using Omika.Core.Configuration;
using Omika.Core.Observability;

namespace Omika.Tests.Observability;

public class TelemetryWorkerTests
{
    [Fact]
    public async Task Worker_DrainsToExporter()
    {
        var (queue, counters) = CreateQueue();
        var exporter = new CollectingExporter();
        var worker = new TelemetryWorker(queue, exporter);

        queue.TryEnqueue(ObservabilityTestHarness.NewEvent(TelemetryEventCodes.MobileAppStarted));
        queue.TryEnqueue(ObservabilityTestHarness.NewEvent(TelemetryEventCodes.MobileAppStarted));

        using var cts = new CancellationTokenSource();
        Task run = worker.ExecuteAsync(cts.Token);

        await ObservabilityTestHarness.WaitUntilAsync(() => exporter.Count == 2);

        cts.Cancel();
        await run;
    }

    [Fact]
    public async Task Worker_DoesNotStarveLowPriority()
    {
        var (queue, _) = CreateQueue();
        var exporter = new CollectingExporter();
        var worker = new TelemetryWorker(queue, exporter);

        // Fort arriéré de P0 + quelques P4 : les P4 doivent quand même être exportés.
        for (int i = 0; i < 100; i++)
        {
            queue.TryEnqueue(ObservabilityTestHarness.NewEvent(
                TelemetryEventCodes.MobileSyncOperationReceived, priority: TelemetryPriority.P0));
        }

        for (int i = 0; i < 10; i++)
        {
            queue.TryEnqueue(ObservabilityTestHarness.NewEvent(
                TelemetryEventCodes.MobileAppStarted, priority: TelemetryPriority.P4));
        }

        using var cts = new CancellationTokenSource();
        Task run = worker.ExecuteAsync(cts.Token);

        await ObservabilityTestHarness.WaitUntilAsync(() => exporter.Count == 110);

        cts.Cancel();
        await run;

        Assert.Equal(100, exporter.ByPriority(TelemetryPriority.P0));
        Assert.Equal(10, exporter.ByPriority(TelemetryPriority.P4));
    }

    [Fact]
    public async Task Worker_ExporterThrows_DoesNotPropagate()
    {
        var (queue, _) = CreateQueue();
        var worker = new TelemetryWorker(queue, new ThrowingExporter());

        queue.TryEnqueue(ObservabilityTestHarness.NewEvent(TelemetryEventCodes.MobileAppStarted));

        using var cts = new CancellationTokenSource();
        Task run = worker.ExecuteAsync(cts.Token);

        // Laisse au worker le temps de tenter l'export, d'échouer et de reprendre.
        await Task.Delay(300);
        cts.Cancel();

        await run;
        // Le lot a été abandonné (perte de log acceptable) ; aucune exception.
        Assert.Equal(0, queue.Count);
    }

    [Fact]
    public async Task Worker_Cancellation_Stops()
    {
        var (queue, _) = CreateQueue();
        var worker = new TelemetryWorker(queue, new NullTelemetryExporter());

        using var cts = new CancellationTokenSource();
        Task run = worker.ExecuteAsync(cts.Token);

        cts.Cancel();
        await run;
    }

    private static (PriorityTelemetryQueue Queue, TelemetryCounters Counters) CreateQueue()
    {
        var options = new ObservabilityOptions();
        var counters = new TelemetryCounters();
        return (new PriorityTelemetryQueue(options, counters), counters);
    }

    private sealed class CollectingExporter : ITelemetryExporter
    {
        private readonly object _lock = new();
        private readonly List<OmikaEvent> _exported = [];

        public int Count
        {
            get
            {
                lock (_lock)
                {
                    return _exported.Count;
                }
            }
        }

        public int ByPriority(TelemetryPriority priority)
        {
            lock (_lock)
            {
                return _exported.Count(e => e.EffectivePriority == priority);
            }
        }

        public Task ExportAsync(IReadOnlyList<OmikaEvent> events, CancellationToken cancellationToken = default)
        {
            lock (_lock)
            {
                _exported.AddRange(events);
            }

            return Task.CompletedTask;
        }
    }

    private sealed class ThrowingExporter : ITelemetryExporter
    {
        public Task ExportAsync(IReadOnlyList<OmikaEvent> events, CancellationToken cancellationToken = default) =>
            throw new InvalidOperationException("exporteur défaillant (test)");
    }
}