/*
    LEAmDNS.h
    (c) 2018, LaborEtArs

    Version 0.9 beta

    Some notes (from LaborEtArs, 2018):
    Essentially, this is an rewrite of the original EPS8266 Multicast DNS code (ESP8266mDNS).
    The target of this rewrite was to keep the existing interface as stable as possible while
    adding and extending the supported set of mDNS features.
    A lot of the additions were basicly taken from Erik Ekman's lwIP mdns app code.

    Supported mDNS features (in some cases somewhat limited):
    - Presenting a DNS-SD service to interested observers, eg. a http server by presenting _http._tcp service
    - Support for multi-level compressed names in input; in output only a very simple one-leven full-name compression is implemented
    - Probing host and service domains for uniqueness in the local network
    - Tiebreaking while probing is supportet in a very minimalistic way (the 'higher' IP address wins the tiebreak)
    - Announcing available services after successful probing
    - Using fixed service TXT items or
    - Using dynamic service TXT items for presented services (via callback)
    - Remove services (and un-announcing them to the observers by sending goodbye-messages)
    - Static queries for DNS-SD services (creating a fixed answer set after a certain timeout period)
    - Dynamic queries for DNS-SD services with cached and updated answers and user notifications


    Usage:
    In most cases, this implementation should work as a 'drop-in' replacement for the original
    ESP8266 Multicast DNS code. Adjustments to the existing code would only be needed, if some
    of the new features should be used.

    For presenting services:
    In 'setup()':
      Install a callback for the probing of host (and service) domains via 'MDNS.setProbeResultCallback(probeResultCallback, &userData);'
      Register DNS-SD services with 'MDNSResponder::hMDNSService hService = MDNS.addService("MyESP", "http", "tcp", 5000);'
      (Install additional callbacks for the probing of these service domains via 'MDNS.setServiceProbeResultCallback(hService, probeResultCallback, &userData);')
      Add service TXT items with 'MDNS.addServiceTxt(hService, "c#", "1");' or by installing a service TXT callback
      using 'MDNS.setDynamicServiceTxtCallback(dynamicServiceTxtCallback, &userData);' or service specific
      'MDNS.setDynamicServiceTxtCallback(hService, dynamicServiceTxtCallback, &userData);'
      Call MDNS.begin("MyHostname");

    In 'probeResultCallback(MDNSResponder* p_MDNSResponder, const char* p_pcDomain, MDNSResponder:hMDNSService p_hService, bool p_bProbeResult, void* p_pUserdata)':
      Check the probe result and update the host or service domain name if the probe failed

    In 'dynamicServiceTxtCallback(MDNSResponder* p_MDNSResponder, const hMDNSService p_hService, void* p_pUserdata)':
      Add dynamic TXT items by calling 'MDNS.addDynamicServiceTxt(p_hService, "c#", "1");'

    In loop():
      Call 'MDNS.update();'


    For querying services:
    Static:
      Call 'uint32_t u32AnswerCount = MDNS.queryService("http", "tcp");'
      Iterate answers by: 'for (uint32_t u=0; u<u32AnswerCount; ++u) { const char* pHostname = MDNS.answerHostname(u); }'
      You should call MDNS.removeQuery() sometimes later (when the answers are nott needed anymore)

    Dynamic:
      Install a dynamic query by calling 'DNSResponder::hMDNSServiceQuery hServiceQuery = MDNS.installServiceQuery("http", "tcp", serviceQueryCallback, &userData);'
      The callback 'serviceQueryCallback(MDNSResponder* p_MDNSResponder, const hMDNSServiceQuery p_hServiceQuery, uint32_t p_u32AnswerIndex,
                                         enuServiceQueryAnswerType p_ServiceQueryAnswerType, bool p_bSetContent, void* p_pUserdata)'
      is called for any change in the answer set.
      Call 'MDNS.removeServiceQuery(hServiceQuery);' when the answers are not needed anymore


    Reference:
    Used mDNS messages:
    A (0x01):               eg. esp8266.local A OP TTL 123.456.789.012
    AAAA (0x1C):            eg. esp8266.local AAAA OP TTL 1234:5678::90
    PTR (0x0C, srv name):   eg. _http._tcp.local PTR OP TTL MyESP._http._tcp.local
    PTR (0x0C, srv type):   eg. _services._dns-sd._udp.local PTR OP TTL _http._tcp.local
    PTR (0x0C, IP4):        eg. 012.789.456.123.in-addr.arpa PTR OP TTL esp8266.local
    PTR (0x0C, IP6):        eg. 90.0.0.0.0.0.0.0.0.0.0.0.78.56.34.12.ip6.arpa PTR OP TTL esp8266.local
    SRV (0x21):             eg. MyESP._http._tcp.local SRV OP TTL PRIORITY WEIGHT PORT esp8266.local
    TXT (0x10):             eg. MyESP._http._tcp.local TXT OP TTL c#=1

    Some NOT used message types:
    OPT (0x29):             eDNS
    NSEC (0x2F):            DNSSEC


    License (MIT license):
      Permission is hereby granted, free of charge, to any person obtaining a copy
      of this software and associated documentation files (the "Software"), to deal
      in the Software without restriction, including without limitation the rights
      to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
      copies of the Software, and to permit persons to whom the Software is
      furnished to do so, subject to the following conditions:

      The above copyright notice and this permission notice shall be included in
      all copies or substantial portions of the Software.

      THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
      IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
      FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
      AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
      LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
      OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
      THE SOFTWARE.

*/

#ifndef MDNS_H
#define MDNS_H

#include <functional>   // for UdpContext.h
#include "WiFiUdp.h"
#include "lwip/udp.h"
#include "debug.h"
#include "include/UdpContext.h"
#include <limits>
#include <PolledTimeout.h>
#include <map>


#include "ESP8266WiFi.h"


namespace esp8266
{

/**
    LEAmDNS
*/
namespace MDNSImplementation
{

//this should be defined at build time
#ifndef ARDUINO_BOARD
#define ARDUINO_BOARD "generic"
#endif

#define MDNS_IP4_SUPPORT
//#define MDNS_IP6_SUPPORT


#ifdef MDNS_IP4_SUPPORT
#define MDNS_IP4_SIZE               4
#endif
#ifdef MDNS_IP6_SUPPORT
#define MDNS_IP6_SIZE               16
#endif
/*
    Maximum length for all service txts for one service
*/
#define MDNS_SERVICE_TXT_MAXLENGTH      1300
/*
    Maximum length for a full domain name eg. MyESP._http._tcp.local
*/
#define MDNS_DOMAIN_MAXLENGTH           256
/*
    Maximum length of on label in a domain name (length info fits into 6 bits)
*/
#define MDNS_DOMAIN_LABEL_MAXLENGTH     63
/*
    Maximum length of a service name eg. http
*/
#define MDNS_SERVICE_NAME_LENGTH        15
/*
    Maximum length of a service protocol name eg. tcp
*/
#define MDNS_SERVICE_PROTOCOL_LENGTH    3
/*
    Default timeout for static service queries
*/
#define MDNS_QUERYSERVICES_WAIT_TIME    1000


/**
    MDNSResponder
*/
class MDNSResponder
{
public:
    /* INTERFACE */
    MDNSResponder(void);
    virtual ~MDNSResponder(void);

    // Start the MDNS responder by setting the default hostname
    // Later call MDNS::update() in every 'loop' to run the process loop
    // (probing, announcing, responding, ...)
    // if interfaceAddress is not specified, default interface is STA, or AP when STA is not set
    bool begin(const char* p_pcHostname, const IPAddress& p_IPAddress = INADDR_ANY, uint32_t p_u32TTL = 120 /*ignored*/);
    bool begin(const String& p_strHostname, const IPAddress& p_IPAddress = INADDR_ANY, uint32_t p_u32TTL = 120 /*ignored*/)
    {
        return begin(p_strHostname.c_str(), p_IPAddress, p_u32TTL);
    }

    // Finish MDNS processing
    bool close(void);
    // for esp32 compatability
    bool end(void);
    // Change hostname (probing is restarted)
    bool setHostname(const char* p_pcHostname);
    // for compatibility...
    bool setHostname(const String& p_strHostname);

    /**
        hMDNSService (opaque handle to access the service)
    */
    typedef const void*     hMDNSService;

    // Add a new service to the MDNS responder. If no name (instance name) is given (p_pcName = 0)
    // the current hostname is used. If the hostname is changed later, the instance names for
    // these 'auto-named' services are changed to the new name also (and probing is restarted).
    // The usual '_' before p_pcService (eg. http) and protocol (eg. tcp) may be given.
    hMDNSService addService(const char* p_pcName,
                            const char* p_pcService,
                            const char* p_pcProtocol,
                            uint16_t p_u16Port);
    // Removes a service from the MDNS responder
    bool removeService(const hMDNSService p_hService);
    bool removeService(const char* p_pcInstanceName,
                       const char* p_pcServiceName,
                       const char* p_pcProtocol);
    // for compatibility...
    bool addService(const String& p_strServiceName,
                    const String& p_strProtocol,
                    uint16_t p_u16Port);


    // Change the services instance name (and restart probing).
    bool setServiceName(const hMDNSService p_hService,
                        const char* p_pcInstanceName);
    //for compatibility
    //Warning: this has the side effect of changing the hostname.
    //TODO: implement instancename different from hostname
    void setInstanceName(const char* p_pcHostname)
    {
        setHostname(p_pcHostname);
    }
    // for esp32 compatibilty
    void setInstanceName(const String& s_pcHostname)
    {
        setInstanceName(s_pcHostname.c_str());
    }

    /**
        hMDNSTxt (opaque handle to access the TXT items)
    */
    typedef void*   hMDNSTxt;

    // Add a (static) MDNS TXT item ('key' = 'value') to the service
    hMDNSTxt addServiceTxt(const hMDNSService p_hService,
                           const char* p_pcKey,
                           const char* p_pcValue);
    hMDNSTxt addServiceTxt(const hMDNSService p_hService,
                           const char* p_pcKey,
                           uint32_t p_u32Value);
    hMDNSTxt addServiceTxt(const hMDNSService p_hService,
                           const char* p_pcKey,
                           uint16_t p_u16Value);
    hMDNSTxt addServiceTxt(const hMDNSService p_hService,
                           const char* p_pcKey,
                           uint8_t p_u8Value);
    hMDNSTxt addServiceTxt(const hMDNSService p_hService,
                           const char* p_pcKey,
                           int32_t p_i32Value);
    hMDNSTxt addServiceTxt(const hMDNSService p_hService,
                           const char* p_pcKey,
                           int16_t p_i16Value);
    hMDNSTxt addServiceTxt(const hMDNSService p_hService,
                           const char* p_pcKey,
                           int8_t p_i8Value);

    // Remove an existing (static) MDNS TXT item from the service
    bool removeServiceTxt(const hMDNSService p_hService,
                          const hMDNSTxt p_hTxt);
    bool removeServiceTxt(const hMDNSService p_hService,
                          const char* p_pcKey);
    bool removeServiceTxt(const char* p_pcinstanceName,
                          const char* p_pcServiceName,
                          const char* p_pcProtocol,
                          const char* p_pcKey);
    // for compatibility...
    bool addServiceTxt(const char* p_pcService,
                       const char* p_pcProtocol,
                       const char* p_pcKey,
                       const char* p_pcValue);
    bool addServiceTxt(const String& p_strService,
                       const String& p_strProtocol,
                       const String& p_strKey,
                       const String& p_strValue);

    /**
        MDNSDynamicServiceTxtCallbackFn
        Callback function for dynamic MDNS TXT items
    */

    typedef std::function<void(const hMDNSService p_hService)> MDNSDynamicServiceTxtCallbackFunc;

    // Set a global callback for dynamic MDNS TXT items. The callback function is called
    // every time, a TXT item is needed for one of the installed services.
    bool setDynamicServiceTxtCallback(MDNSDynamicServiceTxtCallbackFunc p_fnCallback);
    // Set a service specific callback for dynamic MDNS TXT items. The callback function
    // is called every time, a TXT item is needed for the given service.
    bool setDynamicServiceTxtCallback(const hMDNSService p_hService,
                                      MDNSDynamicServiceTxtCallbackFunc p_fnCallback);

    // Add a (dynamic) MDNS TXT item ('key' = 'value') to the service
    // Dynamic TXT items are removed right after one-time use. So they need to be added
    // every time the value s needed (via callback).
    hMDNSTxt addDynamicServiceTxt(hMDNSService p_hService,
                                  const char* p_pcKey,
                                  const char* p_pcValue);
    hMDNSTxt addDynamicServiceTxt(hMDNSService p_hService,
                                  const char* p_pcKey,
                                  uint32_t p_u32Value);
    hMDNSTxt addDynamicServiceTxt(hMDNSService p_hService,
                                  const char* p_pcKey,
                                  uint16_t p_u16Value);
    hMDNSTxt addDynamicServiceTxt(hMDNSService p_hService,
                                  const char* p_pcKey,
                                  uint8_t p_u8Value);
    hMDNSTxt addDynamicServiceTxt(hMDNSService p_hService,
                                  const char* p_pcKey,
                                  int32_t p_i32Value);
    hMDNSTxt addDynamicServiceTxt(hMDNSService p_hService,
                                  const char* p_pcKey,
                                  int16_t p_i16Value);
    hMDNSTxt addDynamicServiceTxt(hMDNSService p_hService,
                                  const char* p_pcKey,
                                  int8_t p_i8Value);

    // Perform a (static) service query. The function returns after p_u16Timeout milliseconds
    // The answers (the number of received answers is returned) can be retrieved by calling
    // - answerHostname (or hostname)
    // - answerIP (or IP)
    // - answerPort (or port)
    uint32_t queryService(const char* p_pcService,
                          const char* p_pcProtocol,
                          const uint16_t p_u16Timeout = MDNS_QUERYSERVICES_WAIT_TIME);
    bool removeQuery(void);
    // for compatibility...
    uint32_t queryService(const String& p_strService,
                          const String& p_strProtocol);

    const char* answerHostname(const uint32_t p_u32AnswerIndex);
    IPAddress answerIP(const uint32_t p_u32AnswerIndex);
    uint16_t answerPort(const uint32_t p_u32AnswerIndex);
    // for compatibility...
    String hostname(const uint32_t p_u32AnswerIndex);
    IPAddress IP(const uint32_t p_u32AnswerIndex);
    uint16_t port(const uint32_t p_u32AnswerIndex);

    /**
        hMDNSServiceQuery (opaque handle to access dynamic service queries)
    */
    typedef const void*     hMDNSServiceQuery;

    /**
        enuServiceQueryAnswerType
    */
    typedef enum _enuServiceQueryAnswerType
    {
        ServiceQueryAnswerType_ServiceDomain        = (1 << 0), // Service instance name
        ServiceQueryAnswerType_HostDomainAndPort    = (1 << 1), // Host domain and service port
        ServiceQueryAnswerType_Txts                 = (1 << 2), // TXT items
#ifdef MDNS_IP4_SUPPORT
        ServiceQueryAnswerType_IP4Address           = (1 << 3), // IP4 address
#endif
#ifdef MDNS_IP6_SUPPORT
        ServiceQueryAnswerType_IP6Address           = (1 << 4), // IP6 address
#endif
    } enuServiceQueryAnswerType;

    enum class AnswerType : uint32_t
    {
        Unknown                             = 0,
        ServiceDomain                       = ServiceQueryAnswerType_ServiceDomain,
        HostDomainAndPort                   = ServiceQueryAnswerType_HostDomainAndPort,
        Txt                                 = ServiceQueryAnswerType_Txts,
#ifdef MDNS_IP4_SUPPORT
        IP4Address                          = ServiceQueryAnswerType_IP4Address,
#endif
#ifdef MDNS_IP6_SUPPORT
        IP6Address                          = ServiceQueryAnswerType_IP6Address,
#endif
    };

    /**
        MDNSServiceQueryCallbackFn
        Callback function for received answers for dynamic service queries
    */
    struct MDNSServiceInfo; // forward declaration
    typedef std::function<void(const MDNSServiceInfo& mdnsServiceInfo,
                               AnswerType answerType,     // flag for the updated answer item
                               bool p_bSetContent                      // true: Answer component set, false: component deleted
                              )> MDNSServiceQueryCallbackFunc;

    // Install a dynamic service query. For every received answer (part) the given callback
    // function is called. The query will be updated every time, the TTL for an answer
    // has timed-out.
    // The answers can also be retrieved by calling
    // - answerCount
    // - answerServiceDomain
    // - hasAnswerHostDomain/answerHostDomain
    // - hasAnswerIP4Address/answerIP4Address
    // - hasAnswerIP6Address/answerIP6Address
    // - hasAnswerPort/answerPort
    // - hasAnswerTxts/answerTxts
    hMDNSServiceQuery installServiceQuery(const char* p_pcService,
                                          const char* p_pcProtocol,
                                          MDNSServiceQueryCallbackFunc p_fnCallback);
    // Remove a dynamic service query
    bool removeServiceQuery(hMDNSServiceQuery p_hServiceQuery);

    uint32_t answerCount(const hMDNSServiceQuery p_hServiceQuery);
    std::vector<MDNSResponder::MDNSServiceInfo> answerInfo(const MDNSResponder::hMDNSServiceQuery p_hServiceQuery);

    const char* answerServiceDomain(const hMDNSServiceQuery p_hServiceQuery,
                                    const uint32_t p_u32AnswerIndex);
    bool hasAnswerHostDomain(const hMDNSServiceQuery p_hServiceQuery,
                             const uint32_t p_u32AnswerIndex);
    const char* answerHostDomain(const hMDNSServiceQuery p_hServiceQuery,
                                 const uint32_t p_u32AnswerIndex);
#ifdef MDNS_IP4_SUPPORT
    bool hasAnswerIP4Address(const hMDNSServiceQuery p_hServiceQuery,
                             const uint32_t p_u32AnswerIndex);
    uint32_t answerIP4AddressCount(const hMDNSServiceQuery p_hServiceQuery,
                                   const uint32_t p_u32AnswerIndex);
    IPAddress answerIP4Address(const hMDNSServiceQuery p_hServiceQuery,
                               const uint32_t p_u32AnswerIndex,
                               const uint32_t p_u32AddressIndex);
#endif
#ifdef MDNS_IP6_SUPPORT
    bool hasAnswerIP6Address(const hMDNSServiceQuery p_hServiceQuery,
                             const uint32_t p_u32AnswerIndex);
    uint32_t answerIP6AddressCount(const hMDNSServiceQuery p_hServiceQuery,
                                   const uint32_t p_u32AnswerIndex);
    IPAddress answerIP6Address(const hMDNSServiceQuery p_hServiceQuery,
                               const uint32_t p_u32AnswerIndex,
                               const uint32_t p_u32AddressIndex);
#endif
    bool hasAnswerPort(const hMDNSServiceQuery p_hServiceQuery,
                       const uint32_t p_u32AnswerIndex);
    uint16_t answerPort(const hMDNSServiceQuery p_hServiceQuery,
                        const uint32_t p_u32AnswerIndex);
    bool hasAnswerTxts(const hMDNSServiceQuery p_hServiceQuery,
                       const uint32_t p_u32AnswerIndex);
    // Get the TXT items as a ';'-separated string
    const char* answerTxts(const hMDNSServiceQuery p_hServiceQuery,
                           const uint32_t p_u32AnswerIndex);

    /**
        MDNSProbeResultCallbackFn
        Callback function for (host and service domain) probe results
    */
    typedef std::function<void(const char* p_pcDomainName,
                               bool p_bProbeResult)> MDNSHostProbeFn;

    typedef std::function<void(MDNSResponder& resp,
                               const char* p_pcDomainName,
                               bool p_bProbeResult)> MDNSHostProbeFn1;

    typedef std::function<void(const char* p_pcServiceName,
                               const hMDNSService p_hMDNSService,
                               bool p_bProbeResult)> MDNSServiceProbeFn;

    typedef std::function<void(MDNSResponder& resp,
                               const char* p_pcServiceName,
                               const hMDNSService p_hMDNSService,
                               bool p_bProbeResult)> MDNSServiceProbeFn1;

    // Set a global callback function for host and service probe results
    // The callback function is called, when the probing for the host domain
    // (or a service domain, which hasn't got a service specific callback)
    // Succeeds or fails.
    // In case of failure, the failed domain name should be changed.
    bool setHostProbeResultCallback(MDNSHostProbeFn p_fnCallback);
    bool setHostProbeResultCallback(MDNSHostProbeFn1 p_fnCallback);

    // Set a service specific probe result callback
    bool setServiceProbeResultCallback(const MDNSResponder::hMDNSService p_hService,
                                       MDNSServiceProbeFn p_fnCallback);
    bool setServiceProbeResultCallback(const MDNSResponder::hMDNSService p_hService,
                                       MDNSServiceProbeFn1 p_fnCallback);

    // Application should call this whenever AP is configured/disabled
    bool notifyAPChange(void);

    // 'update' should be called in every 'loop' to run the MDNS processing
    bool update(void);

    // 'announce' can be called every time, the configuration of some service
    // changes. Mainly, this would be changed content of TXT items.
    bool announce(void);

    // Enable OTA update
    hMDNSService enableArduino(uint16_t p_u16Port,
                               bool p_bAuthUpload = false);

    // Domain name helper
    static bool indexDomain(char*& p_rpcDomain,
                            const char* p_pcDivider = "-",
                            const char* p_pcDefaultDomain = 0);

    /** STRUCTS **/

public:
    /**
        MDNSServiceInfo, used in application callbacks
    */
    struct MDNSServiceInfo
    {
        MDNSServiceInfo(MDNSResponder& p_pM, MDNSResponder::hMDNSServiceQuery p_hS, uint32_t p_u32A)
            : p_pMDNSResponder(p_pM),
              p_hServiceQuery(p_hS),
              p_u32AnswerIndex(p_u32A)
        {};
        struct CompareKey
        {
            bool operator()(char const *a, char const *b) const
            {
                return strcmp(a, b) < 0;
            }
        };
        using KeyValueMap = std::map<const char*, const char*, CompareKey>;
    protected:
        MDNSResponder& p_pMDNSResponder;
        MDNSResponder::hMDNSServiceQuery p_hServiceQuery;
        uint32_t p_u32AnswerIndex;
        KeyValueMap keyValueMap;
    public:
        const char* serviceDomain()
        {
            return p_pMDNSResponder.answerServiceDomain(p_hServiceQuery, p_u32AnswerIndex);
        };
        bool hostDomainAvailable()
        {
            return (p_pMDNSResponder.hasAnswerHostDomain(p_hServiceQuery, p_u32AnswerIndex));
        }
        const char* hostDomain()
        {
            return (hostDomainAvailable()) ?
                   p_pMDNSResponder.answerHostDomain(p_hServiceQuery, p_u32AnswerIndex) : nullptr;
        };
        bool hostPortAvailable()
        {
            return (p_pMDNSResponder.hasAnswerPort(p_hServiceQuery, p_u32AnswerIndex));
        }
        uint16_t hostPort()
        {
            return (hostPortAvailable()) ?
                   p_pMDNSResponder.answerPort(p_hServiceQuery, p_u32AnswerIndex) : 0;
        };
        bool IP4AddressAvailable()
        {
            return (p_pMDNSResponder.hasAnswerIP4Address(p_hServiceQuery, p_u32AnswerIndex));
        }
        std::vector<IPAddress> IP4Adresses()
        {
            std::vector<IPAddress> internalIP;
            if (IP4AddressAvailable())
            {
                uint16_t cntIP4Adress = p_pMDNSResponder.answerIP4AddressCount(p_hServiceQuery, p_u32AnswerIndex);
                for (uint32_t u2 = 0; u2 < cntIP4Adress; ++u2)
                {
                    internalIP.emplace_back(p_pMDNSResponder.answerIP4Address(p_hServiceQuery, p_u32AnswerIndex, u2));
                }
            }
            return internalIP;
        };
        bool txtAvailable()
        {
            return (p_pMDNSResponder.hasAnswerTxts(p_hServiceQuery, p_u32AnswerIndex));
        }
        const char* strKeyValue()
        {
            return (txtAvailable()) ?
                   p_pMDNSResponder.answerTxts(p_hServiceQuery, p_u32AnswerIndex) : nullptr;
        };
        const KeyValueMap& keyValues()
        {
            if (txtAvailable() && keyValueMap.size() == 0)
            {
                for (auto kv = p_pMDNSResponder._answerKeyValue(p_hServiceQuery, p_u32AnswerIndex); kv != nullptr; kv = kv->m_pNext)
                {
                    keyValueMap.emplace(std::pair<const char*, const char*>(kv->m_pcKey, kv->m_pcValue));
                }
            }
            return keyValueMap;
        }
        const char* value(const char* key)
        {
            char* result = nullptr;

            for (stcMDNSServiceTxt* pTxt = p_pMDNSResponder._answerKeyValue(p_hServiceQuery, p_u32AnswerIndex); pTxt; pTxt = pTxt->m_pNext)
            {
                if ((key) &&
                        (0 == strcmp(pTxt->m_pcKey, key)))
                {
                    result = pTxt->m_pcValue;
                    break;
                }
            }
            return result;
        }
    };
protected:

    /**
        stcMDNSServiceTxt
    */
    struct stcMDNSServiceTxt
    {
        stcMDNSServiceTxt* m_pNext;
        char*              m_pcKey;
        char*              m_pcValue;
        bool               m_bTemp;

        stcMDNSServiceTxt(const char* p_pcKey = 0,
                          const char* p_pcValue = 0,
                          bool p_bTemp = false);
        stcMDNSServiceTxt(const stcMDNSServiceTxt& p_Other);
        ~stcMDNSServiceTxt(void);

        stcMDNSServiceTxt& operator=(const stcMDNSServiceTxt& p_Other);
        bool clear(void);

        char* allocKey(size_t p_stLength);
        bool setKey(const char* p_pcKey,
                    size_t p_stLength);
        bool setKey(const char* p_pcKey);
        bool releaseKey(void);

        char* allocValue(size_t p_stLength);
        bool setValue(const char* p_pcValue,
                      size_t p_stLength);
        bool setValue(const char* p_pcValue);
        bool releaseValue(void);

        bool set(const char* p_pcKey,
                 const char* p_pcValue,
                 bool p_bTemp = false);

        bool update(const char* p_pcValue);

        size_t length(void) const;
    };

    /**
        stcMDNSTxts
    */
    struct stcMDNSServiceTxts
    {
        stcMDNSServiceTxt*  m_pTxts;

        stcMDNSServiceTxts(void);
        stcMDNSServiceTxts(const stcMDNSServiceTxts& p_Other);
        ~stcMDNSServiceTxts(void);

        stcMDNSServiceTxts& operator=(const stcMDNSServiceTxts& p_Other);

        bool clear(void);

        bool add(stcMDNSServiceTxt* p_pTxt);
        bool remove(stcMDNSServiceTxt* p_pTxt);

        bool removeTempTxts(void);

        stcMDNSServiceTxt* find(const char* p_pcKey);
        const stcMDNSServiceTxt* find(const char* p_pcKey) const;
        stcMDNSServiceTxt* find(const stcMDNSServiceTxt* p_pTxt);

        uint16_t length(void) const;

        size_t c_strLength(void) const;
        bool c_str(char* p_pcBuffer);

        size_t bufferLength(void) const;
        bool buffer(char* p_pcBuffer);

        bool compare(const stcMDNSServiceTxts& p_Other) const;
        bool operator==(const stcMDNSServiceTxts& p_Other) const;
        bool operator!=(const stcMDNSServiceTxts& p_Other) const;
    };

    /**
        enuContentFlags
    */
    typedef enum _enuContentFlags
    {
        // Host
        ContentFlag_A           = 0x01,
        ContentFlag_PTR_IP4     = 0x02,
        ContentFlag_PTR_IP6     = 0x04,
        ContentFlag_AAAA        = 0x08,
        // Service
        ContentFlag_PTR_TYPE    = 0x10,
        ContentFlag_PTR_NAME    = 0x20,
        ContentFlag_TXT         = 0x40,
        ContentFlag_SRV         = 0x80,
    } enuContentFlags;

    /**
        stcMDNS_MsgHeader
    */
    struct stcMDNS_MsgHeader
    {
        uint16_t        m_u16ID;            // Identifier
        bool            m_1bQR      : 1;    // Query/Response flag
        unsigned char   m_4bOpcode  : 4;    // Operation code
        bool            m_1bAA      : 1;    // Authoritative Answer flag
        bool            m_1bTC      : 1;    // Truncation flag
        bool            m_1bRD      : 1;    // Recursion desired
        bool            m_1bRA      : 1;    // Recursion available
        unsigned char   m_3bZ       : 3;    // Zero
        unsigned char   m_4bRCode   : 4;    // Response code
        uint16_t        m_u16QDCount;       // Question count
        uint16_t        m_u16ANCount;       // Answer count
        uint16_t        m_u16NSCount;       // Authority Record count
        uint16_t        m_u16ARCount;       // Additional Record count

        stcMDNS_MsgHeader(uint16_t p_u16ID = 0,
                          bool p_bQR = false,
                          unsigned char p_ucOpcode = 0,
                          bool p_bAA = false,
                          bool p_bTC = false,
                          bool p_bRD = false,
                          bool p_bRA = false,
                          unsigned char p_ucRCode = 0,
                          uint16_t p_u16QDCount = 0,
                          uint16_t p_u16ANCount = 0,
                          uint16_t p_u16NSCount = 0,
                          uint16_t p_u16ARCount = 0);
    };

    /**
        stcMDNS_RRDomain
    */
    struct stcMDNS_RRDomain
    {
        char            m_acName[MDNS_DOMAIN_MAXLENGTH];    // Encoded domain name
        uint16_t        m_u16NameLength;                    // Length (incl. '\0')

        stcMDNS_RRDomain(void);
        stcMDNS_RRDomain(const stcMDNS_RRDomain& p_Other);

        stcMDNS_RRDomain& operator=(const stcMDNS_RRDomain& p_Other);

        bool clear(void);

        bool addLabel(const char* p_pcLabel,
                      bool p_bPrependUnderline = false);

        bool compare(const stcMDNS_RRDomain& p_Other) const;
        bool operator==(const stcMDNS_RRDomain& p_Other) const;
        bool operator!=(const stcMDNS_RRDomain& p_Other) const;
        bool operator>(const stcMDNS_RRDomain& p_Other) const;

        size_t c_strLength(void) const;
        bool c_str(char* p_pcBuffer);
    };

    /**
        stcMDNS_RRAttributes
    */
    struct stcMDNS_RRAttributes
    {
        uint16_t            m_u16Type;      // Type
        uint16_t            m_u16Class;     // Class, nearly always 'IN'

        stcMDNS_RRAttributes(uint16_t p_u16Type = 0,
                             uint16_t p_u16Class = 1 /*DNS_RRCLASS_IN Internet*/);
        stcMDNS_RRAttributes(const stcMDNS_RRAttributes& p_Other);

        stcMDNS_RRAttributes& operator=(const stcMDNS_RRAttributes& p_Other);
    };

    /**
        stcMDNS_RRHeader
    */
    struct stcMDNS_RRHeader
    {
        stcMDNS_RRDomain        m_Domain;
        stcMDNS_RRAttributes    m_Attributes;

        stcMDNS_RRHeader(void);
        stcMDNS_RRHeader(const stcMDNS_RRHeader& p_Other);

        stcMDNS_RRHeader& operator=(const stcMDNS_RRHeader& p_Other);

        bool clear(void);
    };

    /**
        stcMDNS_RRQuestion
    */
    struct stcMDNS_RRQuestion
    {
        stcMDNS_RRQuestion*     m_pNext;
        stcMDNS_RRHeader        m_Header;
        bool                    m_bUnicast;     // Unicast reply requested

        stcMDNS_RRQuestion(void);
    };

    /**
        enuAnswerType
    */
    typedef enum _enuAnswerType
    {
        AnswerType_A,
        AnswerType_PTR,
        AnswerType_TXT,
        AnswerType_AAAA,
        AnswerType_SRV,
        AnswerType_Generic
    } enuAnswerType;

    /**
        stcMDNS_RRAnswer
    */
    struct stcMDNS_RRAnswer
    {
        stcMDNS_RRAnswer*   m_pNext;
        const enuAnswerType m_AnswerType;
        stcMDNS_RRHeader    m_Header;
        bool                m_bCacheFlush;  // Cache flush command bit
        uint32_t            m_u32TTL;       // Validity time in seconds

        virtual ~stcMDNS_RRAnswer(void);

        enuAnswerType answerType(void) const;

        bool clear(void);

    protected:
        stcMDNS_RRAnswer(enuAnswerType p_AnswerType,
                         const stcMDNS_RRHeader& p_Header,
                         uint32_t p_u32TTL);
    };

#ifdef MDNS_IP4_SUPPORT
    /**
        stcMDNS_RRAnswerA
    */
    struct stcMDNS_RRAnswerA : public stcMDNS_RRAnswer
    {
        IPAddress           m_IPAddress;

        stcMDNS_RRAnswerA(const stcMDNS_RRHeader& p_Header,
                          uint32_t p_u32TTL);
        ~stcMDNS_RRAnswerA(void);

        bool clear(void);
    };
#endif

    /**
        stcMDNS_RRAnswerPTR
    */
    struct stcMDNS_RRAnswerPTR : public stcMDNS_RRAnswer
    {
        stcMDNS_RRDomain    m_PTRDomain;

        stcMDNS_RRAnswerPTR(const stcMDNS_RRHeader& p_Header,
                            uint32_t p_u32TTL);
        ~stcMDNS_RRAnswerPTR(void);

        bool clear(void);
    };

    /**
        stcMDNS_RRAnswerTXT
    */
    struct stcMDNS_RRAnswerTXT : public stcMDNS_RRAnswer
    {
        stcMDNSServiceTxts  m_Txts;

        stcMDNS_RRAnswerTXT(const stcMDNS_RRHeader& p_Header,
                            uint32_t p_u32TTL);
        ~stcMDNS_RRAnswerTXT(void);

        bool clear(void);
    };

#ifdef MDNS_IP6_SUPPORT
    /**
        stcMDNS_RRAnswerAAAA
    */
    struct stcMDNS_RRAnswerAAAA : public stcMDNS_RRAnswer
    {
        //TODO: IP6Address          m_IPAddress;

        stcMDNS_RRAnswerAAAA(const stcMDNS_RRHeader& p_Header,
                             uint32_t p_u32TTL);
        ~stcMDNS_RRAnswerAAAA(void);

        bool clear(void);
    };
#endif

    /**
        stcMDNS_RRAnswerSRV
    */
    struct stcMDNS_RRAnswerSRV : public stcMDNS_RRAnswer
    {
        uint16_t            m_u16Priority;
        uint16_t            m_u16Weight;
        uint16_t            m_u16Port;
        stcMDNS_RRDomain    m_SRVDomain;

        stcMDNS_RRAnswerSRV(const stcMDNS_RRHeader& p_Header,
                            uint32_t p_u32TTL);
        ~stcMDNS_RRAnswerSRV(void);

        bool clear(void);
    };

    /**
        stcMDNS_RRAnswerGeneric
    */
    struct stcMDNS_RRAnswerGeneric : public stcMDNS_RRAnswer
    {
        uint16_t            m_u16RDLength;  // Length of variable answer
        uint8_t*            m_pu8RDData;    // Offset of start of variable answer in packet

        stcMDNS_RRAnswerGeneric(const stcMDNS_RRHeader& p_Header,
                                uint32_t p_u32TTL);
        ~stcMDNS_RRAnswerGeneric(void);

        bool clear(void);
    };


    /**
        enuProbingStatus
    */
    typedef enum _enuProbingStatus
    {
        ProbingStatus_WaitingForData,
        ProbingStatus_ReadyToStart,
        ProbingStatus_InProgress,
        ProbingStatus_Done
    } enuProbingStatus;

    /**
        stcProbeInformation
    */
    struct stcProbeInformation
    {
        enuProbingStatus                  m_ProbingStatus;
        uint8_t                           m_u8SentCount;  // Used for probes and announcements
        esp8266::polledTimeout::oneShotMs m_Timeout;      // Used for probes and announcements
        //clsMDNSTimeFlag                   m_TimeFlag;     // Used for probes and announcements
        bool                              m_bConflict;
        bool                              m_bTiebreakNeeded;
        MDNSHostProbeFn   				m_fnHostProbeResultCallback;
        MDNSServiceProbeFn 				m_fnServiceProbeResultCallback;

        stcProbeInformation(void);

        bool clear(bool p_bClearUserdata = false);
    };


    /**
        stcMDNSService
    */
    struct stcMDNSService
    {
        stcMDNSService*                 m_pNext;
        char*                           m_pcName;
        bool                            m_bAutoName;    // Name was set automatically to hostname (if no name was supplied)
        char*                           m_pcService;
        char*                           m_pcProtocol;
        uint16_t                        m_u16Port;
        uint8_t                         m_u8ReplyMask;
        stcMDNSServiceTxts              m_Txts;
        MDNSDynamicServiceTxtCallbackFunc m_fnTxtCallback;
        stcProbeInformation             m_ProbeInformation;

        stcMDNSService(const char* p_pcName = 0,
                       const char* p_pcService = 0,
                       const char* p_pcProtocol = 0);
        ~stcMDNSService(void);

        bool setName(const char* p_pcName);
        bool releaseName(void);

        bool setService(const char* p_pcService);
        bool releaseService(void);

        bool setProtocol(const char* p_pcProtocol);
        bool releaseProtocol(void);
    };

    /**
        stcMDNSServiceQuery
    */
    struct stcMDNSServiceQuery
    {
        /**
            stcAnswer
        */
        struct stcAnswer
        {
            /**
                stcTTL
            */
            struct stcTTL
            {
                /**
                    timeoutLevel_t
                */
                typedef uint8_t timeoutLevel_t;
                /**
                    TIMEOUTLEVELs
                */
                const timeoutLevel_t    TIMEOUTLEVEL_UNSET      = 0;
                const timeoutLevel_t    TIMEOUTLEVEL_BASE       = 80;
                const timeoutLevel_t    TIMEOUTLEVEL_INTERVAL   = 5;
                const timeoutLevel_t    TIMEOUTLEVEL_FINAL      = 100;

                uint32_t                          m_u32TTL;
                esp8266::polledTimeout::oneShotMs m_TTLTimeout;
                timeoutLevel_t                    m_timeoutLevel;

                stcTTL(void);
                bool set(uint32_t p_u32TTL);

                bool flagged(void);
                bool restart(void);

                bool prepareDeletion(void);
                bool finalTimeoutLevel(void) const;

                unsigned long timeout(void) const;
            };
#ifdef MDNS_IP4_SUPPORT
            /**
                stcIP4Address
            */
            struct stcIP4Address
            {
                stcIP4Address*  m_pNext;
                IPAddress       m_IPAddress;
                stcTTL          m_TTL;

                stcIP4Address(IPAddress p_IPAddress,
                              uint32_t p_u32TTL = 0);
            };
#endif
#ifdef MDNS_IP6_SUPPORT
            /**
                stcIP6Address
            */
            struct stcIP6Address
            {
                stcIP6Address*  m_pNext;
                IP6Address      m_IPAddress;
                stcTTL          m_TTL;

                stcIP6Address(IPAddress p_IPAddress,
                              uint32_t p_u32TTL = 0);
            };
#endif

            stcAnswer*          m_pNext;
            // The service domain is the first 'answer' (from PTR answer, using service and protocol) to be set
            // Defines the key for additional answer, like host domain, etc.
            stcMDNS_RRDomain    m_ServiceDomain;    // 1. level answer (PTR), eg. MyESP._http._tcp.local
            char*               m_pcServiceDomain;
            stcTTL              m_TTLServiceDomain;
            stcMDNS_RRDomain    m_HostDomain;       // 2. level answer (SRV, using service domain), eg. esp8266.local
            char*               m_pcHostDomain;
            uint16_t            m_u16Port;          // 2. level answer (SRV, using service domain), eg. 5000
            stcTTL              m_TTLHostDomainAndPort;
            stcMDNSServiceTxts  m_Txts;             // 2. level answer (TXT, using service domain), eg. c#=1
            char*               m_pcTxts;
            stcTTL              m_TTLTxts;
#ifdef MDNS_IP4_SUPPORT
            stcIP4Address*      m_pIP4Addresses;    // 3. level answer (A, using host domain), eg. 123.456.789.012
#endif
#ifdef MDNS_IP6_SUPPORT
            stcIP6Address*      m_pIP6Addresses;    // 3. level answer (AAAA, using host domain), eg. 1234::09
#endif
            uint32_t            m_u32ContentFlags;

            stcAnswer(void);
            ~stcAnswer(void);

            bool clear(void);

            char* allocServiceDomain(size_t p_stLength);
            bool releaseServiceDomain(void);

            char* allocHostDomain(size_t p_stLength);
            bool releaseHostDomain(void);

            char* allocTxts(size_t p_stLength);
            bool releaseTxts(void);

#ifdef MDNS_IP4_SUPPORT
            bool releaseIP4Addresses(void);
            bool addIP4Address(stcIP4Address* p_pIP4Address);
            bool removeIP4Address(stcIP4Address* p_pIP4Address);
            const stcIP4Address* findIP4Address(const IPAddress& p_IPAddress) const;
            stcIP4Address* findIP4Address(const IPAddress& p_IPAddress);
            uint32_t IP4AddressCount(void) const;
            const stcIP4Address* IP4AddressAtIndex(uint32_t p_u32Index) const;
            stcIP4Address* IP4AddressAtIndex(uint32_t p_u32Index);
#endif
#ifdef MDNS_IP6_SUPPORT
            bool releaseIP6Addresses(void);
            bool addIP6Address(stcIP6Address* p_pIP6Address);
            bool removeIP6Address(stcIP6Address* p_pIP6Address);
            const stcIP6Address* findIP6Address(const IPAddress& p_IPAddress) const;
            stcIP6Address* findIP6Address(const IPAddress& p_IPAddress);
            uint32_t IP6AddressCount(void) const;
            const stcIP6Address* IP6AddressAtIndex(uint32_t p_u32Index) const;
            stcIP6Address* IP6AddressAtIndex(uint32_t p_u32Index);
#endif
        };

        stcMDNSServiceQuery*              m_pNext;
        stcMDNS_RRDomain                  m_ServiceTypeDomain;    // eg. _http._tcp.local
        MDNSServiceQueryCallbackFunc      m_fnCallback;
        bool                              m_bLegacyQuery;
        uint8_t                           m_u8SentCount;
        esp8266::polledTimeout::oneShotMs m_ResendTimeout;
        bool                              m_bAwaitingAnswers;
        stcAnswer*                        m_pAnswers;

        stcMDNSServiceQuery(void);
        ~stcMDNSServiceQuery(void);

        bool clear(void);

        uint32_t answerCount(void) const;
        const stcAnswer* answerAtIndex(uint32_t p_u32Index) const;
        stcAnswer* answerAtIndex(uint32_t p_u32Index);
        uint32_t indexOfAnswer(const stcAnswer* p_pAnswer) const;

        bool addAnswer(stcAnswer* p_pAnswer);
        bool removeAnswer(stcAnswer* p_pAnswer);

        stcAnswer* findAnswerForServiceDomain(const stcMDNS_RRDomain& p_ServiceDomain);
        stcAnswer* findAnswerForHostDomain(const stcMDNS_RRDomain& p_HostDomain);
    };

    /**
        stcMDNSSendParameter
    */
    struct stcMDNSSendParameter
    {
    protected:
        /**
            stcDomainCacheItem
        */
        struct stcDomainCacheItem
        {
            stcDomainCacheItem*     m_pNext;
            const void*             m_pHostnameOrService;   // Opaque id for host or service domain (pointer)
            bool                    m_bAdditionalData;      // Opaque flag for special info (service domain included)
            uint16_t                m_u16Offset;            // Offset in UDP output buffer

            stcDomainCacheItem(const void* p_pHostnameOrService,
                               bool p_bAdditionalData,
                               uint32_t p_u16Offset);
        };

    public:
        uint16_t                m_u16ID;                    // Query ID (used only in lagacy queries)
        stcMDNS_RRQuestion*     m_pQuestions;               // A list of queries
        uint8_t                 m_u8HostReplyMask;          // Flags for reply components/answers
        bool                    m_bLegacyQuery;             // Flag: Legacy query
        bool                    m_bResponse;                // Flag: Response to a query
        bool                    m_bAuthorative;             // Flag: Authorative (owner) response
        bool                    m_bCacheFlush;              // Flag: Clients should flush their caches
        bool                    m_bUnicast;                 // Flag: Unicast response
        bool                    m_bUnannounce;              // Flag: Unannounce service
        uint16_t                m_u16Offset;                // Current offset in UDP write buffer (mainly for domain cache)
        stcDomainCacheItem*     m_pDomainCacheItems;        // Cached host and service domains

        stcMDNSSendParameter(void);
        ~stcMDNSSendParameter(void);

        bool clear(void);

        bool shiftOffset(uint16_t p_u16Shift);

        bool addDomainCacheItem(const void* p_pHostnameOrService,
                                bool p_bAdditionalData,
                                uint16_t p_u16Offset);
        uint16_t findCachedDomainOffset(const void* p_pHostnameOrService,
                                        bool p_bAdditionalData) const;
    };

    // Instance variables
    stcMDNSService*                 m_pServices;
    UdpContext*                     m_pUDPContext;
    char*                           m_pcHostname;
    stcMDNSServiceQuery*            m_pServiceQueries;
    WiFiEventHandler                m_DisconnectedHandler;
    WiFiEventHandler                m_GotIPHandler;
    MDNSDynamicServiceTxtCallbackFunc m_fnServiceTxtCallback;
    bool                            m_bPassivModeEnabled;
    stcProbeInformation             m_HostProbeInformation;
    CONST netif*                    m_netif; // network interface to run on

    /** CONTROL **/
    /* MAINTENANCE */
    bool _process(bool p_bUserContext);
    bool _restart(void);

    /* RECEIVING */
    bool _parseMessage(void);
    bool _parseQuery(const stcMDNS_MsgHeader& p_Header);

    bool _parseResponse(const stcMDNS_MsgHeader& p_Header);
    bool _processAnswers(const stcMDNS_RRAnswer* p_pPTRAnswers);
    bool _processPTRAnswer(const stcMDNS_RRAnswerPTR* p_pPTRAnswer,
                           bool& p_rbFoundNewKeyAnswer);
    bool _processSRVAnswer(const stcMDNS_RRAnswerSRV* p_pSRVAnswer,
                           bool& p_rbFoundNewKeyAnswer);
    bool _processTXTAnswer(const stcMDNS_RRAnswerTXT* p_pTXTAnswer);
#ifdef MDNS_IP4_SUPPORT
    bool _processAAnswer(const stcMDNS_RRAnswerA* p_pAAnswer);
#endif
#ifdef MDNS_IP6_SUPPORT
    bool _processAAAAAnswer(const stcMDNS_RRAnswerAAAA* p_pAAAAAnswer);
#endif

    /* PROBING */
    bool _updateProbeStatus(void);
    bool _resetProbeStatus(bool p_bRestart = true);
    bool _hasProbesWaitingForAnswers(void) const;
    bool _sendHostProbe(void);
    bool _sendServiceProbe(stcMDNSService& p_rService);
    bool _cancelProbingForHost(void);
    bool _cancelProbingForService(stcMDNSService& p_rService);

    /* ANNOUNCE */
    bool _announce(bool p_bAnnounce,
                   bool p_bIncludeServices);
    bool _announceService(stcMDNSService& p_rService,
                          bool p_bAnnounce = true);

    /* SERVICE QUERY CACHE */
    bool _hasServiceQueriesWaitingForAnswers(void) const;
    bool _checkServiceQueryCache(void);

    /** TRANSFER **/
    /* SENDING */
    bool _sendMDNSMessage(stcMDNSSendParameter& p_SendParameter);
    bool _sendMDNSMessage_Multicast(MDNSResponder::stcMDNSSendParameter& p_rSendParameter);
    bool _prepareMDNSMessage(stcMDNSSendParameter& p_SendParameter,
                             IPAddress p_IPAddress);
    bool _sendMDNSServiceQuery(const stcMDNSServiceQuery& p_ServiceQuery);
    bool _sendMDNSQuery(const stcMDNS_RRDomain& p_QueryDomain,
                        uint16_t p_u16QueryType,
                        stcMDNSServiceQuery::stcAnswer* p_pKnownAnswers = 0);

    const IPAddress _getResponseMulticastInterface() const
    {
        return IPAddress(m_netif->ip_addr);
    }

    uint8_t _replyMaskForHost(const stcMDNS_RRHeader& p_RRHeader,
                              bool* p_pbFullNameMatch = 0) const;
    uint8_t _replyMaskForService(const stcMDNS_RRHeader& p_RRHeader,
                                 const stcMDNSService& p_Service,
                                 bool* p_pbFullNameMatch = 0) const;

    /* RESOURCE RECORD */
    bool _readRRQuestion(stcMDNS_RRQuestion& p_rQuestion);
    bool _readRRAnswer(stcMDNS_RRAnswer*& p_rpAnswer);
#ifdef MDNS_IP4_SUPPORT
    bool _readRRAnswerA(stcMDNS_RRAnswerA& p_rRRAnswerA,
                        uint16_t p_u16RDLength);
#endif
    bool _readRRAnswerPTR(stcMDNS_RRAnswerPTR& p_rRRAnswerPTR,
                          uint16_t p_u16RDLength);
    bool _readRRAnswerTXT(stcMDNS_RRAnswerTXT& p_rRRAnswerTXT,
                          uint16_t p_u16RDLength);
#ifdef MDNS_IP6_SUPPORT
    bool _readRRAnswerAAAA(stcMDNS_RRAnswerAAAA& p_rRRAnswerAAAA,
                           uint16_t p_u16RDLength);
#endif
    bool _readRRAnswerSRV(stcMDNS_RRAnswerSRV& p_rRRAnswerSRV,
                          uint16_t p_u16RDLength);
    bool _readRRAnswerGeneric(stcMDNS_RRAnswerGeneric& p_rRRAnswerGeneric,
                              uint16_t p_u16RDLength);

    bool _readRRHeader(stcMDNS_RRHeader& p_rHeader);
    bool _readRRDomain(stcMDNS_RRDomain& p_rRRDomain);
    bool _readRRDomain_Loop(stcMDNS_RRDomain& p_rRRDomain,
                            uint8_t p_u8Depth);
    bool _readRRAttributes(stcMDNS_RRAttributes& p_rAttributes);

    /* DOMAIN NAMES */
    bool _buildDomainForHost(const char* p_pcHostname,
                             stcMDNS_RRDomain& p_rHostDomain) const;
    bool _buildDomainForDNSSD(stcMDNS_RRDomain& p_rDNSSDDomain) const;
    bool _buildDomainForService(const stcMDNSService& p_Service,
                                bool p_bIncludeName,
                                stcMDNS_RRDomain& p_rServiceDomain) const;
    bool _buildDomainForService(const char* p_pcService,
                                const char* p_pcProtocol,
                                stcMDNS_RRDomain& p_rServiceDomain) const;
#ifdef MDNS_IP4_SUPPORT
    bool _buildDomainForReverseIP4(IPAddress p_IP4Address,
                                   stcMDNS_RRDomain& p_rReverseIP4Domain) const;
#endif
#ifdef MDNS_IP6_SUPPORT
    bool _buildDomainForReverseIP6(IPAddress p_IP4Address,
                                   stcMDNS_RRDomain& p_rReverseIP6Domain) const;
#endif

    /* UDP */
    bool _udpReadBuffer(unsigned char* p_pBuffer,
                        size_t p_stLength);
    bool _udpRead8(uint8_t& p_ru8Value);
    bool _udpRead16(uint16_t& p_ru16Value);
    bool _udpRead32(uint32_t& p_ru32Value);

    bool _udpAppendBuffer(const unsigned char* p_pcBuffer,
                          size_t p_stLength);
    bool _udpAppend8(uint8_t p_u8Value);
    bool _udpAppend16(uint16_t p_u16Value);
    bool _udpAppend32(uint32_t p_u32Value);

#if not defined ESP_8266_MDNS_INCLUDE || defined DEBUG_ESP_MDNS_RESPONDER
    bool _udpDump(bool p_bMovePointer = false);
    bool _udpDump(unsigned p_uOffset,
                  unsigned p_uLength);
#endif

    /* READ/WRITE MDNS STRUCTS */
    bool _readMDNSMsgHeader(stcMDNS_MsgHeader& p_rMsgHeader);

    bool _write8(uint8_t p_u8Value,
                 stcMDNSSendParameter& p_rSendParameter);
    bool _write16(uint16_t p_u16Value,
                  stcMDNSSendParameter& p_rSendParameter);
    bool _write32(uint32_t p_u32Value,
                  stcMDNSSendParameter& p_rSendParameter);

    bool _writeMDNSMsgHeader(const stcMDNS_MsgHeader& p_MsgHeader,
                             stcMDNSSendParameter& p_rSendParameter);
    bool _writeMDNSRRAttributes(const stcMDNS_RRAttributes& p_Attributes,
                                stcMDNSSendParameter& p_rSendParameter);
    bool _writeMDNSRRDomain(const stcMDNS_RRDomain& p_Domain,
                            stcMDNSSendParameter& p_rSendParameter);
    bool _writeMDNSHostDomain(const char* m_pcHostname,
                              bool p_bPrependRDLength,
                              stcMDNSSendParameter& p_rSendParameter);
    bool _writeMDNSServiceDomain(const stcMDNSService& p_Service,
                                 bool p_bIncludeName,
                                 bool p_bPrependRDLength,
                                 stcMDNSSendParameter& p_rSendParameter);

    bool _writeMDNSQuestion(stcMDNS_RRQuestion& p_Question,
                            stcMDNSSendParameter& p_rSendParameter);

#ifdef MDNS_IP4_SUPPORT
    bool _writeMDNSAnswer_A(IPAddress p_IPAddress,
                            stcMDNSSendParameter& p_rSendParameter);
    bool _writeMDNSAnswer_PTR_IP4(IPAddress p_IPAddress,
                                  stcMDNSSendParameter& p_rSendParameter);
#endif
    bool _writeMDNSAnswer_PTR_TYPE(stcMDNSService& p_rService,
                                   stcMDNSSendParameter& p_rSendParameter);
    bool _writeMDNSAnswer_PTR_NAME(stcMDNSService& p_rService,
                                   stcMDNSSendParameter& p_rSendParameter);
    bool _writeMDNSAnswer_TXT(stcMDNSService& p_rService,
                              stcMDNSSendParameter& p_rSendParameter);
#ifdef MDNS_IP6_SUPPORT
    bool _writeMDNSAnswer_AAAA(IPAddress p_IPAddress,
                               stcMDNSSendParameter& p_rSendParameter);
    bool _writeMDNSAnswer_PTR_IP6(IPAddress p_IPAddress,
                                  stcMDNSSendParameter& p_rSendParameter);
#endif
    bool _writeMDNSAnswer_SRV(stcMDNSService& p_rService,
                              stcMDNSSendParameter& p_rSendParameter);

    /** HELPERS **/
    /* UDP CONTEXT */
    bool _callProcess(void);
    bool _allocUDPContext(void);
    bool _releaseUDPContext(void);

    /* SERVICE QUERY */
    stcMDNSServiceQuery* _allocServiceQuery(void);
    bool _removeServiceQuery(stcMDNSServiceQuery* p_pServiceQuery);
    bool _removeLegacyServiceQuery(void);
    stcMDNSServiceQuery* _findServiceQuery(hMDNSServiceQuery p_hServiceQuery);
    stcMDNSServiceQuery* _findLegacyServiceQuery(void);
    bool _releaseServiceQueries(void);
    stcMDNSServiceQuery* _findNextServiceQueryByServiceType(const stcMDNS_RRDomain& p_ServiceDomain,
            const stcMDNSServiceQuery* p_pPrevServiceQuery);

    /* HOSTNAME */
    bool _setHostname(const char* p_pcHostname);
    bool _releaseHostname(void);

    /* SERVICE */
    stcMDNSService* _allocService(const char* p_pcName,
                                  const char* p_pcService,
                                  const char* p_pcProtocol,
                                  uint16_t p_u16Port);
    bool _releaseService(stcMDNSService* p_pService);
    bool _releaseServices(void);

    stcMDNSService* _findService(const char* p_pcName,
                                 const char* p_pcService,
                                 const char* p_pcProtocol);
    stcMDNSService* _findService(const hMDNSService p_hService);

    size_t _countServices(void) const;

    /* SERVICE TXT */
    stcMDNSServiceTxt* _allocServiceTxt(stcMDNSService* p_pService,
                                        const char* p_pcKey,
                                        const char* p_pcValue,
                                        bool p_bTemp);
    bool _releaseServiceTxt(stcMDNSService* p_pService,
                            stcMDNSServiceTxt* p_pTxt);
    stcMDNSServiceTxt* _updateServiceTxt(stcMDNSService* p_pService,
                                         stcMDNSServiceTxt* p_pTxt,
                                         const char* p_pcValue,
                                         bool p_bTemp);

    stcMDNSServiceTxt* _findServiceTxt(stcMDNSService* p_pService,
                                       const char* p_pcKey);
    stcMDNSServiceTxt* _findServiceTxt(stcMDNSService* p_pService,
                                       const hMDNSTxt p_hTxt);

    stcMDNSServiceTxt* _addServiceTxt(stcMDNSService* p_pService,
                                      const char* p_pcKey,
                                      const char* p_pcValue,
                                      bool p_bTemp);

    stcMDNSServiceTxt* _answerKeyValue(const hMDNSServiceQuery p_hServiceQuery,
                                       const uint32_t p_u32AnswerIndex);

    bool _collectServiceTxts(stcMDNSService& p_rService);
    bool _releaseTempServiceTxts(stcMDNSService& p_rService);
    const stcMDNSServiceTxt* _serviceTxts(const char* p_pcName,
                                          const char* p_pcService,
                                          const char* p_pcProtocol);

    /* MISC */
#if not defined ESP_8266_MDNS_INCLUDE || defined DEBUG_ESP_MDNS_RESPONDER
    bool _printRRDomain(const stcMDNS_RRDomain& p_rRRDomain) const;
    bool _printRRAnswer(const MDNSResponder::stcMDNS_RRAnswer& p_RRAnswer) const;
#endif
};

}// namespace MDNSImplementation

}// namespace esp8266

#endif // MDNS_H
