Own browser UI sessions and shared navigation

src/apps/browser/BrowserUiScope.ts

@@ -0,0 +1,38 @@
+import type { ServiceContext } from "@vrtmrz/livesync-commonlib/context";
+import { EVENT_PLUGIN_UNLOADED } from "@vrtmrz/livesync-commonlib/compat/events/coreEvents";
+import { _activeDocument } from "@vrtmrz/livesync-commonlib/compat/common/coreEnvFunctions";
+
+export interface BrowserUiOptions {
+    readonly document?: Document;
+    readonly signal?: AbortSignal;
+}
+
+/** Browser presentation target and lifetime owned by one application context. */
+export interface BrowserUiScope {
+    readonly document: Document;
+    readonly signal: AbortSignal;
+}
+
+export function createBrowserUiScope(
+    context: Pick<ServiceContext, "events">,
+    options: BrowserUiOptions = {}
+): BrowserUiScope {
+    const controller = new AbortController();
+    const parent = options.signal;
+    let unregisterUnload: (() => void) | undefined;
+    const end = (reason: unknown): void => {
+        if (controller.signal.aborted) return;
+        unregisterUnload?.();
+        unregisterUnload = undefined;
+        parent?.removeEventListener("abort", onParentAbort);
+        controller.abort(reason);
+    };
+    const onParentAbort = () => end(parent?.reason);
+    if (parent?.aborted) {
+        controller.abort(parent.reason);
+    } else {
+        unregisterUnload = context.events.onceEvent(EVENT_PLUGIN_UNLOADED, () => end(new Error("Plug-in unloaded")));
+        parent?.addEventListener("abort", onParentAbort, { once: true });
+    }
+    return { document: options.document ?? _activeDocument, signal: controller.signal };
+}