refactor(logo): encapsulate shared logo cache with AbortController cleanup

src/lib/logoCache.ts

@@ -0,0 +1,73 @@
+/*
+ * SPDX-FileCopyrightText: 2020 Stalwart Labs LLC <hello@stalw.art>
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
+ */
+
+import { getApiBaseUrl } from '@/services/api';
+
+export type LogoSnapshot = { status: 'loading' } | { status: 'custom'; url: string } | { status: 'default' };
+
+let snapshot: LogoSnapshot = { status: 'loading' };
+let objectUrl: string | null = null;
+let abortController: AbortController | null = null;
+let started = false;
+const listeners = new Set<() => void>();
+
+function emit(): void {
+  for (const listener of listeners) {
+    listener();
+  }
+}
+
+function revokeObjectUrl(): void {
+  if (objectUrl) {
+    URL.revokeObjectURL(objectUrl);
+    objectUrl = null;
+  }
+}
+
+export function getLogoSnapshot(): LogoSnapshot {
+  return snapshot;
+}
+
+export function subscribeLogo(listener: () => void): () => void {
+  listeners.add(listener);
+  return () => {
+    listeners.delete(listener);
+  };
+}
+
+/** Starts a single shared /logo fetch. Safe to call from every Logo mount. */
+export function ensureLogoLoaded(): void {
+  if (started) return;
+  started = true;
+  snapshot = { status: 'loading' };
+  emit();
+
+  abortController?.abort();
+  abortController = new AbortController();
+  const { signal } = abortController;
+
+  fetch(`${getApiBaseUrl()}/logo`, { signal })
+    .then(async (response) => {
+      const contentType = response.headers.get('content-type') ?? '';
+      if (response.ok && contentType.startsWith('image/')) {
+        const blob = await response.blob();
+        if (signal.aborted) return;
+        revokeObjectUrl();
+        objectUrl = URL.createObjectURL(blob);
+        snapshot = { status: 'custom', url: objectUrl };
+        emit();
+        return;
+      }
+      if (signal.aborted) return;
+      snapshot = { status: 'default' };
+      emit();
+    })
+    .catch(() => {
+      if (signal.aborted) return;
+      snapshot = { status: 'default' };
+      emit();
+    });
+}