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 CONNACK message from broker to client
    /// </summary>
    public class MqttMsgConnack : MqttMsgBase
    {
        #region Constants...

        // return codes for CONNACK message
        public const byte CONN_ACCEPTED = 0x00;
        public const byte CONN_REFUSED_PROT_VERS = 0x01;
        public const byte CONN_REFUSED_IDENT_REJECTED = 0x02;
        public const byte CONN_REFUSED_SERVER_UNAVAILABLE = 0x03;
        public const byte CONN_REFUSED_USERNAME_PASSWORD = 0x04;
        public const byte CONN_REFUSED_NOT_AUTHORIZED = 0x05;

        private const byte TOPIC_NAME_COMP_RESP_BYTE_OFFSET = 0;
        private const byte TOPIC_NAME_COMP_RESP_BYTE_SIZE = 1;
        // [v3.1.1] connect acknowledge flags replace "old" topic name compression respone (not used in 3.1)
        private const byte CONN_ACK_FLAGS_BYTE_OFFSET = 0;
        private const byte CONN_ACK_FLAGS_BYTE_SIZE = 1;
        // [v3.1.1] session present flag
        private const byte SESSION_PRESENT_FLAG_MASK = 0x01;
        private const byte SESSION_PRESENT_FLAG_OFFSET = 0x00;
        private const byte SESSION_PRESENT_FLAG_SIZE = 0x01;
        private const byte CONN_RETURN_CODE_BYTE_OFFSET = 1;
        private const byte CONN_RETURN_CODE_BYTE_SIZE = 1;

        #endregion

        #region Properties...

        // [v3.1.1] session present flag
        /// <summary>
        /// Session present flag
        /// </summary>
        public bool SessionPresent
        {
            get { return this.sessionPresent; }
            set { this.sessionPresent = value; }
        }

        /// <summary>
        /// Return Code
        /// </summary>
        public byte ReturnCode
        {
            get { return this.returnCode; }
            set { this.returnCode = value; }
        }

        #endregion

        // [v3.1.1] session present flag
        private bool sessionPresent;

        // return code for CONNACK message
        private byte returnCode;

        /// <summary>
        /// Constructor
        /// </summary>
        public MqttMsgConnack()
        {
            this.type = MQTT_MSG_CONNACK_TYPE;
        }

        /// <summary>
        /// Parse bytes for a CONNACK 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>CONNACK message instance</returns>
        public static MqttMsgConnack Parse(byte fixedHeaderFirstByte, byte protocolVersion, IMqttNetworkChannel channel)
        {
            byte[] buffer;
            MqttMsgConnack msg = new MqttMsgConnack();

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

            // get remaining length and allocate buffer
            int remainingLength = MqttMsgBase.decodeRemainingLength(channel);
            buffer = new byte[remainingLength];

            // read bytes from socket...
            channel.Receive(buffer);
            if (protocolVersion == MqttMsgConnect.PROTOCOL_VERSION_V3_1_1)
            {
                // [v3.1.1] ... set session present flag ...
                msg.sessionPresent = (buffer[CONN_ACK_FLAGS_BYTE_OFFSET] & SESSION_PRESENT_FLAG_MASK) != 0x00;
            }
            // ...and set return code from broker
            msg.returnCode = buffer[CONN_RETURN_CODE_BYTE_OFFSET];

            return msg;
        }

        public override byte[] GetBytes(byte ProtocolVersion)
        {
            int fixedHeaderSize = 0;
            int varHeaderSize = 0;
            int payloadSize = 0;
            int remainingLength = 0;
            byte[] buffer;
            int index = 0;

            if (ProtocolVersion == MqttMsgConnect.PROTOCOL_VERSION_V3_1_1)
                // flags byte and connect return code
                varHeaderSize += (CONN_ACK_FLAGS_BYTE_SIZE + CONN_RETURN_CODE_BYTE_SIZE);
            else
                // topic name compression response and connect return code
                varHeaderSize += (TOPIC_NAME_COMP_RESP_BYTE_SIZE + CONN_RETURN_CODE_BYTE_SIZE);

            remainingLength += (varHeaderSize + payloadSize);

            // first byte of fixed header
            fixedHeaderSize = 1;

            int temp = remainingLength;
            // increase fixed header size based on remaining length
            // (each remaining length byte can encode until 128)
            do
            {
                fixedHeaderSize++;
                temp = temp / 128;
            } while (temp > 0);

            // allocate buffer for message
            buffer = new byte[fixedHeaderSize + varHeaderSize + payloadSize];

            // first fixed header byte
            if (ProtocolVersion == MqttMsgConnect.PROTOCOL_VERSION_V3_1_1)
                buffer[index++] = (MQTT_MSG_CONNACK_TYPE << MSG_TYPE_OFFSET) | MQTT_MSG_CONNACK_FLAG_BITS; // [v.3.1.1]
            else
                buffer[index++] = (byte)(MQTT_MSG_CONNACK_TYPE << MSG_TYPE_OFFSET);

            // encode remaining length
            index = this.encodeRemainingLength(remainingLength, buffer, index);

            if (ProtocolVersion == MqttMsgConnect.PROTOCOL_VERSION_V3_1_1)
                // [v3.1.1] session present flag
                buffer[index++] = this.sessionPresent ? (byte)(1 << SESSION_PRESENT_FLAG_OFFSET) : (byte)0x00;
            else
                // topic name compression response (reserved values. not used);
                buffer[index++] = 0x00;

            // connect return code
            buffer[index++] = this.returnCode;

            return buffer;
        }

        public override string ToString()
        {
#if TRACE
            return this.GetTraceString(
                "CONNACK",
                new object[] { "returnCode" },
                new object[] { this.returnCode });
#else
            return base.ToString();
#endif
        }
    }
}