interface MountContext {}
type MountArgs = [HTMLElement];
type MountReturn = () => void;

interface App {
  mount: (context: MountContext, ...mountArgs: MountArgs) => MountReturn
}

export class ApplicationService {
  private readonly apps$ = new BehaviorSubject<App[]>([]);

  public setup({ context }) {
    this.mountContext = context.createContextContainer<
      MountContext,
      MountArgs,
      MountReturn
    >();
    return {
      registerApp: (plugin: symbol, app: App) =>
        this.apps$.next([
          ...this.apps$.value,
         {
           ...app,
           mount: this.mountContext.createHandler(plugin, app.mount)
         }
      ]),
      registerContext: this.mountContext.registerContext
    };
  }

  public async start() { ... }
}

export class ApplicationService {
  private readonly apps$ = new BehaviorSubject<App[]>([]);

  public setup() { ... }

  public async start({ context }) {
    const mountContext = context.createContextContainer<ApplicationContext>();
    
    // dumb example of mounting an app
    const appToMount = this.apps$.value[0];
    // `appToMount.mount` will automatically invoke each context provider and
    // call the original mount function with it
    const unmount = appToMount.mount(document.createElement('div'));

    return {
      registerContext: mountContext.registerContext
    };
  }
}

class MyPlugin {
  private readonly handlers = new Map();
  setup(core) {
    this.contextContainer = core.context.createContextContainer();
    return {
      registerContext(pluginOpaqueId, contextName, provider) {
        this.contextContainer.registerContext(pluginOpaqueId, contextName, provider);
      },
      registerRoute(pluginOpaqueId, path, handler) {
        this.handlers.set(
          path,
          this.contextContainer.createHandler(pluginOpaqueId, handler)
        );
      }
    }
  }
}