route.ts

import { Configuration, OpenAIApi } from "openai-edge";
import { OpenAIStream, StreamingTextResponse } from "ai";
import { kv } from "@vercel/kv";
import { Ratelimit } from "@upstash/ratelimit";

const config = new Configuration({
  apiKey: process.env.OPENAI_API_KEY,
});
const openai = new OpenAIApi(config);

export const runtime = "edge";

export async function POST(req: Request): Promise<Response> {
  if (
    process.env.NODE_ENV != "development" &&
    process.env.KV_REST_API_URL &&
    process.env.KV_REST_API_TOKEN
  ) {
    const ip = req.headers.get("x-forwarded-for");
    const ratelimit = new Ratelimit({
      redis: kv,
      limiter: Ratelimit.slidingWindow(50, "1 d"),
    });

    const { success, limit, reset, remaining } = await ratelimit.limit(
      `platforms_ratelimit_${ip}`,
    );

    if (!success) {
      return new Response("You have reached your request limit for the day.", {
        status: 429,
        headers: {
          "X-RateLimit-Limit": limit.toString(),
          "X-RateLimit-Remaining": remaining.toString(),
          "X-RateLimit-Reset": reset.toString(),
        },
      });
    }
  }

  let { prompt: content } = await req.json();

  // remove trailing slash,
  // slice the content from the end to prioritize later characters
  content = content.replace(/\/$/, "").slice(-5000);

  const response = await openai.createChatCompletion({
    model: "gpt-3.5-turbo",
    messages: [
      {
        role: "system",
        content:
          "You are an AI writing assistant that continues existing text based on context from prior text. " +
          "Give more weight/priority to the later characters than the beginning ones. " +
          "Limit your response to no more than 200 characters, but make sure to construct complete sentences.",
        // we're disabling markdown for now until we can figure out a way to stream markdown text with proper formatting: https://github.com/steven-tey/novel/discussions/7
        // "Use Markdown formatting when appropriate.",
      },
      {
        role: "user",
        content,
      },
    ],
    temperature: 0.7,
    top_p: 1,
    frequency_penalty: 0,
    presence_penalty: 0,
    stream: true,
    n: 1,
  });

  // Convert the response into a friendly text-stream
  const stream = OpenAIStream(response);

  // Respond with the stream
  return new StreamingTextResponse(stream);
}