logic.py

"""
Contains the core logic for the application in the Controller class.

Copyright (C) 2018  The Freedom of the Press Foundation.

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published
by the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.
"""
import datetime
import functools
import inspect
import logging
import os
import uuid
from gettext import gettext as _
from typing import Any, Dict, List, Tuple, Type, Union  # noqa: F401

import arrow
import sdclientapi
from PyQt5.QtCore import QObject, QProcess, Qt, QThread, QTimer, pyqtSignal
from sdclientapi import RequestTimeoutError, ServerConnectionError
from sqlalchemy.orm.session import sessionmaker

from securedrop_client import db, storage
from securedrop_client.api_jobs.base import ApiInaccessibleError
from securedrop_client.api_jobs.downloads import (
    DownloadChecksumMismatchException,
    DownloadDecryptionException,
    DownloadException,
    FileDownloadJob,
    MessageDownloadJob,
    ReplyDownloadJob,
)
from securedrop_client.api_jobs.sources import DeleteSourceJob, DeleteSourceJobException
from securedrop_client.api_jobs.updatestar import (
    UpdateStarJob,
    UpdateStarJobError,
    UpdateStarJobTimeoutError,
)
from securedrop_client.api_jobs.uploads import (
    SendReplyJob,
    SendReplyJobError,
    SendReplyJobTimeoutError,
)
from securedrop_client.crypto import GpgHelper
from securedrop_client.export import Export
from securedrop_client.queue import ApiJobQueue
from securedrop_client.sync import ApiSync
from securedrop_client.utils import check_dir_permissions

logger = logging.getLogger(__name__)

# 30 seconds between showing the time since the last sync
TIME_BETWEEN_SHOWING_LAST_SYNC_MS = 1000 * 30


def login_required(f):
    @functools.wraps(f)
    def decorated_function(self, *args, **kwargs):
        if not self.api:
            self.on_action_requiring_login()
            return
        else:
            return f(self, *args, **kwargs)

    return decorated_function


class APICallRunner(QObject):
    """
    Used to call the SecureDrop API in a non-blocking manner.

    See the call_api method of the Controller class for how this is
    done (hint: you should be using the call_api method and not directly
    using this class).
    """

    call_succeeded = pyqtSignal()
    call_failed = pyqtSignal()
    call_timed_out = pyqtSignal()

    def __init__(self, api_call, current_object=None, *args, **kwargs):
        """
        Initialise with the function to call the API and any associated
        args and kwargs. If current object is passed in, this represents some
        state which the event handlers may need when they're eventually fired.
        """
        super().__init__()
        self.api_call = api_call
        self.current_object = current_object
        self.args = args
        self.kwargs = kwargs
        self.result = None

    def call_api(self):
        """
        Call the API. Emit a boolean signal to indicate the outcome of the
        call. Any return value or exception raised is stored in self.result.
        """
        # this blocks
        try:
            self.result = self.api_call(*self.args, **self.kwargs)
        except Exception as ex:
            if isinstance(ex, (RequestTimeoutError, ServerConnectionError)):
                self.call_timed_out.emit()

            logger.error(ex)
            self.result = ex
            self.call_failed.emit()
        else:
            self.call_succeeded.emit()


class Controller(QObject):
    """
    Represents the logic for the secure drop client application. In an MVC
    application, this is the controller.
    """

    sync_events = pyqtSignal(str)

    """
    A signal that emits a signal when the authentication state changes.
    - `True` when the client becomes authenticated
    - `False` when the client becomes unauthenticated
    """
    authentication_state = pyqtSignal(bool)

    """
    This signal indicates that a reply was successfully sent and received by the server.

    Emits:
        str: the reply's source UUID
        str: the reply UUID
        str: the content of the reply
    """
    reply_succeeded = pyqtSignal(str, str, str)

    """
    This signal indicates that a reply was not successfully sent or received by the server.

    Emits:
        str: the reply UUID
    """
    reply_failed = pyqtSignal(str)

    """
    This signal indicates that a reply has been successfully downloaded.

    Emits:
        str: the reply's source UUID
        str: the reply UUID
        str: the content of the reply
    """
    reply_ready = pyqtSignal(str, str, str)

    """
    This signal indicates an error while downloading a reply.

    Emits:
        str: the reply's source UUID
        str: the reply UUID
        str: the content of the reply
    """
    reply_download_failed = pyqtSignal(str, str, str)

    """
    This signal indicates that a message has been successfully downloaded.

    Emits:
        str: the message's source UUID
        str: the message UUID
        str: the content of the message
    """
    message_ready = pyqtSignal(str, str, str)

    """
    This signal indicates an error while downloading a message.

    Emits:
        str: the message's source UUID
        str: the message UUID
        str: the content of the message
    """
    message_download_failed = pyqtSignal(str, str, str)

    """
    This signal indicates that a file has been successfully downloaded.

    Emits:
        str: the file's source UUID
        str: the file UUID
        str: the name of the file
    """
    file_ready = pyqtSignal(str, str, str)

    """
    This signal indicates that a file is missing.

    Emits:
        str: the file UUID
    """
    file_missing = pyqtSignal(str, str, str)

    """
    This signal indicates that a deletion request was accepted by the server.

    Emits:
        str: the source UUID
    """
    source_deleted = pyqtSignal(str)

    """
    This signal indicates that a star update request succeeded.

    Emits:
        str: the source UUID
    """
    star_update_successful = pyqtSignal(str)

    """
    This signal indicates that a star update request failed.

    Emits:
        str: the source UUID
        bool: is_starred
    """
    star_update_failed = pyqtSignal(str, bool)

    """
    This signal indicates that a deletion attempt failed at the server.

    Emits:
        str: the source UUID
    """
    source_deletion_failed = pyqtSignal(str)

    """
    This signal lets the queue manager know to add the job to the appropriate
    network queue.

    Emits:
        PyQt_PyObject: the ApiJob to be added
    """
    add_job = pyqtSignal("PyQt_PyObject")

    def __init__(
        self,
        hostname: str,
        gui,
        session_maker: sessionmaker,
        home: str,
        proxy: bool = True,
        qubes: bool = True,
    ) -> None:
        """
        The hostname, gui and session objects are used to coordinate with the
        various other layers of the application: the location of the SecureDrop
        proxy, the user interface and SqlAlchemy local storage respectively.
        """
        check_dir_permissions(home)
        super().__init__()

        # Controller is unauthenticated by default
        self.__is_authenticated = False

        # used for finding DB in sync thread
        self.home = home

        # boolean flag for whether or not the client is operating behind a proxy
        self.proxy = proxy

        # boolean flag for whether the client is running within Qubes
        # (regardless of proxy state, to support local dev in an AppVM)
        self.qubes = qubes

        # Location of the SecureDrop server.
        self.hostname = hostname

        # Reference to the UI window.
        self.gui = gui

        # Reference to the API for secure drop proxy.
        self.api = None  # type: sdclientapi.API

        # Reference to the SqlAlchemy `sessionmaker` and `session`
        self.session_maker = session_maker
        self.session = session_maker()

        # Queue that handles running API job
        self.api_job_queue = ApiJobQueue(self.api, self.session_maker)
        self.api_job_queue.paused.connect(self.on_queue_paused)
        self.add_job.connect(self.api_job_queue.enqueue)

        # Contains active threads calling the API.
        self.api_threads = {}  # type: Dict[str, Dict]

        self.gpg = GpgHelper(home, self.session_maker, proxy)

        self.export = Export()

        # File data.
        self.data_dir = os.path.join(self.home, "data")

        # Background sync to keep client up-to-date with server changes
        self.api_sync = ApiSync(self.api, self.session_maker, self.gpg, self.data_dir)
        self.api_sync.sync_started.connect(self.on_sync_started, type=Qt.QueuedConnection)
        self.api_sync.sync_success.connect(self.on_sync_success, type=Qt.QueuedConnection)
        self.api_sync.sync_failure.connect(self.on_sync_failure, type=Qt.QueuedConnection)

        # Create a timer to show the time since the last sync
        self.show_last_sync_timer = QTimer()
        self.show_last_sync_timer.timeout.connect(self.show_last_sync)

        # Path to the file containing the timestamp since the last sync with the server
        self.last_sync_filepath = os.path.join(home, "sync_flag")

    @property
    def is_authenticated(self) -> bool:
        return self.__is_authenticated

    @is_authenticated.setter
    def is_authenticated(self, is_authenticated: bool) -> None:
        if self.__is_authenticated != is_authenticated:
            self.__is_authenticated = is_authenticated
            self.authentication_state.emit(is_authenticated)

    @is_authenticated.deleter
    def is_authenticated(self) -> None:
        raise AttributeError("Cannot delete is_authenticated")

    def setup(self):
        """
        Setup the application with the default state of:

        * Not logged in.
        * Show most recent state of syncronised sources.
        * Show the login screen.
        * Check the sync status every 30 seconds.
        """
        # The gui needs to reference this "controller" layer to call methods
        # triggered by UI events.
        self.gui.setup(self)

        # Run export object in a separate thread context (a reference to the
        # thread is kept on self such that it does not get garbage collected
        # after this method returns) - we want to keep our export thread around for
        # later processing.
        self.export_thread = QThread()
        self.export.moveToThread(self.export_thread)
        self.export_thread.start()

        storage.clear_download_errors(self.session)

    def call_api(
        self,
        api_call_func,
        success_callback,
        failure_callback,
        *args,
        current_object=None,
        **kwargs,
    ):
        """
        Calls the function in a non-blocking manner. Upon completion calls the
        callback with the result. Calls timeout if the timer associated with
        the call emits a timeout signal. Any further arguments are passed to
        the function to be called.
        """
        new_thread_id = str(uuid.uuid4())  # Uniquely id the new thread.

        new_api_thread = QThread(self.gui)
        new_api_runner = APICallRunner(api_call_func, current_object, *args, **kwargs)
        new_api_runner.moveToThread(new_api_thread)

        # handle completed call: copy response data, reset the
        # client, give the user-provided callback the response
        # data
        new_api_runner.call_succeeded.connect(
            lambda: self.completed_api_call(new_thread_id, success_callback)
        )
        new_api_runner.call_failed.connect(
            lambda: self.completed_api_call(new_thread_id, failure_callback)
        )

        # when the thread starts, we want to run `call_api` on `api_runner`
        new_api_thread.started.connect(new_api_runner.call_api)

        # Add the thread related objects to the api_threads dictionary.
        self.api_threads[new_thread_id] = {"thread": new_api_thread, "runner": new_api_runner}

        # Start the thread and related activity.
        new_api_thread.start()

    def on_queue_paused(self) -> None:
        self.gui.update_error_status(
            _("The SecureDrop server cannot be reached. Trying to reconnect..."), duration=0
        )
        self.show_last_sync_timer.start(TIME_BETWEEN_SHOWING_LAST_SYNC_MS)

    def resume_queues(self) -> None:
        self.api_job_queue.resume_queues()
        self.show_last_sync_timer.stop()

        # clear error status in case queue was paused resulting in a permanent error message
        self.gui.clear_error_status()

    def completed_api_call(self, thread_id, user_callback):
        """
        Manage a completed API call. The actual result *may* be an exception or
        error result from the API. It's up to the handler (user_callback) to
        handle these potential states.
        """
        logger.debug("Completed API call. Cleaning up and running callback.")
        thread_info = self.api_threads.pop(thread_id)
        runner = thread_info["runner"]
        result_data = runner.result

        arg_spec = inspect.getfullargspec(user_callback)
        if "current_object" in arg_spec.args:
            user_callback(result_data, current_object=runner.current_object)
        else:
            user_callback(result_data)

    def login(self, username, password, totp):
        """
        Given a username, password and time based one-time-passcode (TOTP), create a new instance
        representing the SecureDrop api and authenticate.

        Default to 60 seconds until we implement a better request timeout strategy. We lower the
        default_request_timeout for Queue API requests in ApiJobQueue in order to display errors
        faster.
        """
        storage.mark_all_pending_drafts_as_failed(self.session)
        self.api = sdclientapi.API(
            self.hostname, username, password, totp, self.proxy, default_request_timeout=60
        )
        self.call_api(
            self.api.authenticate, self.on_authenticate_success, self.on_authenticate_failure
        )
        self.show_last_sync_timer.stop()
        self.set_status("")

    def on_authenticate_success(self, result):
        """
        Handles a successful authentication call against the API.
        """
        logger.info("{} successfully logged in".format(self.api.username))
        self.gui.hide_login()
        user = storage.create_or_update_user(
            self.api.token_journalist_uuid,
            self.api.username,
            self.api.first_name,
            self.api.last_name,
            self.session,
        )
        # Clear clipboard contents in case of previously pasted creds
        self.gui.clear_clipboard()
        self.gui.show_main_window(user)
        self.update_sources()
        self.api_job_queue.start(self.api)
        self.api_sync.start(self.api)
        self.is_authenticated = True

    def on_authenticate_failure(self, result: Exception) -> None:
        # Failed to authenticate. Reset state with failure message.
        self.invalidate_token()
        error = _(
            "That didn't work. Please check everything and try again.\n"
            "Make sure to use a new two-factor code."
        )
        self.gui.show_login_error(error=error)
        self.api_sync.stop()

    def login_offline_mode(self):
        """
        Allow user to view in offline mode without authentication.
        """
        self.gui.hide_login()
        # Clear clipboard contents in case of previously pasted creds (user
        # may have attempted online mode login, then switched to offline)
        self.gui.clear_clipboard()
        self.gui.show_main_window()
        storage.mark_all_pending_drafts_as_failed(self.session)
        self.is_authenticated = False
        self.update_sources()
        self.show_last_sync()
        self.show_last_sync_timer.start(TIME_BETWEEN_SHOWING_LAST_SYNC_MS)

    def on_action_requiring_login(self):
        """
        Indicate that a user needs to login to perform the specified action.
        """
        error = _("You must sign in to perform this action.")
        self.gui.update_error_status(error)

    def authenticated(self):
        """
        Return a boolean indication that the connection to the API is
        authenticated.
        """
        return bool(self.api and self.api.token is not None)

    def get_last_sync(self):
        """
        Returns the time of last synchronisation with the remote SD server.
        """
        try:
            with open(self.last_sync_filepath) as f:
                return arrow.get(f.read())
        except Exception:
            return None

    def on_sync_started(self) -> None:
        self.sync_events.emit("syncing")

    def on_sync_success(self) -> None:
        """
        Called when syncronisation of data via the API queue succeeds.

            * Set last sync flag
            * Display the last sync time and updated list of sources in GUI
            * Download new messages and replies
            * Update missing files so that they can be re-downloaded
        """
        with open(self.last_sync_filepath, "w") as f:
            f.write(arrow.now().format())

        missing_files = storage.update_missing_files(self.data_dir, self.session)
        for missed_file in missing_files:
            self.file_missing.emit(missed_file.source.uuid, missed_file.uuid, str(missed_file))
        self.update_sources()
        self.gui.refresh_current_source_conversation()
        self.download_new_messages()
        self.download_new_replies()
        self.sync_events.emit("synced")
        self.resume_queues()

    def on_sync_failure(self, result: Exception) -> None:
        """
        Called when syncronisation of data via the API fails after a background sync. If the reason
        a sync fails is ApiInaccessibleError then we need to log the user out for security reasons
        and show them the login window in order to get a new token.
        """
        logger.warning("sync failure: {}".format(result))

        if isinstance(result, ApiInaccessibleError):
            # Don't show login window if the user is already logged out
            if not self.is_authenticated or not self.api:
                return

            self.invalidate_token()
            self.logout()
            self.gui.show_login(error=_("Your session expired. Please log in again."))
        elif isinstance(result, (RequestTimeoutError, ServerConnectionError)):
            self.gui.update_error_status(
                _("The SecureDrop server cannot be reached. Trying to reconnect..."), duration=0
            )

    def show_last_sync(self):
        """
        Updates the UI to show human time of last sync.
        """
        self.gui.show_last_sync(self.get_last_sync())

    def update_sources(self):
        """
        Display the updated list of sources with those found in local storage.
        """
        sources = list(storage.get_local_sources(self.session))
        self.gui.show_sources(sources)

    def on_update_star_success(self, source_uuid: str) -> None:
        self.star_update_successful.emit(source_uuid)

    def on_update_star_failure(
        self, error: Union[UpdateStarJobError, UpdateStarJobTimeoutError]
    ) -> None:
        if isinstance(error, UpdateStarJobError):
            self.gui.update_error_status(_("Failed to update star."))
            source = self.session.query(db.Source).filter_by(uuid=error.source_uuid).one()
            self.star_update_failed.emit(error.source_uuid, source.is_starred)

    @login_required
    def update_star(self, source_uuid: str, is_starred: bool):
        """
        Star or unstar.
        """
        job = UpdateStarJob(source_uuid, is_starred)
        job.success_signal.connect(self.on_update_star_success, type=Qt.QueuedConnection)
        job.failure_signal.connect(self.on_update_star_failure, type=Qt.QueuedConnection)
        self.add_job.emit(job)

    def logout(self):
        """
        If the token is not already invalid, make an api call to logout and invalidate the token.
        Then mark all pending draft replies as failed, stop the queues, and show the user as logged
        out in the GUI.
        """

        # clear error status in case queue was paused resulting in a permanent error message
        self.gui.clear_error_status()

        if self.api is not None:
            self.call_api(self.api.logout, self.on_logout_success, self.on_logout_failure)
            self.invalidate_token()

        failed_replies = storage.mark_all_pending_drafts_as_failed(self.session)
        for failed_reply in failed_replies:
            self.reply_failed.emit(failed_reply.uuid)

        self.api_sync.stop()
        self.api_job_queue.stop()
        self.gui.logout()

        self.show_last_sync_timer.start(TIME_BETWEEN_SHOWING_LAST_SYNC_MS)
        self.show_last_sync()
        self.is_authenticated = False

    def invalidate_token(self):
        self.api = None

    def set_status(self, message, duration=5000):
        """
        Set a textual status message to be displayed to the user for a certain
        duration.
        """
        self.gui.update_activity_status(message, duration)

    @login_required
    def _submit_download_job(
        self, object_type: Union[Type[db.Reply], Type[db.Message], Type[db.File]], uuid: str
    ) -> None:

        if object_type == db.Reply:
            job = ReplyDownloadJob(
                uuid, self.data_dir, self.gpg
            )  # type: Union[ReplyDownloadJob, MessageDownloadJob, FileDownloadJob]
            job.success_signal.connect(self.on_reply_download_success, type=Qt.QueuedConnection)
            job.failure_signal.connect(self.on_reply_download_failure, type=Qt.QueuedConnection)
        elif object_type == db.Message:
            job = MessageDownloadJob(uuid, self.data_dir, self.gpg)
            job.success_signal.connect(self.on_message_download_success, type=Qt.QueuedConnection)
            job.failure_signal.connect(self.on_message_download_failure, type=Qt.QueuedConnection)
        elif object_type == db.File:
            job = FileDownloadJob(uuid, self.data_dir, self.gpg)
            job.success_signal.connect(self.on_file_download_success, type=Qt.QueuedConnection)
            job.failure_signal.connect(self.on_file_download_failure, type=Qt.QueuedConnection)

        self.add_job.emit(job)

    def download_new_messages(self) -> None:
        new_messages = storage.find_new_messages(self.session)
        new_message_count = len(new_messages)
        if new_message_count > 0:
            self.set_status(_("Retrieving new messages"), 2500)

        for message in new_messages:
            if message.download_error:
                logger.info(
                    f"Download of message {message.uuid} failed since client start; not retrying."
                )
            else:
                self._submit_download_job(type(message), message.uuid)

    def on_message_download_success(self, uuid: str) -> None:
        """
        Called when a message has downloaded.
        """
        self.session.commit()  # Needed to flush stale data.
        message = storage.get_message(self.session, uuid)
        self.message_ready.emit(message.source.uuid, message.uuid, message.content)

    def on_message_download_failure(self, exception: DownloadException) -> None:
        """
        Called when a message fails to download.
        """
        if isinstance(exception, DownloadChecksumMismatchException):
            # Keep resubmitting the job if the download is corrupted.
            logger.warning("Failure due to checksum mismatch, retrying {}".format(exception.uuid))
            self._submit_download_job(exception.object_type, exception.uuid)

        self.session.commit()
        try:
            message = storage.get_message(self.session, exception.uuid)
            self.message_download_failed.emit(message.source.uuid, message.uuid, str(message))
        except Exception as e:
            logger.error(f"Could not emit message_download_failed: {e}")

    def download_new_replies(self) -> None:
        replies = storage.find_new_replies(self.session)
        for reply in replies:
            if reply.download_error:
                logger.info(
                    f"Download of reply {reply.uuid} failed since client start; not retrying."
                )
            else:
                self._submit_download_job(type(reply), reply.uuid)

    def on_reply_download_success(self, uuid: str) -> None:
        """
        Called when a reply has downloaded.
        """
        self.session.commit()  # Needed to flush stale data.
        reply = storage.get_reply(self.session, uuid)
        self.reply_ready.emit(reply.source.uuid, reply.uuid, reply.content)

    def on_reply_download_failure(self, exception: DownloadException) -> None:
        """
        Called when a reply fails to download.
        """
        if isinstance(exception, DownloadChecksumMismatchException):
            # Keep resubmitting the job if the download is corrupted.
            logger.warning("Failure due to checksum mismatch, retrying {}".format(exception.uuid))
            self._submit_download_job(exception.object_type, exception.uuid)

        self.session.commit()
        try:
            reply = storage.get_reply(self.session, exception.uuid)
            self.reply_download_failed.emit(reply.source.uuid, reply.uuid, str(reply))
        except Exception as e:
            logger.error(f"Could not emit reply_download_failed: {e}")

    def downloaded_file_exists(self, file: db.File) -> bool:
        """
        Check if the file specified by file_uuid exists. If it doesn't update the local db and
        GUI to show the file as not downloaded.
        """
        if not os.path.exists(file.location(self.data_dir)):
            self.gui.update_error_status(
                _("File does not exist in the data directory. Please try re-downloading.")
            )
            logger.warning(
                "Cannot find file in {}. File does not exist.".format(
                    os.path.dirname(file.filename)
                )
            )
            missing_files = storage.update_missing_files(self.data_dir, self.session)
            for f in missing_files:
                self.file_missing.emit(f.source.uuid, f.uuid, str(f))
            return False
        return True

    def on_file_open(self, file: db.File) -> None:
        """
        Open the file specified by file_uuid. If the file is missing, update the db so that
        is_downloaded is set to False.
        """
        logger.info('Opening file in "{}".'.format(os.path.dirname(file.location(self.data_dir))))

        if not self.downloaded_file_exists(file):
            return

        if not self.qubes:
            return

        command = "qvm-open-in-vm"
        args = ["--view-only", "$dispvm:sd-viewer", file.location(self.data_dir)]
        process = QProcess(self)
        process.start(command, args)

    def run_printer_preflight_checks(self):
        """
        Run preflight checks to make sure the Export VM is configured correctly.
        """
        logger.info("Running printer preflight check")

        if not self.qubes:
            self.export.printer_preflight_success.emit()
            return

        self.export.begin_printer_preflight.emit()

    def run_export_preflight_checks(self):
        """
        Run preflight checks to make sure the Export VM is configured correctly.
        """
        logger.info("Running export preflight check")

        if not self.qubes:
            self.export.preflight_check_call_success.emit()
            return

        self.export.begin_preflight_check.emit()

    def export_file_to_usb_drive(self, file_uuid: str, passphrase: str) -> None:
        """
        Send the file specified by file_uuid to the Export VM with the user-provided passphrase for
        unlocking the attached transfer device.  If the file is missing, update the db so that
        is_downloaded is set to False.
        """
        file = self.get_file(file_uuid)
        file_location = file.location(self.data_dir)
        logger.info("Exporting file in: {}".format(os.path.dirname(file_location)))

        if not self.downloaded_file_exists(file):
            return

        if not self.qubes:
            self.export.export_usb_call_success.emit()
            return

        self.export.begin_usb_export.emit([file_location], passphrase)

    def print_file(self, file_uuid: str) -> None:
        """
        Send the file specified by file_uuid to the Export VM. If the file is missing, update the db
        so that is_downloaded is set to False.
        """
        file = self.get_file(file_uuid)
        file_location = file.location(self.data_dir)
        logger.info("Printing file in: {}".format(os.path.dirname(file_location)))

        if not self.downloaded_file_exists(file):
            return

        if not self.qubes:
            return

        self.export.begin_print.emit([file_location])

    @login_required
    def on_submission_download(
        self, submission_type: Union[Type[db.File], Type[db.Message]], submission_uuid: str
    ) -> None:
        """
        Download the file associated with the Submission (which may be a File or Message).
        """
        self._submit_download_job(submission_type, submission_uuid)

    def on_file_download_success(self, uuid: Any) -> None:
        """
        Called when a file has downloaded.
        """
        self.session.commit()
        file_obj = storage.get_file(self.session, uuid)
        file_obj.download_error = None
        storage.update_file_size(uuid, self.data_dir, self.session)

        self.file_ready.emit(file_obj.source.uuid, uuid, file_obj.filename)

    def on_file_download_failure(self, exception: Exception) -> None:
        """
        Called when a file fails to download.
        """
        # Keep resubmitting the job if the download is corrupted.
        if isinstance(exception, DownloadChecksumMismatchException):
            logger.warning("Failure due to checksum mismatch, retrying {}".format(exception.uuid))
            self._submit_download_job(exception.object_type, exception.uuid)
        else:
            if isinstance(exception, DownloadDecryptionException):
                logger.error("Failed to decrypt %s", exception.uuid)
                f = self.get_file(exception.uuid)
                self.file_missing.emit(f.source.uuid, f.uuid, str(f))
            self.gui.update_error_status(_("The file download failed. Please try again."))

    def on_delete_source_success(self, source_uuid: str) -> None:
        """
        Rely on sync to delete the source locally so we know for sure it was deleted
        """
        pass

    def on_delete_source_failure(self, e: Exception) -> None:
        if isinstance(e, DeleteSourceJobException):
            error = _("Failed to delete source at server")
            self.gui.update_error_status(error)
            self.source_deletion_failed.emit(e.source_uuid)

    @login_required
    def delete_source(self, source: db.Source):
        """
        Performs a delete operation on source record.

        This method will submit a job to delete the source record on
        the server. If the job succeeds, the success handler will
        synchronize the server records with the local state. If not,
        the failure handler will display an error.
        """
        job = DeleteSourceJob(source.uuid)
        job.success_signal.connect(self.on_delete_source_success, type=Qt.QueuedConnection)
        job.failure_signal.connect(self.on_delete_source_failure, type=Qt.QueuedConnection)

        self.add_job.emit(job)
        self.source_deleted.emit(source.uuid)

    @login_required
    def send_reply(self, source_uuid: str, reply_uuid: str, message: str) -> None:
        """
        Send a reply to a source.
        """
        # Before we send the reply, add the draft to the database with a PENDING
        # reply send status.
        source = self.session.query(db.Source).filter_by(uuid=source_uuid).one()
        reply_status = (
            self.session.query(db.ReplySendStatus)
            .filter_by(name=db.ReplySendStatusCodes.PENDING.value)
            .one()
        )
        draft_reply = db.DraftReply(
            uuid=reply_uuid,
            timestamp=datetime.datetime.utcnow(),
            source_id=source.id,
            journalist_id=self.api.token_journalist_uuid,
            file_counter=source.interaction_count,
            content=message,
            send_status_id=reply_status.id,
        )
        self.session.add(draft_reply)
        self.session.commit()

        job = SendReplyJob(source_uuid, reply_uuid, message, self.gpg)
        job.success_signal.connect(self.on_reply_success, type=Qt.QueuedConnection)
        job.failure_signal.connect(self.on_reply_failure, type=Qt.QueuedConnection)

        self.add_job.emit(job)

    def on_reply_success(self, reply_uuid: str) -> None:
        logger.info("{} sent successfully".format(reply_uuid))
        self.session.commit()
        reply = storage.get_reply(self.session, reply_uuid)
        self.reply_succeeded.emit(reply.source.uuid, reply_uuid, reply.content)

    def on_reply_failure(
        self, exception: Union[SendReplyJobError, SendReplyJobTimeoutError]
    ) -> None:
        logger.debug("{} failed to send".format(exception.reply_uuid))

        # only emit failure signal for non-timeout errors
        if isinstance(exception, SendReplyJobError):
            self.reply_failed.emit(exception.reply_uuid)

    def get_file(self, file_uuid: str) -> db.File:
        file = storage.get_file(self.session, file_uuid)
        self.session.refresh(file)
        return file

    def on_logout_success(self, result) -> None:
        logging.info("Client logout successful")

    def on_logout_failure(self, result: Exception) -> None:
        logging.info("Client logout failure")