"""

NAWS - Negotiate About Window Size

This implements the NAWS telnet option as per
https://www.ietf.org/rfc/rfc1073.txt

NAWS allows telnet clients to report their
current window size to the client and update
it when the size changes

"""
from django.conf import settings
from src.utils import utils

NAWS = chr(31)
IS = chr(0)
# default taken from telnet specification
DEFAULT_WIDTH = settings.CLIENT_DEFAULT_WIDTH
DEFAULT_HEIGHT = settings.CLIENT_DEFAULT_HEIGHT

# try to get the customized mssp info, if it exists.

class Naws(object):
    """
    Implements the MSSP protocol. Add this to a
    variable on the telnet protocol to set it up.
    """
    def __init__(self, protocol):
        """
        initialize NAWS by storing protocol on ourselves
        and calling the client to see if it supports
        NAWS.
        """
        self.naws_step = 0
        self.protocol = protocol
        self.protocol.protocol_flags['SCREENWIDTH'] = {0: DEFAULT_WIDTH} # windowID (0 is root):width
        self.protocol.protocol_flags['SCREENHEIGHT'] = {0: DEFAULT_HEIGHT} # windowID:width
        self.protocol.negotiationMap[NAWS] = self.negotiate_sizes
        self.protocol.do(NAWS).addCallbacks(self.do_naws, self.no_naws)

    def no_naws(self, option):
        """
        This is the normal operation.
        """
        self.protocol.handshake_done()

    def do_naws(self, option):
        """
        Negotiate all the information.
        """
        self.protocol.handshake_done()

    def negotiate_sizes(self, options):
        if len(options) == 4:
           # NAWS is negotiated with 16bit words
           width = options[0] + options[1]
           self.protocol.protocol_flags['SCREENWIDTH'][0] = int(width.encode('hex'), 16)
           height = options[2] + options[3]
           self.protocol.protocol_flags['SCREENHEIGHT'][0] = int(height.encode('hex'), 16)