dotnet/src/webdriver/BiDi/BiDiOptionsBuilder.cs

// <copyright file="BiDiOptionsBuilder.cs" company="Selenium Committers">
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//
//   http://www.apache.org/licenses/LICENSE-2.0
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using System.Net.WebSockets;

namespace OpenQA.Selenium.BiDi;

/// <summary>
/// Provides a fluent API for configuring BiDi connection options,
/// such as the underlying transport mechanism.
/// </summary>
public sealed class BiDiOptionsBuilder
{
    private static readonly Func<Uri, CancellationToken, Task<ITransport>> DefaultTransportFactory =
        (uri, ct) => WebSocketTransport.ConnectAsync(uri, null, ct);

    internal Func<Uri, CancellationToken, Task<ITransport>> TransportFactory { get; private set; }
        = DefaultTransportFactory;

    /// <summary>
    /// Configures the BiDi connection to use a WebSocket transport.
    /// </summary>
    /// <remarks>
    /// WebSocket is the default transport; calling this method is only necessary
    /// when you need to customize the underlying <see cref="ClientWebSocketOptions"/>
    /// (e.g., to set headers, proxy, or certificates).
    /// </remarks>
    /// <param name="configure">An optional action to configure the <see cref="ClientWebSocketOptions"/> before connecting.</param>
    /// <returns>The current <see cref="BiDiOptionsBuilder"/> instance for chaining.</returns>
    public BiDiOptionsBuilder UseWebSocket(Action<ClientWebSocketOptions>? configure = null)
    {
        TransportFactory = (uri, ct) => WebSocketTransport.ConnectAsync(uri, configure, ct);
        return this;
    }

    /// <summary>
    /// Composes a transport factory into the current transport pipeline.
    /// </summary>
    /// <remarks>
    /// The <paramref name="next"/> callback receives the current transport factory and returns
    /// the next factory in the chain. BiDi takes ownership of the transport instance returned by
    /// the final factory and will dispose it.
    /// </remarks>
    /// <param name="next">A callback that composes a new transport factory from the current one.</param>
    /// <returns>The current <see cref="BiDiOptionsBuilder"/> instance for chaining.</returns>
    public BiDiOptionsBuilder UseTransport(Func<Func<Uri, CancellationToken, Task<ITransport>>, Func<Uri, CancellationToken, Task<ITransport>>> next)
    {
        ArgumentNullException.ThrowIfNull(next);

        var factory = next(TransportFactory)
            ?? throw new InvalidOperationException("The transport factory decorator must return a non-null factory.");

        TransportFactory = factory;
        return this;
    }
}