Add better control over substreams.

src/utils/substream.ts

@@ -0,0 +1,48 @@
+import { CameraManager } from '../camera-manager/manager';
+import { View } from '../view/view';
+import { getAllDependentCameras } from './camera';
+
+export const createViewWithSelectedSubstream = (
+  view: View,
+  substreamID: string,
+): View | null => {
+  const overrides: Map<string, string> = view.context?.live?.overrides ?? new Map();
+  overrides.set(view.camera, substreamID);
+  return view.clone().mergeInContext({
+    live: { overrides: overrides },
+  });
+};
+
+export const createViewWithoutSubstream = (view: View): View => {
+  const newView = view.clone();
+  const overrides: Map<string, string> | undefined = newView.context?.live?.overrides;
+  if (overrides && overrides.has(view.camera)) {
+    newView.context?.live?.overrides?.delete(view.camera);
+  }
+  return newView;
+};
+
+export const hasSubstream = (view: View): boolean => {
+  const override = view?.context?.live?.overrides?.get(view.camera);
+  return !!override && override !== view.camera;
+};
+
+export const createViewWithNextStream = (
+  cameraManager: CameraManager,
+  view: View,
+): View => {
+  const dependencies = [...getAllDependentCameras(cameraManager, view.camera)];
+  if (dependencies.length <= 1) {
+    return view.clone();
+  }
+
+  const newView = view.clone();
+  const overrides: Map<string, string> = newView.context?.live?.overrides ?? new Map();
+  const currentOverride = overrides.get(newView.camera) ?? newView.camera;
+  const currentIndex = dependencies.indexOf(currentOverride);
+  const newIndex = currentIndex < 0 ? 0 : (currentIndex + 1) % dependencies.length;
+  overrides.set(view.camera, dependencies[newIndex]);
+  newView.mergeInContext({ live: { overrides: overrides } });
+
+  return newView;
+};