app.js

const express = require('express');
const { v4: uuidv4 } = require('uuid');
const zlib = require('zlib');
const protobuf = require('protobufjs');

// 创建 proto 定义字符串
const protoDefinition = `
syntax = "proto3";

message ChatMessage {
    message FileContent {
        message Position {
            int32 line = 1;
            int32 column = 2;
        }
        
        message Range {
            Position start = 1;
            Position end = 2;
        }
        
        string filename = 1;
        string content = 2;
        Position position = 3;
        string language = 5;
        Range range = 6;
        int32 length = 8;
        int32 type = 9;
        int32 error_code = 11;
    }
    
    message UserMessage {
        string content = 1;
        int32 role = 2;
        string message_id = 13;
    }
    
    message Instructions {
        string instruction = 1;
    }
    
    message Model {
        string name = 1;
        string empty = 4;
    }
    
    repeated UserMessage messages = 2;
    Instructions instructions = 4;
    string projectPath = 5;
    Model model = 7;
    string requestId = 9;
    string summary = 11;
    string conversationId = 15;
}

message ResMessage {
    string msg = 1;
}
`;

// 使用 protobuf.parse 解析 proto 定义
const root = protobuf.parse(protoDefinition).root;

// 获取消息类型
const ChatMessage = root.lookupType("ChatMessage");
const ResMessage = root.lookupType("ResMessage");

// 创建 $root 对象
const $root = {
    ChatMessage,
    ResMessage
};

// regex 定义
const regex = /<\|BEGIN_SYSTEM\|>.*?<\|END_SYSTEM\|>.*?<\|BEGIN_USER\|>.*?<\|END_USER\|>/s;

async function stringToHex(messages, modelName) {
    const formattedMessages = messages.map((msg) => ({
        ...msg,
        role: msg.role === 'user' ? 1 : 2,
        message_id: uuidv4(),
    }));

    const message = {
        messages: formattedMessages,
        instructions: {
            instruction: 'Always respond in 中文',
        },
        projectPath: '/path/to/project',
        model: {
            name: modelName,
            empty: '',
        },
        requestId: uuidv4(),
        summary: '',
        conversationId: uuidv4(),
    };

    const errMsg = $root.ChatMessage.verify(message);
    if (errMsg) throw Error(errMsg);

    const messageInstance = $root.ChatMessage.create(message);
    const buffer = $root.ChatMessage.encode(messageInstance).finish();
    const hexString = (buffer.length.toString(16).padStart(10, '0') + 
                      buffer.toString('hex')).toUpperCase();
    return Buffer.from(hexString, 'hex');
}

async function chunkToUtf8String(chunk) {
    try {
        let hex = Buffer.from(chunk).toString('hex');
        let offset = 0;
        let results = [];

        while (offset < hex.length) {
            if (offset + 10 > hex.length) break;
            const dataLength = parseInt(hex.slice(offset, offset + 10), 16);
            offset += 10;
            
            if (offset + dataLength * 2 > hex.length) break;
            const messageHex = hex.slice(offset, offset + dataLength * 2);
            offset += dataLength * 2;
            
            const messageBuffer = Buffer.from(messageHex, 'hex');
            const message = $root.ResMessage.decode(messageBuffer);
            results.push(message.msg);
        }

        if (results.length == 0) {
            return gunzip(chunk);
        }
        return results.join('');
    } catch (err) {
        return gunzip(chunk);
    }
}

function gunzip(chunk) {
    return new Promise((resolve, reject) => {
        zlib.gunzip(chunk.slice(5), (err, decompressed) => {
            if (err) {
                resolve('');
            } else {
                const text = decompressed.toString('utf-8');
                if (regex.test(text)) {
                    resolve('');
                } else {
                    resolve(text);
                }
            }
        });
    });
}

function getRandomIDPro({ size, dictType, customDict }) {
    let random = '';
    if (!customDict) {
        switch (dictType) {
            case 'alphabet':
                customDict = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
                break;
            case 'max':
                customDict = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-';
                break;
            default:
                customDict = '0123456789';
        }
    }
    for (; size--; ) random += customDict[(Math.random() * customDict.length) | 0];
    return random;
}

// Express 应用设置
const app = express();
app.use(express.json());
app.use(express.urlencoded({ extended: true }));

// 主要路由处理
app.post('/ai/v1/chat/completions', async (req, res) => {
    // o1开头的模型，不支持流式输出
    if (req.body.model.startsWith('o1-') && req.body.stream) {
        return res.status(400).json({
            error: 'Model not supported stream',
        });
    }

    let currentKeyIndex = 0;

    try {
        const { model, messages, stream = false } = req.body;
        let authToken = req.headers.authorization?.replace('Bearer ', '');

        // 处理认证token
        const keys = authToken.split(',').map((key) => key.trim());
        if (keys.length > 0) {
            if (currentKeyIndex >= keys.length) {
                currentKeyIndex = 0;
            }
            authToken = keys[currentKeyIndex];
        }

        if (authToken && authToken.includes('%3A%3A')) {
            authToken = authToken.split('%3A%3A')[1];
        }

        // 验证请求
        if (!messages || !Array.isArray(messages) || messages.length === 0 || !authToken) {
            return res.status(400).json({
                error: 'Invalid request. Messages should be a non-empty array and authorization is required',
            });
        }

        const hexData = await stringToHex(messages, model);
        
        // 获取checksum
        const checksum =
            req.headers['x-cursor-checksum'] ??
            process.env['x-cursor-checksum'] ??
            `zo${getRandomIDPro({ dictType: 'max', size: 6 })}${getRandomIDPro({ dictType: 'max', size: 64 })}/${getRandomIDPro({ dictType: 'max', size: 64 })}`;

        // API请求配置
        const response = await fetch('https://api2.cursor.sh/aiserver.v1.AiService/StreamChat', {
            method: 'POST',
            headers: {
                'Content-Type': 'application/connect+proto',
                'authorization': `Bearer ${authToken}`,
                'connect-accept-encoding': 'gzip,br',
                'connect-protocol-version': '1',
                'user-agent': 'connect-es/1.4.0',
                'x-amzn-trace-id': `Root=${uuidv4()}`,
                'x-cursor-checksum': checksum,
                'x-cursor-client-version': '0.42.3',
                'x-cursor-timezone': 'Asia/Shanghai',
                'x-ghost-mode': 'false',
                'x-request-id': uuidv4(),
                'host': 'api2.cursor.sh',
            },
            body: hexData,
        });

        // 处理流式响应
        if (stream) {
            res.setHeader('Content-Type', 'text/event-stream');
            res.setHeader('Cache-Control', 'no-cache');
            res.setHeader('Connection', 'keep-alive');
            
            const responseId = `chatcmpl-${uuidv4()}`;
            
            for await (const chunk of response.body) {
                const text = await chunkToUtf8String(chunk);
                if (text.length > 0) {
                    res.write(
                        `data: ${JSON.stringify({
                            id: responseId,
                            object: 'chat.completion.chunk',
                            created: Math.floor(Date.now() / 1000),
                            model,
                            choices: [
                                {
                                    index: 0,
                                    delta: {
                                        content: text,
                                    },
                                },
                            ],
                        })}\n\n`,
                    );
                }
            }
            
            res.write('data: [DONE]\n\n');
            return res.end();
        } else {
            // 处理非流式响应
            let text = '';
            for await (const chunk of response.body) {
                text += await chunkToUtf8String(chunk);
            }
            
            text = text.replace(/^.*<\|END_USER\|>/s, '');
            text = text.replace(/^\n[a-zA-Z]?/, '').trim();
            
            return res.json({
                id: `chatcmpl-${uuidv4()}`,
                object: 'chat.completion',
                created: Math.floor(Date.now() / 1000),
                model,
                choices: [
                    {
                        index: 0,
                        message: {
                            role: 'assistant',
                            content: text,
                        },
                        finish_reason: 'stop',
                    },
                ],
                usage: {
                    prompt_tokens: 0,
                    completion_tokens: 0,
                    total_tokens: 0,
                },
            });
        }
    } catch (error) {
        console.error('Error:', error);
        if (!res.headersSent) {
            if (req.body.stream) {
                res.write(`data: ${JSON.stringify({ error: 'Internal server error' })}\n\n`);
                return res.end();
            } else {
                return res.status(500).json({ error: 'Internal server error' });
            }
        }
    }
});

// 启动服务器
const PORT = process.env.PORT || 3000;
app.listen(PORT, () => {
    console.log(`服务器运行在端口 ${PORT}`);
});

module.exports = app;