server.js

import Koa from "koa";
import Router from "@koa/router";
import compose from "koa-compose";
import { koaBody } from "koa-body";
import {
  handleTimeStap,
  handleBase64,
  handleNewSession,
  handleErrors,
  initParams,
} from "./handles.js";
import https from "https";
import { createParser } from "eventsource-parser";
const app = new Koa();
const router = new Router();
const params = {};
const break_message = {
  answer_message_id: null,
  query_message_id: null,
  scene: params.scene,
  broken_pos: 0,
  conversation_id: params.conversation_id,
  local_message_id: params.local_message_id,
};

const createNewSession = async (ctx, next) => {
  const { messages } = ctx.request.body;
  const sessionid = ctx.req.headers.authorization.split(" ")[1];
  if (
    messages[0].role === "system" &&
    messages.length === 2 &&
    break_message.answer_message_id !== null &&
    break_message.query_message_id !== null
  ) {
    console.log("new session");
    await handleNewSession(break_message, sessionid);
    params.conversation_id =
      "7337495393033765890_7337496580645339154_2_" + handleTimeStap();
    params.local_message_id = handleBase64();
  }
  await next();
};

// 事件源路由
router.post("/api/v1/chat/completions", async (ctx) => {
  ctx.respond = false;
  ctx.type = "text/event-stream";
  ctx.status = 200;
  // 初始化响应头 sse
  ctx.set({
    "Cache-Control": "no-cache",
    Connection: "keep-alive",
    "Content-Encoding": "none",
  });
  // 获取 post 请求的 body
  const { messages, model } = ctx.request.body;
  const sessionid = ctx.req.headers.authorization.split(" ")[1];
  // 返回的数据
  const sseData = {
    id: null,
    object: "chat.completion.chunk",
    created: handleTimeStap(),
    model: model,
    system_fingerprint: null,
    choices: [
      {
        index: 0,
        delta: { content: null },
        logprobs: null,
        finish_reason: null,
      },
    ],
  };
  // 远程服务器配置
  const options = {
    hostname: "www.coze.com",
    path: "/api/conversation/chat",
    port: 443,
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      Cookie: `sessionid=${sessionid}`,
      "User-Agent":
        "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/122.0.0.0 Safari/537.36",
    },
  };
  params.query = messages[messages.length - 1].content;
  const sse = https.request(options);

  sse.on("response", async (res) => {
    const parser = createParser((event) => {
      if (event.event === "message") {
        const data = JSON.parse(event.data);
        if (data.message.type === "answer") {
          sseData.id = data.conversation_id;
          sseData.choices[0].delta.content = data.message.content;
          if (data.is_finish) {
            sseData.choices[0].finish_reason = "stop";
          } else {
            sseData.choices[0].finish_reason = null;
          }
          ctx.res.write(`data:${JSON.stringify(sseData)}\n\n`);
          if (data.is_finish) {
            break_message.answer_message_id = data.message.reply_id;
            break_message.query_message_id = data.message.message_id;
            break_message.broken_pos = parseInt(
              data.message.extra_info.output_tokens
            );
            ctx.res.end();
          }
        }
      }
    });
    res.setEncoding("utf8");
    res.on("data", (d) => {
      parser.feed(d);
    });
    res.on("end", () => {
      console.log("response end", new Date().toLocaleString());
    });
  });
  sse.on("error", async (e) => {
    console.error(`problem with request: ${e.message}`);
  });
  sse.on("close", async () => {
    console.log("sse closed", new Date().toLocaleString());
  });

  sse.write(JSON.stringify(params));
  sse.end();
  ctx.respond = false;
});

// 组合中间件
const all = compose([
  handleErrors,
  koaBody(),
  createNewSession,
  router.routes(),
  router.allowedMethods(),
]);

// 注册中间件
app.use(all);

// 启动Koa应用
app.listen(3000, () => {
  console.log("Server started on port 3000");
  initParams(params);
});