ScadaBridge/tests/ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests/Adapters/MxGatewaySessionScopedHandleTests.cs

using Microsoft.Extensions.Logging.Abstractions;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Protocol;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Alarms;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
using ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Adapters;

namespace ZB.MOM.WW.ScadaBridge.DataConnectionLayer.Tests.Adapters;

/// <summary>
/// The adapter half of review 2026-10-21 02/C1 + 02/L1. The adapter instance is reused across
/// reconnects, but every reconnect opens a NEW gateway session whose item handles are plain ints
/// that restart (collide) per session. A subscription id handed out by a dead session must
/// therefore never reach the gateway again — it would unadvise whatever the live session gave that
/// number — and the routing maps must not keep dead-session entries alive.
/// </summary>
[Collection("DataConnectionManagerActor")]
public class MxGatewaySessionScopedHandleTests
{
    private static Dictionary<string, string> Details() => new()
    {
        ["Endpoint"] = "http://gw:5000",
        ["ApiKey"] = "key",
        ["ReadTimeoutMs"] = "2000",
    };

    private static MxGatewayDataConnection NewAdapter(FakeMxGatewayClient fake) =>
        new(fake, NullLogger<MxGatewayDataConnection>.Instance);

    /// <summary>
    /// A batch release of a dead-session id never reaches the gateway, even when the new session
    /// has handed the same handle number to a live tag — and that live tag keeps routing.
    /// </summary>
    [Fact]
    public async Task DeadSessionId_IsNeverReleasedAtTheGateway_EvenWhenTheHandleWasReused()
    {
        var fake = new FakeMxGatewayClient { RestartHandlesOnConnect = true };
        var adapter = NewAdapter(fake);
        await adapter.ConnectAsync(Details());
        var dead = (await adapter.SubscribeBatchAsync(["Old.Tag"], (_, _) => { }))[0].SubscriptionId!;

        await adapter.ConnectAsync(Details()); // reconnect: new session, handles restart at 1
        var liveHits = 0;
        var live = (await adapter.SubscribeBatchAsync(["Live.Tag"], (_, _) => liveHits++))[0].SubscriptionId!;

        await adapter.UnsubscribeBatchAsync([dead]);
        await adapter.UnsubscribeAsync(dead);

        Assert.Empty(fake.Unsubscribed);
        Assert.NotEqual(dead, live);

        await WaitUntil(() => fake.OnUpdate is not null);
        fake.OnUpdate!(new MxValueUpdate("Live.Tag", 2, QualityCode.Good, DateTimeOffset.UtcNow));
        Assert.True(liveHits >= 1);

        // A current-session id still releases normally.
        await adapter.UnsubscribeBatchAsync([live]);
        Assert.Single(fake.Unsubscribed);
    }

    /// <summary>
    /// A reconnect drops the previous session's routing entries (L1): an update for a tag the
    /// new session has not (re-)subscribed is not routed to the dead session's callback.
    /// </summary>
    [Fact]
    public async Task Reconnect_ClearsTheDeadSessionsRoutingEntries()
    {
        var fake = new FakeMxGatewayClient();
        var adapter = NewAdapter(fake);
        await adapter.ConnectAsync(Details());
        var hits = 0;
        await adapter.SubscribeBatchAsync(["A.Tag"], (_, _) => hits++);

        await adapter.ConnectAsync(Details());
        await WaitUntil(() => fake.OnUpdate is not null);
        fake.OnUpdate!(new MxValueUpdate("A.Tag", 1, QualityCode.Good, DateTimeOffset.UtcNow));

        Assert.Equal(0, hits);
    }

    /// <summary>
    /// A disconnect drops the routing entries too, so a later update is not delivered to a
    /// subscription that no longer exists at the gateway.
    /// </summary>
    [Fact]
    public async Task Disconnect_ClearsRoutingEntries()
    {
        var fake = new FakeMxGatewayClient();
        var adapter = NewAdapter(fake);
        await adapter.ConnectAsync(Details());
        var hits = 0;
        await adapter.SubscribeBatchAsync(["A.Tag"], (_, _) => hits++);
        await WaitUntil(() => fake.OnUpdate is not null);

        await adapter.DisconnectAsync();
        fake.OnUpdate!(new MxValueUpdate("A.Tag", 1, QualityCode.Good, DateTimeOffset.UtcNow));

        Assert.Equal(0, hits);
    }

    /// <summary>
    /// Releasing an alarm subscription id the adapter does not know (a dead session's) must not
    /// decrement the live feed's reference count — at zero the shared stream is torn down while
    /// live subscribers still depend on it.
    /// </summary>
    [Fact]
    public async Task UnknownAlarmSubscriptionId_DoesNotTearDownTheLiveStream()
    {
        var fake = new FakeMxGatewayClient();
        var adapter = NewAdapter(fake);
        await adapter.ConnectAsync(Details());

        var delivered = 0;
        await adapter.SubscribeAlarmsAsync("Tank01", null, t =>
        {
            if (t.Kind == AlarmTransitionKind.SnapshotComplete)
                Interlocked.Increment(ref delivered);
        });
        await WaitUntil(() => fake.AlarmCallback is not null);

        await adapter.UnsubscribeAlarmsAsync(Guid.NewGuid().ToString());

        fake.AlarmCallback!(MxGatewayAlarmMapper.SnapshotComplete());
        Assert.Equal(1, Volatile.Read(ref delivered));
    }

    /// <summary>
    /// Review 2026-10-21 02/P3: a burst of alarm subscribes (a staggered deploy batch of N
    /// alarm-bound instances) is coalesced into ONE stream reopen on the union prefix instead of N
    /// close/reopen cycles, each with its own connection-wide snapshot replay. Every source in the
    /// burst is still covered by that one fresh snapshot (DC-5's standing-state guarantee).
    /// </summary>
    [Fact]
    public async Task AlarmSubscribeBurst_IsCoalescedIntoOneStreamReopen()
    {
        var fake = new FakeMxGatewayClient();
        var adapter = new MxGatewayDataConnection(
            fake, NullLogger<MxGatewayDataConnection>.Instance,
            alarmStreamReopenDebounce: TimeSpan.FromMilliseconds(300));
        await adapter.ConnectAsync(Details());

        // Spaced like actor-delivered subscribes, so an un-coalesced reopen really reaches the
        // gateway each time (a reopen superseded before its task runs never would).
        foreach (var source in new[] { "Area1.Tank1", "Area1.Tank2", "Area1.Tank3", "Area1.Tank4", "Area1.Tank5" })
        {
            await adapter.SubscribeAlarmsAsync(source, null, _ => { });
            await Task.Delay(20);
        }

        await WaitUntil(() => { lock (fake.AlarmStreamPrefixes) return fake.AlarmStreamPrefixes.Count >= 1; });
        await Task.Delay(400); // well past the window: no trailing reopens

        lock (fake.AlarmStreamPrefixes)
        {
            Assert.Single(fake.AlarmStreamPrefixes);
            Assert.Equal("Area1.Tank", fake.AlarmStreamPrefixes[0]);
        }
    }

    /// <summary>
    /// A subscribe arriving after the coalesced reopen has fired still gets its own fresh
    /// snapshot — coalescing never swallows a source.
    /// </summary>
    [Fact]
    public async Task AlarmSubscribe_AfterTheWindow_StillReopens()
    {
        var fake = new FakeMxGatewayClient();
        var adapter = new MxGatewayDataConnection(
            fake, NullLogger<MxGatewayDataConnection>.Instance,
            alarmStreamReopenDebounce: TimeSpan.FromMilliseconds(50));
        await adapter.ConnectAsync(Details());

        await adapter.SubscribeAlarmsAsync("Area1.Tank1", null, _ => { });
        await WaitUntil(() => { lock (fake.AlarmStreamPrefixes) return fake.AlarmStreamPrefixes.Count == 1; });
        await adapter.SubscribeAlarmsAsync("Area1.Tank2", null, _ => { });
        await WaitUntil(() => { lock (fake.AlarmStreamPrefixes) return fake.AlarmStreamPrefixes.Count == 2; });

        lock (fake.AlarmStreamPrefixes)
            Assert.Equal("Area1.Tank", fake.AlarmStreamPrefixes[1]);
    }

    private static async Task WaitUntil(Func<bool> condition, int timeoutMs = 30_000)
    {
        var deadline = DateTime.UtcNow.AddMilliseconds(timeoutMs);
        while (!condition())
        {
            if (DateTime.UtcNow > deadline)
                throw new TimeoutException("Condition not met in time.");
            await Task.Delay(10);
        }
    }
}