#ifndef MESSAGE_HPP
#define MESSAGE_HPP
#include <cstddef>
#include <memory>

namespace Plains {
namespace Resolver {

using std::size_t;
using std::unique_ptr;

class Message
{
    /*
    0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    |                      ID                       |
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    |QR|   OpCode  |AA|TC|RD|RA|   Z    |   RCODE   |
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    |                    QDCOUNT                    |
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    |                    ANCOUNT                    |
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    |                    NSCOUNT                    |
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    |                    ARCOUNT                    |
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    */

    public:
    struct RCode  { enum FLAG { NO_ERR, FORMAT_ERR, SERVER_FAIL, NAME_ERR, NOT_IMPL, REFUSED, YX_DOM, YX_RR_SET, NX_RR_SET, NOT_AUTH, NOT_ZONE }; };
    struct OpCode { enum FLAG { QUERY, IQUERY, STATUS, reserved, NOTIFY, UPDATE }; };
    struct QR     { enum FLAG { QUERY, RESPONSE }; };
    struct AA     { enum FLAG { NON_AUTHORATATIVE, AUTHORATATIVE }; };
    struct TC     { enum FLAG { NON_TRUNCATED, TRUNCATED }; };
    struct RD     { enum FLAG { NOT_DESIRED, DESIRED }; };
    struct RA     { enum FLAG { NOT_AVAILABLE, AVAILABLE }; };

    struct Buffer {
        size_t size;
        void* data;
    };

    Message();
    Message(const Buffer& buffer);

    unsigned id()       const; // Identifyer
    unsigned rCode()    const; // Response Code
    unsigned qdCount()  const; // Question Count
    unsigned anCount()  const; // Answer Record Count
    unsigned nsCount()  const; // Authority Record Count
    unsigned arCount()  const; // Additional Record Count
    unsigned opCode()   const; // Operation Code
    bool qr()           const; // Query/Respose Flag
    bool aa()           const; // Authoratative Answer Flag
    bool tc()           const; // Truncation Flag
    bool rd()           const; // Recursion Desired Flag
    bool ra()           const; // Recursion Available Flag
    unique_ptr<Buffer> encodeMessage() const; // Creates network byte-orderd message to be sent

    void id     (unsigned value);
    void rCode  (unsigned value);
    void qdCount(unsigned value);
    void anCount(unsigned value);
    void nsCount(unsigned value);
    void arCount(unsigned value);
    void opCode (unsigned value);
    void qr(QR::FLAG flag);
    void aa(AA::FLAG flag);
    void tc(TC::FLAG flag);
    void rd(RD::FLAG flag);
    void ra(RA::FLAG flag);
    void decodeMessage(const Buffer& buffer);

    private:
    struct Header {
        private:
        unsigned _id      :  16; //Identifier: A 16-bit identification field generated by the device that creates the DNS query. It is copied by the server into the response, so it can be used by that device to match that query to the corresponding reply received from a DNS server. This is used in a manner similar to how the Identifier field is used in many of the ICMP message types.
        bool     _qr      :   1; //Query/Response Flag: Differentiates between queries and responses. Set to 0 when the query is generated; changed to 1 when that query is changed to a response by a replying server.
        unsigned _opCode  :   4;
        bool     _aa      :   1; //Authoritative Answer Flag: This bit is set to 1 in a response to indicate that the server that created the response is authoritative for the zone in which the domain name specified in the Question section is located. If it is 0, the response is non-authoritative.
        bool     _tc      :   1; //Truncation Flag: When set to 1, indicates that the message was truncated due to its length being longer than the maximum permitted for the type of transport mechanism used. TCP doesn't have a length limit for messages, while UDP messages are limited to 512 bytes, so this bit being sent usually is an indication that the message was sent using UDP and was too long to fit. The client may need to establish a TCP session to get the full message. On the other hand, if the portion truncated was part of the Additional section, it may choose not to bother.
        bool     _rd      :   1; //Recursion Desired: When set in a query, requests that the server receiving the query attempt to answer the query recursively, if the server supports recursive resolution. The value of this bit is not changed in the response.
        bool     _ra      :   1; //Recursion Available: Set to 1 or cleared to 0 in a response to indicate whether the server creating the response supports recursive queries. This can then be noted by the device that sent the query for future use.
        unsigned _z       :   3; //Zero: Three reserved bits set to zero.
        unsigned _rCode   :   4;
        unsigned _qdCount :  16; //Question Count: Specifies the number of questions in the Question section of the message.
        unsigned _anCount :  16; //Answer Record Count: Specifies the number of resource records in the Answer section of the message.
        unsigned _nsCount :  16; //Authority Record Count: Specifies the number of resource records in the Authority section of the message. (“NS” stands for “name server”, of course. J)
        unsigned _arCount :  16; //Additional Record Count: Specifies the number of resource records in the Additional section of the message.
    };

    unsigned _id;
    bool     _qr;
    unsigned _opCode;
    bool     _aa;
    bool     _tc;
    bool     _rd;
    bool     _ra;
    unsigned _rCode;
    unsigned _qdCount;
    unsigned _anCount;
    unsigned _nsCount;
    unsigned _arCount;

    vector<ResourceRecord> _question;
    vector<ResourceRecord> _answer;
    vector<ResourceRecord> _authority;
    vector<ResourceRecord> _additional;
};





}}

#endif