# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license

# Copyright (C) 2010, 2011 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.

import struct
import binascii

import dns.dnssec
import dns.immutable
import dns.rdata
import dns.rdatatype


@dns.immutable.immutable
class DSBase(dns.rdata.Rdata):

    """Base class for rdata that is like a DS record"""

    __slots__ = ['key_tag', 'algorithm', 'digest_type', 'digest']

    # Digest types registry: https://www.iana.org/assignments/ds-rr-types/ds-rr-types.xhtml
    _digest_length_by_type = {
        1: 20,  # SHA-1, RFC 3658 Sec. 2.4
        2: 32,  # SHA-256, RFC 4509 Sec. 2.2
        3: 32,  # GOST R 34.11-94, RFC 5933 Sec. 4 in conjunction with RFC 4490 Sec. 2.1
        4: 48,  # SHA-384, RFC 6605 Sec. 2
    }

    def __init__(self, rdclass, rdtype, key_tag, algorithm, digest_type,
                 digest):
        super().__init__(rdclass, rdtype)
        self.key_tag = self._as_uint16(key_tag)
        self.algorithm = dns.dnssec.Algorithm.make(algorithm)
        self.digest_type = self._as_uint8(digest_type)
        self.digest = self._as_bytes(digest)
        try:
            if len(self.digest) != self._digest_length_by_type[self.digest_type]:
                raise ValueError('digest length inconsistent with digest type')
        except KeyError:
            if self.digest_type == 0:  # reserved, RFC 3658 Sec. 2.4
                raise ValueError('digest type 0 is reserved')

    def to_text(self, origin=None, relativize=True, **kw):
        kw = kw.copy()
        chunksize = kw.pop('chunksize', 128)
        return '%d %d %d %s' % (self.key_tag, self.algorithm,
                                self.digest_type,
                                dns.rdata._hexify(self.digest,
                                                  chunksize=chunksize,
                                                  **kw))

    @classmethod
    def from_text(cls, rdclass, rdtype, tok, origin=None, relativize=True,
                  relativize_to=None):
        key_tag = tok.get_uint16()
        algorithm = tok.get_string()
        digest_type = tok.get_uint8()
        digest = tok.concatenate_remaining_identifiers().encode()
        digest = binascii.unhexlify(digest)
        return cls(rdclass, rdtype, key_tag, algorithm, digest_type,
                   digest)

    def _to_wire(self, file, compress=None, origin=None, canonicalize=False):
        header = struct.pack("!HBB", self.key_tag, self.algorithm,
                             self.digest_type)
        file.write(header)
        file.write(self.digest)

    @classmethod
    def from_wire_parser(cls, rdclass, rdtype, parser, origin=None):
        header = parser.get_struct("!HBB")
        digest = parser.get_remaining()
        return cls(rdclass, rdtype, header[0], header[1], header[2], digest)
