lots of improvements

src/misc/network.ts

@@ -1 +1,63 @@
+export class NetworkUpdateEvent extends Event {
+    name: string;
+    url: string;
+    constructor(name: string, url: string) {
+        super("update");
+        this.name = name;
+        this.url = url;
+    }
+}
 
+/** Listens for updates and emits events when a model changes */
+export class NetworkManager extends EventTarget {
+    private knownObjectHashes: { [name: string]: string } = {};
+
+    /**
+     * Tries to load a new model (.glb or .glbs) from the given URL.
+     *
+     * If the URL uses the websocket protocol (ws:// or wss://), the server will be continuously monitored for changes.
+     * In this case, it will only trigger updates if the name or hash of any model changes.
+     *
+     * Updates will be emitted as "update" events, including the download URL and the model name.
+     */
+    async load(url: string) {
+        if (url.startsWith("ws://") || url.startsWith("wss://")) {
+            this.monitorWebSocket(url);
+        } else {
+            // Get the last part of the URL as the "name" of the model
+            let name = url.split("/").pop();
+            name = name?.split(".")[0] || `unknown-${Math.random()}`;
+            let prevHash = this.knownObjectHashes[name];
+            // Use a head request to get the hash of the file
+            let response = await fetch(url, { method: "HEAD" });
+            let hash = response.headers.get("etag");
+            // Only trigger an update if the hash has changed
+            if (hash !== prevHash) {
+                this.knownObjectHashes[name] = hash;
+                this.dispatchEvent(new NetworkUpdateEvent(name, url));
+            }
+        }
+    }
+
+    private monitorWebSocket(url: string) {
+        let ws = new WebSocket(url);
+        ws.onmessage = (event) => {
+            let data = JSON.parse(event.data);
+            console.debug("WebSocket message", data);
+            let name = data.name;
+            let prevHash = this.knownObjectHashes[name];
+            let hash = data.hash;
+            if (hash !== prevHash) {
+                this.knownObjectHashes[name] = hash;
+                this.dispatchEvent(new NetworkUpdateEvent(name, data.url));
+            }
+        };
+        ws.onerror = (event) => {
+            console.error("WebSocket error", event);
+        }
+        ws.onclose = () => {
+            console.trace("WebSocket closed, reconnecting very soon");
+            setTimeout(() => this.monitorWebSocket(url), 500);
+        }
+    }
+}