// Copyright 2017 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.

#ifndef PERIDOT_LIB_FIDL_APP_CLIENT_H_
#define PERIDOT_LIB_FIDL_APP_CLIENT_H_

#include <memory>
#include <string>

#include <fuchsia/cpp/component.h>
#include <fuchsia/cpp/modular.h>
#include "lib/fidl/cpp/binding.h"
#include "lib/fidl/cpp/interface_request.h"
#include "lib/fsl/tasks/message_loop.h"
#include "lib/fxl/macros.h"
#include "lib/fxl/tasks/task_runner.h"
#include "lib/fxl/time/time_delta.h"
#include "lib/svc/cpp/services.h"
#include "peridot/lib/common/async_holder.h"

namespace modular {

// A class that holds a connection to a single service instance in an
// application instance. The service instance supports life cycle with a
// Terminate() method. When calling Terminate(), the service is supposed to
// close its connection, and when that happens, we can kill the application, or
// it's gone already anyway. If the service connection doesn't close after a
// timeout, we close it and kill the application anyway.
//
// When starting an application instance, the directory pointed to by
// |data_origin| will be mapped into /data for the newly started application.
// If left empty, it'll be mapped to the root /data.
//
// |additional_services| will allow us to add custom services to an applications
// namespace.
//
// AppClientBase are the non-template parts factored out so they don't need to
// be inline. It can be used on its own too.
class AppClientBase : public AsyncHolderBase {
 public:
  AppClientBase(component::ApplicationLauncher* launcher,
                AppConfig config,
                std::string data_origin = "",
                component::ServiceListPtr additional_services = nullptr);
  virtual ~AppClientBase();

  // Gives access to the services of the started application. Services
  // obtained from it are not involved in life cycle management provided by
  // AppClient, however. This is used for example to obtain the ViewProvider.
  component::Services& services() { return services_; }

  // Registers a handler to receive a notification when this application
  // connection encounters an error. This typically happens when this
  // application stops or crashes. |error_handler| will be deregistered when
  // attempting graceful termination via |AsyncHolderBase::Teardown()|.
  void SetAppErrorHandler(const std::function<void()>& error_handler);

 private:
  // The termination sequence as prescribed by AsyncHolderBase.
  void ImplTeardown(std::function<void()> done) override;
  void ImplReset() override;

  // Service specific parts of the termination sequence.
  virtual void ServiceTerminate(const std::function<void()>& done);
  virtual void ServiceUnbind();

  component::ApplicationControllerPtr app_;
  component::Services services_;
  FXL_DISALLOW_COPY_AND_ASSIGN(AppClientBase);
};

// A generic client that does the standard termination sequence. For a service
// with another termination sequence, another implementation could be created.
template <class Service>
class AppClient : public AppClientBase {
 public:
  AppClient(component::ApplicationLauncher* const launcher,
            AppConfig config,
            std::string data_origin = "",
            component::ServiceListPtr additional_services = nullptr)
      : AppClientBase(launcher,
                      std::move(config),
                      std::move(data_origin),
                      std::move(additional_services)) {
    services().ConnectToService(service_.NewRequest());
  }

  ~AppClient() override = default;

  fidl::InterfacePtr<Service>& primary_service() { return service_; }

 private:
  void ServiceTerminate(const std::function<void()>& done) override {
    // The service is expected to acknowledge the Terminate() request by
    // closing its connection within the timeout set in Teardown().
    service_.set_error_handler(done);
    service_->Terminate();
  }

  void ServiceUnbind() override { service_.Unbind(); }

  fidl::InterfacePtr<Service> service_;
  FXL_DISALLOW_COPY_AND_ASSIGN(AppClient);
};

template <>
void AppClient<Lifecycle>::ServiceTerminate(const std::function<void()>& done);

}  // namespace modular

#endif  // PERIDOT_LIB_FIDL_APP_CLIENT_H_