/*
 *
 * (C) 2003-2012 Anope Team
 * Contact us at team@anope.org
 *
 * Please read COPYING and README for further details.
 *
 * Based on the original code of Epona by Lara.
 * Based on the original code of Services by Andy Church.
 *
 */
	
#ifndef DNS_H
#define DNS_H

#include "sockets.h"
#include "timers.h"
#include "config.h"
	
namespace DNS
{
	
	/** Valid query types
	 */
	enum QueryType
	{
		/* Nothing */
		QUERY_NONE,
		/* A simple A lookup */
		QUERY_A = 1,
		/* An authoritative name server */
		QUERY_NS = 2,
		/* A CNAME lookup */
		QUERY_CNAME = 5,
		/* Start of a zone of authority */
		QUERY_SOA = 6,
		/* Reverse DNS lookup */
		QUERY_PTR = 12,
		/* IPv6 AAAA lookup */
		QUERY_AAAA = 28,
		/* Zone transfer */
		QUERY_AXFR = 252
	};
	
	/** Flags that can be AND'd into DNSPacket::flags to receive certain values
	 */
	enum
	{
		QUERYFLAGS_QR = 0x8000,
		QUERYFLAGS_OPCODE = 0x7800,
		QUERYFLAGS_AA = 0x400,
		QUERYFLAGS_TC = 0x200,
		QUERYFLAGS_RD = 0x100,
		QUERYFLAGS_RA = 0x80,
		QUERYFLAGS_Z = 0x70,
		QUERYFLAGS_RCODE = 0xF
	};
	
	enum Error
	{
		ERROR_NONE,
		ERROR_UNKNOWN,
		ERROR_UNLOADED,
		ERROR_TIMEOUT,
		ERROR_NOT_AN_ANSWER,
		ERROR_NONSTANDARD_QUERY,
		ERROR_FORMAT_ERROR,
		ERROR_SERVER_FAILURE,
		ERROR_DOMAIN_NOT_FOUND,
		ERROR_NOT_IMPLEMENTED,
		ERROR_REFUSED,
		ERROR_NO_RECORDS,
		ERROR_INVALIDTYPE
	};
	
	
	struct CoreExport Question
	{
		Anope::string name;
		QueryType type;
		unsigned short qclass;
	
		Question();
		Question(const Anope::string &, QueryType, unsigned short = 1);
	};
	
	struct CoreExport ResourceRecord : public Question
	{
		unsigned int ttl;
		Anope::string rdata;
		time_t created;
	
		ResourceRecord(const Anope::string &, QueryType, unsigned short = 1);
		ResourceRecord(const Question &);
	};
	
	struct CoreExport Query
	{
		std::vector<Question> questions;
		std::vector<ResourceRecord> answers, authorities, additional;
		Error error;
	
		Query();
		Query(const Question &q);
	};
	
	/** A DNS query.
	 */
	class CoreExport Request : public Timer, public Question
	{
		/* Use result cache if available */
		bool use_cache;
	
	 public:
		/* Request id */
	 	unsigned short id;
	 	/* Creator of this request */
		Module *creator;
	
		Request(const Anope::string &addr, QueryType qt, bool cache = false, Module *c = NULL);
		virtual ~Request();
	
		void Process();
	
		/** Called when this request succeeds
		 * @param r The query sent back from the nameserver
		 */
		virtual void OnLookupComplete(const Query *r) = 0;
	
		/** Called when this request fails or times out.
		 * @param r The query sent back from the nameserver, check the error code.
		 */
		virtual void OnError(const Query *r);
		
		/** Used to time out the query, Calls OnError and lets the TimerManager
		 * delete this request.
		 */
		void Tick(time_t) anope_override;
	};
	
	/** A full packet sent or recieved to/from the nameserver
	 */
	class Packet : public Query
	{
		static const int POINTER = 0xC0;
		static const int LABEL = 0x3F;
	
		void PackName(unsigned char *output, unsigned short output_size, unsigned short &pos, const Anope::string &name);
		Anope::string UnpackName(const unsigned char *input, unsigned short input_size, unsigned short &pos);
		
		Question UnpackQuestion(const unsigned char *input, unsigned short input_size, unsigned short &pos);
		ResourceRecord UnpackResourceRecord(const unsigned char *input, unsigned short input_size, unsigned short &poss);
	 public:
		static const int HEADER_LENGTH = 12;
	
		/* Source or destination of the packet */
		sockaddrs addr;
		/* ID for this packet */
		unsigned short id;
		/* Flags on the packet */
		unsigned short flags;
	
		Packet(sockaddrs *a);
		void Fill(const unsigned char *input, const unsigned short len);
		unsigned short Pack(unsigned char *output, unsigned short output_size);
	};
	
	/** DNS manager
	 */
	class CoreExport Manager : public Timer
	{
		class ReplySocket : public virtual Socket
		{
		 public:
			virtual ~ReplySocket() { }
			virtual void Reply(Packet *p) = 0;
		};
	
		/* Listens for TCP requests */
		class TCPSocket : public ListenSocket
		{
			/* A TCP client */
			class Client : public ClientSocket, public Timer, public ReplySocket
			{
				TCPSocket *tcpsock;
		 		Packet *packet;
				unsigned char packet_buffer[524];
				int length;
	
			 public:
			 	Client(TCPSocket *ls, int fd, const sockaddrs &addr);
				~Client();
	
				/* Times out after a few seconds */
				void Tick(time_t) anope_override { }
				void Reply(Packet *p) anope_override;
			 	bool ProcessRead() anope_override;
				bool ProcessWrite() anope_override;
			};
	
		 public:
			TCPSocket(const Anope::string &ip, int port);
	
			ClientSocket *OnAccept(int fd, const sockaddrs &addr) anope_override;
		};
	
		/* Listens for UDP requests */
		class UDPSocket : public ReplySocket
		{
			std::deque<Packet *> packets;
		 public:
	
			UDPSocket(const Anope::string &ip, int port);
			~UDPSocket();
	
			void Reply(Packet *p) anope_override;
	
			std::deque<Packet *>& GetPackets() { return packets; }
	
		 	bool ProcessRead() anope_override;
	
			bool ProcessWrite() anope_override;
		};
	
		typedef std::multimap<Anope::string, ResourceRecord, ci::less> cache_map;
		cache_map cache;
	
		bool listen;
		uint32_t serial;
	
	 public:
		TCPSocket *tcpsock;
		UDPSocket *udpsock;
	
		sockaddrs addrs;
		std::map<unsigned short, Request *> requests;
	
		Manager(const Anope::string &nameserver, const Anope::string &ip, int port);
		~Manager();
	
		bool HandlePacket(ReplySocket *s, const unsigned char *const data, int len, sockaddrs *from);
	
		/** Add a record to the dns cache
		 * @param r The record
		 */
		void AddCache(Query &r);
	
		/** Check the DNS cache to see if request can be handled by a cached result
		 * @return true if a cached result was found.
		 */
		bool CheckCache(Request *request);
	
		/** Tick this timer, used to clear the DNS cache.
		 */
		void Tick(time_t now) anope_override;
	
		/** Cleanup all pending DNS queries for a module
		 * @param mod The module
		 */
		void Cleanup(Module *mod);
	
		void UpdateSerial();
		uint32_t GetSerial() const;
	
		/** Does a BLOCKING DNS query and returns the first IP.
		 * Only use this if you know what you are doing. Unless you specifically
		 * need a blocking query use the DNSRequest system
		 */
		static Query BlockingQuery(const Anope::string &mask, QueryType qt);
	};
	
	extern CoreExport Manager *Engine;
	
} // namespace DNS
	
#endif // DNS_H