# -*- 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, nativeString, _PY3
from twisted.python.filepath import FilePath



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.

    This manipulates process-global state by calling C{os.umask()}, so it isn't
    thread-safe.

    @param filename: Path to a file that is used to store the state across
        program runs.
    @type filename: L{str}

    @return: a monotonically increasing number
    @rtype: L{str}
    """
    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, zoneID = serialFile.readline().split()

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

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

    serial = serial + ('%02d' % (zoneID,))
    return serial



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

    This is an abstract class that implements record search logic. To create
    a functional resolver, subclass it and override the L{loadFile} method.

    @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}.

    @ivar records: A mapping of domains (as lowercased L{bytes}) to records.
    @type records: L{dict} with L{byte} keys
    """
    # 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


    def loadFile(self, filename):
        """
        Load DNS records from a file.

        This method populates the I{soa} and I{records} attributes. It must be
        overridden in a subclass. It is called once from the initializer.

        @param filename: The I{filename} parameter that was passed to the
        initilizer.

        @returns: L{None} -- the return value is ignored
        """


    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

            # Sort of https://tools.ietf.org/html/rfc1034#section-4.3.2 .
            # 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 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):
        name = dns.domainString(name)
        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 U{BIND zone files
    <https://en.wikipedia.org/wiki/Zone_file>}.

    Supports only C{$ORIGIN} and C{$TTL} directives.
    """
    def loadFile(self, filename):
        """
        Load records from C{filename}.

        @param filename: file to read from
        @type filename: L{bytes}
        """
        fp = FilePath(filename)
        # Not the best way to set an origin. It can be set using $ORIGIN
        # though.
        self.origin = nativeString(fp.basename() + b'.')

        lines = fp.getContent().splitlines(True)
        lines = self.stripComments(lines)
        lines = self.collapseContinuations(lines)
        self.parseLines(lines)


    def stripComments(self, lines):
        """
        Strip comments from C{lines}.

        @param lines: lines to work on
        @type lines: iterable of L{bytes}

        @return: C{lines} sans comments.
        """
        return (
            a.find(b';') == -1 and a or a[:a.find(b';')] for a in [
                b.strip() for b in lines
            ]
        )


    def collapseContinuations(self, lines):
        """
        Transform multiline statements into single lines.

        @param lines: lines to work on
        @type lines: iterable of L{bytes}

        @return: iterable of continuous lines
        """
        l = []
        state = 0
        for line in lines:
            if state == 0:
                if line.find(b'(') == -1:
                    l.append(line)
                else:
                    l.append(line[:line.find(b'(')])
                    state = 1
            else:
                if line.find(b')') != -1:
                    l[-1] += b' ' + line[:line.find(b')')]
                    state = 0
                else:
                    l[-1] += b' ' + line
        return filter(None, (line.split() for line in l))


    def parseLines(self, lines):
        """
        Parse C{lines}.

        @param lines: lines to work on
        @type lines: iterable of L{bytes}
        """
        ttl = 60 * 60 * 3
        origin = self.origin

        self.records = {}

        for line in lines:
            if line[0] == b'$TTL':
                ttl = dns.str2time(line[1])
            elif line[0] == b'$ORIGIN':
                origin = line[1]
            elif line[0] == b'$INCLUDE':
                raise NotImplementedError('$INCLUDE directive not implemented')
            elif line[0] == b'$GENERATE':
                raise NotImplementedError(
                    '$GENERATE directive not implemented'
                )
            else:
                self.parseRecordLine(origin, ttl, line)

        # If the origin changed, reflect that within the instance.
        self.origin = origin


    def addRecord(self, owner, ttl, type, domain, cls, rdata):
        """
        Add a record to our authority.  Expand domain with origin if necessary.

        @param owner: origin?
        @type owner: L{bytes}

        @param ttl: time to live for the record
        @type ttl: L{int}

        @param domain: the domain for which the record is to be added
        @type domain: L{bytes}

        @param type: record type
        @type type: L{str}

        @param cls: record class
        @type cls: L{str}

        @param rdata: record data
        @type rdata: L{list} of L{bytes}
        """
        if not domain.endswith(b'.'):
            domain = domain + b'.' + owner[:-1]
        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):
        """
        Simulate a class IN and recurse into the actual class.

        @param ttl: time to live for the record
        @type ttl: L{int}

        @param type: record type
        @type type: str

        @param domain: the domain
        @type domain: bytes

        @param rdata:
        @type rdate: bytes
        """
        record = getattr(dns, 'Record_%s' % (nativeString(type),), None)
        if record:
            r = record(*rdata)
            r.ttl = ttl
            self.records.setdefault(domain.lower(), []).append(r)

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


    def parseRecordLine(self, origin, ttl, line):
        """
        Parse a C{line} from a zone file respecting C{origin} and C{ttl}.

        Add resulting records to authority.

        @param origin: starting point for the zone
        @type origin: L{bytes}

        @param ttl: time to live for the record
        @type ttl: L{int}

        @param line: zone file line to parse; split by word
        @type line: L{list} of L{bytes}
        """
        if _PY3:
            queryClasses = set(
                qc.encode("ascii") for qc in dns.QUERY_CLASSES.values()
            )
            queryTypes = set(
                qt.encode("ascii") for qt in dns.QUERY_TYPES.values()
            )
        else:
            queryClasses = set(dns.QUERY_CLASSES.values())
            queryTypes = set(dns.QUERY_TYPES.values())

        markers = queryClasses | queryTypes

        cls = b'IN'
        owner = origin

        if line[0] == b'@':
            line = line[1:]
            owner = origin
        elif not line[0].isdigit() and line[0] not in markers:
            owner = line[0]
            line = line[1:]

        if line[0].isdigit() or line[0] in markers:
            domain = owner
            owner = origin
        else:
            domain = line[0]
            line = line[1:]

        if line[0] in queryClasses:
            cls = line[0]
            line = line[1:]
            if line[0].isdigit():
                ttl = int(line[0])
                line = line[1:]
        elif line[0].isdigit():
            ttl = int(line[0])
            line = line[1:]
            if line[0] in queryClasses:
                cls = line[0]
                line = line[1:]

        type = line[0]
        rdata = line[1:]

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