"""
kombu.connection
================

Broker connection and pools.

:copyright: (c) 2009 - 2011 by Ask Solem.
:license: BSD, see LICENSE for more details.

"""
import os
import sys
import socket

from copy import copy
from itertools import count
from Queue import Empty

from kombu import exceptions
from kombu.transport import get_transport_cls
from kombu.utils import retry_over_time
from kombu.utils.compat import OrderedDict, LifoQueue as _LifoQueue
from kombu.utils.functional import wraps

_LOG_CONNECTION = os.environ.get("KOMBU_LOG_CONNECTION", False)
_LOG_CHANNEL = os.environ.get("KOMBU_LOG_CHANNEL", False)


#: Connection info -> URI
URI_FORMAT = """\
%(transport)s://%(userid)s@%(hostname)s%(port)s%(virtual_host)s\
"""


class BrokerConnection(object):
    """A connection to the broker.

    :keyword hostname: Hostname/address of the server to connect to.
      Default is ``"localhost"``.
    :keyword userid: Username. Default is ``"guest"``.
    :keyword password: Password. Default is ``"guest"``.
    :keyword virtual_host: Virtual host. Default is ``"/"``.
    :keyword port: Port of the server. Default is transport specific.
    :keyword insist: Insist on connecting to a server.
      In a configuration with multiple load-sharing servers, the insist
      option tells the server that the client is insisting on a connection
      to the specified server.  Default is ``False``.
    :keyword ssl: Use ssl to connect to the server. Default is ``False``.
    :keyword transport: Transport class to use. Can be a class,
         or a string specifying the path to the class. (e.g.
         ``kombu.transport.pyamqplib.Transport``), or one of the aliases:
         ``amqplib``, ``pika``, ``redis``, ``memory``.
    :keyword connect_timeout: Timeout in seconds for connecting to the
      server. May not be suported by the specified transport.
    :keyword transport_options: A dict of additional connection arguments to
      pass to alternate kombu channel implementations.  Consult the transport
      documentation for available options.

    **Usage**

    Creating a connection::

        >>> conn = BrokerConnection("rabbit.example.com")

    The connection is established lazily when needed. If you need the
    connection to be established, then force it to do so using
    :meth:`connect`::

        >>> conn.connect()

    Remember to always close the connection::

        >>> conn.release()

    """
    URI_FORMAT = URI_FORMAT

    port = None
    virtual_host = "/"
    connect_timeout = 5

    _closed = None
    _connection = None
    _transport = None
    _logger = None

    def __init__(self, hostname="localhost", userid=None,
            password=None, virtual_host="/", port=None, insist=False,
            ssl=False, transport=None, connect_timeout=5, backend_cls=None,
            transport_options=None, login_method=None, **kwargs):
        self.hostname = hostname
        self.userid = userid
        self.password = password
        self.login_method = login_method
        self.virtual_host = virtual_host or self.virtual_host
        self.port = port or self.port
        self.insist = insist
        self.connect_timeout = connect_timeout or self.connect_timeout
        self.ssl = ssl
        # backend_cls argument will be removed shortly.
        self.transport_cls = transport or backend_cls

        if transport_options is None:
            transport_options = {}
        self.transport_options = transport_options

        if _LOG_CONNECTION:
            from kombu.utils.log import get_logger
            self._logger = get_logger("kombu.connection")

    def _debug(self, msg, ident="[Kombu connection:0x%(id)x] ", **kwargs):
        if self._logger:
            self._logger.debug((ident + unicode(msg)) % {"id": id(self)},
                               **kwargs)

    def connect(self):
        """Establish connection to server immediately."""
        self._closed = False
        return self.connection

    def channel(self):
        """Request a new channel."""
        self._debug("create channel")
        chan = self.transport.create_channel(self.connection)
        if _LOG_CHANNEL:
            from kombu.utils.debug import Logwrapped
            return Logwrapped(chan, "kombu.channel",
                    "[Kombu channel:%(channel_id)s] ")
        return chan

    def drain_events(self, **kwargs):
        """Wait for a single event from the server.

        :keyword timeout: Timeout in seconds before we give up.
            Raises :exc:`socket.timeout` if the timeout is execeded.

        Usually used from an event loop.

        """
        return self.transport.drain_events(self.connection, **kwargs)

    def _close(self):
        if self._connection:
            try:
                self.transport.close_connection(self._connection)
            except self.transport.connection_errors + (AttributeError,
                                                       socket.error):
                pass
            self._connection = None
            self._debug("closed")
        if self._transport:
            self._transport.client = None
            self._transport = None
        self._closed = True

    def release(self):
        """Close the connection (if open)."""
        self._close()
    close = release

    def ensure_connection(self, errback=None, max_retries=None,
            interval_start=2, interval_step=2, interval_max=30):
        """Ensure we have a connection to the server.

        If not retry establishing the connection with the settings
        specified.

        :keyword errback: Optional callback called each time the connection
          can't be established. Arguments provided are the exception
          raised and the interval that will be slept ``(exc, interval)``.

        :keyword max_retries: Maximum number of times to retry.
          If this limit is exceeded the connection error will be re-raised.

        :keyword interval_start: The number of seconds we start sleeping for.
        :keyword interval_step: How many seconds added to the interval
          for each retry.
        :keyword interval_max: Maximum number of seconds to sleep between
          each retry.

        """
        retry_over_time(self.connect, self.connection_errors, (), {},
                        errback, max_retries,
                        interval_start, interval_step, interval_max)
        return self

    def ensure(self, obj, fun, errback=None, max_retries=None,
            interval_start=1, interval_step=1, interval_max=1):
        """Ensure operation completes, regardless of any channel/connection
        errors occuring.

        Will retry by establishing the connection, and reapplying
        the function.

        :param fun: Method to apply.

        :keyword errback: Optional callback called each time the connection
          can't be established. Arguments provided are the exception
          raised and the interval that will be slept ``(exc, interval)``.

        :keyword max_retries: Maximum number of times to retry.
          If this limit is exceeded the connection error will be re-raised.

        :keyword interval_start: The number of seconds we start sleeping for.
        :keyword interval_step: How many seconds added to the interval
          for each retry.
        :keyword interval_max: Maximum number of seconds to sleep between
          each retry.

        **Example**

        This is an example ensuring a publish operation::

            >>> def errback(exc, interval):
            ...     print("Couldn't publish message: %r. Retry in %ds" % (
            ...             exc, interval))
            >>> publish = conn.ensure(producer, producer.publish,
            ...                       errback=errback, max_retries=3)
            >>> publish(message, routing_key)

        """

        max_retries = max_retries or 0

        @wraps(fun)
        def _insured(*args, **kwargs):
            got_connection = 0
            for retries in count(0):
                try:
                    return fun(*args, **kwargs)
                except self.connection_errors + self.channel_errors, exc:
                    self._debug("ensure got exception: %r" % (exc, ),
                                exc_info=sys.exc_info())
                    if got_connection or \
                            max_retries and retries > max_retries:
                        raise
                    errback and errback(exc, 0)
                    self._connection = None
                    self.close()
                    remaining_retries = max_retries and \
                                            max(max_retries - retries, 1)
                    self.ensure_connection(errback,
                                           remaining_retries,
                                           interval_start,
                                           interval_step,
                                           interval_max)
                    obj.revive(self.channel())
                    got_connection += 1

        _insured.func_name = _insured.__name__ = "%s(insured)" % fun.__name__
        return _insured

    def create_transport(self):
        return self.get_transport_cls()(client=self)
    create_backend = create_transport   # FIXME

    def get_transport_cls(self):
        """Get the currently used transport class."""
        transport_cls = self.transport_cls
        if not transport_cls or isinstance(transport_cls, basestring):
            transport_cls = get_transport_cls(transport_cls)
        return transport_cls

    def clone(self, **kwargs):
        """Create a copy of the connection with the same connection
        settings."""
        return self.__class__(**dict(self.info(), **kwargs))

    def info(self):
        """Get connection info."""
        transport_cls = self.transport_cls or "amqplib"
        port = self.port or self.transport.default_port
        return OrderedDict((("hostname", self.hostname),
                            ("userid", self.userid),
                            ("password", self.password),
                            ("virtual_host", self.virtual_host),
                            ("port", port),
                            ("insist", self.insist),
                            ("ssl", self.ssl),
                            ("transport", transport_cls),
                            ("transport_options", self.transport_options),
                            ("connect_timeout", self.connect_timeout)))

    def __hash__(self):
        return hash("|".join(map(str, self.info().itervalues())))

    def as_uri(self):
        fields = self.info()
        port = fields["port"]
        if port:
            fields["port"] = ":%s" % (port, )
        vhost = fields["virtual_host"]
        if not vhost.startswith('/'):
            fields["virtual_host"] = '/' + vhost
        return self.URI_FORMAT % fields

    def Pool(self, limit=None, preload=None):
        """Pool of connections.

        See :class:`ConnectionPool`.

        :keyword limit: Maximum number of active connections.
          Default is no limit.
        :keyword preload: Number of connections to preload
          when the pool is created.  Default is 0.

        *Example usage*::

            >>> pool = connection.Pool(2)
            >>> c1 = pool.acquire()
            >>> c2 = pool.acquire()
            >>> c3 = pool.acquire()
            Traceback (most recent call last):
              File "<stdin>", line 1, in <module>
              File "kombu/connection.py", line 354, in acquire
              raise ConnectionLimitExceeded(self.limit)
                kombu.exceptions.ConnectionLimitExceeded: 2
            >>> c1.release()
            >>> c3 = pool.acquire()

        """
        return ConnectionPool(self, limit, preload)

    def ChannelPool(self, limit=None, preload=None):
        """Pool of channels.

        See :class:`ChannelPool`.

        :keyword limit: Maximum number of active channels.
          Default is no limit.
        :keyword preload: Number of channels to preload
          when the pool is created.  Default is 0.

        *Example usage*::

            >>> pool = connection.ChannelPool(2)
            >>> c1 = pool.acquire()
            >>> c2 = pool.acquire()
            >>> c3 = pool.acquire()
            Traceback (most recent call last):
              File "<stdin>", line 1, in <module>
              File "kombu/connection.py", line 354, in acquire
              raise ChannelLimitExceeded(self.limit)
                kombu.connection.ChannelLimitExceeded: 2
            >>> c1.release()
            >>> c3 = pool.acquire()

        """
        return ChannelPool(self, limit, preload)

    def SimpleQueue(self, name, no_ack=None, queue_opts=None,
            exchange_opts=None, channel=None, **kwargs):
        """Create new :class:`~kombu.simple.SimpleQueue`, using a channel
        from this connection.

        If ``name`` is a string, a queue and exchange will be automatically
        created using that name as the name of the queue and exchange,
        also it will be used as the default routing key.

        :param name: Name of the queue/or a :class:`~kombu.entity.Queue`.
        :keyword no_ack: Disable acknowledgements. Default is false.
        :keyword queue_opts: Additional keyword arguments passed to the
          constructor of the automatically created
          :class:`~kombu.entity.Queue`.
        :keyword exchange_opts: Additional keyword arguments passed to the
          constructor of the automatically created
          :class:`~kombu.entity.Exchange`.
        :keyword channel: Channel to use. If not specified a new channel
           from the current connection will be used. Remember to call
           :meth:`~kombu.simple.SimpleQueue.close` when done with the
           object.

        """
        from kombu.simple import SimpleQueue

        channel_autoclose = False
        if channel is None:
            channel = self.channel()
            channel_autoclose = True
        return SimpleQueue(channel, name, no_ack, queue_opts, exchange_opts,
                           channel_autoclose=channel_autoclose, **kwargs)

    def SimpleBuffer(self, name, no_ack=None, queue_opts=None,
            exchange_opts=None, channel=None, **kwargs):
        """Create new :class:`~kombu.simple.SimpleQueue` using a channel
        from this connection.

        Same as :meth:`SimpleQueue`, but configured with buffering
        semantics. The resulting queue and exchange will not be durable, also
        auto delete is enabled. Messages will be transient (not persistent),
        and acknowledgements are disabled (``no_ack``).

        """
        from kombu.simple import SimpleBuffer

        channel_autoclose = False
        if channel is None:
            channel = self.channel()
            channel_autoclose = True
        return SimpleBuffer(channel, name, no_ack, queue_opts, exchange_opts,
                            channel_autoclose=channel_autoclose, **kwargs)

    def _establish_connection(self):
        self._debug("establishing connection...")
        conn = self.transport.establish_connection()
        self._debug("connection established: %r" % (conn, ))
        return conn

    def __repr__(self):
        """``x.__repr__() <==> repr(x)``"""
        return "<BrokerConnection: %s at 0x%x>" % (self.as_uri(), id(self))

    def __copy__(self):
        """``x.__copy__() <==> copy(x)``"""
        return self.clone()

    def __reduce__(self):
        return (self.__class__, tuple(self.info().values()), None)

    def __enter__(self):
        return self

    def __exit__(self, *args):
        self.release()

    @property
    def connection(self):
        """The underlying connection object.

        .. warning::
            This instance is transport specific, so do not
            depend on the interface of this object.

        """
        if self._closed:
            return
        if not self._connection or not \
                self.transport.verify_connection(self._connection):
            self._connection = self._establish_connection()
            self._closed = False
        return self._connection

    @property
    def host(self):
        """The host as a hostname/port pair separated by colon."""
        return ":".join([self.hostname, str(self.port)])

    @property
    def transport(self):
        if self._transport is None:
            self._transport = self.create_transport()
        return self._transport

    @property
    def connection_errors(self):
        """List of exceptions that may be raised by the connection."""
        return self.transport.connection_errors

    @property
    def channel_errors(self):
        """List of exceptions that may be raised by the channel."""
        return self.transport.channel_errors
Connection = BrokerConnection


class Resource(object):

    def __init__(self, limit=None, preload=None):
        self.limit = limit
        self.preload = preload or 0

        self._resource = _LifoQueue()
        self._dirty = set()
        self.setup()

    def setup(self):
        raise NotImplementedError("subclass responsibilty")

    def _add_when_empty(self):
        if self.limit and len(self._dirty) >= self.limit:
            raise self.LimitExceeded(self.limit)
        # All taken, put new on the queue and
        # try get again, this way the first in line
        # will get the resource.
        self._resource.put_nowait(self.new())

    def acquire(self, block=False, timeout=None):
        """Acquire resource.

        :keyword block: If the limit is exceeded,
          block until there is an available item.
        :keyword timeout: Timeout to wait
          if ``block`` is true. Default is :const:`None` (forever).

        :raises LimitExceeded: if block is false
          and the limit has been exceeded.

        """
        if self.limit:
            while 1:
                try:
                    resource = self._resource.get(block=block, timeout=timeout)
                except Empty:
                    self._add_when_empty()
                else:
                    resource = self.prepare(resource)
                    self._dirty.add(resource)
                    break
        else:
            resource = self.prepare(self.new())

        @wraps(self.release)
        def _release():
            self.release(resource)
        resource.release = _release

        return resource

    def prepare(self, resource):
        return resource

    def close_resource(self, resource):
        resource.close()

    def release_resource(self, resource):
        pass

    def release(self, resource):
        """Release resource so it can be used by another thread.

        The caller is responsible for discarding the object,
        and to never use the resource again.  A new resource must
        be acquired if so needed.

        """
        if self.limit:
            self._dirty.discard(resource)
            self._resource.put_nowait(resource)
            self.release_resource(resource)
        else:
            self.close_resource(resource)

    def force_close_all(self):
        """Closes and removes all resources in the pool (also those in use).

        Can be used to close resources from parent processes
        after fork (e.g. sockets/connections).

        """
        dirty = self._dirty
        resource = self._resource
        while 1:
            try:
                dres = dirty.pop()
            except KeyError:
                break
            self.close_resource(dres)

        resource.mutex.acquire()
        try:
            while 1:
                try:
                    res = resource.queue.pop()
                except IndexError:
                    break
                self.close_resource(res)
        finally:
            resource.mutex.release()


class PoolChannelContext(object):

    def __init__(self, pool, block=False):
        self.pool = pool
        self.block = block

    def __enter__(self):
        self.conn = self.pool.acquire(block=self.block)
        self.chan = self.conn.channel()
        return self.conn, self.chan

    def __exit__(self, *exc_info):
        self.chan.close()
        self.conn.release()


class ConnectionPool(Resource):
    LimitExceeded = exceptions.ConnectionLimitExceeded

    def __init__(self, connection, limit=None, preload=None):
        self.connection = connection
        super(ConnectionPool, self).__init__(limit=limit,
                                             preload=preload)

    def new(self):
        return copy(self.connection)

    def release_resource(self, resource):
        resource._debug("released")

    def acquire_channel(self, block=False):
        return PoolChannelContext(self, block)

    def setup(self):
        if self.limit:
            for i in xrange(self.limit):
                conn = self.new()
                if i < self.preload:
                    conn.connect()
                self._resource.put_nowait(conn)

    def prepare(self, resource):
        resource._debug("acquired")
        resource.connect()
        return resource


class ChannelPool(Resource):
    LimitExceeded = exceptions.ChannelLimitExceeded

    def __init__(self, connection, limit=None, preload=None):
        self.connection = connection
        super(ChannelPool, self).__init__(limit=limit,
                                          preload=preload)

    def new(self):
        return self.connection.channel

    def setup(self):
        channel = self.new()
        for i in xrange(self.limit):
            self._resource.put_nowait(
                    i < self.preload and channel() or channel)

    def prepare(self, channel):
        if callable(channel):
            channel = channel()

        return channel
