/*
 * This file is part of PowerDNS or dnsdist.
 * Copyright -- PowerDNS.COM B.V. and its contributors
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * In addition, for the avoidance of any doubt, permission is granted to
 * link this program with OpenSSL and to (re)distribute the binaries
 * produced as the result of such linking.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
#pragma once
#include <sys/types.h>
#include "iputils.hh"
#include "ednssubnet.hh"
#include "ednscookies.hh"
#include <optional>
#include <unordered_set>
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/time.h>
#include <unistd.h>
#include <arpa/inet.h>

#include <iostream>
#include <optional>
#include <string>
#include <vector>
#include "qtype.hh"
#include "dns.hh"
#include "misc.hh"
#include "utility.hh"
#include "logger.hh"
#include "pdnsexception.hh"
#include "dnsrecords.hh"

class UeberBackend;
class DNSSECKeeper;


//! This class represents DNS packets, either received or to be sent.
class DNSPacket
{
public:
  DNSPacket(bool isQuery);
  DNSPacket(const DNSPacket &orig) = default;
  DNSPacket & operator=(const DNSPacket &) = default;

  int noparse(const char *mesg, size_t len); //!< just suck the data inward
  int parse(const char *mesg, size_t len); //!< parse a raw UDP or TCP packet and suck the data inward
  const string& getString(bool throwsOnTruncation=false); //!< for serialization - just passes the whole packet. If throwsOnTruncation is set, an exception will be raised if the records are too large to fit inside a single DNS payload, instead of setting the TC bit

  // address & socket manipulation
  void setRemote(const ComboAddress*, std::optional<ComboAddress> = std::nullopt);
  ComboAddress getRemote() const;
  ComboAddress getInnerRemote() const; // for proxy protocol
  Netmask getRealRemote() const;
  ComboAddress getLocal() const
  {
    ComboAddress ca;
    socklen_t len=sizeof(ca);
    getsockname(d_socket, (sockaddr*)&ca, &len);
    return ca;
  }
  uint16_t getRemotePort() const;

  string getRemoteString() const;
  string getRemoteStringWithPort() const;

  boost::optional<ComboAddress> d_anyLocal;

  Utility::sock_t getSocket() const
  {
    return d_socket;
  }
  void setSocket(Utility::sock_t sock);

  // these manipulate 'd'
  void setA(bool); //!< make this packet authoritative - manipulates 'd'
  void setID(uint16_t); //!< set the DNS id of this packet - manipulates 'd'
  void setRA(bool); //!< set the Recursion Available flag - manipulates 'd'
  void setRD(bool); //!< set the Recursion Desired flag - manipulates 'd'
  void setAnswer(bool); //!< Make this packet an answer - clears the 'stringbuffer' first, if passed 'true', does nothing otherwise, manipulates 'd'

  void setOpcode(uint16_t);  //!< set the Opcode of this packet - manipulates 'd'
  void setRcode(int v); //!< set the Rcode of this packet - manipulates 'd'

  void clearRecords(); //!< when building a packet, wipe all previously added records (clears 'rrs')

  /** Add a DNSZoneRecord to this packet. A DNSPacket (as does a DNS Packet) has 4 kinds of resource records. Questions, 
      Answers, Authority and Additional. See RFC 1034 and 1035 for details. You can specify where a record needs to go in the
      DNSZoneRecord d_place field */
  void addRecord(DNSZoneRecord&&);  // adds to 'rrs'

  void setQuestion(int op, const DNSName &qdomain, int qtype);  // wipes 'd', sets a random id, creates start of packet (domain, type, class etc)

  DTime d_dt; //!< the time this packet was created. replyPacket() copies this in for you, so d_dt becomes the time spent processing the question+answer
  void wrapup(bool throwsOnTruncation=false);  // writes out queued rrs, and generates the binary packet. also shuffles. also rectifies dnsheader 'd', and copies it to the stringbuffer. If throwsOnTruncation is set, an exception will be raised if the records are too large to fit inside a single DNS payload, instead of setting the TC bit
  void spoofQuestion(const DNSPacket& qd); //!< paste in the exact right case of the question. Useful for PacketCache
  unsigned int getMinTTL(); //!< returns lowest TTL of any record in the packet
  bool isEmpty(); //!< returns true if there are no rrs in the packet

  vector<DNSZoneRecord*> getAPRecords(); //!< get a vector with DNSZoneRecords that need additional processing
  vector<DNSZoneRecord*> getAnswerRecords(); //!< get a vector with DNSZoneRecords that are answers
  vector<DNSZoneRecord*> getServiceRecords(); //!< Get a vector with all Service-style (SVCB) records
  void setCompress(bool compress);

  std::unique_ptr<DNSPacket> replyPacket() const; //!< convenience function that creates a virgin answer packet to this question

  void commitD(); //!< copies 'd' into the stringbuffer
  unsigned int getMaxReplyLen(); //!< retrieve the maximum length of the packet we should send in response
  void setMaxReplyLen(int bytes); //!< set the max reply len (used when retrieving from the packet cache, and this changed)

  bool couldBeCached() const; //!< returns 0 if this query should bypass the packet cache
  bool hasEDNSSubnet() const;
  bool hasEDNS() const;
  bool hasEDNSCookie() const;
  bool hasWellFormedEDNSCookie() const;
  bool hasValidEDNSCookie() const;
  uint8_t getEDNSVersion() const { return d_ednsversion; };
  void setEDNSRcode(uint16_t extRCode)
  {
    // WARNING: this is really 12 bits
    d_ednsrcode=extRCode;
  };
  uint8_t getEDNSRCode() const { return d_ednsrcode; };
  uint32_t getHash() const { return d_hash; };
  void setHash(uint32_t hash) { d_hash = hash; };

  //////// DATA !

  DNSName qdomain;  //!< qname of the question 4 - unsure how this is used
  DNSName qdomainwild;  //!< wildcard matched by qname, used by LuaPolicyEngine
  DNSName qdomainzone;  //!< zone name for the answer (as reflected in SOA for negative responses), used by LuaPolicyEngine
  string d_peer_principal;
  const DNSName& getTSIGKeyname() const;

  struct dnsheader d; //!< dnsheader at the start of the databuffer 12

  TSIGRecordContent d_trc; //72

  ComboAddress d_remote; //28
  std::optional<ComboAddress> d_inner_remote; // the 'outer' remote is the IP on the physical packet header. The 'inner' remote lives one layer deeper, in the PROXY header.
  TSIGHashEnum d_tsig_algo{TSIG_MD5}; //4

  int d_ednsRawPacketSizeLimit{-1}; // only used for Lua record
  uint16_t qclass{QClass::IN};  //!< class of the question - should always be INternet 2
  QType qtype;  //!< type of the question 2

  bool d_tcp{false};
  bool d_dnssecOk{false};
  bool d_havetsig{false};

  bool getTSIGDetails(TSIGRecordContent* tr, DNSName* keyname, uint16_t* tsigPos=nullptr) const;
  void setTSIGDetails(const TSIGRecordContent& tr, const DNSName& keyname, const string& secret, const string& previous, bool timersonly=false);
  bool getTKEYRecord(TKEYRecordContent* tr, DNSName* keyname) const;

  vector<DNSZoneRecord>& getRRS() { return d_rrs; }
  bool checkForCorrectTSIG(UeberBackend* B, DNSName* keyname, string* secret, TSIGRecordContent* trc) const;

  static uint16_t s_udpTruncationThreshold; 
  static bool s_doEDNSSubnetProcessing;
  static bool s_doEDNSCookieProcessing;
  static string s_EDNSCookieKey;

#ifdef ENABLE_GSS_TSIG
  void cleanupGSS(int rcode);
#endif

private:
  void pasteQ(const char *question, int length); //!< set the question of this packet, useful for crafting replies

  string d_tsigsecret;
  DNSName d_tsigkeyname;
  string d_tsigprevious;

  vector<DNSZoneRecord> d_rrs; // 8
  std::unordered_set<size_t> d_dedup;
  string d_rawpacket; // this is where everything lives 8
  EDNSSubnetOpts d_eso;
  EDNSCookiesOpt d_eco;

  int d_maxreplylen{0};
  int d_socket{-1}; // 4
  uint32_t d_hash{0};
  // WARNING! This is really 12 bits
  uint16_t d_ednsrcode{0};
  uint8_t d_ednsversion{0};

  bool d_wrapped{false}; // 1
  bool d_compress{true}; // 1
  bool d_tsigtimersonly{false};
  bool d_wantsnsid{false};
  bool d_haveednssubnet{false};
  bool d_haveednscookie{false};
  bool d_ednscookievalid{false};
  bool d_haveednssection{false};
  bool d_isQuery;
};