using System.Diagnostics.Metrics;
using ZB.MOM.WW.ScadaBridge.Commons.Observability;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;

namespace ZB.MOM.WW.ScadaBridge.Commons.Tests.Observability;

/// <summary>
/// ScadaBridge#81: the instruments added beyond the first set. Each is observed through a
/// <see cref="MeterListener"/> filtered to the emitting (test) thread, because the meter is
/// process-global and other tests emit on it concurrently.
/// </summary>
public sealed class ExtendedInstrumentTests
{
    private static List<(long Value, Dictionary<string, object?> Tags)> Capture(string instrument, Action act)
    {
        var tid = Environment.CurrentManagedThreadId;
        var got = new List<(long, Dictionary<string, object?>)>();
        using var listener = new MeterListener
        {
            InstrumentPublished = (i, l) =>
            {
                if (i.Meter.Name == ScadaBridgeTelemetry.MeterName && i.Name == instrument)
                    l.EnableMeasurementEvents(i);
            }
        };
        listener.SetMeasurementEventCallback<long>((_, m, tags, _) =>
        {
            if (Environment.CurrentManagedThreadId != tid) return;
            var d = new Dictionary<string, object?>();
            foreach (var t in tags) d[t.Key] = t.Value;
            got.Add((m, d));
        });
        listener.Start();
        act();
        return got;
    }

    /// <summary>A state change emits one transition tagged with the new state; repeating the same state emits none.</summary>
    [Fact]
    public void DataConnectionTransitions_EmitOnlyOnRealStateChange()
    {
        var name = "xfer-" + Guid.NewGuid().ToString("N");
        try
        {
            var got = Capture("scadabridge.site.data_connections.transitions", () =>
            {
                ScadaBridgeTelemetry.RecordDataConnectionState(name, ConnectionHealth.Connecting);
                ScadaBridgeTelemetry.RecordDataConnectionState(name, ConnectionHealth.Connected);
                ScadaBridgeTelemetry.RecordDataConnectionState(name, ConnectionHealth.Connected);
                ScadaBridgeTelemetry.RecordDataConnectionState(name, ConnectionHealth.Disconnected);
            });

            Assert.Equal(
                new object?[] { "Connecting", "Connected", "Disconnected" },
                got.Select(g => g.Tags["state"]).ToArray());
        }
        finally { ScadaBridgeTelemetry.RemoveDataConnection(name); }
    }

    /// <summary>Store-and-forward activity is counted by action and category.</summary>
    [Fact]
    public void StoreAndForwardActivity_IsCountedByActionAndCategory()
    {
        var got = Capture("scadabridge.store_and_forward.activity",
            () => ScadaBridgeTelemetry.RecordStoreAndForwardActivity("Parked", "ExternalSystem"));

        var m = Assert.Single(got);
        Assert.Equal(1, m.Value);
        Assert.Equal("Parked", m.Tags["action"]);
        Assert.Equal("ExternalSystem", m.Tags["category"]);
    }

    /// <summary>Deployment failures are counted by reason.</summary>
    [Fact]
    public void DeploymentsFailed_IsCountedByReason()
    {
        var got = Capture("scadabridge.deployments.failed",
            () => ScadaBridgeTelemetry.RecordDeploymentFailed("timeout"));

        var m = Assert.Single(got);
        Assert.Equal("timeout", m.Tags["reason"]);
    }

    /// <summary>A script run emits both the run counter and the duration histogram, clamping negatives.</summary>
    [Fact]
    public void ScriptRun_EmitsCounterAndDuration()
    {
        var runs = Capture("scadabridge.site.script.runs",
            () => ScadaBridgeTelemetry.RecordScriptRun("failed", 5));
        Assert.Equal("failed", Assert.Single(runs).Tags["outcome"]);

        var durations = Capture("scadabridge.site.script.duration",
            () => ScadaBridgeTelemetry.RecordScriptRun("completed", -3));
        var d = Assert.Single(durations);
        Assert.Equal(0, d.Value);
        Assert.Equal("completed", d.Tags["outcome"]);
    }
}