##   idlequeue.py
##
##   Copyright (C) 2006 Dimitur Kirov <dkirov@gmail.com>
##
##   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, 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.


"""
Idlequeues are Gajim's network heartbeat. Transports can be plugged as idle
objects and be informed about possible IO
"""

import os
import errno
import select
import logging
import time
import subprocess

# needed for get_idleqeue
try:
    from gi.repository import GLib
    HAVE_GLIB = True
except ImportError:
    HAVE_GLIB = False


if os.name == 'posix':
    import fcntl

log = logging.getLogger('nbxmpp.idlequeue')

if HAVE_GLIB:
    FLAG_WRITE = GLib.IOCondition.OUT | GLib.IOCondition.HUP
    FLAG_READ = GLib.IOCondition.IN  | GLib.IOCondition.PRI | \
                GLib.IOCondition.HUP
    FLAG_READ_WRITE = GLib.IOCondition.OUT | GLib.IOCondition.IN | \
                      GLib.IOCondition.PRI | GLib.IOCondition.HUP
    FLAG_CLOSE = GLib.IOCondition.HUP
    PENDING_READ = GLib.IOCondition.IN  # There is data to read.
    PENDING_WRITE = GLib.IOCondition.OUT # Data CAN be written without blocking
    IS_CLOSED = GLib.IOCondition.HUP # Hung up (connection broken)
else:
    FLAG_WRITE = 20         # write only           10100
    FLAG_READ = 19          # read only            10011
    FLAG_READ_WRITE = 23    # read and write       10111
    FLAG_CLOSE = 16         # wait for close       10000
    PENDING_READ = 3        # waiting read event      11
    PENDING_WRITE = 4       # waiting write event    100
    IS_CLOSED = 16          # channel closed       10000


def get_idlequeue():
    """
    Get an appropriate idlequeue
    """
    if os.name == 'nt':
        # gobject.io_add_watch does not work on windows
        return SelectIdleQueue()

    if HAVE_GLIB:
        # Gajim's default Idlequeue
        return GlibIdleQueue()
    # GUI less implementation
    return SelectIdleQueue()


class IdleObject:
    """
    Idle listener interface. Listed methods are called by IdleQueue.
    """

    def __init__(self):
        self.fd = -1 #: filedescriptor, must be unique for each IdleObject

    def pollend(self):
        """
        Called on stream failure
        """

    def pollin(self):
        """
        Called on new read event
        """

    def pollout(self):
        """
        Called on new write event (connect in sockets is a pollout)
        """

    def read_timeout(self):
        """
        Called when timeout happened
        """


class IdleCommand(IdleObject):
    """
    Can be subclassed to execute commands asynchronously by the idlequeue.
    Result will be optained via file descriptor of created pipe
    """

    def __init__(self, on_result):
        IdleObject.__init__(self)
        # how long (sec.) to wait for result ( 0 - forever )
        # it is a class var, instead of a constant and we can override it.
        self.commandtimeout = 0
        # when we have some kind of result (valid, ot not) we call this handler
        self.result_handler = on_result
        # if it is True, we can safetely execute the command
        self.canexecute = True
        self.idlequeue = None
        self.result = ''
        self.endtime = None
        self.pipe = None

    def set_idlequeue(self, idlequeue):
        self.idlequeue = idlequeue

    def _return_result(self):
        if self.result_handler:
            self.result_handler(self.result)
        self.result_handler = None

    @staticmethod
    def _compose_command_args():
        return ['echo', 'da']

    def _compose_command_line(self):
        """
        Return one line representation of command and its arguments
        """
        return ' '.join(self._compose_command_args())

    def wait_child(self):
        if self.pipe.poll() is None:
            # result timeout
            if self.endtime < self.idlequeue.current_time():
                self._return_result()
                self.pipe.stdout.close()
                self.pipe.stdin.close()
            else:
                # child is still active, continue to wait
                self.idlequeue.set_alarm(self.wait_child, 0.1)
        else:
            # child has quit
            self.result = self.pipe.stdout.read()
            self._return_result()
            self.pipe.stdout.close()
            self.pipe.stdin.close()

    def start(self):
        if not self.canexecute:
            self.result = ''
            self._return_result()
            return
        if os.name == 'nt':
            self._start_nt()
        elif os.name == 'posix':
            self._start_posix()

    def _start_nt(self):
        # if program is started from noninteraactive shells stdin is closed and
        # cannot be forwarded, so we have to keep it open
        self.pipe = subprocess.Popen(self._compose_command_args(),
                                     stdout=subprocess.PIPE,
                                     bufsize=1024,
                                     shell=True,
                                     stderr=subprocess.STDOUT,
                                     stdin=subprocess.PIPE)
        if self.commandtimeout >= 0:
            self.endtime = self.idlequeue.current_time() + self.commandtimeout
            self.idlequeue.set_alarm(self.wait_child, 0.1)

    def _start_posix(self):
        self.pipe = os.popen(self._compose_command_line())
        self.fd = self.pipe.fileno()  # pylint: disable=no-member
        fcntl.fcntl(self.pipe, fcntl.F_SETFL, os.O_NONBLOCK)
        self.idlequeue.plug_idle(self, False, True)
        if self.commandtimeout >= 0:
            self.idlequeue.set_read_timeout(self.fd, self.commandtimeout)

    def end(self):
        self.idlequeue.unplug_idle(self.fd)
        try:
            self.pipe.close()
        except Exception:
            pass

    def pollend(self):
        self.idlequeue.remove_timeout(self.fd)
        self.end()
        self._return_result()

    def pollin(self):
        try:
            res = self.pipe.read()  # pylint: disable=no-member
        except Exception:
            res = ''
        if res == '':
            return self.pollend()

        self.result += res
        return None

    def read_timeout(self):
        self.end()
        self._return_result()


class IdleQueue:
    """
    IdleQueue provide three distinct time based features. Uses select.poll()

        1. Alarm timeout: Execute a callback after foo seconds
        2. Timeout event: Call read_timeout() of an plugged object if a timeout
           has been set, but not removed in time.
        3. Check file descriptor of plugged objects for read, write and error
           events

    """

    # (timeout, boolean)
    # Boolean is True if timeout is specified in seconds,
    # False means miliseconds
    PROCESS_TIMEOUT = (100, False)

    def __init__(self):
        self.queue = {}

        # when there is a timeout it executes obj.read_timeout()
        # timeout is not removed automatically!
        # {fd1: {timeout1: func1, timeout2: func2}}
        # timout are unique (timeout1 must be != timeout2)
        # If func1 is None, read_time function is called
        self.read_timeouts = {}

        # cb, which are executed after XX sec., alarms are removed automatically
        self.alarms = {}
        self._init_idle()

    def _init_idle(self):
        """
        Hook method for subclassed. Will be called by __init__
        """
        self.selector = select.poll()

    def set_alarm(self, alarm_cb, seconds):
        """
        Set up a new alarm. alarm_cb will be called after specified seconds.
        """
        alarm_time = self.current_time() + seconds
        # almost impossible, but in case we have another alarm_cb at this time
        if alarm_time in self.alarms:
            self.alarms[alarm_time].append(alarm_cb)
        else:
            self.alarms[alarm_time] = [alarm_cb]
        return alarm_time

    def remove_alarm(self, alarm_cb, alarm_time):
        """
        Remove alarm callback alarm_cb scheduled on alarm_time. Returns True if
        it was removed sucessfully, otherwise False
        """
        if alarm_time not in self.alarms:
            return False
        i = -1
        for i in range(len(self.alarms[alarm_time])):
            # let's not modify the list inside the loop
            if self.alarms[alarm_time][i] is alarm_cb:
                break
        if i != -1:
            del self.alarms[alarm_time][i]
            if not self.alarms[alarm_time]:
                del self.alarms[alarm_time]
            return True

        return False

    def remove_timeout(self, fd, timeout=None):
        """
        Remove the read timeout
        """
        log.debug('read timeout removed for fd %s', fd)
        if fd in self.read_timeouts:
            if timeout:
                if timeout in self.read_timeouts[fd]:
                    del self.read_timeouts[fd][timeout]
                if len(self.read_timeouts[fd]) == 0:
                    del self.read_timeouts[fd]
            else:
                del self.read_timeouts[fd]

    def set_read_timeout(self, fd, seconds, func=None):
        """
        Seta a new timeout. If it is not removed after specified seconds,
        func or obj.read_timeout() will be called

        A filedescriptor fd can have several timeouts.
        """
        log_txt = 'read timeout set for fd %s on %i seconds' % (fd, seconds)
        if func:
            log_txt += ' with function ' + str(func)
        log.info(log_txt)
        timeout = self.current_time() + seconds
        if fd in self.read_timeouts:
            self.read_timeouts[fd][timeout] = func
        else:
            self.read_timeouts[fd] = {timeout: func}

    def _check_time_events(self):
        """
        Execute and remove alarm callbacks and execute func() or read_timeout()
        for plugged objects if specified time has ellapsed
        """
        current_time = self.current_time()

        for fd, timeouts in list(self.read_timeouts.items()):
            if fd not in self.queue:
                self.remove_timeout(fd)
                continue
            for timeout, func in list(timeouts.items()):
                if timeout > current_time:
                    continue
                if func:
                    log.debug('Calling %s for fd %s', func, fd)
                    func()
                else:
                    log.debug('Calling read_timeout for fd %s', fd)
                    self.queue[fd].read_timeout()
                self.remove_timeout(fd, timeout)

        times = list(self.alarms.keys())
        for alarm_time in times:
            if alarm_time > current_time:
                continue
            if alarm_time in self.alarms:
                for callback in self.alarms[alarm_time]:
                    callback()
                if alarm_time in self.alarms:
                    del self.alarms[alarm_time]

    def plug_idle(self, obj, writable=True, readable=True):
        """
        Plug an IdleObject into idlequeue. Filedescriptor fd must be set

        :param obj: the IdleObject
        :param writable: True if obj has data to sent
        :param readable: True if obj expects data to be received
        """
        if obj.fd == -1:
            return
        if obj.fd in self.queue:
            self.unplug_idle(obj.fd)
        self.queue[obj.fd] = obj
        if writable:
            if not readable:
                flags = FLAG_WRITE
            else:
                flags = FLAG_READ_WRITE
        else:
            if readable:
                flags = FLAG_READ
            else:
                # when we paused a FT, we expect only a close event
                flags = FLAG_CLOSE
        self._add_idle(obj.fd, flags)

    def _add_idle(self, fd, flags):
        """
        Hook method for subclasses, called by plug_idle
        """
        self.selector.register(fd, flags)

    def unplug_idle(self, fd):
        """
        Remove plugged IdleObject, specified by filedescriptor fd
        """
        if fd in self.queue:
            del self.queue[fd]
            self._remove_idle(fd)

    @staticmethod
    def current_time():
        return time.monotonic()

    def _remove_idle(self, fd):
        """
        Hook method for subclassed, called by unplug_idle
        """
        self.selector.unregister(fd)

    def _process_events(self, fd, flags):
        obj = self.queue.get(fd)
        if obj is None:
            self.unplug_idle(fd)
            return False

        read_write = False
        if flags & PENDING_READ:
            #print 'waiting read on %d, flags are %d' % (fd, flags)
            obj.pollin()
            read_write = True

        elif flags & PENDING_WRITE and not flags & IS_CLOSED:
            obj.pollout()
            read_write = True

        if flags & IS_CLOSED:
            # io error, don't expect more events
            self.remove_timeout(obj.fd)
            self.unplug_idle(obj.fd)
            obj.pollend()
            return False

        if read_write:
            return True
        return False

    def process(self):
        """
        This function must be overridden by an implementation of the IdleQueue.

        Process idlequeue. Check for any pending timeout or alarm events.  Call
        IdleObjects on possible and requested read, write and error events on
        their file descriptors

        Call this in regular intervals.
        """
        raise NotImplementedError("You need to define a process() method.")

class SelectIdleQueue(IdleQueue):
    """
    Extends IdleQueue to use select.select() for polling

    This class exisists for the sake of gtk2.8 on windows, which doesn't seem to
    support io_add_watch properly (yet)
    """

    def checkQueue(self):
        """
        Iterates through all known file descriptors and uses os.stat to
        check if they're valid. Greatly improves performance if the caller
        hands us and expects notification on an invalid file handle.
        """
        bad_fds = []
        union = {}
        union.update(self.write_fds)
        union.update(self.read_fds)
        union.update(self.error_fds)
        for fd in union:
            try:
                _status = os.stat(fd)
            except OSError:
                # This file descriptor is invalid. Add to list for closure.
                bad_fds.append(fd)

        for fd in bad_fds:
            obj = self.queue.get(fd)
            if obj is not None:
                self.remove_timeout(fd)
            self.unplug_idle(fd)

    def _init_idle(self):
        """
        Create a dict, which maps file/pipe/sock descriptor to glib event id
        """
        self.read_fds = {}
        self.write_fds = {}
        self.error_fds = {}

    def _add_idle(self, fd, flags):
        """
        This method is called when we plug a new idle object. Add descriptor
        to read/write/error lists, according flags
        """
        if flags & 3:
            self.read_fds[fd] = fd
        if flags & 4:
            self.write_fds[fd] = fd
        self.error_fds[fd] = fd

    def _remove_idle(self, fd):
        """
        This method is called when we unplug a new idle object.
        Remove descriptor from read/write/error lists
        """
        if fd in self.read_fds:
            del self.read_fds[fd]
        if fd in self.write_fds:
            del self.write_fds[fd]
        if fd in self.error_fds:
            del self.error_fds[fd]

    def process(self):
        if not self.write_fds and not self.read_fds:
            self._check_time_events()
            return True
        try:
            waiting_descriptors = select.select(
                list(self.read_fds.keys()),
                list(self.write_fds.keys()),
                list(self.error_fds.keys()),
                0)
        except OSError as error:
            waiting_descriptors = ((), (), ())
            if error.errno != errno.EINTR:
                self.checkQueue()
                raise
        for fd in waiting_descriptors[0]:
            idle_object = self.queue.get(fd)
            if idle_object:
                idle_object.pollin()
        for fd in waiting_descriptors[1]:
            idle_object = self.queue.get(fd)
            if idle_object:
                idle_object.pollout()
        for fd in waiting_descriptors[2]:
            idle_object = self.queue.get(fd)
            if idle_object:
                idle_object.pollend()
        self._check_time_events()
        return True


class GlibIdleQueue(IdleQueue):
    """
    Extends IdleQueue to use glib io_add_wath, instead of select/poll In another
    'non gui' implementation of Gajim IdleQueue can be used safetly
    """

    # (timeout, boolean)
    # Boolean is True if timeout is specified in seconds,
    # False means miliseconds
    PROCESS_TIMEOUT = (2, True)

    def _init_idle(self):
        """
        Creates a dict, which maps file/pipe/sock descriptor to glib event id
        """
        self.events = {}

    def _add_idle(self, fd, flags):
        """
        This method is called when we plug a new idle object.
        Start listening for events from fd
        """
        res = GLib.io_add_watch(fd,
                                GLib.PRIORITY_LOW,
                                flags,
                                self._process_events)

        # store the id of the watch, so that we can remove it on unplug
        self.events[fd] = res

    def _process_events(self, fd, flags):
        try:
            return IdleQueue._process_events(self, fd, flags)
        except Exception:
            self._remove_idle(fd)
            self._add_idle(fd, flags)
            raise

    def _remove_idle(self, fd):
        """
        This method is called when we unplug a new idle object. Stop listening
        for events from fd
        """
        if not fd in self.events:
            return

        GLib.source_remove(self.events[fd])
        del self.events[fd]

    def process(self):
        self._check_time_events()