using System.Diagnostics.Metrics;
using System.Linq;
using FluentAssertions;
using StellaOps.Findings.Ledger.Observability;
using Xunit;

namespace StellaOps.Findings.Ledger.Tests.Observability;

public class LedgerMetricsTests
{
    [Fact]
    public void RecordProjectionApply_emits_histogram_and_counter_with_tags()
    {
        var histogramValues = new List<(double Value, KeyValuePair<string, object?>[] Tags)>();
        var counterValues = new List<(long Value, KeyValuePair<string, object?>[] Tags)>();

        using var listener = new MeterListener
        {
            InstrumentPublished = (instrument, l) =>
            {
                if (instrument.Meter.Name == "StellaOps.Findings.Ledger")
                {
                    l.EnableMeasurementEvents(instrument);
                }
            }
        };

        listener.SetMeasurementEventCallback<double>((instrument, measurement, tags, state) =>
        {
            if (instrument.Name is "ledger_projection_apply_seconds" or "ledger_projection_lag_seconds")
            {
                histogramValues.Add((measurement, tags.ToArray()));
            }
        });

        listener.SetMeasurementEventCallback<long>((instrument, measurement, tags, state) =>
        {
            if (instrument.Name == "ledger_projection_events_total")
            {
                counterValues.Add((measurement, tags.ToArray()));
            }
        });

        listener.Start();

        LedgerMetrics.RecordProjectionApply(
            TimeSpan.FromMilliseconds(40),
            1.2,
            "tenant-x",
            "finding.status.changed",
            "v1.0",
            "affected");

        histogramValues.Should().NotBeEmpty();
        counterValues.Should().NotBeEmpty();

        var tags = histogramValues.First().Tags.ToDictionary(kv => kv.Key, kv => kv.Value?.ToString());
        tags["tenant"].Should().Be("tenant-x");
        tags["event_type"].Should().Be("finding.status.changed");
        tags["policy_version"].Should().Be("v1.0");
        tags["evaluation_status"].Should().Be("affected");
    }
}