#!/usr/bin/env python3

# This file is part of Remote Support Desktop
# https://gitlab.das-netzwerkteam.de/RemoteWebApp/rwa.support.sessionservice
# Copyright 2020, 2021 Jonathan Weth <dev@jonathanweth.de>
# Copyright 2020, 2021 Daniel Teichmann <daniel.teichmann@das-netzwerkteam.de>
# Copyright 2020 Mike Gabriel <mike.gabriel@das-netzwerkteam.de>
# SPDX-License-Identifier: GPL-2.0-or-later
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the
# Free Software Foundation, Inc.,
# 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

import json
import signal
import time
from threading import Thread
from typing import Dict, Union
from uuid import uuid4

import click
import dbus
import dbus.mainloop.glib
import dbus.service
import requests
import usersettings
import validators
from gi.repository import GLib

from config import ALLOW_ONLY_ONE_SESSION, API_PATH, SUPPORTED_API_VERSIONS
from lock import is_locked, lock, unlock
from log import logging
from session import Session, combine
from trigger import TriggerServerThread


class RWASupportSessionService(dbus.service.Object):
    """D-Bus Session Service for RWA.Support.

    D-Bus namespace: ``org.ArcticaProject.RWASupportSessionService``

    D-Bus object name: ``/RWASupportSessionService``

    :param loop: GLib main loop running the service
    :param mockup_mode: Starts the service in mock up mode
    """

    def __init__(self, loop: GLib.MainLoop, mockup_mode: bool = False, one_time: bool = False):
        self.loop = loop
        self.mockup_mode = mockup_mode
        self.one_time = one_time

        self.bus = dbus.SessionBus()
        name = dbus.service.BusName("org.ArcticaProject.RWASupportSessionService", bus=self.bus)

        self.check_lock_thread = Thread(target=self._check_lock)
        self.check_lock_thread.start()

        self.trigger_service = TriggerServerThread(self._trigger)
        self.trigger_service.start()

        self.update_service_running = False
        self.sessions = {}

        self.settings = usersettings.Settings("org.ArcticaProject.RWASupportSessionService")
        self.settings.add_setting("web_app_hosts", dict)
        self.settings.load_settings()

        # Ensure default value for web app hosts settings
        if not self.settings.web_app_hosts:
            self.settings.web_app_hosts = {}
            self.settings.save_settings()

        super().__init__(name, "/RWASupportSessionService")

        logging.info("D-Bus service has been started.")

    def _is_url(self, url: str) -> bool:
        """Test if the given string is an url.

        :param url: The string which should be an URL.
        :return: Whether the string is an URL.
        """
        valid = validators.url(url)
        logging.debug(f"Is '{url}' an URL: {valid}")
        return valid

    def _get_web_app_hosts(self) -> str:
        """Get all registered RWA.Support.WebApp hosts.

        Helper function: No D-Bus API.
        """

        logging.debug("Raw web_app_hosts: %s", self.settings.web_app_hosts.items())
        hosts = [
            self._build_host_dict(key, value) for key, value in self.settings.web_app_hosts.items()
        ]
        return json.dumps(hosts)

    def _build_host_dict(self, host_uuid: str, host: dict) -> dict:
        """Include the host ID in the host dictionary."""
        host.update({'uuid': host_uuid})
        return host

    @dbus.service.method("org.ArcticaProject.RWASupportSessionService", out_signature="s")
    def get_web_app_hosts(self) -> str:
        """Get all registered RWA.Support.WebApp hosts.

        :return: All registered hosts as JSON array (D-Bus string)

        **Structure of returned JSON:**

        ::

            [{"url": "https://example.org", "uuid": <host_uuid>}, {"url": "http://127.0.0.1:8000", "uuid": <host_uuid>}]
        """
        logging.info("D-Bus method call: %s()", "get_web_app_hosts")

        response = self._get_web_app_hosts()
        logging.info('The response to D-Bus caller: "%s"', response)
        return response

    def _do_api_handshake(self, host: str) -> Dict[str, str]:
        """Contact a RWA.Support.WebApp host and find out API version.

        :param host: The full hostname.
        :return: Status information as dictionary.

        **Structure of returned JSON (success):**

        ::

            {"status": "success", "type": "valid_host"}

         **Structure of returned JSON (error):**

        ::

            {"status": "error", "type": "<type>"}

        **Possible choices for error types:**

            * ``connection``
            * ``permission_denied``
            * ``unsupported_server``
        """
        url = host + API_PATH + "handshake/"
        logging.info(f"API handshake with {url} ...")
        try:
            r = requests.post(url)

        except requests.exceptions.ConnectionError:
            logging.warning("Handshake resulted in a connection error.")
            return {"status": "error", "type": "connection"}

        if not r.ok:
            logging.warning("Handshake resulted in a connection error.")
            return {"status": "error", "type": "connection"}

        if not r.json()["allowed"]:
            logging.warning("Handshake was not permitted.")
            return {"status": "error", "type": "permission_denied"}

        if r.json().get("api_version") not in SUPPORTED_API_VERSIONS:
            logging.warning("Handshake resulted in a incompatible API version.")
            return {"status": "error", "type": "unsupported_server"}

        logging.info("Handshake was successful.")

        return {"status": "success", "type": "valid_host"}

    @dbus.service.method(
        "org.ArcticaProject.RWASupportSessionService", in_signature="s", out_signature="s"
    )
    def add_web_app_host(self, host_url: str) -> str:
        """Add a RWA.Support.WebApp host.

        :param host_url: Exact hostname of the RWA.Support.WebApp host (D-Bus string)
        :return: The registered host as JSON object (D-Bus string)

        **Structure of returned JSON (success):**

        ::

            {"status": "success", "host": {"url": "https://example.org", "uuid": <host_uuid>}}

        **Structure of returned JSON (error):**

        ::

            {"status": "error", "type": "<type>"}

        **Possible choices for error types:**

            * ``connection``
            * ``permission_denied``
            * ``unsupported_server``
            * ``invalid_url``
            * ``duplicate``
        """
        host_url = str(host_url).rstrip("/")

        logging.info('D-Bus method call: %s("%s")', "add_web_app_host", host_url)

        if not self._is_url(host_url):
            logging.warning("Given URL is not valid!")
            logging.debug('Did not add "%s" to "web_app_hosts" in user_settings', host_url)

            response = json.dumps({"status": "error", "type": "invalid_url"})
            logging.info('The response to D-Bus caller: "%s"', response)
            return response

        try:
            for uuid, host in self.settings.web_app_hosts.items():
                if host_url == host['url']:
                    logging.warning("Given URL is already present!")
                    logging.debug('Did not add "%s" to "web_app_hosts" in user_settings', host_url)

                    response = json.dumps({"status": "error", "type": "duplicate"})
                    logging.info('The response to D-Bus caller: "%s"', response)
                    return response
        except (KeyError, IndexError):
            logging.warning(
                            'Got an exception while trying to find given url '
                            'in already existing hosts!'
                            )

        res = self._do_api_handshake(host_url)
        if res["status"] == "error":
            logging.debug('Did not add "%s" to "web_app_hosts" in user_settings', host_url)

            response = json.dumps(res)
            logging.info('The response to D-Bus caller: "%s"', response)
            return response

        host_uuid = str(uuid4())
        host_object = {"url": host_url}

        self.settings.web_app_hosts[host_uuid] = host_object
        self.settings.save_settings()

        logging.info('Added "%s" to "web_app_hosts" in user_settings', host_url)

        response = {"status": "success", "host": self._build_host_dict(host_uuid, host_object)}
        response = json.dumps(response)
        logging.info('The response to D-Bus caller: "%s"', response)
        return response

    @dbus.service.method(
        "org.ArcticaProject.RWASupportSessionService", in_signature="i", out_signature="s"
    )
    def remove_web_app_host(self, host_uuid: str) -> str:
        """Remove a RWA.Support.WebApp host.

        :param host_uuid: ID of web app host (D-Bus string)
        :return: All registered hosts as JSON array (D-Bus string)

        **Structure of returned JSON:**

        ::

            [{"url": "https://example.org", "uuid": <host_uuid>}, {"url": "http://127.0.0.1:8000", "uuid": <host_uuid>}]
        """
        logging.info("D-Bus method call: %s(%s)", "remove_web_app_host", host_uuid)

        if host_uuid in self.settings.web_app_hosts:
            host_object = self.settings.web_app_hosts[host_uuid]
            del self.settings.web_app_hosts[host_uuid]
            self.settings.save_settings()
            logging.info('Removed web_app_hosts[%s]="%s" in user settings', host_uuid, host_object)
        else:
            logging.warning("Given host index is not valid!")
            logging.debug(
                "Did not remove web_app_hosts[%s]"
                "(not existent!) in " "user settings", host_uuid
            )
            return json.dumps({"status": "error", "type": "host_not_found"})

        response = self._get_web_app_hosts()
        logging.info('The response to D-Bus caller: "%s"', response)
        return response

    @dbus.service.method(
        "org.ArcticaProject.RWASupportSessionService", in_signature="i", out_signature="s"
    )
    def start(self, host_uuid: str) -> str:
        """Start a new remote session and register it in RWA.Support.WebApp.

        :param host_uuid: ID of web app host (D-Bus string)
        :return: Result as JSON (D-Bus string)

        **Structure of returned JSON (success):**

        ::

            {
                "status": "success",
                "host_uuid": "<host_uuid>",
                "session_id": <session_id>,
                "url": "<url>",
                "pin": <pin>
            }

        **Structure of returned JSON (error):**

        ::

            {"status": "error", "type": "<type>"}

        **Possible choices for error types:**

            * ``multiple``
            * ``connection``
            * ``host_not_found``
            * ``permission_denied``
            * ``unsupported_server``
        """
        logging.info("D-Bus method call: %s(%s)", "start", host_uuid)

        if ALLOW_ONLY_ONE_SESSION and len(self.sessions.values()) > 0:
            logging.warning(
                "There is already one session running and the service "
                "is configured to allow only one "
                "session, so this session won't be started."
            )
            response = json.dumps({"status": "error", "type": "multiple"})
            logging.info("The response to the D-Bus caller: '%s'", response)
            return response

        try:
            host_object = self.settings.web_app_hosts[host_uuid]
            host_object = self._build_host_dict(host_uuid, host_object)
            logging.debug('web_app_hosts[%s] is the following host: "%s"', host_uuid, host_object)
        except (KeyError, IndexError):
            logging.error("web_app_hosts[%s] does not exist!", host_uuid)
            response = json.dumps({"status": "error", "type": "host_not_found"})
            logging.info("The response to the D-Bus caller: '%s'", response)
            return response

        # Check host by doing a handshake
        res = self._do_api_handshake(host_object["url"])
        if res["status"] == "error":
            return json.dumps(res)

        # Start session
        try:
            session = Session(host_object, self.trigger_service.port, self.mockup_mode)

            # Add session to sessions list
            self.sessions[session.combined_id] = session

            # Start session update service
            self._ensure_update_service()

            return_json = session.client_meta
            return_json["status"] = "success"

            logging.info(f"New session #{session.pid} was started.")

            response = json.dumps(return_json)
            logging.info("The response to the D-Bus caller: '%s'", response)
            return response
        except ConnectionError:
            logging.error(
                "There was a connection error while trying to reach "
                "the RWA.Support.WebApp server."
            )

        response = json.dumps({"status": "error", "type": "connection"})
        logging.info("The response to the D-Bus caller: '%s'", response)
        return response

    @dbus.service.method(
        "org.ArcticaProject.RWASupportSessionService", in_signature="si", out_signature="s"
    )
    def status(self, host_uuid: str, session_id: int) -> str:
        """Return the status of a session.

        .. note::

            This uses the last status version got by the update service in the background.

        :param host_uuid: Host ID (D-Bus string)
        :param session_id: Session ID (D-Bus integer)

        :return: Session status as JSON (D-Bus string)

        **Structure of returned JSON:**

        ::

            {"host_uuid": "<host_uuid>", "session_id": <session_id>, "status": <status>}

        **Possible status options:**

        ============ ======================
        ``running``  The session is running and ready for connecting.
        ``active``   The session is running and a the remote connected to the session.
        ``stopped``  The session was stopped.
        ``dead``     There was a problem, so that the session is dead.
        ============ ======================
        """
        logging.info("D-Bus method call: %s(%s, %d)", "status", host_uuid, session_id)
        response = self._get_status(host_uuid, session_id)
        logging.info("The response to the D-Bus caller: '%s'", response)
        return response

    @dbus.service.method(
        "org.ArcticaProject.RWASupportSessionService", in_signature="si", out_signature="s"
    )
    def refresh_status(self, host_uuid: str, session_id: int) -> str:
        """Update status from WebApp before returning it here like :meth:`status`."""
        logging.info("D-Bus method call: %s(%s, %d)", "refresh_status", host_uuid, session_id)

        self._update_session(host_uuid, session_id)
        response = self._get_status(host_uuid, session_id)
        logging.info("The response to the D-Bus caller: '%s'", response)
        return response

    @dbus.service.method(
        "org.ArcticaProject.RWASupportSessionService", in_signature="si", out_signature="s"
    )
    def stop(self, host_uuid: str, session_id: int) -> str:
        """Stop a remote session.

        :param host_uuid: Host ID (D-Bus string)
        :param session_id: Session ID (D-Bus integer)
        :return: Session status as JSON (D-Bus string)

        **Structure of returned JSON:**

        ::

            {"host_uuid": "<host_uuid>", "session_id": <session_id>, "status": "stopped"}
        """
        logging.info("D-Bus method call: %s(%s, %d)", "stop", host_uuid, session_id)

        combined_id = combine(host_uuid, session_id)
        try:
            session = self.sessions[combined_id]
        except KeyError:
            logging.debug("D-Bus method stop(): sessions[%s] does not exist.", combined_id)
            response = json.dumps(
                {"host_uuid": host_uuid, "session_id": session_id, "status": "stopped"}, sort_keys=True
            )
            logging.info("The response to the D-Bus caller: '%s'", response)
            return response
        session.stop()
        response = json.dumps(
            {"host_uuid": host_uuid, "session_id": session_id, "status": "stopped"}, sort_keys=True
        )
        logging.info("The response to the D-Bus caller: '%s'", response)
        return response

    def _get_status(self, host_uuid: str, session_id: int) -> str:
        combined_id = combine(host_uuid, session_id)
        try:
            session = self.sessions[combined_id]
        except KeyError:
            logging.debug("_get_status(): self.sessions[%s] does not exist.", combined_id)
            return json.dumps(
                {"host_uuid": host_uuid, "session_id": session_id, "status": "dead"}, sort_keys=True
            )
        return json.dumps(session.status)

    def _ensure_update_service(self):
        """Start session update thread if it isn't already running."""
        if not self.update_service_running:
            self.update_thread = Thread(target=self._update_sessions)
            self.update_thread.start()

    def _update_session(self, host_uuid: str, session_id: int):
        """Update the status of a session."""
        combined_id = combine(host_uuid, session_id)
        try:
            session = self.sessions[combined_id]
        except KeyError:
            logging.info(f"Update status for session #{session_id} on host {host_uuid} …")
            logging.warning("Session %s is dead.", combined_id)
            return

        # Check if VNC process is still running
        running = session.vnc_process_running
        if running:
            pass
        elif session.status_text == "stopped" and session.pid in self.sessions:
            logging.info(f"Update status for session #{session_id} on host {host_uuid} …")
            logging.warning("Session %s is dead.", combined_id)

            del self.sessions[combined_id]
        else:
            logging.info(f"Update status for session #{session_id} on host {host_uuid} …")
            logging.warning("VNC was stopped, so session %s is dead.", session.combined_id)

            session.stop()
            del self.sessions[combined_id]

    def _update_sessions(self):
        """Go through all running sessions and update their status using ``_update_session``."""
        logging.info("Started update service for sessions.")
        while len(self.sessions.values()) > 0:
            for session in list(self.sessions.values()):
                self._update_session(session.host_uuid, session.session_id)

            time.sleep(2)

        self.update_service_running = False
        logging.info("Stopped update service for sessions.")
        if self.one_time:
            self._stop_all()

    def _trigger(self, session_id: int, data: dict, method: str = "trigger") -> Union[dict, bool]:
        """Trigger a specific session via trigger token."""
        logging.info(f"Event triggered from Django with session ID {session_id} and {data}")

        for session in self.sessions.values():
            if session.session_id == session_id:
                r = session.trigger(data, method)
                logging.info(
                    f"Found matching session #{session.session_id} on host {session.host_uuid}: {r}"
                )
                return r

        logging.warning("Given session ID does not exist!")
        return False

    def _stop_all(self):
        """Stop all sessions."""
        logging.info("Stop all sessions.")
        for session in list(self.sessions.values()):
            session.stop()
            del self.sessions[session.combined_id]

    def _stop_daemon(self):
        """Stop all sessions and this daemon."""
        logging.info("Shut down session service.")
        self._stop_all()
        self.trigger_service.shutdown()
        self.loop.quit()

    def _check_lock(self):
        """Check if lock file exists."""
        while True:
            if not is_locked():
                logging.error("The lock file was removed, so stop this service.")
                self._stop_all()
                break
            time.sleep(1)


@click.command()
@click.option(
    "-m",
    "--mockup",
    is_flag=True,
    default=False,
    help="Activates mock up mode. Acts like the real Session Service "
    "but don't do changes or call RWA.Support.WebApp.",
)
@click.option(
    "-o",
    "--once",
    is_flag=True,
    default=False,
    help="Runs as one-time-service. Stops after one session.",
)
def main(mockup, once):
    # Check for lock file
    if is_locked():
        logging.error("The service is already running.")
        exit(1)

    # Create lock file
    lock()

    if mockup:
        logging.warning("The mockup mode should NOT BE USED IN PRODUCTION!")
        logging.warning("API responses can be faked and deliver dummy values.")

    dbus.mainloop.glib.DBusGMainLoop(set_as_default=True)

    loop = GLib.MainLoop()
    service_object = RWASupportSessionService(loop, mockup, once)

    def sigint_handler(sig, frame):
        logging.info("Service was terminated.")
        service_object._stop_daemon()

    def sigquit_handler(sig, frame):
        logging.info("Session was terminated.")
        service_object._stop_all()

    signal.signal(signal.SIGINT, sigint_handler)
    signal.signal(signal.SIGQUIT, sigquit_handler)

    loop.run()

    logging.info("Remove lock file ...")
    unlock()


if __name__ == "__main__":
    main()