using System;
using ArchestrA.MxAccess;
using Proto = MxGateway.Contracts.Proto;

namespace MxGateway.Worker.MxAccess;

/// <summary>Sink for MXAccess COM events that converts them to protobuf format.</summary>
public sealed class MxAccessBaseEventSink : IMxAccessEventSink
{
    private readonly MxAccessEventMapper eventMapper;
    private readonly MxAccessEventQueue eventQueue;
    private LMXProxyServerClass? server;
    private string sessionId = string.Empty;

    /// <summary>Initializes a new instance of the MxAccessBaseEventSink class with a default queue.</summary>
    public MxAccessBaseEventSink()
        : this(new MxAccessEventQueue())
    {
    }

    /// <summary>Initializes a new instance of the MxAccessBaseEventSink class with a provided queue.</summary>
    /// <param name="eventQueue">Queue for buffering converted MXAccess events.</param>
    public MxAccessBaseEventSink(MxAccessEventQueue eventQueue)
        : this(eventQueue, new MxAccessEventMapper())
    {
    }

    /// <summary>Initializes a new instance of the MxAccessBaseEventSink class with provided queue and mapper.</summary>
    /// <param name="eventQueue">Queue for buffering converted MXAccess events.</param>
    /// <param name="eventMapper">Converter for MXAccess events to protobuf format.</param>
    public MxAccessBaseEventSink(
        MxAccessEventQueue eventQueue,
        MxAccessEventMapper eventMapper)
    {
        this.eventQueue = eventQueue ?? throw new ArgumentNullException(nameof(eventQueue));
        this.eventMapper = eventMapper ?? throw new ArgumentNullException(nameof(eventMapper));
    }

    /// <inheritdoc />
    public void Attach(
        object mxAccessComObject,
        string sessionId)
    {
        this.sessionId = sessionId ?? string.Empty;
        server = (LMXProxyServerClass)mxAccessComObject;
        server.OnDataChange += OnDataChange;
        server.OnWriteComplete += OnWriteComplete;
        server.OperationComplete += OperationComplete;
        server.OnBufferedDataChange += OnBufferedDataChange;
    }

    /// <inheritdoc />
    public void Detach()
    {
        if (server is null)
        {
            return;
        }

        server.OnDataChange -= OnDataChange;
        server.OnWriteComplete -= OnWriteComplete;
        server.OperationComplete -= OperationComplete;
        server.OnBufferedDataChange -= OnBufferedDataChange;
        server = null;
        sessionId = string.Empty;
    }

    private void OnDataChange(
        int hLMXServerHandle,
        int phItemHandle,
        object pvItemValue,
        int pwItemQuality,
        object pftItemTimeStamp,
        ref MXSTATUS_PROXY[] pVars)
    {
        MXSTATUS_PROXY[] statuses = pVars;
        EnqueueEvent(() => eventMapper.CreateOnDataChange(
            sessionId,
            hLMXServerHandle,
            phItemHandle,
            pvItemValue,
            pwItemQuality,
            pftItemTimeStamp,
            statuses));
    }

    private void OnWriteComplete(
        int hLMXServerHandle,
        int phItemHandle,
        ref MXSTATUS_PROXY[] pVars)
    {
        MXSTATUS_PROXY[] statuses = pVars;
        EnqueueEvent(() => eventMapper.CreateOnWriteComplete(
            sessionId,
            hLMXServerHandle,
            phItemHandle,
            statuses));
    }

    private void OperationComplete(
        int hLMXServerHandle,
        int phItemHandle,
        ref MXSTATUS_PROXY[] pVars)
    {
        MXSTATUS_PROXY[] statuses = pVars;
        EnqueueEvent(() => eventMapper.CreateOperationComplete(
            sessionId,
            hLMXServerHandle,
            phItemHandle,
            statuses));
    }

    private void OnBufferedDataChange(
        int hLMXServerHandle,
        int phItemHandle,
        MxDataType dtDataType,
        object pvItemValue,
        object pwItemQuality,
        object pftItemTimeStamp,
        ref MXSTATUS_PROXY[] pVars)
    {
        MXSTATUS_PROXY[] statuses = pVars;
        EnqueueEvent(() => eventMapper.CreateOnBufferedDataChange(
            sessionId,
            hLMXServerHandle,
            phItemHandle,
            (int)dtDataType,
            pvItemValue,
            pwItemQuality,
            pftItemTimeStamp,
            statuses));
    }

    private void EnqueueEvent(Func<Proto.MxEvent> createEvent)
    {
        try
        {
            eventQueue.Enqueue(createEvent());
        }
        catch (Exception exception)
        {
            eventQueue.RecordFault(CreateEventConversionFault(exception));
        }
    }

    private Proto.WorkerFault CreateEventConversionFault(Exception exception)
    {
        return new Proto.WorkerFault
        {
            Category = Proto.WorkerFaultCategory.MxaccessEventConversionFailed,
            ExceptionType = exception.GetType().FullName ?? string.Empty,
            DiagnosticMessage = $"{exception.GetType().FullName}: HRESULT 0x{unchecked((uint)exception.HResult):X8}",
            ProtocolStatus = new Proto.ProtocolStatus
            {
                Code = Proto.ProtocolStatusCode.MxaccessFailure,
                Message = "MXAccess event conversion failed.",
            },
        };
    }
}