# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

"""Implement standard (and unused) TCP protocols.

These protocols are either provided by inetd, or are not provided at all.
"""

from __future__ import absolute_import, division

import time
import struct

from zope.interface import implementer

from twisted.internet import protocol, interfaces



class Echo(protocol.Protocol):
    """
    As soon as any data is received, write it back (RFC 862).
    """

    def dataReceived(self, data):
        self.transport.write(data)



class Discard(protocol.Protocol):
    """
    Discard any received data (RFC 863).
    """

    def dataReceived(self, data):
        # I'm ignoring you, nyah-nyah
        pass



@implementer(interfaces.IProducer)
class Chargen(protocol.Protocol):
    """
    Generate repeating noise (RFC 864).
    """
    noise = b'@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~ !"#$%&?'

    def connectionMade(self):
        self.transport.registerProducer(self, 0)


    def resumeProducing(self):
        self.transport.write(self.noise)


    def pauseProducing(self):
        pass


    def stopProducing(self):
        pass



class QOTD(protocol.Protocol):
    """
    Return a quote of the day (RFC 865).
    """

    def connectionMade(self):
        self.transport.write(self.getQuote())
        self.transport.loseConnection()


    def getQuote(self):
        """
        Return a quote. May be overrriden in subclasses.
        """
        return b"An apple a day keeps the doctor away.\r\n"



class Who(protocol.Protocol):
    """
    Return list of active users (RFC 866)
    """

    def connectionMade(self):
        self.transport.write(self.getUsers())
        self.transport.loseConnection()


    def getUsers(self):
        """
        Return active users. Override in subclasses.
        """
        return b"root\r\n"



class Daytime(protocol.Protocol):
    """
    Send back the daytime in ASCII form (RFC 867).
    """

    def connectionMade(self):
        self.transport.write(time.asctime(time.gmtime(time.time())) + b'\r\n')
        self.transport.loseConnection()



class Time(protocol.Protocol):
    """
    Send back the time in machine readable form (RFC 868).
    """

    def connectionMade(self):
        # is this correct only for 32-bit machines?
        result = struct.pack("!i", int(time.time()))
        self.transport.write(result)
        self.transport.loseConnection()


__all__ = ["Echo", "Discard", "Chargen", "QOTD", "Who", "Daytime", "Time"]