feat(packages/excalidraw): state tracking, api hook, and others (#10870)

excalidraw-app/data/fileStatusStore.ts

@@ -0,0 +1,48 @@
+import { VersionedSnapshotStore } from "@excalidraw/common";
+
+import type { FileId } from "@excalidraw/element/types";
+
+export type FileLoadingStatus = "loading" | "loaded" | "error";
+
+export class FileStatusStore {
+  private static store = new VersionedSnapshotStore<
+    Map<FileId, FileLoadingStatus>
+  >(new Map());
+
+  static getSnapshot() {
+    return this.store.getSnapshot();
+  }
+
+  static pull(sinceVersion?: number) {
+    return this.store.pull(sinceVersion);
+  }
+
+  static updateStatuses(updates: Array<[FileId, FileLoadingStatus]>) {
+    if (!updates.length) {
+      return;
+    }
+    this.store.update((prev) => {
+      let changed = false;
+      const next = new Map(prev);
+      for (const [id, status] of updates) {
+        if (next.get(id) !== status) {
+          next.set(id, status);
+          changed = true;
+        }
+      }
+      return changed ? next : prev;
+    });
+  }
+
+  static getPendingCount(statuses: Map<FileId, FileLoadingStatus>) {
+    let pending = 0;
+    let total = 0;
+    for (const status of statuses.values()) {
+      total++;
+      if (status === "loading") {
+        pending++;
+      }
+    }
+    return { pending, total };
+  }
+}