public/dart/fuchsia_modular_flutter/lib/src/session_shell.dart

// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:fidl_fuchsia_ui_policy/fidl_async.dart' show Presentation;
import 'package:fidl_fuchsia_modular/fidl_async.dart'
    show SessionShellContext, PuppetMaster;
import 'package:fuchsia_services/services.dart' show StartupContext;
import 'package:meta/meta.dart';

import 'session_shell/internal/_session_shell_impl.dart';
import 'story.dart';

/// Defines a class that encapsulates FIDL interfaces used to build a 'Session
/// Shell' for Fuchsia.
///
/// A Session Shell's primary responsibility is to display
/// and manage a set of [Story] instances. As such it provides a Session Shell
/// author a set of callbacks to be notified when a story is started, stopped
/// or changed. It allows stories to be deleted and focused. Only the
/// [onStoryStarted] callback is required, since it returns a concrete [Story].
abstract class SessionShell {
  static SessionShell _sessionShell;

  /// Returns a shared instance of this.
  factory SessionShell({
    @required StartupContext startupContext,
    @required StoryFactory onStoryStarted,
    StoryCallback onStoryChanged,
    StoryCallback onStoryDeleted,
  }) {
    return _sessionShell ??= SessionShellImpl(
      startupContext: startupContext,
      onStoryStarted: onStoryStarted,
      onStoryChanged: onStoryChanged,
      onStoryDeleted: onStoryDeleted,
    );
  }

  /// An interable for stories in the session.
  Iterable<Story> get stories;

  /// The [Story] that is currently focused. It could be [null].
  Story get focusedStory;

  /// Returns the [SessionShellContext].
  SessionShellContext get context;

  /// Returns the [Presentation] used by the session.
  Presentation get presentation;

  /// Returns the [PuppetMaster] used by the session.
  PuppetMaster get puppetMaster;

  /// Register this instance of Session Shell with modular framework. This
  /// needs to be called before any other methods.
  void start();

  /// Unregister and disconnect from modular framework.
  void stop();

  /// Request focus for story with [id]. Ensure [start] is called before
  /// invoking this method. Otherwise this is a no-op.
  void focusStory(String id);

  /// Delete the [Story] given the id. Ensure [start] is called before
  /// invoking this method. Otherwise this is a no-op.
  void deleteStory(String id);

  /// Stop the story with the id. Ensure [start] is called before
  /// invoking this method. Otherwise this is a no-op.
  void stopStory(String id);
}