// Copyright (c) Microsoft. All rights reserved.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Agents.AI.Workflows.Execution;
using Microsoft.Shared.Diagnostics;
using CatchAllF =
    System.Func<
        Microsoft.Agents.AI.Workflows.PortableValue, // message
        Microsoft.Agents.AI.Workflows.IWorkflowContext, // context
        System.Threading.CancellationToken, // cancellation
        System.Threading.Tasks.ValueTask<Microsoft.Agents.AI.Workflows.Execution.CallResult>
    >;
using MessageHandlerF =
    System.Func<
        object, // message
        Microsoft.Agents.AI.Workflows.IWorkflowContext, // context
        System.Threading.CancellationToken, // cancellation
        System.Threading.Tasks.ValueTask<Microsoft.Agents.AI.Workflows.Execution.CallResult>
    >;

using PortHandlerF =
    System.Func<
        Microsoft.Agents.AI.Workflows.ExternalResponse, // message
        Microsoft.Agents.AI.Workflows.IWorkflowContext, // context
        System.Threading.CancellationToken, // cancellation
        System.Threading.Tasks.ValueTask<Microsoft.Agents.AI.Workflows.ExternalResponse?>
    >;

namespace Microsoft.Agents.AI.Workflows;

/// <summary>
/// Provides a builder for configuring message type handlers for an <see cref="Executor"/>.
/// </summary>
public class RouteBuilder
{
    private readonly IExternalRequestContext? _externalRequestContext;
    private readonly Dictionary<Type, MessageHandlerF> _typedHandlers = [];
    private readonly Dictionary<Type, Type> _outputTypes = [];
    private readonly Dictionary<string, PortHandlerF> _portHandlers = [];
    private CatchAllF? _catchAll;

    internal RouteBuilder(IExternalRequestContext? externalRequestContext)
    {
        this._externalRequestContext = externalRequestContext;
    }

    internal RouteBuilder AddHandlerInternal(Type messageType, MessageHandlerF handler, Type? outputType, bool overwrite = false)
    {
        Throw.IfNull(messageType);
        Throw.IfNull(handler);

        if (messageType == typeof(PortableValue))
        {
            throw new InvalidOperationException("Cannot register a handler for PortableValue. Use AddCatchAll() instead.");
        }

        Debug.Assert(typeof(CallResult) != outputType, "Must not double-wrap message handlers in the RouteBuilder. " +
            "Use AddHandlerInternal() or do not wrap user-provided handler.");

        // Overwrite must be false if the type is not registered. Overwrite must be true if the type is registered.
        if (this._typedHandlers.ContainsKey(messageType) == overwrite)
        {
            this._typedHandlers[messageType] = handler;

            if (outputType is not null)
            {
                this._outputTypes[messageType] = outputType;
            }
            else
            {
                this._outputTypes.Remove(messageType);
            }
        }
        else if (overwrite)
        {
            // overwrite is true, but the type is not registered.
            throw new ArgumentException($"A handler for message type {messageType.FullName} has not yet been registered (overwrite = true).");
        }
        else if (!overwrite)
        {
            throw new ArgumentException($"A handler for message type {messageType.FullName} is already registered (overwrite = false).");
        }

        return this;
    }

    internal RouteBuilder AddHandlerUntyped(Type type, Func<object, IWorkflowContext, CancellationToken, ValueTask> handler, bool overwrite = false)
    {
        Throw.IfNull(handler);

        return this.AddHandlerInternal(type, WrappedHandlerAsync, outputType: null, overwrite);

        async ValueTask<CallResult> WrappedHandlerAsync(object message, IWorkflowContext context, CancellationToken cancellationToken)
        {
            await handler.Invoke(message, context, cancellationToken).ConfigureAwait(false);
            return CallResult.ReturnVoid();
        }
    }

    internal RouteBuilder AddHandlerUntyped<TResult>(Type type, Func<object, IWorkflowContext, CancellationToken, ValueTask<TResult>> handler, bool overwrite = false)
    {
        Throw.IfNull(handler);

        return this.AddHandlerInternal(type, WrappedHandlerAsync, outputType: typeof(TResult), overwrite);

        async ValueTask<CallResult> WrappedHandlerAsync(object message, IWorkflowContext context, CancellationToken cancellationToken)
        {
            TResult result = await handler.Invoke(message, context, cancellationToken).ConfigureAwait(false);
            return CallResult.ReturnResult(result);
        }
    }

    /// <summary>
    /// Registers a port and associated handler for external requests originating from the executor. This generates a PortBinding that can be used to
    /// submit requests through to the workflow Run call.
    /// </summary>
    /// <typeparam name="TRequest">The type of request messages that will be sent through this port.</typeparam>
    /// <typeparam name="TResponse">The type of response messages that will be sent through this port.</typeparam>
    /// <param name="id">A unique identifier for the port.</param>
    /// <param name="handler">A delegate that processes messages of type <typeparamref name="TResponse"/> within the workflow context. The
    /// delegate is invoked for each incoming response to requests through this port.</param>
    /// <param name="portBinding">A <see cref="PortBinding"/> representing this port registration providing a means to submit requests.</param>
    /// <param name="overwrite">Set <see langword="true"/> to replace an existing handler for the specified response; if a port with this id is not
    /// this will throw. If set to <see langword="false"/> and a handler is registered, this will throw. </param>
    /// <returns>The current <see cref="RouteBuilder"/> instance, enabling fluent configuration of additional handlers or route
    /// options.</returns>
    /// <exception cref="InvalidOperationException">If a handler is already registered for the specified type, and overwrite is set
    /// to <see langword="false"/>, or if a handler is not already registered, but overwrite is set to <see langword="true"/>.</exception>
    internal RouteBuilder AddPortHandler<TRequest, TResponse>(string id, Func<TResponse, IWorkflowContext, CancellationToken, ValueTask> handler, out PortBinding portBinding, bool overwrite = false)
    {
        if (this._externalRequestContext == null)
        {
            throw new InvalidOperationException("An external request context is required to register port handlers.");
        }

        RequestPort port = RequestPort.Create<TRequest, TResponse>(id);
        IExternalRequestSink sink = this._externalRequestContext!.RegisterPort(port);
        portBinding = new(port, sink);

        if (this._portHandlers.ContainsKey(id) == overwrite)
        {
            this._portHandlers[id] = InvokeHandlerAsync;
        }
        else if (overwrite)
        {
            throw new InvalidOperationException($"A handler for port id {id} is not registered (overwrite = true).");
        }
        else
        {
            throw new InvalidOperationException($"A handler for port id {id} is already registered (overwrite = false).");
        }

        return this;

        async ValueTask<ExternalResponse?> InvokeHandlerAsync(ExternalResponse response, IWorkflowContext context, CancellationToken cancellationToken)
        {
            if (!response.TryGetDataAs(out TResponse? typedResponse))
            {
                throw new InvalidOperationException($"Received response data is not of expected type {typeof(TResponse).FullName} for port {port.Id}.");
            }

            await handler(typedResponse, context, cancellationToken).ConfigureAwait(false);
            return response;
        }
    }

    /// <summary>
    /// Registers a handler for messages of the specified input type in the workflow route.
    /// </summary>
    /// <remarks>If a handler for the specified input type already exists and <paramref name="overwrite"/> is
    /// <see langword="false"/>, the existing handler will not be replaced. Handlers are invoked asynchronously and are
    /// expected to complete their processing before the workflow continues.</remarks>
    /// <typeparam name="TInput"></typeparam>
    /// <param name="handler">A delegate that processes messages of type <typeparamref name="TInput"/> within the workflow context. The
    /// delegate is invoked for each incoming message of the specified type.</param>
    /// <param name="overwrite">Set <see langword="true"/> to replace an existing handler for the specified input type; if no
    /// handler is registered will throw. If set to <see langword="false"/> and a handler is registered, this will throw. </param>
    /// <returns>The current <see cref="RouteBuilder"/> instance, enabling fluent configuration of additional handlers or route
    /// options.</returns>
    /// <exception cref="InvalidOperationException">If a handler is already registered for the specified type, and overwrite is set
    /// to <see langword="false"/>, or if a handler is not already registered, but overwrite is set to <see langword="true"/>.</exception>
    public RouteBuilder AddHandler<TInput>(Action<TInput, IWorkflowContext, CancellationToken> handler, bool overwrite = false)
    {
        Throw.IfNull(handler);

        return this.AddHandlerInternal(typeof(TInput), WrappedHandlerAsync, outputType: null, overwrite);

        async ValueTask<CallResult> WrappedHandlerAsync(object message, IWorkflowContext context, CancellationToken cancellationToken)
        {
            handler.Invoke((TInput)message, context, cancellationToken);
            return CallResult.ReturnVoid();
        }
    }

    /// <summary>
    /// Registers a handler for messages of the specified input type in the workflow route.
    /// </summary>
    /// <remarks>If a handler for the specified input type already exists and <paramref name="overwrite"/> is
    /// <see langword="false"/>, the existing handler will not be replaced. Handlers are invoked asynchronously and are
    /// expected to complete their processing before the workflow continues.</remarks>
    /// <typeparam name="TInput"></typeparam>
    /// <param name="handler">A delegate that processes messages of type <typeparamref name="TInput"/> within the workflow context. The
    /// delegate is invoked for each incoming message of the specified type.</param>
    /// <param name="overwrite">Set <see langword="true"/> to replace an existing handler for the specified input type; if no
    /// handler is registered will throw. If set to <see langword="false"/> and a handler is registered, this will throw. </param>
    /// <returns>The current <see cref="RouteBuilder"/> instance, enabling fluent configuration of additional handlers or route
    /// options.</returns>
    /// <exception cref="InvalidOperationException">If a handler is already registered for the specified type, and overwrite is set
    /// to <see langword="false"/>, or if a handler is not already registered, but overwrite is set to <see langword="true"/>.</exception>
    public RouteBuilder AddHandler<TInput>(Action<TInput, IWorkflowContext> handler, bool overwrite = false)
    {
        Throw.IfNull(handler);

        return this.AddHandlerInternal(typeof(TInput), WrappedHandlerAsync, outputType: null, overwrite);

        async ValueTask<CallResult> WrappedHandlerAsync(object message, IWorkflowContext context, CancellationToken cancellationToken)
        {
            handler.Invoke((TInput)message, context);
            return CallResult.ReturnVoid();
        }
    }

    /// <summary>
    /// Registers a handler for messages of the specified input type in the workflow route.
    /// </summary>
    /// <remarks>If a handler for the specified input type already exists and <paramref name="overwrite"/> is
    /// <see langword="false"/>, the existing handler will not be replaced. Handlers are invoked asynchronously and are
    /// expected to complete their processing before the workflow continues.</remarks>
    /// <typeparam name="TInput"></typeparam>
    /// <param name="handler">A delegate that processes messages of type <typeparamref name="TInput"/> within the workflow context. The
    /// delegate is invoked for each incoming message of the specified type.</param>
    /// <param name="overwrite">Set <see langword="true"/> to replace an existing handler for the specified input type; if no
    /// handler is registered will throw. If set to <see langword="false"/> and a handler is registered, this will throw. </param>
    /// <returns>The current <see cref="RouteBuilder"/> instance, enabling fluent configuration of additional handlers or route
    /// options.</returns>
    /// <exception cref="InvalidOperationException">If a handler is already registered for the specified type, and overwrite is set
    /// to <see langword="false"/>, or if a handler is not already registered, but overwrite is set to <see langword="true"/>.</exception>
    public RouteBuilder AddHandler<TInput>(Func<TInput, IWorkflowContext, CancellationToken, ValueTask> handler, bool overwrite = false)
    {
        Throw.IfNull(handler);

        return this.AddHandlerInternal(typeof(TInput), WrappedHandlerAsync, outputType: null, overwrite);

        async ValueTask<CallResult> WrappedHandlerAsync(object message, IWorkflowContext context, CancellationToken cancellationToken)
        {
            await handler.Invoke((TInput)message, context, cancellationToken).ConfigureAwait(false);
            return CallResult.ReturnVoid();
        }
    }

    /// <summary>
    /// Registers a handler for messages of the specified input type in the workflow route.
    /// </summary>
    /// <remarks>If a handler for the specified input type already exists and <paramref name="overwrite"/> is
    /// <see langword="false"/>, the existing handler will not be replaced. Handlers are invoked asynchronously and are
    /// expected to complete their processing before the workflow continues.</remarks>
    /// <typeparam name="TInput"></typeparam>
    /// <param name="handler">A delegate that processes messages of type <typeparamref name="TInput"/> within the workflow context. The
    /// delegate is invoked for each incoming message of the specified type.</param>
    /// <param name="overwrite">Set <see langword="true"/> to replace an existing handler for the specified input type; if no
    /// handler is registered will throw. If set to <see langword="false"/> and a handler is registered, this will throw. </param>
    /// <returns>The current <see cref="RouteBuilder"/> instance, enabling fluent configuration of additional handlers or route
    /// options.</returns>
    /// <exception cref="InvalidOperationException">If a handler is already registered for the specified type, and overwrite is set
    /// to <see langword="false"/>, or if a handler is not already registered, but overwrite is set to <see langword="true"/>.</exception>
    public RouteBuilder AddHandler<TInput>(Func<TInput, IWorkflowContext, ValueTask> handler, bool overwrite = false)
    {
        Throw.IfNull(handler);

        return this.AddHandlerInternal(typeof(TInput), WrappedHandlerAsync, outputType: null, overwrite);

        async ValueTask<CallResult> WrappedHandlerAsync(object message, IWorkflowContext context, CancellationToken cancellationToken)
        {
            await handler.Invoke((TInput)message, context).ConfigureAwait(false);
            return CallResult.ReturnVoid();
        }
    }

    /// <summary>
    /// Registers a handler function for messages of the specified input type in the workflow route.
    /// </summary>
    /// <remarks>If a handler for the given input type already exists, setting <paramref name="overwrite"/> to
    /// <see langword="true"/> will replace the existing handler; otherwise, an exception may be thrown. The handler
    /// receives the input message and workflow context, and returns a result asynchronously.</remarks>
    /// <typeparam name="TInput">The type of input message the handler will process.</typeparam>
    /// <typeparam name="TResult">The type of result produced by the handler.</typeparam>
    /// <param name="handler">A function that processes messages of type <typeparamref name="TInput"/> within the workflow context and returns
    /// a <see cref="ValueTask{TResult}"/> representing the asynchronous result.</param>
    /// <param name="overwrite">Set <see langword="true"/> to replace an existing handler for the specified input type; if no
    /// handler is registered will throw. If set to <see langword="false"/> and a handler is registered, this will throw. </param>
    /// <returns>The current <see cref="RouteBuilder"/> instance, enabling fluent configuration of workflow routes.</returns>
    /// <exception cref="InvalidOperationException">If a handler is already registered for the specified type, and overwrite is set
    /// to <see langword="false"/>, or if a handler is not already registered, but overwrite is set to <see langword="true"/>.</exception>
    public RouteBuilder AddHandler<TInput, TResult>(Func<TInput, IWorkflowContext, CancellationToken, TResult> handler, bool overwrite = false)
    {
        Throw.IfNull(handler);

        return this.AddHandlerInternal(typeof(TInput), WrappedHandlerAsync, outputType: typeof(TResult), overwrite);

        async ValueTask<CallResult> WrappedHandlerAsync(object message, IWorkflowContext context, CancellationToken cancellationToken)
        {
            TResult result = handler.Invoke((TInput)message, context, cancellationToken);
            return CallResult.ReturnResult(result);
        }
    }

    /// <summary>
    /// Registers a handler function for messages of the specified input type in the workflow route.
    /// </summary>
    /// <remarks>If a handler for the given input type already exists, setting <paramref name="overwrite"/> to
    /// <see langword="true"/> will replace the existing handler; otherwise, an exception may be thrown. The handler
    /// receives the input message and workflow context, and returns a result asynchronously.</remarks>
    /// <typeparam name="TInput">The type of input message the handler will process.</typeparam>
    /// <typeparam name="TResult">The type of result produced by the handler.</typeparam>
    /// <param name="handler">A function that processes messages of type <typeparamref name="TInput"/> within the workflow context and returns
    /// a <see cref="ValueTask{TResult}"/> representing the asynchronous result.</param>
    /// <param name="overwrite">Set <see langword="true"/> to replace an existing handler for the specified input type; if no
    /// handler is registered will throw. If set to <see langword="false"/> and a handler is registered, this will throw. </param>
    /// <returns>The current <see cref="RouteBuilder"/> instance, enabling fluent configuration of workflow routes.</returns>
    /// <exception cref="InvalidOperationException">If a handler is already registered for the specified type, and overwrite is set
    /// to <see langword="false"/>, or if a handler is not already registered, but overwrite is set to <see langword="true"/>.</exception>
    public RouteBuilder AddHandler<TInput, TResult>(Func<TInput, IWorkflowContext, TResult> handler, bool overwrite = false)
    {
        Throw.IfNull(handler);

        return this.AddHandlerInternal(typeof(TInput), WrappedHandlerAsync, outputType: typeof(TResult), overwrite);

        async ValueTask<CallResult> WrappedHandlerAsync(object message, IWorkflowContext context, CancellationToken cancellationToken)
        {
            TResult result = handler.Invoke((TInput)message, context);
            return CallResult.ReturnResult(result);
        }
    }

    /// <summary>
    /// Registers a handler function for messages of the specified input type in the workflow route.
    /// </summary>
    /// <remarks>If a handler for the given input type already exists, setting <paramref name="overwrite"/> to
    /// <see langword="true"/> will replace the existing handler; otherwise, an exception may be thrown. The handler
    /// receives the input message and workflow context, and returns a result asynchronously.</remarks>
    /// <typeparam name="TInput">The type of input message the handler will process.</typeparam>
    /// <typeparam name="TResult">The type of result produced by the handler.</typeparam>
    /// <param name="handler">A function that processes messages of type <typeparamref name="TInput"/> within the workflow context and returns
    /// a <see cref="ValueTask{TResult}"/> representing the asynchronous result.</param>
    /// <param name="overwrite">Set <see langword="true"/> to replace an existing handler for the specified input type; if no
    /// handler is registered will throw. If set to <see langword="false"/> and a handler is registered, this will throw. </param>
    /// <returns>The current <see cref="RouteBuilder"/> instance, enabling fluent configuration of workflow routes.</returns>
    /// <exception cref="InvalidOperationException">If a handler is already registered for the specified type, and overwrite is set
    /// to <see langword="false"/>, or if a handler is not already registered, but overwrite is set to <see langword="true"/>.</exception>
    public RouteBuilder AddHandler<TInput, TResult>(Func<TInput, IWorkflowContext, CancellationToken, ValueTask<TResult>> handler, bool overwrite = false)
    {
        Throw.IfNull(handler);

        return this.AddHandlerInternal(typeof(TInput), WrappedHandlerAsync, outputType: typeof(TResult), overwrite);

        async ValueTask<CallResult> WrappedHandlerAsync(object message, IWorkflowContext context, CancellationToken cancellationToken)
        {
            TResult result = await handler((TInput)message, context, cancellationToken).ConfigureAwait(false);
            return CallResult.ReturnResult(result);
        }
    }

    /// <summary>
    /// Registers a handler function for messages of the specified input type in the workflow route.
    /// </summary>
    /// <remarks>If a handler for the given input type already exists, setting <paramref name="overwrite"/> to
    /// <see langword="true"/> will replace the existing handler; otherwise, an exception may be thrown. The handler
    /// receives the input message and workflow context, and returns a result asynchronously.</remarks>
    /// <typeparam name="TInput">The type of input message the handler will process.</typeparam>
    /// <typeparam name="TResult">The type of result produced by the handler.</typeparam>
    /// <param name="handler">A function that processes messages of type <typeparamref name="TInput"/> within the workflow context and returns
    /// a <see cref="ValueTask{TResult}"/> representing the asynchronous result.</param>
    /// <param name="overwrite">Set <see langword="true"/> to replace an existing handler for the specified input type; if no
    /// handler is registered will throw. If set to <see langword="false"/> and a handler is registered, this will throw. </param>
    /// <returns>The current <see cref="RouteBuilder"/> instance, enabling fluent configuration of workflow routes.</returns>
    /// <exception cref="InvalidOperationException">If a handler is already registered for the specified type, and overwrite is set
    /// to <see langword="false"/>, or if a handler is not already registered, but overwrite is set to <see langword="true"/>.</exception>
    public RouteBuilder AddHandler<TInput, TResult>(Func<TInput, IWorkflowContext, ValueTask<TResult>> handler, bool overwrite = false)
    {
        Throw.IfNull(handler);

        return this.AddHandlerInternal(typeof(TInput), WrappedHandlerAsync, outputType: typeof(TResult), overwrite);

        async ValueTask<CallResult> WrappedHandlerAsync(object message, IWorkflowContext context, CancellationToken cancellationToken)
        {
            TResult result = await handler.Invoke((TInput)message, context).ConfigureAwait(false);
            return CallResult.ReturnResult(result);
        }
    }

    private RouteBuilder AddCatchAll(CatchAllF handler, bool overwrite = false)
    {
        if (!overwrite && this._catchAll != null)
        {
            throw new InvalidOperationException("A catch-all is already registered (overwrite = false).");
        }

        this._catchAll = handler;

        return this;
    }

    /// <summary>
    /// Register a handler function as a catch-all handler: It will be used if not type-matching handler is registered.
    /// </summary>
    /// <remarks>If a catch-all handler for already exists, setting <paramref name="overwrite"/> to <see langword="true"/>
    /// will replace the existing handler; otherwise, an exception may be thrown. The handler receives the input message
    /// wrapped as <see cref="PortableValue"/> and workflow context, and returns a result asynchronously.</remarks>
    /// <param name="handler">A function that processes messages wrapped as <see cref="PortableValue"/> within the
    /// workflow context. The delegate is invoked for each incoming message not otherwise handled.</param>
    /// <param name="overwrite">Set <see langword="true"/> to replace an existing handler for the specified input type; if no
    /// handler is registered will throw. If set to <see langword="false"/> and a handler is registered, this will throw. </param>
    /// <returns>The current <see cref="RouteBuilder"/> instance, enabling fluent configuration of workflow routes.</returns>
    /// <exception cref="InvalidOperationException">If a handler is already registered for the specified type, and overwrite is set
    /// to <see langword="false"/>, or if a handler is not already registered, but overwrite is set to <see langword="true"/>.</exception>
    public RouteBuilder AddCatchAll(Func<PortableValue, IWorkflowContext, CancellationToken, ValueTask> handler, bool overwrite = false)
    {
        Throw.IfNull(handler);

        return this.AddCatchAll(WrappedHandlerAsync, overwrite);

        async ValueTask<CallResult> WrappedHandlerAsync(PortableValue message, IWorkflowContext context, CancellationToken cancellationToken)
        {
            await handler.Invoke(message, context, cancellationToken).ConfigureAwait(false);
            return CallResult.ReturnVoid();
        }
    }

    /// <summary>
    /// Register a handler function as a catch-all handler: It will be used if not type-matching handler is registered.
    /// </summary>
    /// <remarks>If a catch-all handler for already exists, setting <paramref name="overwrite"/> to <see langword="true"/>
    /// will replace the existing handler; otherwise, an exception may be thrown. The handler receives the input message
    /// wrapped as <see cref="PortableValue"/> and workflow context, and returns a result asynchronously.</remarks>
    /// <param name="handler">A function that processes messages wrapped as <see cref="PortableValue"/> within the
    /// workflow context. The delegate is invoked for each incoming message not otherwise handled.</param>
    /// <param name="overwrite">Set <see langword="true"/> to replace an existing handler for the specified input type; if no
    /// handler is registered will throw. If set to <see langword="false"/> and a handler is registered, this will throw. </param>
    /// <returns>The current <see cref="RouteBuilder"/> instance, enabling fluent configuration of workflow routes.</returns>
    /// <exception cref="InvalidOperationException">If a handler is already registered for the specified type, and overwrite is set
    /// to <see langword="false"/>, or if a handler is not already registered, but overwrite is set to <see langword="true"/>.</exception>
    public RouteBuilder AddCatchAll(Func<PortableValue, IWorkflowContext, ValueTask> handler, bool overwrite = false)
    {
        Throw.IfNull(handler);

        return this.AddCatchAll(WrappedHandlerAsync, overwrite);

        async ValueTask<CallResult> WrappedHandlerAsync(PortableValue message, IWorkflowContext context, CancellationToken cancellationToken)
        {
            await handler.Invoke(message, context).ConfigureAwait(false);
            return CallResult.ReturnVoid();
        }
    }

    /// <summary>
    /// Register a handler function as a catch-all handler: It will be used if not type-matching handler is registered.
    /// </summary>
    /// <remarks>If a catch-all handler for already exists, setting <paramref name="overwrite"/> to <see langword="true"/>
    /// will replace the existing handler; otherwise, an exception may be thrown. The handler receives the input message
    /// wrapped as <see cref="PortableValue"/> and workflow context, and returns a result asynchronously.</remarks>
    /// <param name="handler">A function that processes messages wrapped as <see cref="PortableValue"/> within the
    /// workflow context and returns a <see cref="ValueTask{TResult}"/> representing the asynchronous result.</param>
    /// <param name="overwrite">Set <see langword="true"/> to replace an existing handler for the specified input type; if no
    /// handler is registered will throw. If set to <see langword="false"/> and a handler is registered, this will throw. </param>
    /// <returns>The current <see cref="RouteBuilder"/> instance, enabling fluent configuration of workflow routes.</returns>
    /// <exception cref="InvalidOperationException">If a handler is already registered for the specified type, and overwrite is set
    /// to <see langword="false"/>, or if a handler is not already registered, but overwrite is set to <see langword="true"/>.</exception>
    public RouteBuilder AddCatchAll<TResult>(Func<PortableValue, IWorkflowContext, CancellationToken, ValueTask<TResult>> handler, bool overwrite = false)
    {
        Throw.IfNull(handler);

        return this.AddCatchAll(WrappedHandlerAsync, overwrite);

        async ValueTask<CallResult> WrappedHandlerAsync(PortableValue message, IWorkflowContext context, CancellationToken cancellationToken)
        {
            TResult result = await handler.Invoke(message, context, cancellationToken).ConfigureAwait(false);
            return CallResult.ReturnResult(result);
        }
    }

    /// <summary>
    /// Register a handler function as a catch-all handler: It will be used if not type-matching handler is registered.
    /// </summary>
    /// <remarks>If a catch-all handler for already exists, setting <paramref name="overwrite"/> to <see langword="true"/>
    /// will replace the existing handler; otherwise, an exception may be thrown. The handler receives the input message
    /// wrapped as <see cref="PortableValue"/> and workflow context, and returns a result asynchronously.</remarks>
    /// <param name="handler">A function that processes messages wrapped as <see cref="PortableValue"/> within the
    /// workflow context and returns a <see cref="ValueTask{TResult}"/> representing the asynchronous result.</param>
    /// <param name="overwrite">Set <see langword="true"/> to replace an existing handler for the specified input type; if no
    /// handler is registered will throw. If set to <see langword="false"/> and a handler is registered, this will throw. </param>
    /// <returns>The current <see cref="RouteBuilder"/> instance, enabling fluent configuration of workflow routes.</returns>
    /// <exception cref="InvalidOperationException">If a handler is already registered for the specified type, and overwrite is set
    /// to <see langword="false"/>, or if a handler is not already registered, but overwrite is set to <see langword="true"/>.</exception>
    public RouteBuilder AddCatchAll<TResult>(Func<PortableValue, IWorkflowContext, ValueTask<TResult>> handler, bool overwrite = false)
    {
        Throw.IfNull(handler);

        return this.AddCatchAll(WrappedHandlerAsync, overwrite);

        async ValueTask<CallResult> WrappedHandlerAsync(PortableValue message, IWorkflowContext context, CancellationToken cancellationToken)
        {
            TResult result = await handler.Invoke(message, context).ConfigureAwait(false);
            return CallResult.ReturnResult(result);
        }
    }

    /// <summary>
    /// Register a handler function as a catch-all handler: It will be used if not type-matching handler is registered.
    /// </summary>
    /// <remarks>If a catch-all handler for already exists, setting <paramref name="overwrite"/> to <see langword="true"/>
    /// will replace the existing handler; otherwise, an exception may be thrown. The handler receives the input message
    /// wrapped as <see cref="PortableValue"/> and workflow context, and returns a result asynchronously.</remarks>
    /// <param name="handler">A function that processes messages wrapped as <see cref="PortableValue"/> within the
    /// workflow context. The delegate is invoked for each incoming message not otherwise handled.</param>
    /// <param name="overwrite">Set <see langword="true"/> to replace an existing handler for the specified input type; if no
    /// handler is registered will throw. If set to <see langword="false"/> and a handler is registered, this will throw. </param>
    /// <returns>The current <see cref="RouteBuilder"/> instance, enabling fluent configuration of workflow routes.</returns>
    /// <exception cref="InvalidOperationException">If a handler is already registered for the specified type, and overwrite is set
    /// to <see langword="false"/>, or if a handler is not already registered, but overwrite is set to <see langword="true"/>.</exception>
    public RouteBuilder AddCatchAll(Action<PortableValue, IWorkflowContext, CancellationToken> handler, bool overwrite = false)
    {
        Throw.IfNull(handler);

        return this.AddCatchAll(WrappedHandlerAsync, overwrite);

        ValueTask<CallResult> WrappedHandlerAsync(PortableValue message, IWorkflowContext ctx, CancellationToken cancellationToken)
        {
            handler.Invoke(message, ctx, cancellationToken);
            return new(CallResult.ReturnVoid());
        }
    }

    /// <summary>
    /// Register a handler function as a catch-all handler: It will be used if not type-matching handler is registered.
    /// </summary>
    /// <remarks>If a catch-all handler for already exists, setting <paramref name="overwrite"/> to <see langword="true"/>
    /// will replace the existing handler; otherwise, an exception may be thrown. The handler receives the input message
    /// wrapped as <see cref="PortableValue"/> and workflow context, and returns a result asynchronously.</remarks>
    /// <param name="handler">A function that processes messages wrapped as <see cref="PortableValue"/> within the
    /// workflow context. The delegate is invoked for each incoming message not otherwise handled.</param>
    /// <param name="overwrite">Set <see langword="true"/> to replace an existing handler for the specified input type; if no
    /// handler is registered will throw. If set to <see langword="false"/> and a handler is registered, this will throw. </param>
    /// <returns>The current <see cref="RouteBuilder"/> instance, enabling fluent configuration of workflow routes.</returns>
    /// <exception cref="InvalidOperationException">If a handler is already registered for the specified type, and overwrite is set
    /// to <see langword="false"/>, or if a handler is not already registered, but overwrite is set to <see langword="true"/>.</exception>
    public RouteBuilder AddCatchAll(Action<PortableValue, IWorkflowContext> handler, bool overwrite = false)
    {
        Throw.IfNull(handler);

        return this.AddCatchAll(WrappedHandlerAsync, overwrite);

        ValueTask<CallResult> WrappedHandlerAsync(PortableValue message, IWorkflowContext ctx, CancellationToken cancellationToken)
        {
            handler.Invoke(message, ctx);
            return new(CallResult.ReturnVoid());
        }
    }

    /// <summary>
    /// Register a handler function as a catch-all handler: It will be used if not type-matching handler is registered.
    /// </summary>
    /// <remarks>If a catch-all handler for already exists, setting <paramref name="overwrite"/> to <see langword="true"/>
    /// will replace the existing handler; otherwise, an exception may be thrown. The handler receives the input message
    /// wrapped as <see cref="PortableValue"/> and workflow context, and returns a result asynchronously.</remarks>
    /// <param name="handler">A function that processes messages wrapped as <see cref="PortableValue"/> within the
    /// workflow context and returns a <see cref="ValueTask{TResult}"/> representing the asynchronous result.</param>
    /// <param name="overwrite">Set <see langword="true"/> to replace an existing handler for the specified input type; if no
    /// handler is registered will throw. If set to <see langword="false"/> and a handler is registered, this will throw. </param>
    /// <returns>The current <see cref="RouteBuilder"/> instance, enabling fluent configuration of workflow routes.</returns>
    /// <exception cref="InvalidOperationException">If a handler is already registered for the specified type, and overwrite is set
    /// to <see langword="false"/>, or if a handler is not already registered, but overwrite is set to <see langword="true"/>.</exception>
    public RouteBuilder AddCatchAll<TResult>(Func<PortableValue, IWorkflowContext, CancellationToken, TResult> handler, bool overwrite = false)
    {
        Throw.IfNull(handler);

        return this.AddCatchAll(WrappedHandlerAsync, overwrite);

        ValueTask<CallResult> WrappedHandlerAsync(PortableValue message, IWorkflowContext context, CancellationToken cancellationToken)
        {
            TResult result = handler.Invoke(message, context, cancellationToken);
            return new(CallResult.ReturnResult(result));
        }
    }

    /// <summary>
    /// Register a handler function as a catch-all handler: It will be used if not type-matching handler is registered.
    /// </summary>
    /// <remarks>If a catch-all handler for already exists, setting <paramref name="overwrite"/> to <see langword="true"/>
    /// will replace the existing handler; otherwise, an exception may be thrown. The handler receives the input message
    /// wrapped as <see cref="PortableValue"/> and workflow context, and returns a result asynchronously.</remarks>
    /// <param name="handler">A function that processes messages wrapped as <see cref="PortableValue"/> within the
    /// workflow context and returns a <see cref="ValueTask{TResult}"/> representing the asynchronous result.</param>
    /// <param name="overwrite">Set <see langword="true"/> to replace an existing handler for the specified input type; if no
    /// handler is registered will throw. If set to <see langword="false"/> and a handler is registered, this will throw. </param>
    /// <returns>The current <see cref="RouteBuilder"/> instance, enabling fluent configuration of workflow routes.</returns>
    /// <exception cref="InvalidOperationException">If a handler is already registered for the specified type, and overwrite is set
    /// to <see langword="false"/>, or if a handler is not already registered, but overwrite is set to <see langword="true"/>.</exception>
    public RouteBuilder AddCatchAll<TResult>(Func<PortableValue, IWorkflowContext, TResult> handler, bool overwrite = false)
    {
        Throw.IfNull(handler);

        return this.AddCatchAll(WrappedHandlerAsync, overwrite);

        ValueTask<CallResult> WrappedHandlerAsync(PortableValue message, IWorkflowContext context, CancellationToken cancellationToken)
        {
            TResult result = handler.Invoke(message, context);
            return new(CallResult.ReturnResult(result));
        }
    }

    private void RegisterPortHandlerRouter()
    {
        Dictionary<string, PortHandlerF> portHandlers = this._portHandlers;
        this.AddHandler<ExternalResponse, ExternalResponse?>(InvokeHandlerAsync);

        ValueTask<ExternalResponse?> InvokeHandlerAsync(ExternalResponse response, IWorkflowContext context, CancellationToken cancellationToken)
        {
            if (portHandlers.TryGetValue(response.PortInfo.PortId, out PortHandlerF? portHandler))
            {
                return portHandler(response, context, cancellationToken);
            }

            throw new InvalidOperationException($"Unknown port {response.PortInfo}");
        }
    }

    internal IEnumerable<Type> OutputTypes => this._outputTypes.Values;

    internal MessageRouter Build()
    {
        if (this._portHandlers.Count > 0)
        {
            this.RegisterPortHandlerRouter();
        }

        return new(this._typedHandlers, [.. this._outputTypes.Values], this._catchAll);
    }
}