'''
This module contains the RpcConnection class, more informations about this
class are located in it docstring.
'''

from __future__ import absolute_import

import ssl
import struct
import socket
import logging

from sjrpc.core.protocols.rpc import RpcProtocol
from sjrpc.core.exceptions import RpcError, SocketRpcError


class RpcConnection(object):
    '''
    This class manage a single peer connection.

    :param sock: the socket object of this newly created :class:`RpcConnection`
    :param *args, **kwargs: arguments to pass to the default rpc protocol
        automatically registered on label 0.
    '''

    MESSAGE_HEADER = '!HL'
    SHORTCUTS_MAINRPC = ('call', 'async_call')

    def __init__(self, sock, *args, **kwargs):
        #super(RpcConnection, self).__init__()
        # Sock of this connection:
        self._sock = sock
        self._sock.settimeout(None)

        # Activate TCP keepalive on the connection:
        #self._sock.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)

        # Is the RpcConnection connected to its peer:
        self._connected = True

        # Setup self.logger.facility:
        self.logger = logging.getLogger('sjrpc.%s' % self.getpeername())

        # Protocols registered on this connection:
        self._protocols = {}
        self.register_protocol(0, RpcProtocol, *args, **kwargs)

        # Create shortcuts to the main rpc (protocol 0) for convenience:
        for name in RpcConnection.SHORTCUTS_MAINRPC:
            setattr(self, name, getattr(self.get_protocol(0), name))

    @classmethod
    def from_addr(cls, addr, port, conn_timeout=30.0, *args, **kwargs):
        '''
        Construct the instance of :class:`RpcConnection` without providing
        the :class:`socket` object. Socket is automatically created and passed
        to the standard constructor before to return the new instance.

        :param addr: the target ip address
        :param port: the target port
        :param conn_timeout: the connection operation timeout
        :param *args, **kwargs: extra argument to pass to the constructor (see
            constructor doctring)
        '''
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        sock.settimeout(conn_timeout)
        sock.connect((addr, port))
        return cls(sock, *args, **kwargs)

    @classmethod
    def from_addr_ssl(cls, addr, port, cert=None,
                      conn_timeout=30, *args, **kwargs):
        '''
        Construct :class:`RpcConnection` instance like :meth:`from_addr`, but
        enable ssl on socket.

        :param cert: ssl certificate or None for ssl without certificat
        '''
        connection = cls.from_addr(addr, port, conn_timeout, *args, **kwargs)
        req = ssl.CERT_NONE if cert is None else ssl.CERT_REQUIRED
        connection._sock = ssl.wrap_socket(connection._sock, certfile=cert,
                                           cert_reqs=req,
                                           ssl_version=ssl.PROTOCOL_TLSv1)
        return connection

    def __repr__(self):
        return '<RpcConnection object>'

    def __hash__(self):
        return self._sock.__hash__()

    def run(self):
        '''
        Inbound message processing loop.
        '''
        while self._connected:
            try:
                self._dispatch()
            except SocketRpcError:
                # If SocketRpcError occurs while dispatching, shutdown the
                # connection if it not already shutdown:
                if self._connected:
                    self.shutdown()

    def _dispatch(self):
        '''
        Read next message from socket and dispatch it to accoding protocol
        handler.
        '''

        # Read the header:
        buf = self.recv_until(struct.calcsize(RpcConnection.MESSAGE_HEADER))
        label, pl_size = struct.unpack(RpcConnection.MESSAGE_HEADER, buf)
        # Get the registered protocol for the specified label
        proto = self._protocols.get(label)
        if proto is not None:
            proto.handle(label, pl_size)

    def send(self, label, payload):
        '''
        Low level method to send a message through the socket, generally
        used by protocols.
        '''
        if not self._connected:
            raise RpcError('RpcError', 'Not connected to the peer')
        size = len(payload)
        header = struct.pack(RpcConnection.MESSAGE_HEADER, label, size)
        try:
            self._sock.sendall(header + payload)
        except socket.error as err:
            errmsg = 'Fatal error while sending through socket: %s' % err
            self.logger.error(errmsg)
            raise RpcError('SocketError', errmsg)

#
# Public API
#

    def register_protocol(self, label, protocol_class, *args, **kwargs):
        '''
        Register a new protocol for the specified label.
        '''

        if label in self._protocols:
            raise KeyError('A protocol is already registered for this label')
        elif not isinstance(label, int):
            raise ValueError('Label must be an integer')
        self._protocols[label] = protocol_class(self, label, *args, **kwargs)
        return self._protocols[label]

    def unregister_protocol(self, label):
        '''
        Unregister the specified protocol label for this connection.
        '''

        if label in self._protocols and label != 0:
            del self._protocols[label]
        else:
            raise KeyError('No protocol registered for this label')

    def get_protocol(self, label):
        '''
        Get the protocol registered for specified label.
        '''

        proto = self._protocols.get(label)
        if proto is None:
            raise KeyError('No protocol registered for this label')
        return proto

    def shutdown(self):
        '''
        Shutdown this connection.
        '''

        # Shutdown each registered protocols:
        for proto in self._protocols.itervalues():
            proto.shutdown()

        # Close the connection socket:
        self._connected = False
        try:
            self._sock.shutdown(socket.SHUT_RDWR)
            self._sock.close()
        except socket.error as err:
            #self.logger.warn('Error while socket close: %s', err)
            pass

    def get_handler(self):
        '''
        Return the handler binded to the :class:`RpcConnection`.

        :return: binded handler
        '''
        return self._handler

    def set_handler(self, handler):
        '''
        Define a new handler for this connection.

        :param handler: the new handler to define.
        '''
        self._handler = handler

    def get_fd(self):
        '''
        Get the file descriptor of the socket managed by this connection.

        :return: the file descriptor number of the socket
        '''
        try:
            return self._sock.fileno()
        except socket.error:
            return None

    def getpeername(self):
        '''
        Get the peer name.

        :return: string representing the peer name
        '''
        return '%s:%s' % self._sock.getpeername()

    def recv_until(self, bufsize, flags=None):
        '''
        Read socket until bufsize is received.
        '''
        buf = ''
        while len(buf) < bufsize:
            remains = bufsize - len(buf)
            try:
                received = self._sock.recv(remains)
            except socket.error as err:
                if not self._connected:
                    raise SocketRpcError('Not connected to the peer')
                errmsg = 'Fatal error while receiving from socket: %s' % err
                self.logger.error(errmsg)
                raise SocketRpcError(errmsg)

            # Handle peer disconnection:
            if not received:
                self.logger.info('Connection reset by peer')
                self.shutdown()

            buf += received
        return buf


class GreenRpcConnection(RpcConnection):

    '''
    Cooperative RpcConnection to use with Gevent.
    '''

    def __init__(self, *args, **kwargs):
        super(GreenRpcConnection, self).__init__(*args, **kwargs)
        self._greenlet = None

    @classmethod
    def from_addr(cls, addr, port, conn_timeout=30.0, *args, **kwargs):
        '''
        Construct the instance of :class:`RpcConnection` without providing
        the :class:`socket` object. Socket is automatically created and passed
        to the standard constructor before to return the new instance.

        :param addr: the target ip address
        :param port: the target port
        :param conn_timeout: the connection operation timeout
        :param *args, **kwargs: extra argument to pass to the constructor (see
            constructor doctring)
        '''
        import gevent.socket
        sock = gevent.socket.create_connection((addr, port), conn_timeout)
        return cls(sock, *args, **kwargs)

    @classmethod
    def from_addr_ssl(cls, addr, port, cert, conn_timeout=30, *args, **kwargs):
        '''
        Construct :class:`RpcConnection` instance like :meth:`from_addr`, but
        enable ssl on socket.

        :param cert: ssl certificate or None for ssl without certificat
        '''
        import gevent.socket
        sock = gevent.socket.create_connection((addr, port), conn_timeout)
        req = ssl.CERT_NONE if cert is None else ssl.CERT_REQUIRED
        sock = gevent.ssl.SSLSocket(sock, certfile=None, cert_reqs=req,
                                    ssl_version=ssl.PROTOCOL_TLSv1)
        return cls(sock, *args, **kwargs)

    def run(self):
        import gevent
        self._greenlet = gevent.spawn(self.run)
        self._greenlet.join()

    def shutdown(self):
        super(GreenRpcConnection, self).shutdown()
        if self._greenlet is not None:
            self._greenlet.kill()