tbf/TBF/Rig/RegisterReaders/iPerlASICReader/communication/C4/TouchReadFrameBuilder.cs

using System;
using System.Collections.Generic;

namespace TBF.Rig.RegisterReaders.iPerlASICReader.communication.C4
{
    public sealed class TouchReadFrameBuilder
    {
        private const byte START = 0x0D;
        private byte _control;
        private readonly List<byte> _information = new List<byte>();

        public TouchReadFrameBuilder RequestResponse(bool enabled)
        {
            _control = enabled ? (byte)0x08 : (byte)0x00;
            return this;
        }

        public TouchReadFrameBuilder AddCommand(TouchReadCommand command)
        {
            _information.Add((byte)command);
            return this;
        }
        
        public TouchReadFrameBuilder AddSubCommand(TouchReadDeviceSubCommand subCommand)
        {
            if (_information.Count == 0 ||
                _information[0] != (byte)TouchReadCommand.DeviceSpecific)
                throw new InvalidOperationException(
                    "Sub-command is only valid for DeviceSpecific (0xFD) commands.");

            _information.Add((byte)subCommand);
            return this;
        }

        public TouchReadFrameBuilder AddDeviceCommand(
            TouchReadDeviceSubCommand subCommand)
        {
            _information.Add((byte)TouchReadCommand.DeviceSpecific);
            _information.Add((byte)subCommand);
            return this;
        }

        public TouchReadFrameBuilder AddPayload(byte[] payload)
        {
            if (payload != null)
                _information.AddRange(payload);

            return this;
        }

        public TouchReadFrameBuilder AddNullTerminatedAscii(string text)
        {
            if (!string.IsNullOrEmpty(text))
                _information.AddRange(
                    System.Text.Encoding.ASCII.GetBytes(text));

            _information.Add(0x00);
            return this;
        }

        public TouchReadFrame BuildFrame()
        {
            if (_information.Count == 0)
                throw new InvalidOperationException("No command specified.");

            byte length = (byte)(1 + _information.Count + 2);

            var raw = new List<byte>
            {
                START,
                length,
                _control
            };

            raw.AddRange(_information);

            ushort checksum = CalculateChecksum(raw);
            raw.Add((byte)(checksum >> 8));
            raw.Add((byte)(checksum & 0xFF));

            return new TouchReadFrame(
                START,
                length,
                _control,
                _information.ToArray(),
                checksum);
        }

        public byte[] BuildBytes()
        {
            TouchReadFrame frame = BuildFrame();

            var bytes = new List<byte>
            {
                frame.Start,
                frame.Length,
                frame.Control
            };

            bytes.AddRange(frame.Information);
            bytes.Add((byte)(frame.Checksum >> 8));
            bytes.Add((byte)(frame.Checksum & 0xFF));

            return bytes.ToArray();
        }

        private static ushort CalculateChecksum(IEnumerable<byte> data)
        {
            ushort sum = 0;
            foreach (var b in data)
                sum += b;
            return sum;
        }
    }
}