using System;
using System.Threading;
using System.Threading.Tasks;
using Serilog;
using ZB.MOM.WW.LmxOpcUa.Host.Domain;

namespace ZB.MOM.WW.LmxOpcUa.Host.MxAccess
{
    public sealed partial class MxAccessClient
    {
        public async Task<Vtq> ReadAsync(string fullTagReference, CancellationToken ct = default)
        {
            if (_state != ConnectionState.Connected)
                return Vtq.Bad(Quality.BadNotConnected);

            await _operationSemaphore.WaitAsync(ct);
            try
            {
                using var scope = _metrics.BeginOperation("Read");
                var tcs = new TaskCompletionSource<Vtq>();

                // Subscribe, get first value, unsubscribe
                void OnValue(string addr, Vtq vtq) => tcs.TrySetResult(vtq);

                var itemHandle = await _staThread.RunAsync(() =>
                {
                    var h = _proxy.AddItem(_connectionHandle, fullTagReference);
                    _proxy.AdviseSupervisory(_connectionHandle, h);
                    return h;
                });

                _handleToAddress[itemHandle] = fullTagReference;
                _addressToHandle[fullTagReference] = itemHandle;
                _storedSubscriptions[fullTagReference] = OnValue;

                try
                {
                    using var cts = CancellationTokenSource.CreateLinkedTokenSource(ct);
                    cts.CancelAfter(TimeSpan.FromSeconds(_config.ReadTimeoutSeconds));
                    cts.Token.Register(() => tcs.TrySetResult(Vtq.Bad(Quality.BadCommFailure)));

                    return await tcs.Task;
                }
                catch
                {
                    scope.SetSuccess(false);
                    return Vtq.Bad(Quality.BadCommFailure);
                }
                finally
                {
                    _storedSubscriptions.TryRemove(fullTagReference, out _);
                    _handleToAddress.TryRemove(itemHandle, out _);
                    _addressToHandle.TryRemove(fullTagReference, out _);

                    try
                    {
                        await _staThread.RunAsync(() =>
                        {
                            _proxy.UnAdviseSupervisory(_connectionHandle, itemHandle);
                            _proxy.RemoveItem(_connectionHandle, itemHandle);
                        });
                    }
                    catch (Exception ex)
                    {
                        Log.Warning(ex, "Error cleaning up read subscription for {Address}", fullTagReference);
                    }
                }
            }
            finally
            {
                _operationSemaphore.Release();
            }
        }

        public async Task<bool> WriteAsync(string fullTagReference, object value, CancellationToken ct = default)
        {
            if (_state != ConnectionState.Connected) return false;

            await _operationSemaphore.WaitAsync(ct);
            try
            {
                using var scope = _metrics.BeginOperation("Write");

                var itemHandle = await _staThread.RunAsync(() =>
                {
                    var h = _proxy.AddItem(_connectionHandle, fullTagReference);
                    _proxy.AdviseSupervisory(_connectionHandle, h);
                    return h;
                });

                _handleToAddress[itemHandle] = fullTagReference;
                _addressToHandle[fullTagReference] = itemHandle;

                var tcs = new TaskCompletionSource<bool>();
                _pendingWrites[itemHandle] = tcs;

                try
                {
                    await _staThread.RunAsync(() => _proxy.Write(_connectionHandle, itemHandle, value, -1));

                    using var cts = CancellationTokenSource.CreateLinkedTokenSource(ct);
                    cts.CancelAfter(TimeSpan.FromSeconds(_config.WriteTimeoutSeconds));
                    cts.Token.Register(() => tcs.TrySetResult(true)); // timeout assumes success

                    return await tcs.Task;
                }
                catch (Exception ex)
                {
                    scope.SetSuccess(false);
                    Log.Error(ex, "Write failed for {Address}", fullTagReference);
                    return false;
                }
                finally
                {
                    _pendingWrites.TryRemove(itemHandle, out _);
                    _handleToAddress.TryRemove(itemHandle, out _);
                    _addressToHandle.TryRemove(fullTagReference, out _);

                    try
                    {
                        await _staThread.RunAsync(() =>
                        {
                            _proxy.UnAdviseSupervisory(_connectionHandle, itemHandle);
                            _proxy.RemoveItem(_connectionHandle, itemHandle);
                        });
                    }
                    catch (Exception ex)
                    {
                        Log.Warning(ex, "Error cleaning up write subscription for {Address}", fullTagReference);
                    }
                }
            }
            finally
            {
                _operationSemaphore.Release();
            }
        }
    }
}