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

"""
Utilities for Twisted.names tests.
"""


from random import randrange

from zope.interface import implementer
from zope.interface.verify import verifyClass

from twisted.internet.address import IPv4Address
from twisted.internet.defer import succeed
from twisted.internet.interfaces import IReactorUDP, IUDPTransport
from twisted.internet.task import Clock


@implementer(IUDPTransport)
class MemoryDatagramTransport:
    """
    This L{IUDPTransport} implementation enforces the usual connection rules
    and captures sent traffic in a list for later inspection.

    @ivar _host: The host address to which this transport is bound.
    @ivar _protocol: The protocol connected to this transport.
    @ivar _sentPackets: A C{list} of two-tuples of the datagrams passed to
        C{write} and the addresses to which they are destined.

    @ivar _connectedTo: L{None} if this transport is unconnected, otherwise an
        address to which all traffic is supposedly sent.

    @ivar _maxPacketSize: An C{int} giving the maximum length of a datagram
        which will be successfully handled by C{write}.
    """

    def __init__(self, host, protocol, maxPacketSize):
        self._host = host
        self._protocol = protocol
        self._sentPackets = []
        self._connectedTo = None
        self._maxPacketSize = maxPacketSize

    def getHost(self):
        """
        Return the address which this transport is pretending to be bound
        to.
        """
        return IPv4Address("UDP", *self._host)

    def connect(self, host, port):
        """
        Connect this transport to the given address.
        """
        if self._connectedTo is not None:
            raise ValueError("Already connected")
        self._connectedTo = (host, port)

    def write(self, datagram, addr=None):
        """
        Send the given datagram.
        """
        if addr is None:
            addr = self._connectedTo
        if addr is None:
            raise ValueError("Need an address")
        if len(datagram) > self._maxPacketSize:
            raise ValueError("Packet too big")
        self._sentPackets.append((datagram, addr))

    def stopListening(self):
        """
        Shut down this transport.
        """
        self._protocol.stopProtocol()
        return succeed(None)

    def setBroadcastAllowed(self, enabled):
        """
        Dummy implementation to satisfy L{IUDPTransport}.
        """
        pass

    def getBroadcastAllowed(self):
        """
        Dummy implementation to satisfy L{IUDPTransport}.
        """
        pass


verifyClass(IUDPTransport, MemoryDatagramTransport)


@implementer(IReactorUDP)
class MemoryReactor(Clock):
    """
    An L{IReactorTime} and L{IReactorUDP} provider.

    Time is controlled deterministically via the base class, L{Clock}.  UDP is
    handled in-memory by connecting protocols to instances of
    L{MemoryDatagramTransport}.

    @ivar udpPorts: A C{dict} mapping port numbers to instances of
        L{MemoryDatagramTransport}.
    """

    def __init__(self):
        Clock.__init__(self)
        self.udpPorts = {}

    def listenUDP(self, port, protocol, interface="", maxPacketSize=8192):
        """
        Pretend to bind a UDP port and connect the given protocol to it.
        """
        if port == 0:
            while True:
                port = randrange(1, 2**16)
                if port not in self.udpPorts:
                    break
        if port in self.udpPorts:
            raise ValueError("Address in use")
        transport = MemoryDatagramTransport((interface, port), protocol, maxPacketSize)
        self.udpPorts[port] = transport
        protocol.makeConnection(transport)
        return transport


verifyClass(IReactorUDP, MemoryReactor)