FCC/Devices/Sensors/GasConcentrations_Yt95h/StateMachineMessageCutter.cs

using Edge.Core.Processor.Communicator;
using System;
using System.Linq;

namespace GasConcentrations_Yt95h
{
    public class StateMachineMessageCutter : IMessageCutter<byte[]>
    {
        public byte[] Message { get; private set; }

        public event EventHandler OnMessageCut;
        public event EventHandler<MessageCutterInvalidMessageReadEventArg> OnInvalidMessageRead;

        static NLog.Logger innerLogger = NLog.LogManager.LoadConfiguration("nlog.config").GetLogger("StateMachineMessageCutter");
        private string loggerAppendix = "Yt95hEx_Handler msgCutter";

        private readonly SizableWindow<byte> window;
        private State nextState = State.Uninitialized;

        public StateMachineMessageCutter()
        {
            this.window = new SizableWindow<byte>(2);
            this.window.OnWindowFull += (data) =>
            {
                switch (nextState)
                {
                    case State.Uninitialized:
                        if (0 < data[0] && data[0] <= 255)
                        {
                            if (data[1] == 3 || data[1] == 4)
                            {
                                this.nextState = State.LengthReady;
                                this.window.NewSize += 1;
                                innerLogger.Debug($"{this.loggerAppendix} state is State.Uninitialized, will switch to LengthReady");
                            }
                            else if (data[1] == 6 || data[1] == 16)
                            {
                                this.nextState = State.DataAddressReady;
                                this.window.NewSize += 2;
                                innerLogger.Debug($"{this.loggerAppendix} state is State.Uninitialized, will switch to DataAddressReady");
                            }
                            else
                            {
                                ReadInvalidMessage();
                            }
                        }
                        else
                        {
                            ReadInvalidMessage();
                        }
                        break;
                    case State.LengthReady:
                        //this.DumpWindowToQueue();
                        this.nextState = State.BodyReady;
                        this.window.NewSize += (data[2] + 2); // data[2] The number of data bytes to follow
                        innerLogger.Debug($"{this.loggerAppendix} MsgBodyLen caculated with: {this.window.NewSize}");
                        break;
                    case State.DataAddressReady:
                        this.nextState = State.BodyReady;
                        this.window.NewSize += 4;
                        innerLogger.Debug($"{this.loggerAppendix} MsgBodyLen caculated with: {this.window.NewSize}");
                        break;
                    case State.BodyReady:
                        this.Message = this.window.ToArray();
                        var safe = this.OnMessageCut;
                        safe?.Invoke(this, null);
                        this.nextState = State.Uninitialized;
                        this.window.Clear();
                        break;
                    default:
                        throw new ArgumentOutOfRangeException();
                }
            };
        }

        private enum State
        {
            Uninitialized,
            LengthReady,
            DataAddressReady,
            BodyReady,
        }

        private void ReadInvalidMessage()
        {
            this.Message = this.window.ToArray();
            var safeHandler = this.OnInvalidMessageRead;
            safeHandler?.Invoke(this, null);
            this.window.Clear();
        }

        public void Feed(byte[] next)
        {
            for (int i = 0; i < next.Length; i++)
            {
                window.Add(next[i]);
            }
        }
    }
}