Initial commit

index.js

@@ -0,0 +1,60 @@
+// development endpoint (use ngrok)
+
+const http = require('http');
+const argv = require('minimist')(process.argv.slice(2));
+const port = parseInt(argv.port || 3000);
+const record_prefix = 'forward-domain=';
+
+const {
+    default: axios
+} = require('axios');
+
+/**
+ * @type {Object<string, {expire: number, expand: boolean, url: string}>}
+ */
+const resolveCache = {};
+
+async function buildCache(host) {
+    const resolve = await axios(`https://dns.google/resolve?name=${encodeURIComponent(host)}&type=TXT`);
+    for (const head of resolve.data.Answer) {
+        let url = head.data.slice(record_prefix.length);
+        let expand = false;
+        if (url.endsWith('*')) {
+            url = url.substr(0, -1);
+            expand = true;
+        }
+        return {
+            url,
+            expand,
+            expire: Date.now() + Math.max(head.TTL, 86400) * 1000,
+        };
+    }
+    throw new Error(record_prefix + ' TXT is missing');
+}
+
+const server = http.createServer(async function (req, res) {
+    try {
+        let cache = resolveCache[req.headers.host];
+        if (!cache || (Date.now() > cache.expire)) {
+            cache = await buildCache(req.headers.host);
+            resolveCache[req.headers.host] = cache;
+        }
+        req.statusCode = 301;
+        req.headers.location = cache.expand ? cache.url + req.url : cache.url;
+        return;
+    } catch (error) {
+        res.statusCode = 400;
+        res.write(error.message || 'Unknown error');
+    } finally {
+        res.end();
+    }
+})
+
+
+if (require.main === module) {
+    server.listen(port, function () {
+        console.log(`server start at port ${port}`);
+    });
+} else {
+    module.exports = server
+}