public/lib/module/fidl/module.fidl

// Copyright 2016 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.

library modular;

// import "lib/story/fidl/link.fidl";
// import "lib/module/fidl/module_context.fidl";

// This service is implemented by an application that is meant to be run under a
// ModuleContext in a Story.
//
// When ModuleContext.StartModuleDeprecated() is invoked, the Module instance is requested
// from its application and its dependent services and parameters are passed to
// it by Initialize().
//
// If a module application implements the |Lifecycle| interface, then invocation
// of the Terminate() method on its |Lifecycle| service is a signal that it
// should stop. If the module application does not implement the |Lifecycle|
// interface, the application instance is simply terminated in order to stop it.
//
// A module may be stopped for the following reasons:
//
// (1) StoryController.Stop() is called to stop the whole story. A plausible
//     occasion for this to happen is that the root module in the story has
//     signalled that it's Done(), or that the user logs out.
//
// (2) ModuleController.Stop() is called by the caller that started this
//     Module. A plausible occasion for this to happen is that the module has
//     signalled that it's Done().
//
// Other connections the Module instance may hold, such as to Link, LinkWatcher,
// ModuleController of other Module instances, are closed after
// Lifecycle.Terminate() is called.
[ServiceName="modular.Module"]  // Created by each module component.
interface Module {
  // The arguments to Initialize() are the ModuleContext instance that created
  // the Module instance and a Link instance provided by the caller of
  // ModuleContext.StartModuleDeprecated().
  //
  // The default Link instance available from ModuleContext.GetLink() with a
  // null link name is shared with the calling module and can be used to
  // exchange data.
  //
  // Additionally, this module may provide its services to the calling module by
  // implementing its |outgoing_services|.
  //
  // The ModuleContext instance can be used to start more Module instances, and
  // to create Link instances to share data with those Module instances. Calling
  // ModuleContext.Done() signals this module requests to be stopped.
  //
  // TODO(vardhan): Move outgoing_services as getter into ModuleContext.
  1: Initialize(ModuleContext module_context,
               request<component.ServiceProvider>? outgoing_services);
};