node swr http proxy

gistfile1.txt

import express from 'express';
import fs from 'fs-extra';
import path from 'path';

const app = express();
const port = 3000;
const targetUrl = 'https://www.vivid-planet.com'; // Hardcoded target URL
const cacheDir = path.join(__dirname, 'cache');
const revalidateAfter = 5*60;
const maxAge = 24*60*60;

// Ensure the cache directory exists
fs.ensureDirSync(cacheDir);

// Define a function to generate a cache key from the request URL
function getCacheKey(url: string): string {
  return encodeURIComponent(url);
}

async function isCacheFileValid(cacheFilePath: string) {
  if (!await fs.existsSync(cacheFilePath)) return false;
  const stat = await fs.stat(cacheFilePath)
  if (new Date().getTime() - stat.mtime.getTime() > 1000*maxAge) return false;
  return true;
}

// Define a route that will proxy incoming requests to the fixed target server with stale-while-revalidate caching
app.all('*', async (req, res) => {
  const cacheKey = getCacheKey(req.url);
  const cacheFilePath = path.join(cacheDir, cacheKey);

    // Check if the response is cached
    if (await isCacheFileValid(cacheFilePath)) {
      console.log('serving from cache', req.url);
      const cachedResponse = await fs.readFile(cacheFilePath, 'utf-8');
      //res.status(200);
      res.send(cachedResponse);

      // Asynchronously revalidate the cache in the background
      (async () => {
        const stat = await fs.stat(cacheFilePath);
        if (new Date().getTime() - stat.mtime.getTime() > 1000*revalidateAfter) {
            console.log('async refresh', req.url);
            const freshResponse = await fetch(`${targetUrl}${req.url}`, {
              method: req.method,
              //headers: req.headers,
              body: req.method === 'GET' ? undefined : req.body,
            });

            const freshResponseBody = await freshResponse.text();

            // Update the cache with the fresh response
            await fs.writeFile(cacheFilePath, freshResponseBody);
        }
      })();

    } else {
      console.log('fetching', req.url);

      // Fetch the response from the fixed target URL
      const response = await fetch(`${targetUrl}${req.url}`, {
        method: req.method,
        //headers: req.headers,
        body: req.method === 'GET' ? undefined : req.body,
      });

      const responseBody = await response.text();

      // Cache the response
      await fs.writeFile(cacheFilePath, responseBody);

      // Send the response to the client
      //res.status(response.status);
      //res.set(response.headers);
      res.send(responseBody);

    }

});

app.listen(port, () => {
  console.log(`Proxy server is running on port ${port}`);
});