using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using Google.Protobuf.WellKnownTypes;
using MxGateway.Contracts.Proto;

namespace MxGateway.Worker.MxAccess;

public sealed class MxAccessSession : IDisposable
{
    private readonly object mxAccessComObject;
    private readonly IMxAccessServer mxAccessServer;
    private readonly IMxAccessEventSink eventSink;
    private readonly MxAccessHandleRegistry handleRegistry;
    private bool disposed;

    private MxAccessSession(
        object mxAccessComObject,
        IMxAccessServer mxAccessServer,
        IMxAccessEventSink eventSink,
        MxAccessHandleRegistry handleRegistry,
        int creationThreadId)
    {
        this.mxAccessComObject = mxAccessComObject ?? throw new ArgumentNullException(nameof(mxAccessComObject));
        this.mxAccessServer = mxAccessServer ?? throw new ArgumentNullException(nameof(mxAccessServer));
        this.eventSink = eventSink ?? throw new ArgumentNullException(nameof(eventSink));
        this.handleRegistry = handleRegistry ?? throw new ArgumentNullException(nameof(handleRegistry));
        CreationThreadId = creationThreadId;
    }

    public int CreationThreadId { get; }

    public MxAccessHandleRegistry HandleRegistry => handleRegistry;

    public WorkerReady CreateWorkerReady(int workerProcessId)
    {
        return new WorkerReady
        {
            WorkerProcessId = workerProcessId,
            MxaccessProgid = MxAccessInteropInfo.ProgId,
            MxaccessClsid = MxAccessInteropInfo.Clsid,
            ReadyTimestamp = Timestamp.FromDateTime(DateTime.UtcNow),
        };
    }

    public static MxAccessSession Create(
        IMxAccessComObjectFactory factory,
        IMxAccessEventSink eventSink,
        string sessionId)
    {
        if (factory is null)
        {
            throw new ArgumentNullException(nameof(factory));
        }

        if (eventSink is null)
        {
            throw new ArgumentNullException(nameof(eventSink));
        }

        object? mxAccessComObject = null;

        try
        {
            mxAccessComObject = factory.Create();
            if (mxAccessComObject is null)
            {
                throw new InvalidOperationException("MXAccess COM factory returned null.");
            }

            eventSink.Attach(mxAccessComObject, sessionId);

            return new MxAccessSession(
                mxAccessComObject,
                new MxAccessComServer(mxAccessComObject),
                eventSink,
                new MxAccessHandleRegistry(),
                Environment.CurrentManagedThreadId);
        }
        catch (Exception exception)
        {
            eventSink.Detach();

            if (mxAccessComObject is not null && Marshal.IsComObject(mxAccessComObject))
            {
                Marshal.FinalReleaseComObject(mxAccessComObject);
            }

            throw MxAccessCreationException.From(exception);
        }
    }

    public int Register(string clientName)
    {
        ThrowIfDisposed();

        int serverHandle = mxAccessServer.Register(clientName);
        handleRegistry.RegisterServerHandle(serverHandle, clientName);

        return serverHandle;
    }

    public void Unregister(int serverHandle)
    {
        ThrowIfDisposed();

        mxAccessServer.Unregister(serverHandle);
        handleRegistry.UnregisterServerHandle(serverHandle);
    }

    public int AddItem(
        int serverHandle,
        string itemDefinition)
    {
        ThrowIfDisposed();

        int itemHandle = mxAccessServer.AddItem(serverHandle, itemDefinition);
        handleRegistry.RegisterItemHandle(
            serverHandle,
            itemHandle,
            itemDefinition,
            string.Empty,
            hasItemContext: false);

        return itemHandle;
    }

    public int AddItem2(
        int serverHandle,
        string itemDefinition,
        string itemContext)
    {
        ThrowIfDisposed();

        int itemHandle = mxAccessServer.AddItem2(serverHandle, itemDefinition, itemContext);
        handleRegistry.RegisterItemHandle(
            serverHandle,
            itemHandle,
            itemDefinition,
            itemContext,
            hasItemContext: true);

        return itemHandle;
    }

    public void RemoveItem(
        int serverHandle,
        int itemHandle)
    {
        ThrowIfDisposed();

        mxAccessServer.RemoveItem(serverHandle, itemHandle);
        handleRegistry.RemoveItemHandle(serverHandle, itemHandle);
    }

    public void Advise(
        int serverHandle,
        int itemHandle)
    {
        ThrowIfDisposed();

        mxAccessServer.Advise(serverHandle, itemHandle);
        handleRegistry.RegisterAdviceHandle(
            serverHandle,
            itemHandle,
            MxAccessAdviceKind.Plain);
    }

    public void UnAdvise(
        int serverHandle,
        int itemHandle)
    {
        ThrowIfDisposed();

        mxAccessServer.UnAdvise(serverHandle, itemHandle);
        handleRegistry.RemoveAdviceHandles(serverHandle, itemHandle);
    }

    public void AdviseSupervisory(
        int serverHandle,
        int itemHandle)
    {
        ThrowIfDisposed();

        mxAccessServer.AdviseSupervisory(serverHandle, itemHandle);
        handleRegistry.RegisterAdviceHandle(
            serverHandle,
            itemHandle,
            MxAccessAdviceKind.Supervisory);
    }

    public MxAccessShutdownResult ShutdownGracefully()
    {
        if (disposed)
        {
            return new MxAccessShutdownResult(Array.Empty<MxAccessShutdownFailure>());
        }

        List<MxAccessShutdownFailure> failures = new();

        CleanupAdviceHandles(failures);
        CleanupItemHandles(failures);
        CleanupServerHandles(failures);
        DisposeCore(failures);

        return new MxAccessShutdownResult(failures);
    }

    public void Dispose()
    {
        if (disposed)
        {
            return;
        }

        DisposeCore(failures: null);
    }

    private void CleanupAdviceHandles(ICollection<MxAccessShutdownFailure> failures)
    {
        HashSet<long> cleanedPairs = new();
        foreach (RegisteredAdviceHandle adviceHandle in handleRegistry.AdviceHandles)
        {
            long key = CreateItemKey(adviceHandle.ServerHandle, adviceHandle.ItemHandle);
            if (!cleanedPairs.Add(key))
            {
                continue;
            }

            try
            {
                mxAccessServer.UnAdvise(adviceHandle.ServerHandle, adviceHandle.ItemHandle);
                handleRegistry.RemoveAdviceHandles(adviceHandle.ServerHandle, adviceHandle.ItemHandle);
            }
            catch (Exception exception)
            {
                failures.Add(new MxAccessShutdownFailure(
                    nameof(UnAdvise),
                    adviceHandle.ServerHandle,
                    adviceHandle.ItemHandle,
                    exception));
            }
        }
    }

    private void CleanupItemHandles(ICollection<MxAccessShutdownFailure> failures)
    {
        foreach (RegisteredItemHandle itemHandle in handleRegistry.ItemHandles)
        {
            try
            {
                mxAccessServer.RemoveItem(itemHandle.ServerHandle, itemHandle.ItemHandle);
                handleRegistry.RemoveItemHandle(itemHandle.ServerHandle, itemHandle.ItemHandle);
            }
            catch (Exception exception)
            {
                failures.Add(new MxAccessShutdownFailure(
                    nameof(RemoveItem),
                    itemHandle.ServerHandle,
                    itemHandle.ItemHandle,
                    exception));
            }
        }
    }

    private void CleanupServerHandles(ICollection<MxAccessShutdownFailure> failures)
    {
        foreach (RegisteredServerHandle serverHandle in handleRegistry.ServerHandles)
        {
            try
            {
                mxAccessServer.Unregister(serverHandle.ServerHandle);
                handleRegistry.UnregisterServerHandle(serverHandle.ServerHandle);
            }
            catch (Exception exception)
            {
                failures.Add(new MxAccessShutdownFailure(
                    nameof(Unregister),
                    serverHandle.ServerHandle,
                    itemHandle: null,
                    exception));
            }
        }
    }

    private static long CreateItemKey(
        int serverHandle,
        int itemHandle)
    {
        return ((long)serverHandle << 32) | (uint)itemHandle;
    }

    private void DisposeCore(ICollection<MxAccessShutdownFailure>? failures)
    {
        try
        {
            eventSink.Detach();
        }
        catch (Exception exception) when (failures is not null)
        {
            failures.Add(new MxAccessShutdownFailure(
                "DetachEvents",
                serverHandle: null,
                itemHandle: null,
                exception));
        }

        try
        {
            if (Marshal.IsComObject(mxAccessComObject))
            {
                Marshal.FinalReleaseComObject(mxAccessComObject);
            }
        }
        catch (Exception exception) when (failures is not null)
        {
            failures.Add(new MxAccessShutdownFailure(
                "ReleaseComObject",
                serverHandle: null,
                itemHandle: null,
                exception));
        }

        disposed = true;
    }

    private void ThrowIfDisposed()
    {
        if (disposed)
        {
            throw new ObjectDisposedException(nameof(MxAccessSession));
        }
    }
}