// Copyright 2020 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "federated/daemon.h"

#include <sysexits.h>

#include <memory>
#include <utility>

#include <base/bind.h>
#include <base/check.h>
#include <base/files/file_util.h>
#include <chromeos/dbus/service_constants.h>
#include <dbus/bus.h>
#include <dbus/message.h>
#include <mojo/core/embedder/embedder.h>
#include <mojo/public/cpp/system/invitation.h>

#include "federated/federated_service_impl.h"
#include "federated/storage_manager.h"

namespace federated {

Daemon::Daemon() : weak_ptr_factory_(this) {}

Daemon::~Daemon() = default;

int Daemon::OnInit() {
  int exit_code = DBusDaemon::OnInit();
  if (exit_code != EX_OK)
    return exit_code;

  // Initializes storage_manager_.
  StorageManager::GetInstance()->InitializeSessionManagerProxy(bus_.get());

  // Creates the scheduler and schedules the tasks.
  scheduler_ =
      std::make_unique<Scheduler>(StorageManager::GetInstance(), bus_.get());
  scheduler_->Schedule();

  mojo::core::Init();
  ipc_support_ = std::make_unique<mojo::core::ScopedIPCSupport>(
      base::ThreadTaskRunnerHandle::Get(),
      mojo::core::ScopedIPCSupport::ShutdownPolicy::FAST);
  InitDBus();

  return 0;
}

void Daemon::InitDBus() {
  // Gets or create the ExportedObject for the Federated service.
  dbus::ExportedObject* const federated_service_exported_object =
      bus_->GetExportedObject(dbus::ObjectPath(kFederatedServicePath));
  CHECK(federated_service_exported_object);

  // Registers a handler of the BootstrapMojoConnection method.
  CHECK(federated_service_exported_object->ExportMethodAndBlock(
      kFederatedInterfaceName, kBootstrapMojoConnectionMethod,
      base::BindRepeating(&Daemon::BootstrapMojoConnection,
                          weak_ptr_factory_.GetWeakPtr())));

  // Takes ownership of the Federated service.
  CHECK(bus_->RequestOwnershipAndBlock(kFederatedServiceName,
                                       dbus::Bus::REQUIRE_PRIMARY));
}

void Daemon::BootstrapMojoConnection(
    dbus::MethodCall* method_call,
    dbus::ExportedObject::ResponseSender response_sender) {
  if (federated_service_) {
    LOG(ERROR) << "FederatedService already instantiated";
    std::move(response_sender)
        .Run(dbus::ErrorResponse::FromMethodCall(
            method_call, DBUS_ERROR_FAILED, "Bootstrap already completed"));
    return;
  }

  base::ScopedFD file_handle;
  dbus::MessageReader reader(method_call);

  if (!reader.PopFileDescriptor(&file_handle)) {
    LOG(ERROR) << "Couldn't extract file descriptor from D-Bus call";
    std::move(response_sender)
        .Run(dbus::ErrorResponse::FromMethodCall(
            method_call, DBUS_ERROR_INVALID_ARGS, "Expected file descriptor"));
    return;
  }

  if (!file_handle.is_valid()) {
    LOG(ERROR) << "ScopedFD extracted from D-Bus call was invalid (i.e. empty)";
    std::move(response_sender)
        .Run(dbus::ErrorResponse::FromMethodCall(
            method_call, DBUS_ERROR_INVALID_ARGS,
            "Invalid (empty) file descriptor"));
    return;
  }

  if (!base::SetCloseOnExec(file_handle.get())) {
    PLOG(ERROR) << "Failed setting FD_CLOEXEC on file descriptor";
    std::move(response_sender)
        .Run(dbus::ErrorResponse::FromMethodCall(
            method_call, DBUS_ERROR_FAILED,
            "Failed setting FD_CLOEXEC on file descriptor"));
    return;
  }

  // Connects to mojo in the requesting process.
  mojo::IncomingInvitation invitation =
      mojo::IncomingInvitation::Accept(mojo::PlatformChannelEndpoint(
          mojo::PlatformHandle(std::move(file_handle))));

  // Binds primordial message pipe to a FederatedService implementation.
  federated_service_ = std::make_unique<FederatedServiceImpl>(
      invitation.ExtractMessagePipe(kBootstrapMojoConnectionChannelToken),
      base::BindOnce(&Daemon::OnMojoDisconnection, base::Unretained(this)),
      StorageManager::GetInstance());

  // Sends success response.
  std::move(response_sender).Run(dbus::Response::FromMethodCall(method_call));
}

void Daemon::OnMojoDisconnection() {
  // Die upon disconnection. Reconnection can occur when the daemon is
  // restarted.
  Quit();
}

}  // namespace federated