main.js

const express = require('express');
const axios = require('axios');
const { appendToFile } = require('./fileWriter');
const path = require('path');
const db = require('./database');

const app = express();
const PORT = 3000;
const UPSTREAM_URL = 'http://127.0.0.1:8300';

app.use(express.json());
app.use(express.text());

function isValidJson(str) {
    try {
        JSON.parse(str);
        return true;
    } catch (e) {
        return false;
    }
}

// 发送消息
app.post('/backend-api/conversation', async (req, res) => {
    try {

        // res.status(429).json({ detail: '测试' });
        // return;

        console.log(UPSTREAM_URL + req.url);

        const response = await axios({
            method: req.method,
            url: UPSTREAM_URL + req.url,
            headers: req.headers,
            data: req.body,
            responseType: 'stream'
        });

        // 设置状态码和响应头
        res.status(response.status);
        res.set(response.headers);

        // 处理json响应
        let jsonData = '';

        // 处理响应数据
        if (response.headers['content-type'].includes('application/json')) 
        {
            response.data.on('data', (chunk) => { jsonData += chunk; });
            response.data.on('end', () => {
                res.send(jsonData);
            });
        } 
        else if (response.headers['content-type'].includes('text/event-stream')) 
        {
            const fileName = Date.now() + '.txt';
            const filePath = path.join(__dirname, 'msg', fileName);
            let msg_id = '';
            let conversation_id = '';

            // 处理sse响应
            response.data.on('data', chunk => {
                // console.log(`Received chunk: ${chunk}`);
                res.write(chunk);
                jsonData += chunk;

                // 把数据写入文件(此处换成写入数据库)
                // appendToFile(chunk, filePath);

                // // 解析数据，如果以data: 开头，则截取其中的消息内容并转换成json格式
                // const data = chunk.toString();
                // if (data.startsWith('data:')) {
                //     const msg = (data.slice(5)).trim();
                //     if(isValidJson(msg))
                //     {
                //         const jsonMsg = JSON.parse(msg);
                //         if(jsonMsg.conversation_id && !conversation_id) {
                //             conversation_id = jsonMsg.conversation_id;
                //         }
                //         if(jsonMsg.message.id && !msg_id) {
                //             msg_id = jsonMsg.message.id;
                //         }
                //     }
                // }
            });

            // 响应结束后关闭连接
            response.data.on('end', () => {

                let body = JSON.stringify(req.body);
                // console.log(body);

                // 删除会话内容
                db.deleteRecord('chat_conversation_detail', conversation_id, (err, result) => {});

                // 写入数据库
                db.addRecord('chat_msg', {
                    conversation_id: conversation_id,
                    msg_id: msg_id,
                    body: body, 
                    result: jsonData,
                    createtime: Math.floor(Date.now() / 1000)
                }, (err, result) => {
                    if (err) {
                        console.log(err);
                    }
                    console.log(result);
                });

                res.end();
            });
        } 
        else 
        {
            // 处理其他响应
            response.data.pipe(res);
        }
    } 
    catch (error) 
    {
        console.log(error);
        // res.status(429).json({ detail: error.message });
    }
});

// 获取历史会话记录
app.get('/backend-api/conversations', async (req, res) => {
    // const { offset, limit, order } = req.query;
    try {
        const response = await axios({
            method: req.method,
            url: UPSTREAM_URL + req.url,
            headers: req.headers,
            data: req.body,
            responseType: 'stream'
        });
        res.status(response.status);
        res.set(response.headers);
        response.data.pipe(res);
        
        // 处理业务逻辑
        if (response.headers['content-type'].includes('application/json')) {
            let jsonData = '';
            response.data.on('data', (chunk) => { jsonData += chunk; });
            response.data.on('end', () => {
                // res.send(jsonData);
            });
        } 

    } catch (error) {
        res.status(429).json({ detail: error.message });
    }
});

// 获取单条消息详情
app.get('/backend-api/conversation/:id', async (req, res) => {
    try {

       // 获取会话id
       const conversation_id = req.params.id;

        // 根据会话id，然后查询数据库，如何数据库存在。则返回数据，否则返回上游数据并写入数据库
        db.getRecord('chat_conversation_detail', { conversation_id: conversation_id }, async (err, result) => {
            if (err) {
                console.log(err);
            }
            if (result) {
                console.log(result);
                res.send(result.content);
            } else {

                // 不存在则查询上游数据并写入数据库
                const response = await axios({
                    method: req.method,
                    url: UPSTREAM_URL + req.url,
                    headers: req.headers,
                    data: req.body,
                    responseType: 'stream'
                });
                res.status(response.status);
                res.set(response.headers);
        
                // 处理响应数据
                let jsonData = '';
                response.data.on('data', (chunk) => { jsonData += chunk; });
                response.data.on('end', () => {

                    // 写入数据库
                    db.addRecord('chat_conversation_detail', {
                        conversation_id: conversation_id,
                        content: jsonData,
                        createtime: Math.floor(Date.now() / 1000)
                    }, (err, result) => {
                        if (err) {
                            console.log(err);
                        }
                        console.log(result);
                    });

                    // 响应数据
                    res.send(jsonData);
                });
            }
        });

        // response.data.pipe(res);
    } 
    catch (error) 
    {
        res.status(429).json({ detail: error.message });
    }
});

// 修改标题接口
app.post('/backend-api/conversation/gen_title/:id', async (req, res) => {
    try {
        const response = await axios({
            method: req.method,
            url: UPSTREAM_URL + req.url,
            headers: req.headers,
            data: req.body,
            responseType: 'stream'
        });
        res.status(response.status);
        res.set(response.headers);
        response.data.pipe(res);
    } 
    catch (error) 
    {
        res.status(429).json({ detail: error.message });
    }
});

// 查询chatgpt模型接口
app.post('/backend-api/models', async (req, res) => {
    try {
        const response = await axios({
            method: 'get',
            url: 'https://free.18230.work/chatgpt/backend-api/models',
            headers: {
                'Authorization': 'Bearer ' + req.headers.token
            }
        });
        res.status(200);
        response.data.pipe(res);
    } 
    catch (error) 
    {
        res.status(200).json({ detail: error.message });
    }
});

// 启动服务器
app.listen(PORT, () => {
    console.log(`Server is running on http://localhost:${PORT}`);
});


// res.type('txt');  // Content-Type: text/plain
// res.type('html'); // Content-Type: text/html
// res.type('json'); // Content-Type: application/json
// res.type('text/event-stream'); // Content-Type: text/event-stream