Improve networking

server/main.ts

@@ -70,7 +70,7 @@ game.onmessage = (event: MessageEvent<GameToHost>) => {
 };
 
 // what deno task build made. no index means the build failed or never ran, and the game never runs without its mods
-function read_mods(): Extract<HostToGame, { type: "init" }>["mods"] {
+function read_mods(): Pick<Extract<HostToGame, { type: "init" }>, "mods" | "atlas"> {
 	let index: ServerModIndex;
 	try {
 		index = JSON.parse(Deno.readTextFileSync(`${SERVER_MODS_DIR}/index.json`));
@@ -78,12 +78,15 @@ function read_mods(): Extract<HostToGame, { type: "init" }>["mods"] {
 		console.error(`No ${SERVER_MODS_DIR}/index.json, run deno task build first (it also reports mod errors)`);
 		Deno.exit(1);
 	}
-	return index.mods.map(({ listing, server }) => ({
-		listing,
-		data: JSON.parse(Deno.readTextFileSync(`${STATIC_ROOT}/${listing.data}`)),
-		server_code: server ? Deno.readTextFileSync(server) : undefined,
-		worldgen_code: listing.worldgen ? Deno.readTextFileSync(`${STATIC_ROOT}/${listing.worldgen}`) : undefined,
-	}));
+	return {
+		atlas: index.atlas,
+		mods: index.mods.map(({ listing, server }) => ({
+			listing,
+			data: JSON.parse(Deno.readTextFileSync(`${STATIC_ROOT}/${listing.data}`)),
+			server_code: server ? Deno.readTextFileSync(server) : undefined,
+			worldgen_code: listing.worldgen ? Deno.readTextFileSync(`${STATIC_ROOT}/${listing.worldgen}`) : undefined,
+		})),
+	};
 }
 
 game.onerror = (event) => {
@@ -91,10 +94,25 @@ game.onerror = (event) => {
 	Deno.exit(1);
 };
 
-const mods = read_mods();
+const { mods, atlas } = read_mods();
 console.log(`Mods: ${mods.map((mod) => `${mod.listing.id} ${mod.listing.version}`).join(", ") || "none"}`);
 const save = read_world();
-post({ type: "init", save, default_seed: Deno.env.get("SEED") ?? crypto.randomUUID(), mods });
+post({ type: "init", save, default_seed: Deno.env.get("SEED") ?? crypto.randomUUID(), atlas, mods });
+
+// mod files and the atlas are named by their hash, so they never change and pages on other origins can load them
+async function serve_static(req: Request, url: URL) {
+	const response = await serveDir(req, { fsRoot: STATIC_ROOT, quiet: true });
+	const shared = url.pathname.startsWith("/mods/") || url.pathname.startsWith("/assets/");
+	if (shared && response.ok) {
+		const headers = new Headers(response.headers);
+		headers.set("Access-Control-Allow-Origin", "*");
+		if (url.pathname.startsWith("/mods/") || /^\/assets\/sprites\/textures\.[0-9a-f]+\./.test(url.pathname)) {
+			headers.set("Cache-Control", "public, max-age=31536000, immutable");
+		}
+		return new Response(response.body, { status: response.status, statusText: response.statusText, headers });
+	}
+	return response;
+}
 
 function handle_socket(socket: WebSocket) {
 	const conn = next_conn++;
@@ -147,5 +165,5 @@ Deno.serve({ port: PORT, onListen: ({ port }) => console.log(`bworld server on h
 		return Response.redirect(new URL("/client/", url), 302);
 	}
 
-	return serveDir(req, { fsRoot: STATIC_ROOT, quiet: true });
+	return serve_static(req, url);
 });