Implement main game as a mod

server/main.ts

@@ -1,9 +1,11 @@
 import { serveDir } from "@std/http/file-server";
 import { GameToHost, HostToGame } from "./game/host_protocol.ts";
+import type { ServerModIndex } from "../build.ts";
 
 const PORT = Number(Deno.env.get("PORT") ?? 8000);
 const WORLD_FILE = Deno.env.get("WORLD_FILE") ?? "world.json";
-const STATIC_ROOT = "build";
+const STATIC_ROOT = Deno.env.get("BUILD_DIR") ?? "build";
+const SERVER_MODS_DIR = Deno.env.get("SERVER_MODS_DIR") ?? "server_mods";
 const MAX_MESSAGE_SIZE = 4096;
 const SHUTDOWN_TIMEOUT_MS = 5000;
 
@@ -43,6 +45,10 @@ game.onmessage = (event: MessageEvent<GameToHost>) => {
 		case "ready":
 			console.log(`World ${WORLD_FILE} ready, seed ${message.seed}`);
 			break;
+		case "failed":
+			console.error(`Couldn't start the game: ${message.error}`);
+			Deno.exit(1);
+			break;
 		case "send": {
 			const socket = sockets.get(message.conn);
 			if (socket?.readyState === WebSocket.OPEN) {
@@ -63,13 +69,32 @@ 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"] {
+	let index: ServerModIndex;
+	try {
+		index = JSON.parse(Deno.readTextFileSync(`${SERVER_MODS_DIR}/index.json`));
+	} catch {
+		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,
+	}));
+}
+
 game.onerror = (event) => {
 	console.error("Game server crashed:", event.message);
 	Deno.exit(1);
 };
 
+const mods = 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() });
+post({ type: "init", save, default_seed: Deno.env.get("SEED") ?? crypto.randomUUID(), mods });
 
 function handle_socket(socket: WebSocket) {
 	const conn = next_conn++;