initial commit

.gitignore

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+servers.json

.vscode/settings.json

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+{
+  "deno.enable": true,
+}

app.ts

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+import { createError, opine } from "./deps.ts";
+import { ErrorRequestHandler, Router, Request, ParamsDictionary } from "./deps.ts";
+import { createHash } from "https://deno.land/std@0.87.0/hash/mod.ts";
+
+interface server { host: string; secret: string }
+
+// store your BBB servers in servers.json
+const file: string = await Deno.readTextFile('servers.json')
+const servers: server[] = JSON.parse(file)
+
+// create an iterator so that we can trat all servers equally
+let iterator = servers[Symbol.iterator]();
+console.log(servers)
+
+// give your tinyscale server a secret so it looks like a BBB server
+const secret = Deno.env.get("TINYSCALE_SECRET") || ""
+if (!secret) throw "No secret set for tinyscale"
+
+const router = Router()
+
+// check if request is autheticated with correct checksum
+function authenticated(req: Request<ParamsDictionary, any, any>): boolean {
+  const hash = createHash("sha1");
+  const checksum = req.query.checksum
+  const query = req._parsedUrl?.query
+  hash.update(`${req.params.call}${query?.replace(/[?|&]checksum.*$/, secret)}`);
+  const hashInHex = hash.toString();
+  return hashInHex === checksum
+}
+// pick the next server
+function get_available_server(): server {
+  // simple server selection, just cycle through all servers available
+  let candidate = iterator.next()
+  if (candidate.done) {
+    iterator = servers[Symbol.iterator]()
+    candidate = iterator.next()
+  }
+  return candidate.value;
+}
+function gen_checksum(call: string, query: string, secret: string): string {
+  const hash = createHash("sha1");
+  console.log(`${call}${query}${secret}`)
+  hash.update(`${call}${query}${secret}`);
+  return hash.toString();
+}
+// fetch a getMeetingInfo from all available servers and see if meeting exists
+async function find_server(id: string): Promise<server> {
+  if (!id) return get_available_server()
+  const promises = servers.map(async s => {
+    const checksum = gen_checksum(`getMeetingInfo`, `meetingID=${id}`, s.secret)
+    const res = await fetch(`${s.host}/bigbluebutton/api/getMeetingInfo?meetingID=${id}&checksum=${checksum}`)
+    if (!res.ok) throw Error
+    const text = await res.text()
+    if (text.includes(id)) return s
+    else throw Error
+  })
+  try {
+    // if any of the responses resolves it is our server
+    const server = await Promise.any(promises)
+    console.log("RES: ", server)
+    // use that server for our response
+    return server
+  } catch (e) {
+    console.log("Kein Server gefunden")
+    return get_available_server()
+  }
+}
+// redirect api call to proper BBB Server
+function rewrite_api_call(req: Request<ParamsDictionary, any, any>, server: server) {
+  const hash = createHash("sha1");
+  const checksum = req.query.checksum
+  const query = req._parsedUrl?.query
+  hash.update(`${req.params.call}${query?.replace(/[?|&]checksum.*$/g, server.secret)}`);
+  const hashInHex = hash.toString();
+  return `${server.host}/${req.originalUrl.replace(checksum, hashInHex)}`
+}
+
+// the api itself answering to every call
+router.get("/bigbluebutton/api/:call", async (req, res, next) => {
+  console.log("Calling: ", req.params.call)
+  if (!authenticated(req)) {
+    res.setStatus(401).end()
+    console.log('rejected')
+    return
+  }
+  const meeting_id: string = req.query.meetingID;
+  const server: server = await find_server(meeting_id)
+  const url = rewrite_api_call(req, server)
+  console.log(url)
+  res.redirect(url)
+});
+// the fake answering machine to make sure we are recognized as a proper api
+router.get("/bigbluebutton/api", (req, res, next) => {
+  console.log('sending fake xml response')
+  res.set('Content-Type', 'text/xml');
+  res.send(`<response>
+<returncode>SUCCESS</returncode>
+<version>2.0</version>
+</response>`);
+})
+
+const app = opine();
+
+// Mount our routers
+app.use("/", router);
+
+// catch 404 and forward to error handler
+app.use((req, res, next) => {
+  next(createError(404));
+});
+
+// Error handler
+const errorHandler: ErrorRequestHandler = (err, req, res, next) => {
+  // Set locals, only providing error in development
+  res.locals.message = err.message;
+  res.locals.error = req.app.get("env") === "development" ? err : {};
+
+  // Render the error page
+  res.setStatus(err.status ?? 500);
+  console.log(err, req)
+  res.send(err);
+};
+
+app.use(errorHandler);
+
+export default app;

deps.ts

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+export {
+  dirname,
+  fromFileUrl,
+  join,
+} from "https://deno.land/std@0.86.0/path/mod.ts";
+export {
+  json,
+  opine,
+  Router,
+  serveStatic,
+  urlencoded,
+} from "https://deno.land/x/opine@1.1.0/mod.ts";
+export type {
+  ErrorRequestHandler,
+  Request,
+  ParamsDictionary
+ } from "https://deno.land/x/opine@1.1.0/mod.ts";
+export { createError } from "https://deno.land/x/http_errors@2.1.0/mod.ts";
+export { renderFileToString } from "https://deno.land/x/dejs@0.9.3/mod.ts";

mod.ts

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+import app from "./app.ts";
+
+// Get the PORT from the environment variables and store in Opine.
+const port = parseInt(Deno.env.get("PORT") ?? "3000");
+app.set("port", port);
+
+// Get the DENO_ENV from the environment variables and store in Opine.
+const env = Deno.env.get("DENO_ENV") ?? "development";
+app.set("env", env);
+
+// Start our Opine server on the provided or default port.
+app.listen(port, () => console.log(`listening on port ${port}`));

servers.json.example

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+[
+  {
+    "host": "http://bbb1.schule.de",
+    "secret": "secret_string"
+  },
+  {
+    "host": "http://bbb2.schule.de",
+    "secret": "secret_string"
+  }
+]