scadalink-design/src/ScadaLink.DataConnectionLayer/Adapters/ILmxProxyClient.cs

namespace ScadaLink.DataConnectionLayer.Adapters;

/// <summary>
/// WP-8: Abstraction over the LmxProxy SDK client for testability.
/// The actual LmxProxyClient SDK lives in a separate repo; this interface
/// defines the contract the adapter depends on.
///
/// LmxProxy uses gRPC streaming for subscriptions and a session-based model
/// with keep-alive for connection management.
/// </summary>
public interface ILmxProxyClient : IAsyncDisposable
{
    /// <summary>
    /// Opens a session to the LmxProxy server. Returns a session ID.
    /// </summary>
    Task<string> OpenSessionAsync(string host, int port, CancellationToken cancellationToken = default);

    /// <summary>
    /// Closes the current session.
    /// </summary>
    Task CloseSessionAsync(CancellationToken cancellationToken = default);

    /// <summary>
    /// Sends a keep-alive to maintain the session.
    /// </summary>
    Task SendKeepAliveAsync(CancellationToken cancellationToken = default);

    bool IsConnected { get; }
    string? SessionId { get; }

    /// <summary>
    /// Subscribes to tag value changes via gRPC streaming. Returns a subscription handle.
    /// </summary>
    Task<string> SubscribeTagAsync(
        string tagPath,
        Action<string, object?, DateTime, bool> onValueChanged,
        CancellationToken cancellationToken = default);

    Task UnsubscribeTagAsync(string subscriptionHandle, CancellationToken cancellationToken = default);

    Task<(object? Value, DateTime Timestamp, bool IsGood)> ReadTagAsync(
        string tagPath, CancellationToken cancellationToken = default);

    Task<bool> WriteTagAsync(string tagPath, object? value, CancellationToken cancellationToken = default);
}

/// <summary>
/// Factory for creating ILmxProxyClient instances.
/// </summary>
public interface ILmxProxyClientFactory
{
    ILmxProxyClient Create();
}

/// <summary>
/// Default factory that creates stub LmxProxy clients.
/// In production, this would create real LmxProxy SDK client instances.
/// </summary>
public class DefaultLmxProxyClientFactory : ILmxProxyClientFactory
{
    public ILmxProxyClient Create() => new StubLmxProxyClient();
}

/// <summary>
/// Stub LmxProxy client for development/testing.
/// </summary>
internal class StubLmxProxyClient : ILmxProxyClient
{
    public bool IsConnected { get; private set; }
    public string? SessionId { get; private set; }

    public Task<string> OpenSessionAsync(string host, int port, CancellationToken cancellationToken = default)
    {
        SessionId = Guid.NewGuid().ToString();
        IsConnected = true;
        return Task.FromResult(SessionId);
    }

    public Task CloseSessionAsync(CancellationToken cancellationToken = default)
    {
        IsConnected = false;
        SessionId = null;
        return Task.CompletedTask;
    }

    public Task SendKeepAliveAsync(CancellationToken cancellationToken = default)
    {
        return Task.CompletedTask;
    }

    public Task<string> SubscribeTagAsync(
        string tagPath, Action<string, object?, DateTime, bool> onValueChanged,
        CancellationToken cancellationToken = default)
    {
        return Task.FromResult(Guid.NewGuid().ToString());
    }

    public Task UnsubscribeTagAsync(string subscriptionHandle, CancellationToken cancellationToken = default)
    {
        return Task.CompletedTask;
    }

    public Task<(object? Value, DateTime Timestamp, bool IsGood)> ReadTagAsync(
        string tagPath, CancellationToken cancellationToken = default)
    {
        return Task.FromResult<(object?, DateTime, bool)>((null, DateTime.UtcNow, true));
    }

    public Task<bool> WriteTagAsync(string tagPath, object? value, CancellationToken cancellationToken = default)
    {
        return Task.FromResult(true);
    }

    public ValueTask DisposeAsync()
    {
        IsConnected = false;
        SessionId = null;
        return ValueTask.CompletedTask;
    }
}