webring

index.mjs

@@ -0,0 +1,33 @@
+import * as fs from 'node:fs';
+import express from 'express';
+
+const sites = fs.readFileSync('./webring.txt', 'utf-8')
+	// split lines
+	.split(/\r?\n/)
+	// trim whitespace from each line
+	.map(site => site.trim())
+	// exclude empty lines and lines that start with # because why not
+	.filter(site => site && !site.startsWith('#'));
+
+console.log(sites);
+
+// modulo that does the right thing with negatives
+// https://stackoverflow.com/a/4467559
+const mod = (n, m) => ((n % m) + m) % m;
+
+function handle (offset, request, response) {
+	const from = request.query.from;
+	const index = sites.findIndex(site => site === from);
+	if (!from || index === -1) {
+		response.status(400).send('the provided site is not in the webring');
+		return;
+	}
+	response.redirect(301, sites[mod(index + offset, sites.length)]);
+}
+
+express()
+	.get('/prev', (request, response) => handle(-1, request, response))
+	.get('/next', (request, response) => handle(+1, request, response))
+	.listen(process.env.PORT || 8080, () => {
+		console.log('doing the thing');
+	})