sveltekit-node-adapter-proxy-socketio.js

import { readFileSync, writeFileSync } from 'node:fs';

import adapter from '@sveltejs/adapter-node';

export default function (opts = {}) {
    
    const PORT = 3001;
    const HOST = 'localhost';
    
    const adapterNode = adapter(opts);
    
    adapterNode.originalAdapt = adapterNode.adapt;
    adapterNode.adapt = async function (builder) {
        
        const result = await adapterNode.originalAdapt(builder);
        
        console.log('> Adding proxy middleware to server');
        
        const buildDir = opts.out || 'build';
        const indexJsPath = `./${buildDir}/index.js`;


        const importProxyMiddleWare = `import { createProxyMiddleware } from "http-proxy-middleware";`;

        const serverInitString = `const server = polka()`;
        const proxyJs = `.use('/socket.io', createProxyMiddleware({ target: 'http://${HOST}:${PORT}', ws: true }))`;

        let indexJs = readFileSync(indexJsPath, 'utf8');

        indexJs = indexJs.replace(serverInitString, serverInitString + proxyJs);
        indexJs = importProxyMiddleWare + '\n' + indexJs;

        writeFileSync(indexJsPath, indexJs, 'utf8');
        
        console.log('> Proxy middleware added to server');
        
        return result;
    }
    return adapterNode;
}