# Copyright 2013-2015 DataStax, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import gevent
import gevent.event
from gevent.queue import Queue
from gevent import select, socket
import gevent.ssl

from collections import defaultdict
from functools import partial
import logging
import os
import time

from six.moves import range

from errno import EALREADY, EINPROGRESS, EWOULDBLOCK, EINVAL

from cassandra.connection import Connection, ConnectionShutdown, Timer, TimerManager


log = logging.getLogger(__name__)


def is_timeout(err):
    return (
        err in (EINPROGRESS, EALREADY, EWOULDBLOCK) or
        (err == EINVAL and os.name in ('nt', 'ce'))
    )


class GeventConnection(Connection):
    """
    An implementation of :class:`.Connection` that utilizes ``gevent``.
    """

    _read_watcher = None
    _write_watcher = None

    _socket_impl = gevent.socket
    _ssl_impl = gevent.ssl

    _timers = None
    _timeout_watcher = None
    _new_timer = None

    @classmethod
    def initialize_reactor(cls):
        if not cls._timers:
            cls._timers = TimerManager()
            cls._timeout_watcher = gevent.spawn(cls.service_timeouts)
            cls._new_timer = gevent.event.Event()

    @classmethod
    def create_timer(cls, timeout, callback):
        timer = Timer(timeout, callback)
        cls._timers.add_timer(timer)
        cls._new_timer.set()
        return timer

    @classmethod
    def service_timeouts(cls):
        timer_manager = cls._timers
        timer_event = cls._new_timer
        while True:
            next_end = timer_manager.service_timeouts()
            sleep_time = max(next_end - time.time(), 0) if next_end else 10000
            timer_event.wait(sleep_time)
            timer_event.clear()

    def __init__(self, *args, **kwargs):
        Connection.__init__(self, *args, **kwargs)

        self._write_queue = Queue()

        self._connect_socket()

        self._read_watcher = gevent.spawn(self.handle_read)
        self._write_watcher = gevent.spawn(self.handle_write)
        self._send_options_message()

    def close(self):
        with self.lock:
            if self.is_closed:
                return
            self.is_closed = True

        log.debug("Closing connection (%s) to %s" % (id(self), self.host))
        if self._read_watcher:
            self._read_watcher.kill(block=False)
        if self._write_watcher:
            self._write_watcher.kill(block=False)
        if self._socket:
            self._socket.close()
        log.debug("Closed socket to %s" % (self.host,))

        if not self.is_defunct:
            self.error_all_requests(
                ConnectionShutdown("Connection to %s was closed" % self.host))
            # don't leave in-progress operations hanging
            self.connected_event.set()

    def handle_close(self):
        log.debug("connection closed by server")
        self.close()

    def handle_write(self):
        run_select = partial(select.select, (), (self._socket,), ())
        while True:
            try:
                next_msg = self._write_queue.get()
                run_select()
            except Exception as exc:
                if not self.is_closed:
                    log.debug("Exception during write select() for %s: %s", self, exc)
                    self.defunct(exc)
                return

            try:
                self._socket.sendall(next_msg)
            except socket.error as err:
                log.debug("Exception during socket sendall for %s: %s", self, err)
                self.defunct(err)
                return  # Leave the write loop

    def handle_read(self):
        run_select = partial(select.select, (self._socket,), (), ())
        while True:
            try:
                run_select()
            except Exception as exc:
                if not self.is_closed:
                    log.debug("Exception during read select() for %s: %s", self, exc)
                    self.defunct(exc)
                return

            try:
                while True:
                    buf = self._socket.recv(self.in_buffer_size)
                    self._iobuf.write(buf)
                    if len(buf) < self.in_buffer_size:
                        break
            except socket.error as err:
                if not is_timeout(err):
                    log.debug("Exception during socket recv for %s: %s", self, err)
                    self.defunct(err)
                    return  # leave the read loop

            if self._iobuf.tell():
                self.process_io_buffer()
            else:
                log.debug("Connection %s closed by server", self)
                self.close()
                return

    def push(self, data):
        chunk_size = self.out_buffer_size
        for i in range(0, len(data), chunk_size):
            self._write_queue.put(data[i:i + chunk_size])
