using Microsoft.Extensions.Logging.Abstractions;
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>
/// P2-2 (arch-review 2026-08-19, High): before the fix, <c>ConnectAsync</c> reset the
/// event loop and the client but left the alarm-stream state (<c>_alarmCts</c>,
/// <c>_alarmSubCount</c>, <c>_alarmSubSources</c>, <c>_alarmStreamPrefix</c>) untouched.
/// After a reconnect, the DataConnectionActor's transparent re-subscribe
/// (<c>ReSubscribeAllAlarms</c>) called <c>SubscribeAlarmsAsync</c> again, but the stale
/// non-null <c>_alarmCts</c> plus the coverage check made it short-circuit and return
/// success WITHOUT ever opening a new stream on the new client — leaving the orphaned
/// old stream loop retrying the disposed old client forever and the native-alarm mirror
/// frozen until failover/redeploy.
/// </summary>
[Collection("DataConnectionManagerActor")]
public class MxGatewayDataConnectionAlarmReconnectTests
{
    private static Dictionary<string, string> Details() => new()
    {
        ["Endpoint"] = "http://gw:5000",
        ["ApiKey"] = "key",
    };



    [Fact]
    public async Task DC5_EachTransportRefreshHasItsOwnConnectionWideEpoch()
    {
        var clients = new List<PerInstanceFakeMxGatewayClient>();
        var adapter = new MxGatewayDataConnection(new RecordingFactory(clients), NullLogger<MxGatewayDataConnection>.Instance);
        var received = new System.Collections.Concurrent.ConcurrentQueue<NativeAlarmTransition>();
        await adapter.ConnectAsync(Details());
        await adapter.SubscribeAlarmsAsync("Area1", null, received.Enqueue);
        await WaitUntilAsync(() => clients[0].AlarmStreamOpens.Count == 1);
        clients[0].EmitAlarm(MakeTransition(AlarmTransitionKind.SnapshotComplete));
        clients[0].EmitAlarm(MakeTransition(AlarmTransitionKind.SnapshotStart));
        clients[0].EmitAlarm(MakeTransition(AlarmTransitionKind.SnapshotComplete));
        var starts = received.Where(t => t.Kind == AlarmTransitionKind.SnapshotStart).ToArray();
        var ends = received.Where(t => t.Kind == AlarmTransitionKind.SnapshotComplete).ToArray();
        Assert.Equal(2, starts.Length);
        Assert.Equal(2, ends.Length);
        Assert.NotNull(starts[0].SnapshotId);
        Assert.NotEqual(starts[0].SnapshotId, starts[1].SnapshotId);
        Assert.Equal(starts[0].SnapshotId, ends[0].SnapshotId);
        Assert.Equal(starts[1].SnapshotId, ends[1].SnapshotId);
        Assert.All(starts, t => Assert.Null(t.SnapshotSourceReference));
        await adapter.DisconnectAsync();
    }

    [Fact]
    public async Task DC5_CoveredNewSourceRequestsFreshStandingSnapshot()
    {
        var clients = new List<PerInstanceFakeMxGatewayClient>();
        var adapter = new MxGatewayDataConnection(new RecordingFactory(clients), NullLogger<MxGatewayDataConnection>.Instance);
        await adapter.ConnectAsync(Details());
        await adapter.SubscribeAlarmsAsync("Area1", null, _ => { });
        await WaitUntilAsync(() => clients[0].AlarmStreamOpens.Count == 1);
        await adapter.SubscribeAlarmsAsync("Area1.Tank1", null, _ => { });
        await WaitUntilAsync(() => clients[0].AlarmStreamOpens.Count == 2);
        Assert.True(clients[0].AlarmStreamTokens[0].IsCancellationRequested);
        await adapter.DisconnectAsync();
    }

    [Fact]
    public async Task Reconnect_ThenSubscribeAlarms_OpensNewStreamOnNewClient()
    {
        var clients = new List<PerInstanceFakeMxGatewayClient>();
        var factory = new RecordingFactory(clients);
        var adapter = new MxGatewayDataConnection(factory, NullLogger<MxGatewayDataConnection>.Instance);

        await adapter.ConnectAsync(Details());
        await adapter.SubscribeAlarmsAsync("Area1.Tank1", null, _ => { });
        await WaitUntilAsync(() => clients[0].AlarmStreamOpens.Count == 1);

        // Reconnect (same source set as before — the coverage check would previously
        // treat this as already-covered and never touch the new client at all).
        await adapter.ConnectAsync(Details());
        Assert.Equal(2, clients.Count);

        await adapter.SubscribeAlarmsAsync("Area1.Tank1", null, _ => { });

        await WaitUntilAsync(() => clients[1].AlarmStreamOpens.Count == 1);
        Assert.Equal("Area1.Tank1", clients[1].AlarmStreamOpens[0]);
        // The OLD client must never see a second alarm-stream open after reconnect.
        Assert.Single(clients[0].AlarmStreamOpens);
    }

    [Fact]
    public async Task Reconnect_CancelsTheOldAlarmStreamToken()
    {
        var clients = new List<PerInstanceFakeMxGatewayClient>();
        var factory = new RecordingFactory(clients);
        var adapter = new MxGatewayDataConnection(factory, NullLogger<MxGatewayDataConnection>.Instance);

        await adapter.ConnectAsync(Details());
        await adapter.SubscribeAlarmsAsync("Area1.Tank1", null, _ => { });
        await WaitUntilAsync(() => clients[0].AlarmStreamTokens.Count == 1);
        var oldStreamToken = clients[0].AlarmStreamTokens[0];
        Assert.False(oldStreamToken.IsCancellationRequested);

        await adapter.ConnectAsync(Details()); // reconnect

        // The token the OLD RunAlarmStreamAsync loop was given must now be cancelled —
        // that is what stops it retrying against the disposed old client every 5s.
        Assert.True(oldStreamToken.IsCancellationRequested);
    }

    [Fact]
    public async Task Reconnect_AlarmEventsFlowAgainOnTheNewClient()
    {
        var clients = new List<PerInstanceFakeMxGatewayClient>();
        var factory = new RecordingFactory(clients);
        var adapter = new MxGatewayDataConnection(factory, NullLogger<MxGatewayDataConnection>.Instance);

        var received = new List<NativeAlarmTransition>();
        await adapter.ConnectAsync(Details());
        await adapter.SubscribeAlarmsAsync("Area1.Tank1", null, t => { if (t.Kind != AlarmTransitionKind.SnapshotStart) received.Add(t); });
        await WaitUntilAsync(() => clients[0].AlarmStreamOpens.Count == 1);

        // Prove the feed works pre-reconnect.
        clients[0].EmitAlarm(MakeTransition(AlarmTransitionKind.Snapshot));
        await WaitUntilAsync(() => received.Count == 1);

        await adapter.ConnectAsync(Details()); // reconnect
        await adapter.SubscribeAlarmsAsync("Area1.Tank1", null, t => { if (t.Kind != AlarmTransitionKind.SnapshotStart) received.Add(t); });
        await WaitUntilAsync(() => clients[1].AlarmStreamOpens.Count == 1);

        // A transition on the OLD (disposed, orphaned) client must never reach the
        // callback again — only the NEW client's feed is live post-reconnect.
        clients[0].EmitAlarm(MakeTransition(AlarmTransitionKind.Raise));
        await Task.Delay(100);
        Assert.Single(received);

        clients[1].EmitAlarm(MakeTransition(AlarmTransitionKind.Snapshot));
        await WaitUntilAsync(() => received.Count == 2);
    }

    private static NativeAlarmTransition MakeTransition(AlarmTransitionKind kind) => new(
        "Area1.Tank1.HiAlarm", "Area1.Tank1", "HiAlarm", kind,
        new AlarmConditionState(true, false, null, AlarmShelveState.Unshelved, false, 400),
        "Area", "", "", "", "", null, DateTimeOffset.UtcNow, "", "");

    private static async Task WaitUntilAsync(Func<bool> condition)
    {
        for (var i = 0; i < 100 && !condition(); i++)
            await Task.Delay(50);
        Assert.True(condition(), "condition not met within timeout");
    }

    /// <summary>Builds a NEW client instance per <c>Create()</c> call, mirroring the real
    /// factory and <see cref="MxGatewayDataConnectionReconnectTests"/>'s NSubstitute-based
    /// setup — needed here (unlike <c>FakeMxGatewayClient</c>) because the test must tell
    /// the pre- and post-reconnect clients apart.</summary>
    private sealed class RecordingFactory : IMxGatewayClientFactory
    {
        private readonly List<PerInstanceFakeMxGatewayClient> _clients;
        public RecordingFactory(List<PerInstanceFakeMxGatewayClient> clients) => _clients = clients;

        public IMxGatewayClient Create()
        {
            var c = new PerInstanceFakeMxGatewayClient();
            _clients.Add(c);
            return c;
        }
    }

    /// <summary>Minimal per-instance fake — only the members this test exercises are
    /// implemented meaningfully; the rest are unused no-ops for the connect/alarm-only
    /// path under test.</summary>
    private sealed class PerInstanceFakeMxGatewayClient : IMxGatewayClient
    {
        public readonly List<string?> AlarmStreamOpens = new();
        public readonly List<CancellationToken> AlarmStreamTokens = new();
        private Action<NativeAlarmTransition>? _onTransition;
        private CancellationToken _streamToken;

        public Task ConnectAsync(MxGatewayConnectionOptions o, CancellationToken ct = default) => Task.CompletedTask;
        public Task DisconnectAsync(CancellationToken ct = default) => Task.CompletedTask;
        public Task<string> SubscribeAsync(string tagPath, CancellationToken ct = default) => Task.FromResult(Guid.NewGuid().ToString());
        public Task UnsubscribeAsync(string subscriptionId, CancellationToken ct = default) => Task.CompletedTask;
        public Task<IReadOnlyList<MxSubscribeOutcome>> SubscribeBulkAsync(IReadOnlyList<string> tagPaths, CancellationToken ct = default)
            => Task.FromResult<IReadOnlyList<MxSubscribeOutcome>>(Array.Empty<MxSubscribeOutcome>());
        public Task UnsubscribeBulkAsync(IReadOnlyList<string> subscriptionIds, CancellationToken ct = default) => Task.CompletedTask;
        public Task<IReadOnlyList<MxReadOutcome>> ReadAsync(IReadOnlyList<string> tagPaths, CancellationToken ct = default)
            => Task.FromResult<IReadOnlyList<MxReadOutcome>>(Array.Empty<MxReadOutcome>());
        public Task<IReadOnlyList<MxWriteOutcome>> WriteAsync(IReadOnlyList<(string TagPath, object? Value)> writes, CancellationToken ct = default)
            => Task.FromResult<IReadOnlyList<MxWriteOutcome>>(Array.Empty<MxWriteOutcome>());
        public Task<(IReadOnlyList<MxBrowseChild> Children, bool Truncated)> BrowseChildrenAsync(string? parentNodeId, CancellationToken ct = default)
            => Task.FromResult<(IReadOnlyList<MxBrowseChild>, bool)>((Array.Empty<MxBrowseChild>(), false));
        public Task RunEventLoopAsync(Action<MxValueUpdate> onUpdate, CancellationToken ct = default)
            => Task.Delay(Timeout.Infinite, ct).ContinueWith(_ => { }, TaskScheduler.Default);

        public Task RunAlarmStreamAsync(string? alarmFilterPrefix, Action<NativeAlarmTransition> onTransition, CancellationToken ct = default)
        {
            // Mirrors the real RunAlarmStreamAsync seam: records the open, then just
            // parks on the token like the live gateway stream would between events —
            // the adapter-level bug under test is about which CLIENT/TOKEN the loop was
            // started on, not the internal 5s retry loop inside RealMxGatewayClient.
            lock (AlarmStreamOpens)
            {
                AlarmStreamOpens.Add(alarmFilterPrefix);
                AlarmStreamTokens.Add(ct);
            }
            _onTransition = onTransition;
            _streamToken = ct;
            return Task.Delay(Timeout.Infinite, ct).ContinueWith(_ => { }, TaskScheduler.Default);
        }

        public ValueTask DisposeAsync() => ValueTask.CompletedTask;

        /// <summary>Simulates a transition arriving on this client's live stream. Gated on
        /// the stream token exactly like the real gateway stream would be — once cancelled,
        /// no more events are delivered — so a test can prove the OLD client's feed is
        /// genuinely dead post-reconnect rather than just unobserved.</summary>
        public void EmitAlarm(NativeAlarmTransition transition)
        {
            if (_streamToken.IsCancellationRequested)
                return;
            _onTransition?.Invoke(transition);
        }
    }
}