using System.Diagnostics.Metrics;
using JdeScoping.DataSync.Telemetry;
using Microsoft.Extensions.DependencyInjection;
using Shouldly;

namespace JdeScoping.DataSync.Tests;

/// <summary>
/// Unit tests for DataSyncMetrics.
/// Tests counter increments and histogram recordings.
/// </summary>
public class DataSyncMetricsTests : IDisposable
{
    private readonly MeterListener _meterListener;
    private readonly DataSyncMetrics _sut;
    private readonly List<Measurement<long>> _longMeasurements = [];
    private readonly List<Measurement<double>> _doubleMeasurements = [];

    public DataSyncMetricsTests()
    {
        var services = new ServiceCollection();
        services.AddMetrics();
        var provider = services.BuildServiceProvider();
        var meterFactory = provider.GetRequiredService<IMeterFactory>();

        _sut = new DataSyncMetrics(meterFactory);

        // Set up meter listener to capture measurements
        _meterListener = new MeterListener();
        _meterListener.InstrumentPublished = (instrument, listener) =>
        {
            if (instrument.Meter.Name == "JdeScoping.DataSync")
            {
                listener.EnableMeasurementEvents(instrument);
            }
        };

        _meterListener.SetMeasurementEventCallback<long>(OnMeasurementRecorded);
        _meterListener.SetMeasurementEventCallback<double>(OnDoubleMeasurementRecorded);
        _meterListener.Start();
    }

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

    private void OnMeasurementRecorded(
        Instrument instrument,
        long measurement,
        ReadOnlySpan<KeyValuePair<string, object?>> tags,
        object? state)
    {
        _longMeasurements.Add(new Measurement<long>(measurement, tags.ToArray()));
    }

    private void OnDoubleMeasurementRecorded(
        Instrument instrument,
        double measurement,
        ReadOnlySpan<KeyValuePair<string, object?>> tags,
        object? state)
    {
        _doubleMeasurements.Add(new Measurement<double>(measurement, tags.ToArray()));
    }

    #region Operation Started Counter Tests

    [Fact]
    public void RecordOperationStarted_IncrementsCounter()
    {
        // Act
        _sut.RecordOperationStarted("WorkOrder", "Mass");
        _meterListener.RecordObservableInstruments();

        // Assert
        var measurement = _longMeasurements.FirstOrDefault(m =>
            m.Tags.Any(t => t.Key == "table" && t.Value?.ToString() == "WorkOrder") &&
            m.Tags.Any(t => t.Key == "type" && t.Value?.ToString() == "Mass"));

        measurement.Value.ShouldBe(1);
    }

    [Fact]
    public void RecordOperationStarted_MultipleCalls_AccumulatesCount()
    {
        // Act
        _sut.RecordOperationStarted("WorkOrder", "Mass");
        _sut.RecordOperationStarted("WorkOrder", "Mass");
        _sut.RecordOperationStarted("LotUsage", "Daily");
        _meterListener.RecordObservableInstruments();

        // Assert
        var workOrderMeasurements = _longMeasurements
            .Where(m => m.Tags.Any(t => t.Key == "table" && t.Value?.ToString() == "WorkOrder"))
            .ToList();

        workOrderMeasurements.Count.ShouldBe(2);
    }

    [Fact]
    public void RecordOperationStarted_DifferentTables_TrackedSeparately()
    {
        // Act
        _sut.RecordOperationStarted("WorkOrder", "Mass");
        _sut.RecordOperationStarted("LotUsage", "Daily");
        _meterListener.RecordObservableInstruments();

        // Assert
        _longMeasurements.Any(m =>
            m.Tags.Any(t => t.Key == "table" && (t.Value as string) == "WorkOrder")).ShouldBeTrue();
        _longMeasurements.Any(m =>
            m.Tags.Any(t => t.Key == "table" && (t.Value as string) == "LotUsage")).ShouldBeTrue();
    }

    #endregion

    #region Operation Completed Counter Tests

    [Fact]
    public void RecordOperationCompleted_IncrementsCounterAndRecordsHistograms()
    {
        // Act
        _sut.RecordOperationCompleted("WorkOrder", "Mass", recordCount: 5000, durationSeconds: 12.5);
        _meterListener.RecordObservableInstruments();

        // Assert: Counter incremented
        var counterMeasurement = _longMeasurements.FirstOrDefault(m =>
            m.Tags.Any(t => t.Key == "table" && t.Value?.ToString() == "WorkOrder"));
        counterMeasurement.Value.ShouldBe(1);

        // Assert: Duration histogram recorded
        var durationMeasurement = _doubleMeasurements.FirstOrDefault(m =>
            m.Tags.Any(t => t.Key == "table" && t.Value?.ToString() == "WorkOrder"));
        durationMeasurement.Value.ShouldBe(12.5);

        // Assert: Records histogram recorded
        var recordsMeasurement = _longMeasurements.FirstOrDefault(m =>
            m.Value == 5000);
        recordsMeasurement.Value.ShouldBe(5000);
    }

    [Fact]
    public void RecordOperationCompleted_WithZeroRecords_StillRecords()
    {
        // Act
        _sut.RecordOperationCompleted("Item", "Hourly", recordCount: 0, durationSeconds: 0.5);
        _meterListener.RecordObservableInstruments();

        // Assert
        _longMeasurements.ShouldContain(m => m.Value == 0);
    }

    [Fact]
    public void RecordOperationCompleted_WithLargeRecordCount_HandlesCorrectly()
    {
        // Act
        _sut.RecordOperationCompleted("WorkOrder", "Mass", recordCount: 10_000_000, durationSeconds: 300.0);
        _meterListener.RecordObservableInstruments();

        // Assert
        _longMeasurements.ShouldContain(m => m.Value == 10_000_000);
    }

    #endregion

    #region Operation Failed Counter Tests

    [Fact]
    public void RecordOperationFailed_IncrementsCounter()
    {
        // Act
        _sut.RecordOperationFailed("WorkOrder", "Daily");
        _meterListener.RecordObservableInstruments();

        // Assert
        var measurement = _longMeasurements.FirstOrDefault(m =>
            m.Tags.Any(t => t.Key == "table" && t.Value?.ToString() == "WorkOrder") &&
            m.Tags.Any(t => t.Key == "type" && t.Value?.ToString() == "Daily"));

        measurement.Value.ShouldBe(1);
    }

    [Fact]
    public void RecordOperationFailed_MultipleFailures_AccumulatesCount()
    {
        // Act
        _sut.RecordOperationFailed("WorkOrder", "Daily");
        _sut.RecordOperationFailed("WorkOrder", "Daily");
        _sut.RecordOperationFailed("WorkOrder", "Daily");
        _meterListener.RecordObservableInstruments();

        // Assert
        var failedMeasurements = _longMeasurements
            .Where(m => m.Tags.Any(t => t.Key == "table" && t.Value?.ToString() == "WorkOrder"))
            .ToList();

        failedMeasurements.Count.ShouldBe(3);
    }

    #endregion

    #region Cycle Error Counter Tests

    [Fact]
    public void RecordCycleError_IncrementsCounter()
    {
        // Act
        _sut.RecordCycleError();
        _meterListener.RecordObservableInstruments();

        // Assert
        _longMeasurements.ShouldContain(m => m.Value == 1);
    }

    #endregion

    #region Cycle Completed Counter Tests

    [Fact]
    public void RecordCycleCompleted_IncrementsCounterWithTags()
    {
        // Act
        _sut.RecordCycleCompleted(successCount: 5, failedCount: 2, durationSeconds: 45.0);
        _meterListener.RecordObservableInstruments();

        // Assert
        var measurement = _longMeasurements.FirstOrDefault(m =>
            m.Tags.Any(t => t.Key == "success_count" && (int)t.Value! == 5) &&
            m.Tags.Any(t => t.Key == "failed_count" && (int)t.Value! == 2));

        measurement.Value.ShouldBe(1);
    }

    [Fact]
    public void RecordCycleCompleted_AllSuccessful_RecordsCorrectly()
    {
        // Act
        _sut.RecordCycleCompleted(successCount: 10, failedCount: 0, durationSeconds: 30.0);
        _meterListener.RecordObservableInstruments();

        // Assert
        _longMeasurements.ShouldContain(m =>
            m.Tags.Any(t => t.Key == "success_count" && (int)t.Value! == 10) &&
            m.Tags.Any(t => t.Key == "failed_count" && (int)t.Value! == 0));
    }

    [Fact]
    public void RecordCycleCompleted_AllFailed_RecordsCorrectly()
    {
        // Act
        _sut.RecordCycleCompleted(successCount: 0, failedCount: 5, durationSeconds: 10.0);
        _meterListener.RecordObservableInstruments();

        // Assert
        _longMeasurements.ShouldContain(m =>
            m.Tags.Any(t => t.Key == "success_count" && (int)t.Value! == 0) &&
            m.Tags.Any(t => t.Key == "failed_count" && (int)t.Value! == 5));
    }

    #endregion

    #region Tag Verification Tests

    [Fact]
    public void AllOperationMetrics_IncludeTableAndTypeTags()
    {
        // Act
        _sut.RecordOperationStarted("TestTable", "TestType");
        _sut.RecordOperationCompleted("TestTable", "TestType", 100, 1.0);
        _sut.RecordOperationFailed("TestTable", "TestType");
        _meterListener.RecordObservableInstruments();

        // Assert: All measurements should have both table and type tags
        foreach (var measurement in _longMeasurements.Take(3)) // First 3 are from the calls above
        {
            measurement.Tags.ShouldContain(t => t.Key == "table");
            measurement.Tags.ShouldContain(t => t.Key == "type");
        }
    }

    #endregion
}

/// <summary>
/// Represents a recorded measurement with its value and tags.
/// </summary>
/// <typeparam name="T">The measurement value type.</typeparam>
public struct Measurement<T>
{
    public T Value { get; }
    public KeyValuePair<string, object?>[] Tags { get; }

    public Measurement(T value, KeyValuePair<string, object?>[] tags)
    {
        Value = value;
        Tags = tags;
    }
}