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

namespace MxGateway.Worker.MxAccess;

public sealed class MxAccessCommandExecutor : IStaCommandExecutor
{
    private readonly MxAccessSession session;
    private readonly VariantConverter variantConverter;

    public MxAccessCommandExecutor(MxAccessSession session)
        : this(session, new VariantConverter())
    {
    }

    public MxAccessCommandExecutor(
        MxAccessSession session,
        VariantConverter variantConverter)
    {
        this.session = session ?? throw new ArgumentNullException(nameof(session));
        this.variantConverter = variantConverter ?? throw new ArgumentNullException(nameof(variantConverter));
    }

    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),
            _ => 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 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 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,
        };
    }
}