using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using uPLibrary.Networking.M2Mqtt.Exceptions;

namespace uPLibrary.Networking.M2Mqtt.Messages
{
    /// <summary>
    /// Class for PINGRESP message from client to broker
    /// </summary>
    public class MqttMsgPingResp : MqttMsgBase
    {
        /// <summary>
        /// Constructor
        /// </summary>
        public MqttMsgPingResp()
        {
            this.type = MQTT_MSG_PINGRESP_TYPE;
        }

        /// <summary>
        /// Parse bytes for a PINGRESP message
        /// </summary>
        /// <param name="fixedHeaderFirstByte">First fixed header byte</param>
        /// <param name="protocolVersion">Protocol Version</param>
        /// <param name="channel">Channel connected to the broker</param>
        /// <returns>PINGRESP message instance</returns>
        public static MqttMsgPingResp Parse(byte fixedHeaderFirstByte, byte protocolVersion, IMqttNetworkChannel channel)
        {
            MqttMsgPingResp msg = new MqttMsgPingResp();

            if (protocolVersion == MqttMsgConnect.PROTOCOL_VERSION_V3_1_1)
            {
                // [v3.1.1] check flag bits
                if ((fixedHeaderFirstByte & MSG_FLAG_BITS_MASK) != MQTT_MSG_PINGRESP_FLAG_BITS)
                    throw new MqttClientException(MqttClientErrorCode.InvalidFlagBits);
            }

            // already know remaininglength is zero (MQTT specification),
            // so it isn't necessary to read other data from socket
            int remainingLength = MqttMsgBase.decodeRemainingLength(channel);

            return msg;
        }

        public override byte[] GetBytes(byte protocolVersion)
        {
            byte[] buffer = new byte[2];
            int index = 0;

            // first fixed header byte
            if (protocolVersion == MqttMsgConnect.PROTOCOL_VERSION_V3_1_1)
                buffer[index++] = (MQTT_MSG_PINGRESP_TYPE << MSG_TYPE_OFFSET) | MQTT_MSG_PINGRESP_FLAG_BITS; // [v.3.1.1]
            else
                buffer[index++] = (MQTT_MSG_PINGRESP_TYPE << MSG_TYPE_OFFSET);
            buffer[index++] = 0x00;

            return buffer;
        }

        public override string ToString()
        {
#if TRACE
            return this.GetTraceString(
                "PINGRESP",
                null,
                null);
#else
            return base.ToString();
#endif
        }
    }
}