# Copyright (C) 2003-2007 Nominum, Inc.
#
# Permission to use, copy, modify, and distribute this software and its
# documentation for any purpose with or without fee is hereby granted,
# provided that the above copyright notice and this permission notice
# appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

"""MX-like base classes."""

import struct

import dns.exception
import dns.rdata
import dns.name

class MXBase(dns.rdata.Rdata):
    """Base class for rdata that is like an MX record.

    @ivar preference: the preference value
    @type preference: int
    @ivar exchange: the exchange name
    @type exchange: dns.name.Name object"""

    __slots__ = ['preference', 'exchange']
    
    def __init__(self, rdclass, rdtype, preference, exchange):
        super(MXBase, self).__init__(rdclass, rdtype)
        self.preference = preference
        self.exchange = exchange

    def to_text(self, origin=None, relativize=True, **kw):
        exchange = self.exchange.choose_relativity(origin, relativize)
        return '%d %s' % (self.preference, exchange)
        
    def from_text(cls, rdclass, rdtype, tok, origin = None, relativize = True):
        preference = tok.get_uint16()
        exchange = tok.get_name()
        exchange = exchange.choose_relativity(origin, relativize)
        tok.get_eol()
        return cls(rdclass, rdtype, preference, exchange)
    
    from_text = classmethod(from_text)

    def to_wire(self, file, compress = None, origin = None):
        pref = struct.pack("!H", self.preference)
        file.write(pref)
        self.exchange.to_wire(file, compress, origin)
        
    def from_wire(cls, rdclass, rdtype, wire, current, rdlen, origin = None):
        (preference, ) = struct.unpack('!H', wire[current : current + 2])
        current += 2
        rdlen -= 2
        (exchange, cused) = dns.name.from_wire(wire[: current + rdlen],
                                               current)
        if cused != rdlen:
            raise dns.exception.FormError
        if not origin is None:
            exchange = exchange.relativize(origin)
        return cls(rdclass, rdtype, preference, exchange)

    from_wire = classmethod(from_wire)

    def choose_relativity(self, origin = None, relativize = True):
        self.exchange = self.exchange.choose_relativity(origin, relativize)
        
    def _cmp(self, other):
        sp = struct.pack("!H", self.preference)
        op = struct.pack("!H", other.preference)
        v = cmp(sp, op)
        if v == 0:
            v = cmp(self.exchange, other.exchange)
        return v

class UncompressedMX(MXBase):
    """Base class for rdata that is like an MX record, but whose name
    is not compressed when convert to DNS wire format."""

    def to_wire(self, file, compress = None, origin = None):
        super(UncompressedMX, self).to_wire(file, None, origin)
