === "user" ? "user" : "model",
+            parts: [{ text: msg.content }],
+        }));
+        const h2 = history.map(msg => ({
+            role: msg.role === "user" ? "user" : "model",
+            parts: [{ text: msg.content }],
+        }));
+        const h3 = history.map(h => ({
+            role: h.role === "ai" ? "assistant" : "user" as any,
+            content: h.content
+        }));
+        const h4 = history.map(h => ({
+            role: h.role === "ai" ? "assistant" : "user" as any,
+            content: h.content
+        }));
+
+        if (h1.length === 0 || h2.length === 0 || h3.length === 0 || h4.length === 0) { /* prevent optimize */ }
+    }
+    return performance.now() - start;
+}
+
+function benchmarkPrecalculatedMapping() {
+    const start = performance.now();
+    for (let i = 0; i < ITERATIONS; i++) {
+        const geminiHistory = history.map(msg => ({
+            role: msg.role === "user" ? "user" : "model",
+            parts: [{ text: msg.content }],
+        }));
+        const groqHistory = history.map(h => ({
+            role: h.role === "ai" ? "assistant" : "user" as any,
+            content: h.content
+        }));
+
+        // Simulating use in 4 blocks
+        const h1 = geminiHistory;
+        const h2 = geminiHistory;
+        const h3 = groqHistory;
+        const h4 = groqHistory;
+
+        if (h1.length === 0 || h2.length === 0 || h3.length === 0 || h4.length === 0) { /* prevent optimize */ }
+    }
+    return performance.now() - start;
+}
+
+console.log(`Benchmarking with ${ITERATIONS} iterations and history length ${history.length}...`);
+
+const repeatedTime = benchmarkRepeatedMapping();
+console.log(`Repeated mapping: ${repeatedTime.toFixed(2)}ms`);
+
+const precalculatedTime = benchmarkPrecalculatedMapping();
+console.log(`Precalculated mapping: ${precalculatedTime.toFixed(2)}ms`);
+
+if (repeatedTime > 0) {
+    const improvement = ((repeatedTime - precalculatedTime) / repeatedTime * 100).toFixed(2);
+    console.log(`Improvement: ${improvement}%`);
+}