using System;
using System.Collections.Generic;
using MxGateway.Contracts.Proto;
using MxGateway.Worker.Conversion;
using MxGateway.Worker.Sta;

namespace MxGateway.Worker.MxAccess;

/// <summary>
/// Executes MXAccess commands on an STA session.
/// </summary>
public sealed class MxAccessCommandExecutor : IStaCommandExecutor
{
    private readonly MxAccessSession session;
    private readonly VariantConverter variantConverter;

    /// <summary>
    /// Initializes a command executor with an MXAccess session.
    /// </summary>
    /// <param name="session">MXAccess session on the STA thread.</param>
    public MxAccessCommandExecutor(MxAccessSession session)
        : this(session, new VariantConverter())
    {
    }

    /// <summary>
    /// Initializes a command executor with an MXAccess session and a variant converter.
    /// </summary>
    /// <param name="session">MXAccess session on the STA thread.</param>
    /// <param name="variantConverter">Converter for MXAccess variant values to MxValue protobuf messages.</param>
    public MxAccessCommandExecutor(
        MxAccessSession session,
        VariantConverter variantConverter)
    {
        this.session = session ?? throw new ArgumentNullException(nameof(session));
        this.variantConverter = variantConverter ?? throw new ArgumentNullException(nameof(variantConverter));
    }

    /// <summary>
    /// Executes an MXAccess command and returns the reply.
    /// </summary>
    /// <param name="command">STA command to execute.</param>
    /// <returns>Command reply with result or error details.</returns>
    public MxCommandReply Execute(StaCommand command)
    {
        if (command is null)
        {
            throw new ArgumentNullException(nameof(command));
        }

        return command.Kind switch
        {
            MxCommandKind.Register => ExecuteRegister(command),
            MxCommandKind.Unregister => ExecuteUnregister(command),
            MxCommandKind.AddItem => ExecuteAddItem(command),
            MxCommandKind.AddItem2 => ExecuteAddItem2(command),
            MxCommandKind.RemoveItem => ExecuteRemoveItem(command),
            MxCommandKind.Advise => ExecuteAdvise(command),
            MxCommandKind.UnAdvise => ExecuteUnAdvise(command),
            MxCommandKind.AdviseSupervisory => ExecuteAdviseSupervisory(command),
            MxCommandKind.AddItemBulk => ExecuteAddItemBulk(command),
            MxCommandKind.AdviseItemBulk => ExecuteAdviseItemBulk(command),
            MxCommandKind.RemoveItemBulk => ExecuteRemoveItemBulk(command),
            MxCommandKind.UnAdviseItemBulk => ExecuteUnAdviseItemBulk(command),
            MxCommandKind.SubscribeBulk => ExecuteSubscribeBulk(command),
            MxCommandKind.UnsubscribeBulk => ExecuteUnsubscribeBulk(command),
            _ => CreateInvalidRequestReply(command, $"Unsupported MXAccess command kind {command.Kind}."),
        };
    }

    private MxCommandReply ExecuteRegister(StaCommand command)
    {
        if (command.Command.PayloadCase != MxCommand.PayloadOneofCase.Register)
        {
            return CreateInvalidRequestReply(command, "Register command payload is required.");
        }

        int serverHandle = session.Register(command.Command.Register.ClientName);
        MxCommandReply reply = CreateOkReply(command);
        reply.ReturnValue = variantConverter.Convert(serverHandle);
        reply.Register = new RegisterReply
        {
            ServerHandle = serverHandle,
        };

        return reply;
    }

    private MxCommandReply ExecuteUnregister(StaCommand command)
    {
        if (command.Command.PayloadCase != MxCommand.PayloadOneofCase.Unregister)
        {
            return CreateInvalidRequestReply(command, "Unregister command payload is required.");
        }

        session.Unregister(command.Command.Unregister.ServerHandle);
        return CreateOkReply(command);
    }

    private MxCommandReply ExecuteAddItem(StaCommand command)
    {
        if (command.Command.PayloadCase != MxCommand.PayloadOneofCase.AddItem)
        {
            return CreateInvalidRequestReply(command, "AddItem command payload is required.");
        }

        AddItemCommand addItemCommand = command.Command.AddItem;
        int itemHandle = session.AddItem(
            addItemCommand.ServerHandle,
            addItemCommand.ItemDefinition);

        MxCommandReply reply = CreateOkReply(command);
        reply.ReturnValue = variantConverter.Convert(itemHandle);
        reply.AddItem = new AddItemReply
        {
            ItemHandle = itemHandle,
        };

        return reply;
    }

    private MxCommandReply ExecuteAddItem2(StaCommand command)
    {
        if (command.Command.PayloadCase != MxCommand.PayloadOneofCase.AddItem2)
        {
            return CreateInvalidRequestReply(command, "AddItem2 command payload is required.");
        }

        AddItem2Command addItem2Command = command.Command.AddItem2;
        int itemHandle = session.AddItem2(
            addItem2Command.ServerHandle,
            addItem2Command.ItemDefinition,
            addItem2Command.ItemContext);

        MxCommandReply reply = CreateOkReply(command);
        reply.ReturnValue = variantConverter.Convert(itemHandle);
        reply.AddItem2 = new AddItem2Reply
        {
            ItemHandle = itemHandle,
        };

        return reply;
    }

    private MxCommandReply ExecuteRemoveItem(StaCommand command)
    {
        if (command.Command.PayloadCase != MxCommand.PayloadOneofCase.RemoveItem)
        {
            return CreateInvalidRequestReply(command, "RemoveItem command payload is required.");
        }

        RemoveItemCommand removeItemCommand = command.Command.RemoveItem;
        session.RemoveItem(
            removeItemCommand.ServerHandle,
            removeItemCommand.ItemHandle);

        return CreateOkReply(command);
    }

    private MxCommandReply ExecuteAdvise(StaCommand command)
    {
        if (command.Command.PayloadCase != MxCommand.PayloadOneofCase.Advise)
        {
            return CreateInvalidRequestReply(command, "Advise command payload is required.");
        }

        AdviseCommand adviseCommand = command.Command.Advise;
        session.Advise(
            adviseCommand.ServerHandle,
            adviseCommand.ItemHandle);

        return CreateOkReply(command);
    }

    private MxCommandReply ExecuteUnAdvise(StaCommand command)
    {
        if (command.Command.PayloadCase != MxCommand.PayloadOneofCase.UnAdvise)
        {
            return CreateInvalidRequestReply(command, "UnAdvise command payload is required.");
        }

        UnAdviseCommand unAdviseCommand = command.Command.UnAdvise;
        session.UnAdvise(
            unAdviseCommand.ServerHandle,
            unAdviseCommand.ItemHandle);

        return CreateOkReply(command);
    }

    private MxCommandReply ExecuteAdviseSupervisory(StaCommand command)
    {
        if (command.Command.PayloadCase != MxCommand.PayloadOneofCase.AdviseSupervisory)
        {
            return CreateInvalidRequestReply(command, "AdviseSupervisory command payload is required.");
        }

        AdviseSupervisoryCommand adviseSupervisoryCommand = command.Command.AdviseSupervisory;
        session.AdviseSupervisory(
            adviseSupervisoryCommand.ServerHandle,
            adviseSupervisoryCommand.ItemHandle);

        return CreateOkReply(command);
    }

    private MxCommandReply ExecuteAddItemBulk(StaCommand command)
    {
        if (command.Command.PayloadCase != MxCommand.PayloadOneofCase.AddItemBulk)
        {
            return CreateInvalidRequestReply(command, "AddItemBulk command payload is required.");
        }

        AddItemBulkCommand addItemBulkCommand = command.Command.AddItemBulk;
        return CreateBulkReply(
            command,
            session.AddItemBulk(addItemBulkCommand.ServerHandle, addItemBulkCommand.TagAddresses));
    }

    private MxCommandReply ExecuteAdviseItemBulk(StaCommand command)
    {
        if (command.Command.PayloadCase != MxCommand.PayloadOneofCase.AdviseItemBulk)
        {
            return CreateInvalidRequestReply(command, "AdviseItemBulk command payload is required.");
        }

        AdviseItemBulkCommand adviseItemBulkCommand = command.Command.AdviseItemBulk;
        return CreateBulkReply(
            command,
            session.AdviseItemBulk(adviseItemBulkCommand.ServerHandle, adviseItemBulkCommand.ItemHandles));
    }

    private MxCommandReply ExecuteRemoveItemBulk(StaCommand command)
    {
        if (command.Command.PayloadCase != MxCommand.PayloadOneofCase.RemoveItemBulk)
        {
            return CreateInvalidRequestReply(command, "RemoveItemBulk command payload is required.");
        }

        RemoveItemBulkCommand removeItemBulkCommand = command.Command.RemoveItemBulk;
        return CreateBulkReply(
            command,
            session.RemoveItemBulk(removeItemBulkCommand.ServerHandle, removeItemBulkCommand.ItemHandles));
    }

    private MxCommandReply ExecuteUnAdviseItemBulk(StaCommand command)
    {
        if (command.Command.PayloadCase != MxCommand.PayloadOneofCase.UnAdviseItemBulk)
        {
            return CreateInvalidRequestReply(command, "UnAdviseItemBulk command payload is required.");
        }

        UnAdviseItemBulkCommand unAdviseItemBulkCommand = command.Command.UnAdviseItemBulk;
        return CreateBulkReply(
            command,
            session.UnAdviseItemBulk(unAdviseItemBulkCommand.ServerHandle, unAdviseItemBulkCommand.ItemHandles));
    }

    private MxCommandReply ExecuteSubscribeBulk(StaCommand command)
    {
        if (command.Command.PayloadCase != MxCommand.PayloadOneofCase.SubscribeBulk)
        {
            return CreateInvalidRequestReply(command, "SubscribeBulk command payload is required.");
        }

        SubscribeBulkCommand subscribeBulkCommand = command.Command.SubscribeBulk;
        return CreateBulkReply(
            command,
            session.SubscribeBulk(subscribeBulkCommand.ServerHandle, subscribeBulkCommand.TagAddresses));
    }

    private MxCommandReply ExecuteUnsubscribeBulk(StaCommand command)
    {
        if (command.Command.PayloadCase != MxCommand.PayloadOneofCase.UnsubscribeBulk)
        {
            return CreateInvalidRequestReply(command, "UnsubscribeBulk command payload is required.");
        }

        UnsubscribeBulkCommand unsubscribeBulkCommand = command.Command.UnsubscribeBulk;
        return CreateBulkReply(
            command,
            session.UnsubscribeBulk(unsubscribeBulkCommand.ServerHandle, unsubscribeBulkCommand.ItemHandles));
    }

    private static MxCommandReply CreateOkReply(StaCommand command)
    {
        return new MxCommandReply
        {
            SessionId = command.SessionId,
            CorrelationId = command.CorrelationId,
            Kind = command.Kind,
            Hresult = 0,
            ProtocolStatus = new ProtocolStatus
            {
                Code = ProtocolStatusCode.Ok,
                Message = "OK",
            },
        };
    }

    private static MxCommandReply CreateBulkReply(
        StaCommand command,
        IEnumerable<SubscribeResult> results)
    {
        MxCommandReply reply = CreateOkReply(command);
        BulkSubscribeReply bulkReply = new();
        bulkReply.Results.Add(results);

        switch (command.Kind)
        {
            case MxCommandKind.AddItemBulk:
                reply.AddItemBulk = bulkReply;
                break;
            case MxCommandKind.AdviseItemBulk:
                reply.AdviseItemBulk = bulkReply;
                break;
            case MxCommandKind.RemoveItemBulk:
                reply.RemoveItemBulk = bulkReply;
                break;
            case MxCommandKind.UnAdviseItemBulk:
                reply.UnAdviseItemBulk = bulkReply;
                break;
            case MxCommandKind.SubscribeBulk:
                reply.SubscribeBulk = bulkReply;
                break;
            case MxCommandKind.UnsubscribeBulk:
                reply.UnsubscribeBulk = bulkReply;
                break;
            default:
                throw new InvalidOperationException($"Unsupported bulk command kind {command.Kind}.");
        }

        return reply;
    }

    private static MxCommandReply CreateInvalidRequestReply(
        StaCommand command,
        string message)
    {
        return new MxCommandReply
        {
            SessionId = command.SessionId,
            CorrelationId = command.CorrelationId,
            Kind = command.Kind,
            ProtocolStatus = new ProtocolStatus
            {
                Code = ProtocolStatusCode.InvalidRequest,
                Message = message,
            },
            DiagnosticMessage = message,
        };
    }
}