using Akka.Actor;
using Akka.TestKit.Xunit2;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging.Abstractions;
using ScadaLink.AuditLog.Central;
using ScadaLink.Commons.Entities.Audit;
using ScadaLink.Commons.Interfaces.Repositories;
using ScadaLink.Commons.Messages.Audit;
using ScadaLink.Commons.Types.Audit;
using ScadaLink.Commons.Types.Enums;

namespace ScadaLink.AuditLog.Tests.Central;

/// <summary>
/// Bundle E (M6-T8) regression coverage for the central-side audit-write
/// failure counter. <see cref="CentralAuditWriter"/> and
/// <see cref="AuditLogIngestActor"/> both swallow repository throws (audit
/// must NEVER abort the user-facing action, alog.md §13) but bump the
/// <see cref="ICentralAuditWriteFailureCounter"/> so the central health
/// surface (<see cref="AuditCentralHealthSnapshot"/>) can flag a sustained
/// outage.
/// </summary>
public class CentralAuditWriteFailuresTests : TestKit
{
    private static AuditEvent NewEvent() => new()
    {
        EventId = Guid.NewGuid(),
        OccurredAtUtc = DateTime.UtcNow,
        Channel = AuditChannel.ApiOutbound,
        Kind = AuditKind.ApiCall,
        Status = AuditStatus.Delivered,
    };

    /// <summary>
    /// Repository stub that always throws on insert — exercises the failure
    /// path in both <see cref="CentralAuditWriter"/> and
    /// <see cref="AuditLogIngestActor"/>.
    /// </summary>
    private sealed class ThrowingRepo : IAuditLogRepository
    {
        public Task InsertIfNotExistsAsync(AuditEvent evt, CancellationToken ct = default) =>
            throw new InvalidOperationException("simulated repo failure");
        public Task<IReadOnlyList<AuditEvent>> QueryAsync(
            AuditLogQueryFilter filter, AuditLogPaging paging, CancellationToken ct = default) =>
            Task.FromResult<IReadOnlyList<AuditEvent>>(Array.Empty<AuditEvent>());
        public Task<long> SwitchOutPartitionAsync(DateTime monthBoundary, CancellationToken ct = default) =>
            Task.FromResult(0L);
        public Task<IReadOnlyList<DateTime>> GetPartitionBoundariesOlderThanAsync(
            DateTime threshold, CancellationToken ct = default) =>
            Task.FromResult<IReadOnlyList<DateTime>>(Array.Empty<DateTime>());
    }

    /// <summary>
    /// In-memory <see cref="ICentralAuditWriteFailureCounter"/> recording
    /// every <see cref="Increment"/> call so tests can assert on the count.
    /// </summary>
    private sealed class RecordingFailureCounter : ICentralAuditWriteFailureCounter
    {
        private int _count;
        public int Count => Volatile.Read(ref _count);
        public void Increment() => Interlocked.Increment(ref _count);
    }

    [Fact]
    public async Task Forced_Failure_Increments_Counter()
    {
        // Direct test: build the writer with a throwing scope and verify the
        // injected counter is bumped on the swallowed insert exception.
        var counter = new RecordingFailureCounter();
        var services = new ServiceCollection();
        services.AddScoped<IAuditLogRepository, ThrowingRepo>();
        var sp = services.BuildServiceProvider();

        var writer = new CentralAuditWriter(
            sp,
            NullLogger<CentralAuditWriter>.Instance,
            filter: null,
            failureCounter: counter);

        // WriteAsync swallows the exception and increments the counter.
        await writer.WriteAsync(NewEvent());

        Assert.Equal(1, counter.Count);
    }

    [Fact]
    public async Task AuditLogIngestActor_Failure_Increments_Counter()
    {
        // The actor's production ctor resolves both IAuditLogRepository AND
        // ICentralAuditWriteFailureCounter from the scope per-message; we
        // register both and verify the per-row catch bumps the counter for
        // every row in the batch.
        var counter = new RecordingFailureCounter();
        var services = new ServiceCollection();
        services.AddScoped<IAuditLogRepository, ThrowingRepo>();
        // Counter is a singleton — the actor's per-message scope still
        // resolves the same instance via the scope's parent provider.
        services.AddSingleton<ICentralAuditWriteFailureCounter>(counter);
        var sp = services.BuildServiceProvider();

        var actor = Sys.ActorOf(Props.Create(() => new AuditLogIngestActor(
            sp, NullLogger<AuditLogIngestActor>.Instance)));

        var batch = new[] { NewEvent(), NewEvent(), NewEvent() };
        var reply = await actor.Ask<IngestAuditEventsReply>(
            new IngestAuditEventsCommand(batch), TimeSpan.FromSeconds(5));

        // Every row threw → none accepted, counter bumped once per row.
        Assert.Empty(reply.AcceptedEventIds);
        Assert.Equal(batch.Length, counter.Count);
    }

    [Fact]
    public void Snapshot_Aggregates_Counters_And_StalledState()
    {
        // AuditCentralHealthSnapshot implements both writer surfaces; bumping
        // through the writer interfaces is reflected on the read surface, and
        // the per-site stalled state is fed in via ApplyStalled — production
        // wires that to a SiteAuditTelemetryStalledTracker, but the snapshot
        // is testable in isolation against the same Apply surface.
        var snapshot = new AuditCentralHealthSnapshot();

        Assert.Equal(0, snapshot.CentralAuditWriteFailures);
        Assert.Equal(0, snapshot.AuditRedactionFailure);
        Assert.Empty(snapshot.SiteAuditTelemetryStalled);

        ((ICentralAuditWriteFailureCounter)snapshot).Increment();
        ((ICentralAuditWriteFailureCounter)snapshot).Increment();
        ((ScadaLink.AuditLog.Payload.IAuditRedactionFailureCounter)snapshot).Increment();

        // Wire the tracker so an EventStream publish reaches the snapshot.
        // The tracker pushes into the snapshot's ApplyStalled when given
        // the snapshot in its ctor; the tracker also keeps its own latch,
        // but the snapshot read surface is what the central UI reads.
        using var tracker = new SiteAuditTelemetryStalledTracker(Sys, snapshot);
        Sys.EventStream.Publish(new SiteAuditTelemetryStalledChanged("siteA", Stalled: true));
        AwaitAssert(() =>
            {
                var stalledMap = snapshot.SiteAuditTelemetryStalled;
                Assert.True(stalledMap.TryGetValue("siteA", out var s) && s,
                    "expected siteA to be stalled in snapshot");
            },
            duration: TimeSpan.FromSeconds(2),
            interval: TimeSpan.FromMilliseconds(20));

        Assert.Equal(2, snapshot.CentralAuditWriteFailures);
        Assert.Equal(1, snapshot.AuditRedactionFailure);
    }

    [Fact]
    public void Snapshot_Empty_OnConstruction()
    {
        // Sanity: the snapshot's three properties start at their zero values
        // before any writer or stalled-event publication.
        var snapshot = new AuditCentralHealthSnapshot();
        Assert.Equal(0, snapshot.CentralAuditWriteFailures);
        Assert.Equal(0, snapshot.AuditRedactionFailure);
        Assert.Empty(snapshot.SiteAuditTelemetryStalled);
    }
}