lmxopcua/tests/Client/ZB.MOM.WW.OtOpcUa.Client.Shared.Tests/Fakes/FakeSessionFactory.cs

using Opc.Ua;
using ZB.MOM.WW.OtOpcUa.Client.Shared.Adapters;

namespace ZB.MOM.WW.OtOpcUa.Client.Shared.Tests.Fakes;

internal sealed class FakeSessionFactory : ISessionFactory
{
    private readonly List<FakeSessionAdapter> _createdSessions = [];
    private readonly Queue<FakeSessionAdapter> _sessions = new();

    /// <summary>Gets the number of times CreateSessionAsync has been called.</summary>
    public int CreateCallCount { get; private set; }
    /// <summary>Gets or sets a value indicating whether CreateSessionAsync should throw.</summary>
    public bool ThrowOnCreate { get; set; }
    /// <summary>Gets the endpoint URL from the last CreateSessionAsync call.</summary>
    public string? LastEndpointUrl { get; private set; }

    /// <summary>
    /// Optional gate that, when set, blocks <see cref="CreateSessionAsync" /> until completed.
    /// Lets tests hold a failover loop in-flight to exercise re-entrancy.
    /// </summary>
    public TaskCompletionSource? CreateGate { get; set; }

    /// <summary>Completed when a call observes <see cref="CreateGate" />.</summary>
    public TaskCompletionSource CreateEntered { get; } = new(TaskCreationOptions.RunContinuationsAsynchronously);

    /// <summary>Gets the list of sessions created via CreateSessionAsync.</summary>
    public IReadOnlyList<FakeSessionAdapter> CreatedSessions => _createdSessions;

    /// <summary>Creates a session asynchronously (fake implementation).</summary>
    /// <param name="config">The application configuration.</param>
    /// <param name="endpoint">The endpoint description.</param>
    /// <param name="sessionName">The session name.</param>
    /// <param name="sessionTimeoutMs">The session timeout in milliseconds.</param>
    /// <param name="identity">The user identity.</param>
    /// <param name="ct">Cancellation token.</param>
    /// <returns>A task containing the session adapter.</returns>
    public async Task<ISessionAdapter> CreateSessionAsync(
        ApplicationConfiguration config, EndpointDescription endpoint, string sessionName,
        uint sessionTimeoutMs, UserIdentity identity, CancellationToken ct)
    {
        CreateCallCount++;
        LastEndpointUrl = endpoint.EndpointUrl ?? string.Empty;

        // One-shot: the gate holds only the call that observed it, so a later call (e.g. a user's Connect while a
        // failover is held) runs freely.
        if (CreateGate is { } gate)
        {
            CreateGate = null;
            CreateEntered.TrySetResult();
            await gate.Task;
        }

        if (ThrowOnCreate)
            throw new InvalidOperationException("FakeSessionFactory configured to fail.");

        FakeSessionAdapter session;
        if (_sessions.Count > 0)
            session = _sessions.Dequeue();
        else
            session = new FakeSessionAdapter
            {
                EndpointUrl = endpoint.EndpointUrl ?? string.Empty,
                ServerName = endpoint.Server?.ApplicationName.Text ?? "FakeServer",
                SecurityMode = endpoint.SecurityMode.ToString(),
                SecurityPolicyUri = endpoint.SecurityPolicyUri ?? string.Empty
            };

        // Ensure endpoint URL matches
        session.EndpointUrl = endpoint.EndpointUrl ?? string.Empty;
        _createdSessions.Add(session);
        return session;
    }

    /// <summary>
    ///     Enqueues a session adapter to be returned on the next call to CreateSessionAsync.
    /// </summary>
    /// <param name="session">The session adapter to enqueue.</param>
    public void EnqueueSession(FakeSessionAdapter session)
    {
        _sessions.Enqueue(session);
    }
}