# Copyright (C) 2011, 2012 Nippon Telegraph and Telephone Corporation.
# Copyright (C) 2011, 2012 Isaku Yamahata <yamahata at valinux co jp>
#
# 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 contextlib
import gflags
import logging
import gevent
import traceback
import random
import greenlet
from gevent.server import StreamServer
from gevent.queue import Queue

from ryu.ofproto import ofproto_common
from ryu.ofproto import ofproto_parser
from ryu.ofproto import ofproto_v1_0
from ryu.ofproto import ofproto_v1_0_parser
from ryu.ofproto import ofproto_v1_2
from ryu.ofproto import ofproto_v1_2_parser
from ryu.ofproto import nx_match

from ryu.controller import dispatcher
from ryu.controller import handler
from ryu.controller import ofp_event

LOG = logging.getLogger('ryu.controller.controller')

FLAGS = gflags.FLAGS
gflags.DEFINE_string('ofp_listen_host', '', 'openflow listen host')
gflags.DEFINE_integer('ofp_tcp_listen_port', ofproto_common.OFP_TCP_PORT,
                      'openflow tcp listen port')


class OpenFlowController(object):
    def __init__(self):
        super(OpenFlowController, self).__init__()

    # entry point
    def __call__(self):
        #LOG.debug('call')
        self.server_loop()

    def server_loop(self):
        server = StreamServer((FLAGS.ofp_listen_host,
                               FLAGS.ofp_tcp_listen_port),
                              datapath_connection_factory)
        #LOG.debug('loop')
        server.serve_forever()


def _deactivate(method):
    def deactivate(self):
        try:
            method(self)
        except greenlet.GreenletExit:
            pass
        except:
            traceback.print_stack()
            raise
        finally:
            self.is_active = False
    return deactivate


class Datapath(object):
    supported_ofp_version = {
        ofproto_v1_0.OFP_VERSION: (ofproto_v1_0,
                                   ofproto_v1_0_parser),
        ofproto_v1_2.OFP_VERSION: (ofproto_v1_2,
                                   ofproto_v1_2_parser),
        }

    def __init__(self, socket, address):
        super(Datapath, self).__init__()

        self.socket = socket
        self.address = address
        self.is_active = True

        # The limit is arbitrary. We need to limit queue size to
        # prevent it from eating memory up
        self.send_q = Queue(16)

        # circular reference self.ev_q.aux == self
        self.ev_q = dispatcher.EventQueue(handler.QUEUE_NAME_OFP_MSG,
                                          handler.HANDSHAKE_DISPATCHER,
                                          self)

        self.set_version(max(self.supported_ofp_version))
        self.xid = random.randint(0, self.ofproto.MAX_XID)
        self.id = None  # datapath_id is unknown yet
        self.ports = None
        self.flow_format = ofproto_v1_0.NXFF_OPENFLOW10

    def close(self):
        """
        Call this before discarding this datapath object
        The circular refernce as self.ev_q.aux == self must be broken.
        """
        # tell this datapath is dead
        self.ev_q.set_dispatcher(handler.DEAD_DISPATCHER)
        self.ev_q.close()

    def set_version(self, version):
        assert version in self.supported_ofp_version
        self.ofproto, self.ofproto_parser = self.supported_ofp_version[version]

    # Low level socket handling layer
    @_deactivate
    def _recv_loop(self):
        buf = bytearray()
        required_len = ofproto_common.OFP_HEADER_SIZE

        count = 0
        while self.is_active:
            ret = self.socket.recv(required_len)
            if len(ret) == 0:
                self.is_active = False
                break
            buf += ret
            while len(buf) >= required_len:
                (version, msg_type, msg_len, xid) = ofproto_parser.header(buf)
                required_len = msg_len
                if len(buf) < required_len:
                    break

                msg = ofproto_parser.msg(self,
                                         version, msg_type, msg_len, xid, buf)
                #LOG.debug('queue msg %s cls %s', msg, msg.__class__)
                self.ev_q.queue(ofp_event.ofp_msg_to_ev(msg))

                buf = buf[required_len:]
                required_len = ofproto_common.OFP_HEADER_SIZE

                # We need to schedule other greenlets. Otherwise, ryu
                # can't accept new switches or handle the existing
                # switches. The limit is arbitrary. We need the better
                # approach in the future.
                count += 1
                if count > 2048:
                    count = 0
                    gevent.sleep(0)

    @_deactivate
    def _send_loop(self):
        while self.is_active:
            buf = self.send_q.get()
            self.socket.sendall(buf)

    def send(self, buf):
        self.send_q.put(buf)

    def set_xid(self, msg):
        self.xid += 1
        self.xid &= self.ofproto.MAX_XID
        msg.set_xid(self.xid)
        return self.xid

    def send_msg(self, msg):
        assert isinstance(msg, self.ofproto_parser.MsgBase)
        if msg.xid is None:
            self.set_xid(msg)
        msg.serialize()
        # LOG.debug('send_msg %s', msg)
        self.send(msg.buf)

    def serve(self):
        send_thr = gevent.spawn(self._send_loop)

        # send hello message immediately
        hello = self.ofproto_parser.OFPHello(self)
        self.send_msg(hello)

        try:
            self._recv_loop()
        finally:
            gevent.kill(send_thr)
            gevent.joinall([send_thr])

    def send_ev(self, ev):
        #LOG.debug('send_ev %s', ev)
        self.ev_q.queue(ev)

    #
    # Utility methods for convenience
    #
    def send_packet_out(self, buffer_id=0xffffffff, in_port=None,
                        actions=None, data=None):
        if in_port is None:
            in_port = self.ofproto.OFPP_NONE
        packet_out = self.ofproto_parser.OFPPacketOut(
            self, buffer_id, in_port, actions, data)
        self.send_msg(packet_out)

    def send_flow_mod(self, rule, cookie, command, idle_timeout, hard_timeout,
                      priority=None, buffer_id=0xffffffff,
                      out_port=None, flags=0, actions=None):
        if priority is None:
            priority = self.ofproto.OFP_DEFAULT_PRIORITY
        if out_port is None:
            out_port = self.ofproto.OFPP_NONE
        flow_format = rule.flow_format()
        assert (flow_format == ofproto_v1_0.NXFF_OPENFLOW10 or
                flow_format == ofproto_v1_0.NXFF_NXM)
        if self.flow_format < flow_format:
            self.send_nxt_set_flow_format(flow_format)
        if flow_format == ofproto_v1_0.NXFF_OPENFLOW10:
            match_tuple = rule.match_tuple()
            match = self.ofproto_parser.OFPMatch(*match_tuple)
            flow_mod = self.ofproto_parser.OFPFlowMod(
                self, match, cookie, command, idle_timeout, hard_timeout,
                priority, buffer_id, out_port, flags, actions)
        else:
            flow_mod = self.ofproto_parser.NXTFlowMod(
                self, cookie, command, idle_timeout, hard_timeout,
                priority, buffer_id, out_port, flags, rule, actions)
        self.send_msg(flow_mod)

    def send_flow_del(self, rule, cookie, out_port=None):
        self.send_flow_mod(rule=rule, cookie=cookie,
                           command=self.ofproto.OFPFC_DELETE,
                           idle_timeout=0, hard_timeout=0, priority=0,
                           out_port=out_port)

    def send_delete_all_flows(self):
        rule = nx_match.ClsRule()
        self.send_flow_mod(
            rule=rule, cookie=0, command=self.ofproto.OFPFC_DELETE,
            idle_timeout=0, hard_timeout=0, priority=0, buffer_id=0,
            out_port=self.ofproto.OFPP_NONE, flags=0, actions=None)

    def send_barrier(self):
        barrier_request = self.ofproto_parser.OFPBarrierRequest(self)
        self.send_msg(barrier_request)

    def send_nxt_set_flow_format(self, flow_format):
        assert (flow_format == ofproto_v1_0.NXFF_OPENFLOW10 or
                flow_format == ofproto_v1_0.NXFF_NXM)
        if self.flow_format == flow_format:
            # Nothing to do
            return
        self.flow_format = flow_format
        set_format = self.ofproto_parser.NXTSetFlowFormat(self, flow_format)
        # FIXME: If NXT_SET_FLOW_FORMAT or NXFF_NXM is not supported by
        # the switch then an error message will be received. It may be
        # handled by setting self.flow_format to
        # ofproto_v1_0.NXFF_OPENFLOW10 but currently isn't.
        self.send_msg(set_format)
        self.send_barrier()


def datapath_connection_factory(socket, address):
    LOG.debug('connected socket:%s address:%s', socket, address)
    with contextlib.closing(Datapath(socket, address)) as datapath:
        try:
            datapath.serve()
        except:
            # Something went wrong.
            # Especially malicious switch can send malformed packet,
            # the parser raise exception.
            # Can we do anything more graceful?
            LOG.error("Error in the datapath %s from %s",
                      datapath.id, address)
            raise