from __future__ import absolute_import

import socket

from sjrpc.core.protocols import Protocol

import pyev

class TunnelProtocol(Protocol):

    '''
    A Tunneling protocol used to 
    '''

    GET_SIZE = 1024 * 1024 # 1MB
    DEFAULT_GET_SIZE = GET_SIZE

    def __init__(self, *args, **kwargs):
        endpoint = kwargs.pop('endpoint', None)
        super(TunnelProtocol, self).__init__(*args, **kwargs)

        if endpoint is None:
            self._endpoint, self._socket = socket.socketpair()
        else:
            self._endpoint = endpoint

        self._from_tun_to_endpoint_buf = ''
        self._asked = 0 # Data asked to the peer
        self._ok_to_send = 0 # Data I can send to the peer

        # Set the endpoint as non-blocking socket:
        self._endpoint.setblocking(False)

        # Create watcher to handle data coming from the endpoint:
        props = dict(fd=self._endpoint, events=pyev.EV_READ,
                     callback=self._handle_from_endpoint)
        self._endpoint_reader = self._connection.create_watcher(pyev.Io, **props)

        # Create watcher to handle data going to the endpoint:
        props = dict(fd=self._endpoint, events=pyev.EV_WRITE,
                     callback=self._handle_from_tunnel)
        self._endpoint_writer = self._connection.create_watcher(pyev.Io, **props)

        # Ask some data to the peer:
        self._send_get(TunnelProtocol.GET_SIZE)

    def _handle_from_endpoint(self, watcher, revents):
        '''
        Handle data coming from the endpoint socket and push it through the
        sjRpc tunnel.
        '''
        read = self._endpoint.recv(self._ok_to_send)
        self._ok_to_send -= len(read)
        self.send(read)
        if not self._ok_to_send:
            watcher.stop()

    def _handle_from_tunnel(self, watcher, revent):
        '''
        Handle writing of the data already received from the tunnel and stored
        into the incoming buffer. Data are writed only when the endpoint socket
        is ready to write.

        This method is also responsible of asking more data to the peer when
        the incoming buffer is empty.
        '''
        sent = self._endpoint.send(self._from_tun_to_endpoint_buf)
        self._from_tun_to_endpoint_buf = self._from_tun_to_endpoint_buf[sent:]
        self._asked -= sent
        if self._asked < TunnelProtocol.GET_SIZE * 2:
            self._send_get(TunnelProtocol.GET_SIZE)
        if not self._from_tun_to_endpoint_buf:
            watcher.stop()

    def _send_get(self, size):
        self._connection.rpc.send_special('protoctl', label=self._label,
                                          type='get', payload=dict(size=size))
        self._asked += size

#
# Public methods:
#

    def end_of_message(self):
        '''
        Handle inbound data from the :class:`RpcConnection` peer and place it
        on the incoming buffer.
        '''
        self._from_tun_to_endpoint_buf += self._incoming_buf
        self._endpoint_writer.start()

    def handle_control(self, control_type, payload):
        if control_type == 'get':
            size = payload.get('size', TunnelProtocol.DEFAULT_GET_SIZE)
            self._ok_to_send += size
            self._endpoint_reader.start()