chromium/components/fuchsia_component_support/dynamic_component_host.h

// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_FUCHSIA_COMPONENT_SUPPORT_DYNAMIC_COMPONENT_HOST_H_
#define COMPONENTS_FUCHSIA_COMPONENT_SUPPORT_DYNAMIC_COMPONENT_HOST_H_

#include <fuchsia/component/cpp/fidl.h>
#include <fuchsia/io/cpp/fidl.h>

#include <memory>
#include <string>
#include <string_view>

#include "base/functional/callback.h"

namespace sys {
class ServiceDirectory;
}  // namespace sys

namespace fuchsia_component_support {

// Helper class used to manage a dynamic child component running in a
// collection, via the Component Framework.
class DynamicComponentHost {
 public:
  // Creates a component instance named `child_id` in `collection`, which must
  // be a defined in the calling component's manifest.
  // The new instance will run the component defined by `component_url`.
  //
  // `on_teardown` will be run if the Component fails to start, or is observed
  // to have stopped. The callback may delete the `DynamicComponentHost` before
  // returning.
  //
  // If `services` is set then it will be offered to the new instance as the
  // directory capability "svc". This requires that the calling component's
  // manifest defines a writable directory capability
  // "for_dynamic_component_host", in which `services` may be bound to be
  // dynamically offered to the child.
  DynamicComponentHost(std::string_view collection,
                       std::string_view child_id,
                       std::string_view component_url,
                       base::OnceClosure on_teardown,
                       fidl::InterfaceHandle<fuchsia::io::Directory> services);

  // Used by tests to create a child component via a `realm` other than the
  // calling component.
  // TODO(crbug.com/40261626): Remove this once tests have an easy way to
  // "bridge" sub-Realms to the TestComponentContextForProcess.
  DynamicComponentHost(fuchsia::component::RealmHandle realm,
                       std::string_view collection,
                       std::string_view child_id,
                       std::string_view component_url,
                       base::OnceClosure on_teardown,
                       fidl::InterfaceHandle<fuchsia::io::Directory> services);

  // Deleting the Component implicitly `Destroy()`s it if necessary, without
  // causing `on_teardown_` to be run.
  ~DynamicComponentHost();

  // Requests that the underlying Component be destroyed. When the Component
  // has actually been destroyed the `on_teardown_` closure will be run.
  void Destroy();

  // Returns the directory of capabilities exposed by the Component.
  sys::ServiceDirectory& exposed() const { return *exposed_; }

 private:
  const std::string collection_;
  const std::string child_id_;

  // Run if the Component stops, or fails to start.
  // `this` may be invalid after the callback returns.
  base::OnceClosure on_teardown_;

  // Set during construction, and used to create and manage the Component.
  // Remains valid until `DestroyChild()` has been dispatched, or the
  // attempt to create the Component is observed to have failed.
  fuchsia::component::RealmPtr realm_;

  // Wraps the directory of capabilities exposed by the Component.
  std::unique_ptr<sys::ServiceDirectory> exposed_;

  // Used to monitor the Component for termination.
  fuchsia::component::BinderPtr binder_;
};

}  // namespace fuchsia_component_support

#endif  // COMPONENTS_FUCHSIA_COMPONENT_SUPPORT_DYNAMIC_COMPONENT_HOST_H_