# -*- test-case-name: twisted.names.test.test_names -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

"""
Authoritative resolvers.
"""

from __future__ import absolute_import, division

import os
import time

from twisted.names import dns, error, common
from twisted.internet import defer
from twisted.python import failure
from twisted.python.compat import execfile


def getSerial(filename = '/tmp/twisted-names.serial'):
    """Return a monotonically increasing (across program runs) integer.

    State is stored in the given file.  If it does not exist, it is
    created with rw-/---/--- permissions.
    """
    serial = time.strftime('%Y%m%d')

    o = os.umask(0o177)
    try:
        if not os.path.exists(filename):
            with open(filename, 'w') as f:
                f.write(serial + ' 0')
    finally:
        os.umask(o)

    with open(filename, 'r') as serialFile:
        lastSerial, ID = serialFile.readline().split()

    ID = (lastSerial == serial) and (int(ID) + 1) or 0

    with open(filename, 'w') as serialFile:
        serialFile.write('%s %d' % (serial, ID))

#class LookupCacherMixin(object):
#    _cache = None
#
#    def _lookup(self, name, cls, type, timeout = 10):
#        if not self._cache:
#            self._cache = {}
#            self._meth = super(LookupCacherMixin, self)._lookup
#
#        if self._cache.has_key((name, cls, type)):
#            return self._cache[(name, cls, type)]
#        else:
#            r = self._meth(name, cls, type, timeout)
#            self._cache[(name, cls, type)] = r
#            return r
    serial = serial + ('%02d' % (ID,))
    return serial



class FileAuthority(common.ResolverBase):
    """
    An Authority that is loaded from a file.

    @ivar _ADDITIONAL_PROCESSING_TYPES: Record types for which additional
        processing will be done.

    @ivar _ADDRESS_TYPES: Record types which are useful for inclusion in the
        additional section generated during additional processing.

    @ivar soa: A 2-tuple containing the SOA domain name as a L{bytes} and a
        L{dns.Record_SOA}.
    """
    # See https://twistedmatrix.com/trac/ticket/6650
    _ADDITIONAL_PROCESSING_TYPES = (dns.CNAME, dns.MX, dns.NS)
    _ADDRESS_TYPES = (dns.A, dns.AAAA)

    soa = None
    records = None

    def __init__(self, filename):
        common.ResolverBase.__init__(self)
        self.loadFile(filename)
        self._cache = {}


    def __setstate__(self, state):
        self.__dict__ = state
#        print 'setstate ', self.soa


    def _additionalRecords(self, answer, authority, ttl):
        """
        Find locally known information that could be useful to the consumer of
        the response and construct appropriate records to include in the
        I{additional} section of that response.

        Essentially, implement RFC 1034 section 4.3.2 step 6.

        @param answer: A L{list} of the records which will be included in the
            I{answer} section of the response.

        @param authority: A L{list} of the records which will be included in
            the I{authority} section of the response.

        @param ttl: The default TTL for records for which this is not otherwise
            specified.

        @return: A generator of L{dns.RRHeader} instances for inclusion in the
            I{additional} section.  These instances represent extra information
            about the records in C{answer} and C{authority}.
        """
        for record in answer + authority:
            if record.type in self._ADDITIONAL_PROCESSING_TYPES:
                name = record.payload.name.name
                for rec in self.records.get(name.lower(), ()):
                    if rec.TYPE in self._ADDRESS_TYPES:
                        yield dns.RRHeader(
                            name, rec.TYPE, dns.IN,
                            rec.ttl or ttl, rec, auth=True)


    def _lookup(self, name, cls, type, timeout = None):
        """
        Determine a response to a particular DNS query.

        @param name: The name which is being queried and for which to lookup a
            response.
        @type name: L{bytes}

        @param cls: The class which is being queried.  Only I{IN} is
            implemented here and this value is presently disregarded.
        @type cls: L{int}

        @param type: The type of records being queried.  See the types defined
            in L{twisted.names.dns}.
        @type type: L{int}

        @param timeout: All processing is done locally and a result is
            available immediately, so the timeout value is ignored.

        @return: A L{Deferred} that fires with a L{tuple} of three sets of
            response records (to comprise the I{answer}, I{authority}, and
            I{additional} sections of a DNS response) or with a L{Failure} if
            there is a problem processing the query.
        """
        cnames = []
        results = []
        authority = []
        additional = []
        default_ttl = max(self.soa[1].minimum, self.soa[1].expire)

        domain_records = self.records.get(name.lower())

        if domain_records:
            for record in domain_records:
                if record.ttl is not None:
                    ttl = record.ttl
                else:
                    ttl = default_ttl

                if record.TYPE == dns.NS and name.lower() != self.soa[0].lower():
                    # NS record belong to a child zone: this is a referral.  As
                    # NS records are authoritative in the child zone, ours here
                    # are not.  RFC 2181, section 6.1.
                    authority.append(
                        dns.RRHeader(name, record.TYPE, dns.IN, ttl, record, auth=False)
                    )
                elif record.TYPE == type or type == dns.ALL_RECORDS:
                    results.append(
                        dns.RRHeader(name, record.TYPE, dns.IN, ttl, record, auth=True)
                    )
                if record.TYPE == dns.CNAME:
                    cnames.append(
                        dns.RRHeader(name, record.TYPE, dns.IN, ttl, record, auth=True)
                    )
            if not results:
                results = cnames

            # https://tools.ietf.org/html/rfc1034#section-4.3.2 - sort of.
            # See https://twistedmatrix.com/trac/ticket/6732
            additionalInformation = self._additionalRecords(
                results, authority, default_ttl)
            if cnames:
                results.extend(additionalInformation)
            else:
                additional.extend(additionalInformation)

            if not results and not authority:
                # Empty response. Include SOA record to allow clients to cache
                # this response.  RFC 1034, sections 3.7 and 4.3.4, and RFC 2181
                # section 7.1.
                authority.append(
                    dns.RRHeader(self.soa[0], dns.SOA, dns.IN, ttl, self.soa[1], auth=True)
                    )
            return defer.succeed((results, authority, additional))
        else:
            if dns._isSubdomainOf(name, self.soa[0]):
                # We may be the authority and we didn't find it.
                # XXX: The QNAME may also be a in a delegated child zone. See
                # #6581 and #6580
                return defer.fail(failure.Failure(dns.AuthoritativeDomainError(name)))
            else:
                # The QNAME is not a descendant of this zone. Fail with
                # DomainError so that the next chained authority or
                # resolver will be queried.
                return defer.fail(failure.Failure(error.DomainError(name)))


    def lookupZone(self, name, timeout = 10):
        if self.soa[0].lower() == name.lower():
            # Wee hee hee hooo yea
            default_ttl = max(self.soa[1].minimum, self.soa[1].expire)
            if self.soa[1].ttl is not None:
                soa_ttl = self.soa[1].ttl
            else:
                soa_ttl = default_ttl
            results = [dns.RRHeader(self.soa[0], dns.SOA, dns.IN, soa_ttl, self.soa[1], auth=True)]
            for (k, r) in self.records.items():
                for rec in r:
                    if rec.ttl is not None:
                        ttl = rec.ttl
                    else:
                        ttl = default_ttl
                    if rec.TYPE != dns.SOA:
                        results.append(dns.RRHeader(k, rec.TYPE, dns.IN, ttl, rec, auth=True))
            results.append(results[0])
            return defer.succeed((results, (), ()))
        return defer.fail(failure.Failure(dns.DomainError(name)))

    def _cbAllRecords(self, results):
        ans, auth, add = [], [], []
        for res in results:
            if res[0]:
                ans.extend(res[1][0])
                auth.extend(res[1][1])
                add.extend(res[1][2])
        return ans, auth, add


class PySourceAuthority(FileAuthority):
    """A FileAuthority that is built up from Python source code."""

    def loadFile(self, filename):
        g, l = self.setupConfigNamespace(), {}
        execfile(filename, g, l)
        if 'zone' not in l:
            raise ValueError("No zone defined in " + filename)

        self.records = {}
        for rr in l['zone']:
            if isinstance(rr[1], dns.Record_SOA):
                self.soa = rr
            self.records.setdefault(rr[0].lower(), []).append(rr[1])


    def wrapRecord(self, type):
        return lambda name, *arg, **kw: (name, type(*arg, **kw))


    def setupConfigNamespace(self):
        r = {}
        items = dns.__dict__.iterkeys()
        for record in [x for x in items if x.startswith('Record_')]:
            type = getattr(dns, record)
            f = self.wrapRecord(type)
            r[record[len('Record_'):]] = f
        return r


class BindAuthority(FileAuthority):
    """An Authority that loads BIND configuration files"""

    def loadFile(self, filename):
        self.origin = os.path.basename(filename) + '.' # XXX - this might suck

        with open(filename, 'rb') as f:
            lines = f.readlines()
        lines = self.stripComments(lines)
        lines = self.collapseContinuations(lines)
        self.parseLines(lines)


    def stripComments(self, lines):
        return [
            a.find(';') == -1 and a or a[:a.find(';')] for a in [
                b.strip() for b in lines
            ]
        ]


    def collapseContinuations(self, lines):
        L = []
        state = 0
        for line in lines:
            if state == 0:
                if line.find('(') == -1:
                    L.append(line)
                else:
                    L.append(line[:line.find('(')])
                    state = 1
            else:
                if line.find(')') != -1:
                    L[-1] += ' ' + line[:line.find(')')]
                    state = 0
                else:
                    L[-1] += ' ' + line
        lines = L
        L = []
        for line in lines:
            L.append(line.split())
        return filter(None, L)


    def parseLines(self, lines):
        TTL = 60 * 60 * 3
        ORIGIN = self.origin

        self.records = {}

        for (line, index) in zip(lines, range(len(lines))):
            if line[0] == '$TTL':
                TTL = dns.str2time(line[1])
            elif line[0] == '$ORIGIN':
                ORIGIN = line[1]
            elif line[0] == '$INCLUDE': # XXX - oh, fuck me
                raise NotImplementedError('$INCLUDE directive not implemented')
            elif line[0] == '$GENERATE':
                raise NotImplementedError('$GENERATE directive not implemented')
            else:
                self.parseRecordLine(ORIGIN, TTL, line)


    def addRecord(self, owner, ttl, type, domain, cls, rdata):
        if not domain.endswith('.'):
            domain = domain + '.' + owner
        else:
            domain = domain[:-1]
        f = getattr(self, 'class_%s' % cls, None)
        if f:
            f(ttl, type, domain, rdata)
        else:
            raise NotImplementedError("Record class %r not supported" % cls)


    def class_IN(self, ttl, type, domain, rdata):
        record = getattr(dns, 'Record_%s' % type, None)
        if record:
            r = record(*rdata)
            r.ttl = ttl
            self.records.setdefault(domain.lower(), []).append(r)

            print('Adding IN Record', domain, ttl, r)
            if type == 'SOA':
                self.soa = (domain, r)
        else:
            raise NotImplementedError("Record type %r not supported" % type)


    #
    # This file ends here.  Read no further.
    #
    def parseRecordLine(self, origin, ttl, line):
        MARKERS = dns.QUERY_CLASSES.values() + dns.QUERY_TYPES.values()
        cls = 'IN'
        owner = origin

        if line[0] == '@':
            line = line[1:]
            owner = origin
#            print 'default owner'
        elif not line[0].isdigit() and line[0] not in MARKERS:
            owner = line[0]
            line = line[1:]
#            print 'owner is ', owner

        if line[0].isdigit() or line[0] in MARKERS:
            domain = owner
            owner = origin
#            print 'woops, owner is ', owner, ' domain is ', domain
        else:
            domain = line[0]
            line = line[1:]
#            print 'domain is ', domain

        if line[0] in dns.QUERY_CLASSES.values():
            cls = line[0]
            line = line[1:]
#            print 'cls is ', cls
            if line[0].isdigit():
                ttl = int(line[0])
                line = line[1:]
#                print 'ttl is ', ttl
        elif line[0].isdigit():
            ttl = int(line[0])
            line = line[1:]
#            print 'ttl is ', ttl
            if line[0] in dns.QUERY_CLASSES.values():
                cls = line[0]
                line = line[1:]
#                print 'cls is ', cls

        type = line[0]
#        print 'type is ', type
        rdata = line[1:]
#        print 'rdata is ', rdata

        self.addRecord(owner, ttl, type, domain, cls, rdata)