using ZB.MOM.WW.OtOpcUa.Commons.OpcUa;
using ZB.MOM.WW.OtOpcUa.Commons.Types;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;

namespace ZB.MOM.WW.OtOpcUa.Runtime.Tests.Drivers;

/// <summary>
///     Shared <see cref="IDriver"/> stub harness used by <c>DriverInstanceActorTests</c> and
///     <c>DriverInstanceActorWriteAndSubscribeTests</c>. Promoted from the superset copy in
///     <c>DriverInstanceActorTests</c> so both suites compile against a single definition.
/// </summary>
internal class StubDriver : IDriver
{
    /// <summary>Gets or sets a value indicating whether initialization should throw.</summary>
    public bool InitializeShouldThrow { get; set; }
    /// <summary>Gets the number of times initialization was called.</summary>
    public int InitializeCount;
    /// <summary>Gets the number of times reinitialization was called.</summary>
    public int ReinitializeCount;

    private readonly object _initConfigsLock = new();
    /// <summary>Every config string passed to <see cref="InitializeAsync"/>, in call order.</summary>
    public List<string> InitConfigs { get; } = new();
    /// <summary>Optional per-config init behaviour. When set, it fully owns the init outcome for that
    /// config (await/throw); <see cref="InitializeShouldThrow"/> is ignored. Null ⇒ legacy behaviour.</summary>
    public Func<string, Task>? InitBehavior { get; set; }

    /// <summary>Gets the driver instance ID.</summary>
    public string DriverInstanceId => "stub-driver-1";
    /// <summary>Gets the driver type.</summary>
    public string DriverType => "Stub";

    /// <summary>Initializes the driver with the specified configuration JSON.</summary>
    /// <param name="driverConfigJson">The driver configuration JSON.</param>
    /// <param name="cancellationToken">Cancellation token for the operation.</param>
    public async Task InitializeAsync(string driverConfigJson, CancellationToken cancellationToken)
    {
        Interlocked.Increment(ref InitializeCount);
        lock (_initConfigsLock) InitConfigs.Add(driverConfigJson);
        if (InitBehavior is not null) { await InitBehavior(driverConfigJson); return; }
        if (InitializeShouldThrow) throw new InvalidOperationException("stub-init-fail");
    }

    /// <summary>Reinitializes the driver with the specified configuration JSON.</summary>
    /// <param name="driverConfigJson">The driver configuration JSON.</param>
    /// <param name="cancellationToken">Cancellation token for the operation.</param>
    public Task ReinitializeAsync(string driverConfigJson, CancellationToken cancellationToken)
    {
        Interlocked.Increment(ref ReinitializeCount);
        return Task.CompletedTask;
    }

    /// <summary>Number of <see cref="ShutdownAsync"/> calls — a child actor stopping raises it, so a test
    /// can observe a driver child being torn down (e.g. by the #516 config-change respawn).</summary>
    public int ShutdownCount;

    /// <summary>Shuts down the driver.</summary>
    /// <param name="cancellationToken">Cancellation token for the operation.</param>
    public Task ShutdownAsync(CancellationToken cancellationToken)
    {
        Interlocked.Increment(ref ShutdownCount);
        return Task.CompletedTask;
    }
    /// <summary>Gets the health status of the driver.</summary>
    public DriverHealth GetHealth() => new(DriverState.Healthy, DateTime.UtcNow, null);
    /// <summary>Gets the memory footprint of the driver.</summary>
    public long GetMemoryFootprint() => 0;
    /// <summary>Flushes optional caches in the driver.</summary>
    /// <param name="cancellationToken">Cancellation token for the operation.</param>
    public Task FlushOptionalCachesAsync(CancellationToken cancellationToken) => Task.CompletedTask;
}

/// <summary>
///     A <see cref="StubDriver"/> that also implements <see cref="IWritable"/>, recording every
///     write call and returning a configurable status code.
/// </summary>
internal sealed class WritableStubDriver : StubDriver, IWritable
{
    /// <summary>Gets or sets the next status code to return from write operations.</summary>
    public uint NextStatusCode { get; set; } = 0u;
    /// <summary>Gets the list of write requests received.</summary>
    public List<WriteRequest> Writes { get; } = new();

    /// <summary>Writes the specified requests.</summary>
    /// <param name="writes">The write requests.</param>
    /// <param name="cancellationToken">Cancellation token for the operation.</param>
    public Task<IReadOnlyList<WriteResult>> WriteAsync(
        IReadOnlyList<WriteRequest> writes, CancellationToken cancellationToken)
    {
        Writes.AddRange(writes);
        IReadOnlyList<WriteResult> results = writes.Select(_ => new WriteResult(NextStatusCode)).ToList();
        return Task.FromResult(results);
    }
}

/// <summary>
///     A <see cref="StubDriver"/> that also implements <see cref="ISubscribable"/>, firing
///     <see cref="OnDataChange"/> on demand and counting subscribe calls.
/// </summary>
internal sealed class SubscribableStubDriver : StubDriver, ISubscribable
{
    /// <summary>Occurs when data changes.</summary>
    public event EventHandler<DataChangeEventArgs>? OnDataChange;

    private readonly StubHandle _handle = new();

    /// <summary>Gets the number of subscribers to OnDataChange.</summary>
    public int OnDataChangeSubscriberCount => OnDataChange?.GetInvocationList().Length ?? 0;

    /// <summary>Number of times <see cref="SubscribeAsync"/> was called (re-subscribe asserts).</summary>
    public int SubscribeCount;
    /// <summary>The reference set passed to the most recent <see cref="SubscribeAsync"/> call.</summary>
    public IReadOnlyList<string>? LastSubscribedRefs;

    /// <summary>Number of times <see cref="UnsubscribeAsync"/> was called — the observable for a live
    /// subscription being torn down (an EMPTY desired set drops the handle rather than re-subscribing).</summary>
    public int UnsubscribeCount;

    /// <summary>When true, <see cref="UnsubscribeAsync"/> genuinely yields (<c>await Task.Yield()</c>)
    /// before completing, so a <c>ConfigureAwait(false)</c> continuation in the actor resumes off the
    /// Akka ActorContext on a thread-pool thread — reproducing the no-ActorContext race that a
    /// synchronously-completed stub task hides (the continuation otherwise runs inline).</summary>
    public bool UnsubscribeYields { get; set; }

    /// <summary>
    ///     How many of the first <see cref="SubscribeAsync"/> calls throw before one succeeds. Default 0
    ///     (always succeed) leaves existing behaviour untouched.
    /// </summary>
    /// <remarks>
    ///     This is how a test reaches the state the #488 reconcile exists for: the actor is Connected and
    ///     holds a desired ref set, but the subscribe that should have established the handle failed, so
    ///     <c>_subscriptionHandle</c> is null and nothing else will ever re-assert it — there is no
    ///     connect transition coming, and no deploy.
    /// </remarks>
    public int SubscribeFailuresBeforeSuccess { get; set; }

    /// <summary>Subscribes to the specified full references.</summary>
    /// <param name="fullReferences">The full references to subscribe to.</param>
    /// <param name="publishingInterval">The publishing interval.</param>
    /// <param name="cancellationToken">Cancellation token for the operation.</param>
    public Task<ISubscriptionHandle> SubscribeAsync(
        IReadOnlyList<string> fullReferences, TimeSpan publishingInterval, CancellationToken cancellationToken)
    {
        var attempt = Interlocked.Increment(ref SubscribeCount);
        LastSubscribedRefs = fullReferences;
        if (attempt <= SubscribeFailuresBeforeSuccess)
        {
            throw new InvalidOperationException($"stub subscribe failure #{attempt}");
        }

        return Task.FromResult<ISubscriptionHandle>(_handle);
    }

    /// <summary>Unsubscribes from the specified subscription handle.</summary>
    /// <param name="handle">The subscription handle.</param>
    /// <param name="cancellationToken">Cancellation token for the operation.</param>
    public async Task UnsubscribeAsync(ISubscriptionHandle handle, CancellationToken cancellationToken)
    {
        Interlocked.Increment(ref UnsubscribeCount);
        if (UnsubscribeYields)
        {
            // Complete the awaited task from a fresh background thread that has NO Akka actor
            // cell on it, so the caller's `ConfigureAwait(false)` continuation resumes on a
            // clean thread-pool thread where InternalCurrentActorCellKeeper.Current is null —
            // a deterministic repro of the real async-backend no-ActorContext race.
            var tcs = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
            _ = Task.Run(() => tcs.SetResult());
            await tcs.Task.ConfigureAwait(false);
        }
    }

    /// <summary>Fires a data change event with the specified parameters.</summary>
    /// <param name="fullRef">The full reference of the data that changed.</param>
    /// <param name="value">The new value.</param>
    /// <param name="statusCode">The OPC UA status code.</param>
    public void FireDataChange(string fullRef, object? value, uint statusCode)
    {
        var snapshot = new DataValueSnapshot(value, statusCode, DateTime.UtcNow, DateTime.UtcNow);
        OnDataChange?.Invoke(this, new DataChangeEventArgs(_handle, fullRef, snapshot));
    }
}

/// <summary>Minimal <see cref="ISubscriptionHandle"/> for use by <see cref="SubscribableStubDriver"/>.</summary>
internal sealed class StubHandle : ISubscriptionHandle
{
    /// <summary>Gets the diagnostic ID of the subscription.</summary>
    public string DiagnosticId => "stub-sub";
}
