server.js

const net = require('net');
const { EventEmitter } = require('events');
const { executeSELECTQuery, executeINSERTQuery, executeDELETEQuery } = require('./queryExecuter');

class QueryQueue extends EventEmitter {
    constructor() {
        super();
        this.queue = [];
        this.isProcessing = false;
    }

    addQuery(queryId, query, callback) {
        this.queue.push({ query, callback, queryId });
        this.emit('newQuery');
    }

    processQueue() {
        if (this.isProcessing || this.queue.length === 0) {
            return;
        }
        this.isProcessing = true;
        const { query, callback, queryId } = this.queue.shift();
        this.execute(query)
            .then(result => callback(null, queryId, result))
            .catch(error => callback(error, queryId))
            .finally(() => {
                this.isProcessing = false;
                this.processQueue();
            });
    }

    async execute(query) {
        if (query.toLowerCase().startsWith('select')) {
            return await executeSELECTQuery(query);
        } else if (query.toLowerCase().startsWith('insert into')) {
            return await executeINSERTQuery(query);
        } else if (query.toLowerCase().startsWith('delete from')) {
            return await executeDELETEQuery(query);
        } else {
            throw new Error('Unsupported command');
        }
    }
}

const queryQueue = new QueryQueue();
queryQueue.on('newQuery', () => queryQueue.processQueue());

const server = net.createServer();
let activeConnection = false;

server.on('connection', (socket) => {
    if (activeConnection) {
        socket.end('Another connection is already active.');
        return;
    }
    activeConnection = true;

    socket.write('Connected\n');

    socket.on('data', (data) => {
        const [queryId, query] = data.toString().trim().split(':', 2);
        queryQueue.addQuery(queryId, query, (error, queryId, result) => {
            let response;
            if (error) {
                response = `${queryId}<|>Error: ${error.message}`;
            } else {
                response = `${queryId}<|>${JSON.stringify(result)}`;
            }
            socket.write(response + '\n');
        });
    });

    socket.on('close', () => {
        activeConnection = false;
    });
});

server.listen(5432, () => {
    console.log('Server listening on port 5432');
});