Add perplexity chat API route

Implement a new route that integrates with the Perplexity API to handle chat completions. The route processes incoming messages, requests a response from the Perplexity API, and returns the response as a text stream.

app/api/chat/perplexity/route.ts

@@ -0,0 +1,25 @@
+import { OpenAIStream, StreamingTextResponse } from 'ai';
+import OpenAI from 'openai';
+
+const perplexity = new OpenAI({
+    apiKey: process.env.PERPLEXITY_API_KEY || '',
+    baseURL: 'https://api.perplexity.ai',
+});
+
+export async function POST(req: Request) {
+    // Extract the `messages` from the body of the request
+    const { messages } = await req.json();
+
+    // Request the OpenAI-compatible API for the response based on the prompt
+    const response = await perplexity.chat.completions.create({
+        model: 'llama-3-sonar-large-32k-online',
+        stream: true,
+        messages: messages,
+    });
+
+    // Convert the response into a friendly text-stream
+    const stream = OpenAIStream(response);
+
+    // Respond with the stream
+    return new StreamingTextResponse(stream);
+}