Improve networking

build.ts

@@ -1,7 +1,7 @@
 import { copy } from "@std/fs";
 import { createCanvas, loadImage } from "@gfx/canvas-wasm";
 import { ENGINE_TEXTURE_DIR, load_and_check, load_order, LoadedMod } from "./tools/check_mods.ts";
-import type { ModData, ModListing } from "./common/mod_loader.ts";
+import type { AtlasListing, ModData, ModListing } from "./common/mod_loader.ts";
 
 // all overridable so tests can build somewhere else
 const BUILD_FOLDER = Deno.env.get("BUILD_DIR") ?? "build";
@@ -11,6 +11,7 @@ const SERVER_MODS_FOLDER = Deno.env.get("SERVER_MODS_DIR") ?? "server_mods";
 
 // what the server reads at startup, see server/main.ts
 export interface ServerModIndex {
+	atlas: AtlasListing;
 	mods: { listing: ModListing; server?: string }[];
 }
 
@@ -74,8 +75,9 @@ function calculate_atlas_size(count: number) {
 	};
 }
 
-// one atlas with the engine's textures (engine:<file>) and every mod's (<mod>:<file>)
-async function build_atlas(mods: LoadedMod[]) {
+// one atlas with the engine's textures (engine:<file>) and every mod's (<mod>:<file>).
+// named by its hash, so clients can cache it forever and download it from other origins
+async function build_atlas(mods: LoadedMod[]): Promise<AtlasListing> {
 	const textures = new Map<string, string>();
 	for (const entry of Deno.readDirSync(ENGINE_TEXTURE_DIR)) {
 		if (entry.isFile && entry.name.endsWith(".png")) {
@@ -115,8 +117,13 @@ async function build_atlas(mods: LoadedMod[]) {
 		atlas_info[id] = { x: column, y: row };
 	}
 
-	Deno.writeFileSync(`${BUILD_FOLDER}/assets/sprites/textures.png`, canvas.toBuffer());
-	Deno.writeTextFileSync(`${BUILD_FOLDER}/assets/sprites/textures.json`, JSON.stringify(atlas_info));
+	const png = new Uint8Array(canvas.toBuffer());
+	const json = new TextEncoder().encode(JSON.stringify(atlas_info));
+	const hashes = { png: await sha256(png), json: await sha256(json) };
+	const name = `assets/sprites/textures.${(hashes.png + hashes.json).slice(0, 12)}`;
+	Deno.writeFileSync(`${BUILD_FOLDER}/${name}.png`, png);
+	Deno.writeFileSync(`${BUILD_FOLDER}/${name}.json`, json);
+	return { png: `${name}.png`, json: `${name}.json`, sha256: hashes };
 }
 
 async function build_sprites(mods: LoadedMod[]) {
@@ -125,16 +132,16 @@ async function build_sprites(mods: LoadedMod[]) {
 			await copy(`assets/sprites/${entry.name}`, `${BUILD_FOLDER}/assets/sprites/${entry.name}`);
 		}
 	}
-	await build_atlas(mods);
+	return await build_atlas(mods);
 }
 
-async function build_assets(mods: LoadedMod[]) {
+async function build_assets(mods: LoadedMod[]): Promise<AtlasListing> {
 	Deno.mkdirSync(`${BUILD_FOLDER}/assets`, { recursive: true });
 	await copy("assets/ASSETS.md", `${BUILD_FOLDER}/assets/ASSETS.md`);
 
 	await build_fonts();
 	Deno.mkdirSync(`${BUILD_FOLDER}/assets/sprites`, { recursive: true });
-	await build_sprites(mods);
+	return await build_sprites(mods);
 }
 
 // every mod in mods/, checked and sorted so dependencies load first. a broken mod fails the whole build,
@@ -156,15 +163,21 @@ async function bundle_script(path: string, platform: "browser" | "deno"): Promis
 	return result.outputFiles[0].text();
 }
 
+async function sha256(bytes: Uint8Array<ArrayBuffer> | string) {
+	const data = typeof bytes === "string" ? new TextEncoder().encode(bytes) : bytes;
+	const digest = await crypto.subtle.digest("SHA-256", data);
+	return [...new Uint8Array(digest)].map((b) => b.toString(16).padStart(2, "0")).join("");
+}
+
 async function short_hash(parts: string[]) {
 	const digest = await crypto.subtle.digest("SHA-256", new TextEncoder().encode(parts.join("\0")));
 	return [...new Uint8Array(digest)].slice(0, 6).map((b) => b.toString(16).padStart(2, "0")).join("");
 }
 
 // build/mods/<id>/<hash>/ gets what players download, server_mods/ the server scripts
-async function build_mods(mods: LoadedMod[]) {
+async function build_mods(mods: LoadedMod[], atlas: AtlasListing) {
 	clear_folder(SERVER_MODS_FOLDER);
-	const index: ServerModIndex = { mods: [] };
+	const index: ServerModIndex = { atlas, mods: [] };
 
 	for (const mod of mods) {
 		const manifest = mod.manifest as { name: string; version: string; scripts?: Record<string, string> };
@@ -193,14 +206,17 @@ async function build_mods(mods: LoadedMod[]) {
 			version: manifest.version,
 			hash,
 			data: `${public_dir}/data.json`,
+			sha256: { data: await sha256(data_json) },
 		};
 		Deno.writeTextFileSync(`${BUILD_FOLDER}/${listing.data}`, data_json);
 		if (client) {
 			listing.client = `${public_dir}/client.js`;
+			listing.sha256.client = await sha256(client);
 			Deno.writeTextFileSync(`${BUILD_FOLDER}/${listing.client}`, client);
 		}
 		if (worldgen) {
 			listing.worldgen = `${public_dir}/worldgen.js`;
+			listing.sha256.worldgen = await sha256(worldgen);
 			Deno.writeTextFileSync(`${BUILD_FOLDER}/${listing.worldgen}`, worldgen);
 		}
 
@@ -234,9 +250,9 @@ async function build() {
 		const now = performance.now();
 		clear_folder(BUILD_FOLDER);
 		const mods = load_mods();
-		await build_assets(mods);
+		const atlas = await build_assets(mods);
 		await build_client();
-		await build_mods(mods);
+		await build_mods(mods, atlas);
 		console.log(`Built in ${(performance.now() - now).toFixed(2)}ms`);
 	} catch (e) {
 		// no index means the server refuses to start, instead of running without some mods