+/* Redirect any requests to a game ID at the top-level.
+ *
+ * Specifically, after obtaining the game ID (from the path) we simply
+ * lookup the game engine for the corresponding game and then redirect
+ * to the engine- and game-specific path.
+ */
+app.get('/[a-zA-Z0-9]{4}', (request, response) => {
+ const game_id = request.path.replace(/\//g, "");
+ const canon_id = lmno_canonize(game_id);
+
+ /* Redirect user to page with the canonical ID in it. */
+ if (game_id !== canon_id) {
+ response.redirect(301, `/${canon_id}/`);
+ return;
+ }
+
+ const game = lmno.ids[game_id];
+ if (game === undefined) {
+ response.sendStatus(404);
+ return;
+ }
+ response.redirect(301, `/${game.engine}/${game.id}/`);
+});
+
+/* LMNO middleware to lookup the game. */
+app.use('/empires/:game_id([a-zA-Z0-9]{4})', (request, response, next) => {
+ const game_id = request.params.game_id;
+ const canon_id = lmno_canonize(game_id);
+
+ /* Redirect user to page with the canonical ID in it. */
+ if (game_id !== canon_id) {
+ const new_url = request.originalUrl.replace("/empires/" + game_id,
+ "/empires/" + canon_id);
+ response.redirect(301, new_url);
+ return;
+ }
+
+ /* See if there is any game with this ID. */
+ const game = lmno.ids[game_id];
+ if (game === undefined) {
+ response.sendStatus(404);
+ return;
+ }
+
+ /* Stash the game onto the request to be used by the game-specific code. */
+ request.game = game.game;
+ next();
+});
+
+/* Mount sub apps. only _after_ we have done all the middleware we need. */
+app.use('/empires/[a-zA-Z0-9]{4}/', empires.app);
+