using Common.Logging;
using Common.Messaging;
using CommunityToolkit.Mvvm.Messaging;
using MultiTerm.Protocols.Types;

namespace MultiTerm.Protocols;

public abstract class CommunicationProtocol : ICommunicationProtocol
{
    protected readonly ILogger logger;
    protected readonly IMessenger messenger;
    private CancellationTokenSource cancellationTokenSource;
    private Thread? readingThread;

    public event EventHandler<ReceivedDataEventArgs>? ReceivedDataEvent;
    public event EventHandler<SentDataEventArgs>? SentDataEvent;
    public event EventHandler<DisconnectedEventArgs>? DisconnectedEvent;

    public abstract ProtocolType ProtocolType { get; }
    public abstract string InstanceIdentifier { get; protected set; }

    public bool IsConnected { get; private set; } = false;

    public CommunicationProtocol(ILogger logger, IMessenger messenger)
    {
        // initialize other
        this.cancellationTokenSource = new CancellationTokenSource();
        this.logger = logger;
        this.messenger = messenger;
    }

    /// <summary>
    /// To be called when data was received from the connected device.
    /// </summary>
    protected void OnReceivedData(ReceivedDataEventArgs e) { this.ReceivedDataEvent?.Invoke(this, e); }

    /// <summary>
    /// To be called when data was sent to the connected device.
    /// </summary>
    protected void OnSentData(SentDataEventArgs e) { this.SentDataEvent?.Invoke(this, e); }

    /// <summary>
    /// To be called whenever the protocol detected that it is disconnected, but this is not a known fact.
    /// </summary>
    protected void OnUnintentionallyDisconnected()
    {
        // update state
        this.IsConnected = false;
        // log
        this.logger.LogError($"'{nameof(OnUnintentionallyDisconnected)}()' called.", nameof(CommunicationProtocol));
        // raise event indicating an unintentional disconnect
        this.DisconnectedEvent?.Invoke(this, new DisconnectedEventArgs(true));
    }

    /// <summary>
    /// Allows to send bytes using the implemented protocol.
    /// </summary>
    /// <param name="bytes">data as bytes</param>
    /// <returns>true if the data was sent successfully</returns>
    protected abstract bool InternalSendBytes(byte[] bytes);

    public void SendBytes(byte[] bytes)
    {
        // guard is not connected => log warning. user of this function shall only use SendBytes if IsConnected is true
        if (this.IsConnected == false) { this.logger.LogWarn($"'{nameof(SendBytes)}()' was reached with {nameof(IsConnected)} being false", nameof(CommunicationProtocol)); }

        if (this.InternalSendBytes(bytes))
        {
            // todo implement sent bytes
            // ONsentBytes()
        }
        else
        {
            this.logger.LogError($"'{nameof(SendBytes)}()' failed to send during {nameof(InternalSendBytes)}.", nameof(CommunicationProtocol));
            this.messenger.Send<IUserInterfaceMessage>(new GenericUserInterfaceMessage("Failed to send message", MessageImportance.High));
        }
    }

    /// <summary>
    /// Allows to connect to the selected device using the implemented protocol.
    /// </summary>
    /// <param name="settings">protocol settings required to connect</param>
    /// <returns>true on success</returns>
    protected abstract bool InternalConnect(IProtocolSettings settings);

    /// <summary>
    /// Reads from the connected device in an endless loop.
    /// The endless loop must be ended when the <paramref name="ct"/> has <see cref="CancellationToken.IsCancellationRequested"/> set.
    /// </summary>
    /// <param name="ct">cancellation token</param>
    protected abstract void InternalRead(CancellationToken ct);

    public bool Connect(IProtocolSettings settings)
    {
        // check if not already connected
        if (this.IsConnected == true)
        {
            this.logger.LogWarn($"'{nameof(Connect)}()' was reached even if {nameof(IsConnected)} is already true.", nameof(CommunicationProtocol));
            return true;
        }

        // check if settings are valid, cancel if not
        if (settings.AreValid() == false)
        {
            this.logger.LogError($"'{nameof(Connect)}()' failed since the provided protocol settings are invalid", nameof(CommunicationProtocol));
            return false;
        }

        // try connecting if settings are valid
        if (this.InternalConnect(settings))
        {
            // renew token source
            this.cancellationTokenSource = new CancellationTokenSource();
            // start internal reading thread
            this.readingThread = new Thread(() => this.InternalRead(this.cancellationTokenSource.Token));
            this.readingThread.Start();
            // update state
            this.IsConnected = true;
            return true;
        }
        else
        {
            this.logger.LogWarn($"'{nameof(Connect)}()' failed to connect to protocol, did not start reading thread.", nameof(CommunicationProtocol));
            return false;
        }
    }

    /// <summary>
    /// Allows to disconnect from the connected device.
    /// </summary>
    protected abstract void InternalDisconnect();
    public void Disconnect()
    {
        // if reading thread exists and is running => cancel it and wait 
        if (this.readingThread != null && this.readingThread.IsAlive)
        {
            this.cancellationTokenSource.Cancel();
            this.readingThread.Join();
        }
        this.InternalDisconnect();
        this.IsConnected = false;

        // raise event indicating an intentional disconnect
        this.DisconnectedEvent?.Invoke(this, new DisconnectedEventArgs(false));
    }
}