#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# This file is part of tornadis library released under the MIT license.
# See the LICENSE file for more information.

import tornado.gen
import tornado.ioloop
import tornado.locks
import logging
import functools
from collections import deque

from tornadis.client import Client
from tornadis.utils import ContextManagerFuture
from tornadis.exceptions import ClientError

LOG = logging.getLogger(__name__)


class ClientPool(object):
    """High level object to deal with a pool of redis clients."""

    def __init__(self, max_size=-1, client_timeout=-1, autoclose=False,
                 **client_kwargs):
        """Constructor.

        Args:
            max_size (int): max size of the pool (-1 means "no limit").
            client_timeout (int): timeout in seconds of a connection released
                to the pool (-1 means "no timeout").
            autoclose (boolean): automatically disconnect released connections
                with lifetime > client_timeout (test made every
                client_timeout/10 seconds).
            client_kwargs (dict): Client constructor arguments.
        """
        self.max_size = max_size
        self.client_timeout = client_timeout
        self.client_kwargs = client_kwargs
        self.__ioloop = client_kwargs.get('ioloop',
                                          tornado.ioloop.IOLoop.instance())
        self.autoclose = autoclose
        self.__pool = deque()
        if self.max_size != -1:
            self.__sem = tornado.locks.Semaphore(self.max_size)
        else:
            self.__sem = None
        self.__autoclose_periodic = None
        if self.autoclose and self.client_timeout > 0:
            every = int(self.client_timeout) * 100
            if int(tornado.version[0]) >= 5:
                cb = tornado.ioloop.PeriodicCallback(self._autoclose,
                                                     every)
            else:
                cb = tornado.ioloop.PeriodicCallback(self._autoclose,
                                                     every, self.__ioloop)
            self.__autoclose_periodic = cb
            self.__autoclose_periodic.start()

    def _get_client_from_pool_or_make_it(self):
        try:
            while True:
                client = self.__pool.popleft()
                if client.is_connected():
                    if self._is_expired_client(client):
                        client.disconnect()
                        continue
                    break
        except IndexError:
            client = self._make_client()
            return (True, client)
        return (False, client)

    @tornado.gen.coroutine
    def get_connected_client(self):
        """Gets a connected Client object.

        If max_size is reached, this method will block until a new client
        object is available.

        Returns:
            A Future object with connected Client instance as a result
                (or ClientError if there was a connection problem)
        """
        if self.__sem is not None:
            yield self.__sem.acquire()
        client = None
        newly_created, client = self._get_client_from_pool_or_make_it()
        if newly_created:
            res = yield client.connect()
            if not res:
                LOG.warning("can't connect to %s", client.title)
                raise tornado.gen.Return(
                    ClientError("can't connect to %s" % client.title))
        raise tornado.gen.Return(client)

    def get_client_nowait(self):
        """Gets a Client object (not necessary connected).

        If max_size is reached, this method will return None (and won't block).

        Returns:
            A Client instance (not necessary connected) as result (or None).
        """
        if self.__sem is not None:
            if self.__sem._value == 0:
                return None
            self.__sem.acquire()
        _, client = self._get_client_from_pool_or_make_it()
        return client

    def _autoclose(self):
        newpool = deque()
        try:
            while True:
                client = self.__pool.popleft()
                if client.is_connected():
                    if self._is_expired_client(client):
                        client.disconnect()
                    else:
                        newpool.append(client)
        except IndexError:
            self.__pool = newpool

    def _is_expired_client(self, client):
        if self.client_timeout != -1 and client.is_connected():
            delta = client.get_last_state_change_timedelta()
            if delta.total_seconds() >= self.client_timeout:
                return True
        return False

    def connected_client(self):
        """Returns a ContextManagerFuture to be yielded in a with statement.

        Returns:
            A ContextManagerFuture object.

        Examples:
            >>> with (yield pool.connected_client()) as client:
                    # client is a connected tornadis.Client instance
                    # it will be automatically released to the pool thanks to
                    # the "with" keyword
                    reply = yield client.call("PING")
        """
        future = self.get_connected_client()
        cb = functools.partial(self._connected_client_release_cb, future)
        return ContextManagerFuture(future, cb)

    def _connected_client_release_cb(self, future=None):
        client = future.result()
        self.release_client(client)

    def release_client(self, client):
        """Releases a client object to the pool.

        Args:
            client: Client object.
        """
        if isinstance(client, Client):
            if not self._is_expired_client(client):
                LOG.debug('Client is not expired. Adding back to pool')
                self.__pool.append(client)
            elif client.is_connected():
                LOG.debug('Client is expired and connected. Disconnecting')
                client.disconnect()
        if self.__sem is not None:
            self.__sem.release()

    def destroy(self):
        """Disconnects all pooled client objects."""
        while True:
            try:
                client = self.__pool.popleft()
                if isinstance(client, Client):
                    client.disconnect()
            except IndexError:
                break

    @tornado.gen.coroutine
    def preconnect(self, size=-1):
        """(pre)Connects some or all redis clients inside the pool.

        Args:
            size (int): number of redis clients to build and to connect
                (-1 means all clients if pool max_size > -1)

        Raises:
            ClientError: when size == -1 and pool max_size == -1
        """
        if size == -1 and self.max_size == -1:
            raise ClientError("size=-1 not allowed with pool max_size=-1")
        limit = min(size, self.max_size) if size != -1 else self.max_size
        clients = yield [self.get_connected_client() for _ in range(0, limit)]
        for client in clients:
            self.release_client(client)

    def _make_client(self):
        """Makes and returns a Client object."""
        kwargs = self.client_kwargs
        client = Client(**kwargs)
        return client
