New modding system

desktop/main.ts

@@ -6,7 +6,7 @@
 import { fromFileUrl, join } from "@std/path";
 import { type Host, serve_static, start_host } from "../server/host.ts";
 
-// where the project was built from: build/ and server_mods/ are bundled into the app with --include
+// where the project was built from: build/ and server_mods/ (the .bmod files) are bundled into the app with --include
 const ROOT = fromFileUrl(new URL("../", import.meta.url));
 const BUILD_DIR = join(ROOT, "build");
 
@@ -19,17 +19,16 @@ const default_server = Deno.env.get("BWORLD_SERVER") ?? config.server ?? "";
 const win = new Deno.BrowserWindow({ title: "bworld", width: 1280, height: 720 });
 
 // the singleplayer game server, started the first time singleplayer connects so players who only join other servers
-// don't get a world made for them
-let host: Host | undefined;
+// don't get a world made for them. it plays the .bmod files the app was built with
+let host: Promise<Host> | undefined;
 
-function singleplayer_host(): Host {
-	if (!host) {
+function singleplayer_host(): Promise<Host> {
+	host ??= (async () => {
 		const worlds = join(data_dir(), "worlds");
 		Deno.mkdirSync(worlds, { recursive: true });
-		host = start_host({
+		return await start_host({
 			build_dir: BUILD_DIR,
 			server_mods_dir: join(ROOT, "server_mods"),
-			root: ROOT,
 			world_file: join(worlds, "world.json"),
 			on_fatal(message) {
 				console.error(message);
@@ -37,7 +36,7 @@ function singleplayer_host(): Host {
 				Deno.exit(1);
 			},
 		});
-	}
+	})();
 	return host;
 }
 
@@ -48,7 +47,7 @@ win.addEventListener("close", async (event) => {
 	}
 	event.preventDefault();
 	try {
-		await host.shutdown();
+		await (await host).shutdown();
 	} catch (e) {
 		console.error((e as Error).message);
 	}
@@ -56,7 +55,7 @@ win.addEventListener("close", async (event) => {
 });
 
 // deno desktop binds this to a private local address and opens the window on it, the port given here is ignored
-Deno.serve((req) => {
+Deno.serve(async (req) => {
 	const url = new URL(req.url);
 	if (url.pathname === "/") {
 		// ?server= fills in the address field, without it the field would start with this app's own address.
@@ -66,8 +65,16 @@ Deno.serve((req) => {
 		start.searchParams.set("singleplayer", "");
 		return Response.redirect(start, 302);
 	}
-	if (url.pathname === "/ws") {
-		return singleplayer_host().handle(req);
+	// the singleplayer server's socket and its .bmod downloads
+	if (url.pathname === "/ws" || url.pathname.startsWith("/mods/")) {
+		try {
+			return (await singleplayer_host()).handle(req);
+		} catch (e) {
+			// its mods have problems, the title screen shows why the connection failed
+			console.error((e as Error).message);
+			host = undefined;
+			return new Response((e as Error).message, { status: 500 });
+		}
 	}
 	return serve_static(BUILD_DIR, req, url);
 });