// Copyright 2018 The ChromiumOS Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "ml/daemon.h"

#include <memory>
#include <utility>

#include <sys/types.h>
#include <sysexits.h>
#include <unistd.h>

#include <base/check.h>
#include <base/files/file_util.h>
#include <base/functional/bind.h>
#include <base/logging.h>
#include <base/task/single_thread_task_runner.h>
#include <base/memory/ref_counted.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 "ml/dlcservice_client.h"
#include "ml/machine_learning_service_impl.h"
#include "ml/request_metrics.h"

namespace ml {

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

Daemon::~Daemon() {}

int Daemon::OnInit() {
  int exit_code = DBusDaemon::OnInit();
  if (exit_code != EX_OK) {
    LOG(ERROR) << "DBusDaemon::OnInit() failed";
    return exit_code;
  }
  // For control process, we need to change euid back to 0. We need the control
  // process to be root in the user namespace because it needs to spawn worker
  // processes and sandbox them.
  if (seteuid(0) != 0) {
    RecordProcessErrorEvent(ProcessError::kChangeEuidBackToRootFailed);
    LOG(ERROR) << "Unable to change effective uid back to 0";
    exit(EX_OSERR);
  }

  metrics_.StartCollectingProcessMetrics();
  mojo::core::Init();
  ipc_support_ = std::make_unique<mojo::core::ScopedIPCSupport>(
      base::SingleThreadTaskRunner::GetCurrentDefault(),
      mojo::core::ScopedIPCSupport::ShutdownPolicy::FAST);
  InitDBus();

  return 0;
}

void Daemon::InitDBus() {
  // Get or create the ExportedObject for the ML service.
  dbus::ExportedObject* const ml_service_exported_object =
      bus_->GetExportedObject(dbus::ObjectPath(kMachineLearningServicePath));
  CHECK(ml_service_exported_object);

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

  // Take ownership of the ML service.
  CHECK(bus_->RequestOwnershipAndBlock(kMachineLearningServiceName,
                                       dbus::Bus::REQUIRE_PRIMARY));
}

void Daemon::BootstrapMojoConnection(
    dbus::MethodCall* method_call,
    dbus::ExportedObject::ResponseSender response_sender) {
  metrics_.RecordMojoConnectionEvent(
      Metrics::MojoConnectionEvent::kBootstrapRequested);
  if (machine_learning_service_) {
    LOG(ERROR) << "MachineLearningService 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;
  }

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

  // Bind primordial message pipe to a MachineLearningService implementation.
  machine_learning_service_ = std::make_unique<MachineLearningServiceImpl>(
      mojo::PendingReceiver<
          chromeos::machine_learning::mojom::MachineLearningService>(
          invitation.ExtractMessagePipe(kBootstrapMojoConnectionChannelToken)),
      base::BindOnce(&Daemon::OnMojoDisconnection, base::Unretained(this)),
      bus_.get());

  metrics_.RecordMojoConnectionEvent(
      Metrics::MojoConnectionEvent::kBootstrapSucceeded);

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

void Daemon::OnMojoDisconnection() {
  metrics_.RecordMojoConnectionEvent(
      Metrics::MojoConnectionEvent::kConnectionClosed);
  // Die upon disconnection . Reconnection can occur when the daemon is
  // restarted. (A future Mojo API may enable Mojo re-bootstrap without a
  // process restart.)
  Quit();
}

}  // namespace ml