# -*- coding: utf-8 -*-
# process.py
# Copyright (C) 2013-2017 LEAP
#
# 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 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

"""
VPN Process management.

A custom processProtocol launches the VPNProcess and connects to its management
interface.
"""

import os
import shutil
import sys
import time
from collections import OrderedDict

from twisted.internet import protocol, reactor, defer
from twisted.internet import error as internet_error
from twisted.internet.endpoints import clientFromString, connectProtocol
from twisted.logger import Logger
from zope.interface import implementer

from leap.bitmask.vpn.utils import get_vpn_launcher
from leap.bitmask.vpn.management import ManagementProtocol
from leap.bitmask.vpn.launchers import darwin
from leap.bitmask.system import IS_MAC, IS_LINUX
from leap.common.events import catalog, emit_async

from zope.interface import Interface

from ._state import State


OPENVPN_VERBOSITY = 4


class IStateListener(Interface):

    def changeState(self, state):
        pass

    def appendToStateLog(self, state):
        pass

    def getState(sef):
        pass

    def getStateHistory(self):
        pass


@implementer(IStateListener)
class _VPNProcess(protocol.ProcessProtocol):

    """
    A ProcessProtocol class that can be used to spawn a process that will
    launch openvpn and connect to its management interface to control it
    programmatically.
    """

    log = Logger()

    # HACK - reactor is expected to set this up when the process is spawned.
    # should try to get it from the management protocol instead.
    # XXX or, at least, we can check if they match.
    pid = None

    # TODO do we really need the vpnconfig/providerconfig objects in here???

    def __init__(self, vpnconfig, providerconfig, socket_host, socket_port,
                 openvpn_verb, remotes, restartfun=None):
        """
        :param vpnconfig: vpn configuration object
        :type vpnconfig: VPNConfig

        :param providerconfig: provider specific configuration
        :type providerconfig: ProviderConfig

        :param socket_host: either socket path (unix) or socket IP
        :type socket_host: str

        :param socket_port: either string "unix" if it's a unix
                            socket, or port otherwise
        :type socket_port: str
        """
        self._host = socket_host
        self._port = socket_port

        if socket_port == 'unix':
            folder = os.path.split(self._host)[0]
            if not os.path.isdir(folder):
                os.makedirs(folder)
            self._management_endpoint = clientFromString(
                reactor, b"unix:path=%s" % socket_host)
        else:
            raise ValueError('tcp endpoint not configured')

        self._vpnconfig = vpnconfig
        self._providerconfig = providerconfig
        self._launcher = get_vpn_launcher()
        self._restartfun = restartfun

        self.restarting = True
        self.failed = False
        self.errmsg = None
        self.proto = None
        self._remotes = remotes
        self._statelog = OrderedDict()
        self._turn_state_off()

    def _turn_state_off(self):
        ts = time.time()
        off = State('OFF', ts)
        self.changeState(off)

    # IStateListener methods

    def changeState(self, state):
        self.appendToStateLog(state)
        emit_async(catalog.VPN_STATUS_CHANGED, state.simple)

    def appendToStateLog(self, state):
        ts = state.timestamp
        self._statelog[ts] = state

    def getState(self):
        if self._statelog.values():
            return self._statelog.values()[-1]
        else:
            return None

    # TODO -- expose on the API, wanted by UI
    def getStateHistory(self):
        return self._statelog

    # processProtocol methods

    def outReceived(self, data):
        # use this to debug failed invocations.
        # print("DEBUG VPN: %s" % data)
        pass

    @defer.inlineCallbacks
    def _got_management_protocol(self, proto):
        self.proto = proto
        proto.addStateListener(self)

        try:
            yield proto.logOn()
            yield proto.getVersion()
            yield proto.getPid()
            yield proto.stateOn()
            yield proto.byteCount(2)
        except Exception as exc:
            print('[!] Error: %s' % exc)

    def _connect_to_management(self, retries=30):
        if retries == 0:
            self.log.error('Timeout while connecting to management')
            self.failed = True
            return

        def retry(retries):
            ctr = retries - 1
            self.log.warn(
                'Error connecting to management, retrying. '
                'Retries left:  %s' % ctr)
            reactor.callLater(
                0.1, self._connect_to_management, ctr)

        self._d = connectProtocol(
            self._management_endpoint,
            ManagementProtocol(verbose=True))
        self._d.addCallbacks(
            self._got_management_protocol,
            lambda f: retry(retries))

    def connectionMade(self):
        self.failed = False
        reactor.callLater(0.1, self._connect_to_management)

    def processExited(self, failure):
        err = failure.trap(
            internet_error.ProcessDone, internet_error.ProcessTerminated)

        if err == internet_error.ProcessDone:
            pass

        elif err == internet_error.ProcessTerminated:
            self.failed = True
            self.errmsg = failure.value.exitCode
            if self.errmsg:
                self.log.debug('Process Exited, status %d' % (self.errmsg,))
            else:
                self.log.warn('%r' % failure.value)
        if IS_MAC:
            # TODO: need to exit properly!
            self.errmsg = None
        self.proto = None
        self._turn_state_off()

    def processEnded(self, reason):
        """
        Called when the child process exits and all file descriptors associated
        with it have been closed.
        """
        self.proto = None
        exit_code = reason.value.exitCode

        if isinstance(exit_code, int):
            self.log.debug('processEnded, status %d' % (exit_code,))
            if self.restarting:
                self.log.debug('Restarting VPN process')
                self._cleanup()
                self._restartfun()

    def _cleanup(self):
        """
        Remove all temporal files we might have left behind.

        Iif self.port is 'unix', we have created a temporal socket path that,
        under normal circumstances, we should be able to delete.
        """
        if self._port == "unix":
            tempfolder = os.path.split(self._host)[0]
            if tempfolder and os.path.isdir(tempfolder):
                try:
                    shutil.rmtree(tempfolder)
                except OSError:
                    self.log.error(
                        'Could not delete VPN temp folder %s' % tempfolder)

    # status handling

    @property
    def status(self):
        if self.failed:
            return {'status': 'failed', 'error': self.errmsg}
        try:
            state = self.getState()
            if state:
                _status = state.simple.lower()
            status = {'status': _status, 'error': None}
        except AttributeError:
            raise
            # BUG -- glitch due to proto.state transition?
            # still needed?
            # state = self.getState()
            # if state:
            #    _status = state.simple.lower()
            # status = {'status': _status, 'error': None}

        if self.proto and self.proto.traffic:
            remote = self.proto.remote
            rport = self.proto.rport
            status['remote'] = '%s:%s' % (remote, rport)
            down, up = self.proto.traffic.get_rate()
            status['up'] = up
            status['down'] = down
        if status['status'] == 'off' and self.restarting:
            status['status'] = 'starting'
        return status

    # launcher

    def preUp(self):
        self._launcher.kill_previous_openvpn()

    def preDown(self):
        pass

    def getCommand(self):
        """
        Gets the vpn command from the aproppriate launcher.

        Might throw:
            VPNLauncherException,
            OpenVPNNotFoundException.

        :rtype: list of str
        """
        print("GETTING COMMAND", self._launcher)
        try:
            command = self._launcher.get_vpn_command(
                vpnconfig=self._vpnconfig,
                providerconfig=self._providerconfig,
                socket_host=self._host,
                socket_port=self._port,
                remotes=self._remotes)
            print("Command: %s", command)
        except Exception as exc:
            print("ERROR: %r" % exc)

        encoding = sys.getfilesystemencoding()
        print("encoding", encoding)
        for i, c in enumerate(command):
            if not isinstance(c, str):
                command[i] = c.encode(encoding)
        print("command: %s", command)

        self.log.debug("Running VPN with command: ")
        self.log.debug("{0}".format(" ".join(command)))
        return command

    # shutdown

    def terminate(self):
        if self.proto:
            self.proto.signal('SIGTERM')

    def kill(self):
        try:
            self.transport.signalProcess('KILL')
        except internet_error.ProcessExitedAlready:
            self.log.debug('Process Exited Already')

    def terminate_or_kill(self):
        return self._launcher.terminate_or_kill(
            self.terminate, self.kill, self)


if IS_LINUX:

    VPNProcess = _VPNProcess

elif IS_MAC:

    class _VPNCanary(_VPNProcess):

        """
        Special form of _VPNProcess, for Darwin Launcher (windows might end up
        using the same strategy).

        This is a Canary Process that does not run openvpn itself, but it's
        notified by the privileged process when the process dies.

        This is a workaround to allow the state machine to be notified when
        openvpn process is spawned by the privileged helper.
        """

        def setupHelper(self):
            # TODO use get_vpn_launcher instead
            self.helper = darwin.HelperCommand()

        def preUp(self):
            self.setupHelper()
            cmd = self.getVPNCommand()
            self.helper.send('openvpn_start %s' % ' '.join(cmd))

        def preDown(self):
            self.helper.send('openvpn_stop')

        def connectionMade(self):
            self.setupHelper()
            reactor.callLater(2, self.registerPID)
            _VPNProcess.connectionMade(self)

        def registerPID(self):
            cmd = 'openvpn_set_watcher %s' % self.pid
            self.helper.send(cmd)

        def killProcess(self):
            cmd = 'openvpn_force_stop'
            self.helper.send(cmd)

        def getVPNCommand(self):
            vpncmd = _VPNProcess.getCommand(self)
            return vpncmd

        def getCommand(self):
            canary = '''import sys, signal, time
def receive_signal(signum, stack): sys.exit()
signal.signal(signal.SIGTERM, receive_signal)
while True: time.sleep(90)'''
            return ['python', '-c', '%s' % canary]

    VPNProcess = _VPNCanary