using Common.Logging;
using CommunityToolkit.Mvvm.Messaging;
using HidApi;
using MultiTerm.Protocols.Model;
using MultiTerm.Protocols.Types;
using System.Diagnostics;

namespace MultiTerm.Protocols.UsbHid;

public class UsbHidProtocol : CommunicationProtocol
{
    public override ProtocolType ProtocolType => ProtocolType.UsbHid;

    public override string InstanceIdentifier { get; protected set; } = string.Empty;

    private const uint ReadTimeoutMs = 100;         // timeout after which a new read cycle is started
    private const uint MaxBytesPerReport = 100;     // maximum number of bytes to send per report, including report ID and pther prefixes

    private IUsbHidProtocolSettings? usbHidSettings;
    private Device? usbHidDevice = null;


    public UsbHidProtocol(ILogger logger, IMessenger messenger) : base(logger, messenger) { }

    protected override bool InternalConnect(IProtocolSettings settings)
    {
        // check if settings are of correct type
        if (settings is not IUsbHidProtocolSettings usbHidProtocolSettings)
        {
            this.usbHidSettings = null;
            throw new ArgumentException($"Cannot connect due to wrong type of Protocol Settings. " +
                $"Check parameter {nameof(settings)}' of '{nameof(InternalConnect)}()' in {nameof(UsbHidProtocol)}.");
        }

        // store locally
        this.usbHidSettings = usbHidProtocolSettings;

        // update Identifier
        this.InstanceIdentifier = $"V:{this.usbHidSettings.VendorId:X4} P:{this.usbHidSettings.ProductId:X4}";

        // try create usb hid device
        try
        {
            // if serial number is emtpy => connect without serial number
            if (string.IsNullOrEmpty(this.usbHidSettings.SerialNumber))
            {
                this.usbHidDevice = new Device(this.usbHidSettings.VendorId, this.usbHidSettings.ProductId);
            }
            else
            {
                this.usbHidDevice = new Device(this.usbHidSettings.VendorId, this.usbHidSettings.ProductId, this.usbHidSettings.SerialNumber);
            }
        }
        catch (Exception ex)
        {
            this.logger.LogException(ex, $"'{nameof(InternalConnect)}()'Opening USB HID Device failed:", nameof(UsbHidProtocol));
            this.usbHidDevice = null;
        }

        // device not found or had exception
        if (usbHidDevice == null)
        {
            return false;
        }

        return true;
    }

    protected override void InternalDisconnect()
    {
        this.usbHidDevice?.Dispose();
        this.usbHidDevice = null;
        this.usbHidSettings = null;
    }

    protected override void InternalRead(CancellationToken ct)
    {
        while (ct.IsCancellationRequested == false)
        {
            // if usb hid device is null => something is wrong => break loop
            if (this.usbHidDevice == null)
            {
                this.OnUnintentionallyDisconnected();
                break;
            }

            ReadOnlySpan<byte> readData;
            try
            {
                // read with timeout
                readData = this.usbHidDevice.ReadTimeout(200, (int)ReadTimeoutMs);
            }
            catch  // on exception => break loop
            {
                this.OnUnintentionallyDisconnected();
                break;
            }

            // any data received?
            if (readData.Length > 0)
            {
                foreach (var readByte in readData)
                {
                    // report new byte with event
                    this.OnReceivedData(new ExtendedByte((byte)readByte));
                }
            }
        }
    }

    protected override bool InternalSendBytes(byte[] bytes)
    {
        List<byte> bytesToSend = new(bytes);
        int numBytesToTake = (int)MaxBytesPerReport - 2;

        Debug.WriteLine($"{nameof(InternalSendBytes)}() of {nameof(UsbHidProtocol)} has {bytesToSend.Count} bytes to send.");

        while (bytesToSend.Count > 0)
        {
            // take from the list the amount of bytes to send. ToList creates a shallow copy.
            //bytesToSend.CopyTo(0, nextBytes, 0, Math.Min(numBytesToTake, bytesToSend.Count));
            var nextBytes = bytesToSend.Take(numBytesToTake).ToList();
            // remove from start of original list either; taken amount of bytes or remaining count of bytes in list
            bytesToSend.RemoveRange(0, Math.Min(numBytesToTake, bytesToSend.Count));

            Debug.WriteLine($"{nameof(InternalSendBytes)}() of {nameof(UsbHidProtocol)} took {nextBytes.Count()} bytes and has {bytesToSend.Count} left on queue.");

            // check number of bytes to send
            int numBytesToSend = nextBytes.Count();
            if (numBytesToSend > MaxBytesPerReport || numBytesToSend > byte.MaxValue || numBytesToSend <= 0)
            {
                throw new Exception($"'{nameof(InternalSendBytes)}()': Invalid of bytes to send ({nameof(numBytesToSend)})");
            }

            // create list with sendable bytes
            // Structure: (1Byte)Report Id, (1Byte)Payload Num Bytes, (n Bytes)Payload
            List<byte> sendableBytes = new() { 0x00, (byte)numBytesToSend };
            sendableBytes.AddRange(nextBytes);

            // if usb hid device is null => something is wrong => quit sending
            if (this.usbHidDevice == null)
            {
                this.OnUnintentionallyDisconnected();
                return false;
            }

            try
            {
                this.usbHidDevice.Write(sendableBytes.ToArray());
            }
            catch(Exception ex) 
            {
                this.logger.LogException(ex, $"Failed to Write Data to USB HID device " +
                    $"VID={this.usbHidSettings!.VendorId}, PID={this.usbHidSettings.ProductId}.", nameof(UsbHidProtocol));
                return false;
            }

            // report sent bytes
            foreach (byte b in sendableBytes)
            {
                this.OnSentData(new ExtendedByte(b));
            }
        }

        return true;
    }

    public static IEnumerable<UsbHidDeviceInfo> GetDevices()
    {
        var libDevicesInfo = Hid.Enumerate();
        var usbHidDevicesInfo = new List<UsbHidDeviceInfo>();
        foreach (var deviceInfo in libDevicesInfo)
        {
            usbHidDevicesInfo.Add(new UsbHidDeviceInfo
            {
                VendorId = $"{deviceInfo.VendorId:X4}",
                ProductId = $"{deviceInfo.ProductId:X4}",
                Manufacturer = deviceInfo.ManufacturerString,
                SerialNumber = deviceInfo.SerialNumber
            });
        }
        return usbHidDevicesInfo;
    }
}