using System;
using System.Collections.Generic;
using System.Diagnostics.Metrics;
using System.Text.Json;
using StellaOps.Concelier.Core.Diagnostics;
using StellaOps.Concelier.Core.Linksets;
using Xunit;


using StellaOps.TestKit;
namespace StellaOps.Concelier.WebService.Tests;

public sealed class VulnExplorerTelemetryTests : IDisposable
{
    private readonly MeterListener _listener;
    private readonly List<(string Name, double Value, KeyValuePair<string, object?>[] Tags)> _histogramMeasurements = new();
    private readonly List<(string Name, long Value, KeyValuePair<string, object?>[] Tags)> _counterMeasurements = new();

    public VulnExplorerTelemetryTests()
    {
        _listener = new MeterListener
        {
            InstrumentPublished = (instrument, listener) =>
            {
                if (instrument.Meter.Name == VulnExplorerTelemetry.MeterName)
                {
                    listener.EnableMeasurementEvents(instrument);
                }
            }
        };

        _listener.SetMeasurementEventCallback<long>((instrument, measurement, tags, state) =>
        {
            if (instrument.Meter.Name == VulnExplorerTelemetry.MeterName)
            {
                _counterMeasurements.Add((instrument.Name, measurement, tags.ToArray()));
            }
        });

        _listener.SetMeasurementEventCallback<double>((instrument, measurement, tags, state) =>
        {
            if (instrument.Meter.Name == VulnExplorerTelemetry.MeterName)
            {
                _histogramMeasurements.Add((instrument.Name, measurement, tags.ToArray()));
            }
        });

        _listener.Start();
    }

    [Trait("Category", TestCategories.Unit)]
        [Fact]
    public void CountAliasCollisions_FiltersAliasConflicts()
    {
        var conflicts = new List<AdvisoryLinksetConflict>
        {
            new("aliases", "alias-inconsistency", Array.Empty<string>()),
            new("ranges", "range-divergence", Array.Empty<string>()),
            new("alias-field", "ALIAS-INCONSISTENCY", Array.Empty<string>())
        };

        var count = VulnExplorerTelemetry.CountAliasCollisions(conflicts);

        Assert.Equal(2, count);
    }

    [Trait("Category", TestCategories.Unit)]
        [Fact]
    public void IsWithdrawn_DetectsWithdrawnFlagsAndTimestamps()
    {
        using var json = JsonDocument.Parse("{\"withdrawn\":true,\"withdrawn_at\":\"2024-10-10T00:00:00Z\"}");
        Assert.True(VulnExplorerTelemetry.IsWithdrawn(json.RootElement));
    }

    [Trait("Category", TestCategories.Unit)]
        [Fact]
    public void RecordChunkLatency_EmitsHistogramMeasurement()
    {
        VulnExplorerTelemetry.RecordChunkLatency("tenant-a", "vendor-a", TimeSpan.FromMilliseconds(42));

        var measurement = Assert.Single(_histogramMeasurements);
        Assert.Equal("vuln.chunk_latency_ms", measurement.Name);
        Assert.Equal(42, measurement.Value);
    }

    [Trait("Category", TestCategories.Unit)]
        [Fact]
    public void RecordWithdrawnStatement_EmitsCounter()
    {
        VulnExplorerTelemetry.RecordWithdrawnStatement("tenant-b", "vendor-b");

        var measurement = Assert.Single(_counterMeasurements);
        Assert.Equal("vuln.withdrawn_statements_total", measurement.Name);
        Assert.Equal(1, measurement.Value);
    }

    public void Dispose()
    {
        _listener.Dispose();
    }
}