using Akka.Actor;
using Akka.TestKit.Xunit2;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using ScadaLink.AuditLog.Central;
using ScadaLink.Commons.Entities.Audit;
using ScadaLink.Commons.Interfaces.Repositories;
using ScadaLink.Commons.Messages.Integration;
using ScadaLink.Commons.Types.Audit;
using ScadaLink.Commons.Types.Enums;
using ScadaLink.ConfigurationDatabase;
using ScadaLink.ConfigurationDatabase.Repositories;
using ScadaLink.ConfigurationDatabase.Tests.Migrations;

namespace ScadaLink.AuditLog.Tests.Central;

/// <summary>
/// Bundle B (M6-T3) tests for <see cref="SiteAuditReconciliationActor"/>. Most
/// tests substitute the <see cref="IAuditLogRepository"/> with an in-memory
/// recording stub so the actor's tick / cursor / stalled state machinery can
/// be exercised in milliseconds without an MSSQL container. The duplicate /
/// idempotency assertion uses the real <see cref="AuditLogRepository"/> against
/// the <see cref="MsSqlMigrationFixture"/> so we verify InsertIfNotExistsAsync
/// actually swallows duplicate-key collisions (the M2 Bundle A race-fix the
/// reconciliation puller depends on).
/// </summary>
public class SiteAuditReconciliationActorTests : TestKit, IClassFixture<MsSqlMigrationFixture>
{
    private readonly MsSqlMigrationFixture _fixture;

    public SiteAuditReconciliationActorTests(MsSqlMigrationFixture fixture)
    {
        _fixture = fixture;
    }

    private static AuditEvent NewEvent(
        string siteId,
        DateTime? occurredAt = null,
        Guid? id = null) => new()
    {
        EventId = id ?? Guid.NewGuid(),
        OccurredAtUtc = occurredAt ?? new DateTime(2026, 5, 20, 10, 0, 0, DateTimeKind.Utc),
        Channel = AuditChannel.ApiOutbound,
        Kind = AuditKind.ApiCall,
        Status = AuditStatus.Delivered,
        SourceSiteId = siteId,
    };

    private static SiteAuditReconciliationOptions FastTickOptions(
        int batchSize = 256,
        int stalledAfter = 2) =>
        new()
        {
            // 100 ms tick keeps each test under a second. AwaitAssert covers
            // schedule jitter so a 100 ms tick has up to ~3 s to fire.
            ReconciliationIntervalSeconds = 300,
            ReconciliationIntervalOverride = TimeSpan.FromMilliseconds(100),
            BatchSize = batchSize,
            StalledAfterNonDrainingCycles = stalledAfter,
        };

    /// <summary>
    /// In-memory recording stub used for non-MSSQL tests. Captures every
    /// <see cref="InsertIfNotExistsAsync"/> call AND deduplicates on
    /// <see cref="AuditEvent.EventId"/> so duplicate-handling assertions don't
    /// need a real database for the simple cases.
    /// </summary>
    private sealed class RecordingRepo : IAuditLogRepository
    {
        public List<AuditEvent> Inserted { get; } = new();
        private readonly HashSet<Guid> _seen = new();
        public int InsertCallCount { get; private set; }

        public Task InsertIfNotExistsAsync(AuditEvent evt, CancellationToken ct = default)
        {
            InsertCallCount++;
            if (_seen.Add(evt.EventId))
            {
                Inserted.Add(evt);
            }
            return Task.CompletedTask;
        }

        public Task<IReadOnlyList<AuditEvent>> QueryAsync(
            AuditLogQueryFilter filter, AuditLogPaging paging, CancellationToken ct = default) =>
            Task.FromResult<IReadOnlyList<AuditEvent>>(Inserted);

        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>());

        public Task<ScadaLink.Commons.Types.AuditLogKpiSnapshot> GetKpiSnapshotAsync(
            TimeSpan window, DateTime? nowUtc = null, CancellationToken ct = default) =>
            Task.FromResult(new ScadaLink.Commons.Types.AuditLogKpiSnapshot(0L, 0L, 0L, nowUtc ?? DateTime.UtcNow));
    }

    /// <summary>
    /// In-memory enumerator returning a static list of sites.
    /// </summary>
    private sealed class StaticEnumerator : ISiteEnumerator
    {
        private readonly IReadOnlyList<SiteEntry> _sites;
        public StaticEnumerator(params SiteEntry[] sites) => _sites = sites;
        public Task<IReadOnlyList<SiteEntry>> EnumerateAsync(CancellationToken ct = default) =>
            Task.FromResult(_sites);
    }

    /// <summary>
    /// Scripted pull client — returns the next queued response for the site
    /// on each call, looping the last entry if the queue is exhausted. Also
    /// records every invocation so tests can assert call counts + arguments.
    /// </summary>
    private sealed class ScriptedPullClient : IPullAuditEventsClient
    {
        public List<(string SiteId, DateTime SinceUtc, int BatchSize)> Calls { get; } = new();
        private readonly Dictionary<string, Queue<PullAuditEventsResponse>> _scripted = new();
        private readonly Dictionary<string, Exception> _throwOnSite = new();

        public ScriptedPullClient Script(string siteId, params PullAuditEventsResponse[] responses)
        {
            _scripted[siteId] = new Queue<PullAuditEventsResponse>(responses);
            return this;
        }

        public ScriptedPullClient ThrowFor(string siteId, Exception ex)
        {
            _throwOnSite[siteId] = ex;
            return this;
        }

        public Task<PullAuditEventsResponse> PullAsync(
            string siteId, DateTime sinceUtc, int batchSize, CancellationToken ct)
        {
            Calls.Add((siteId, sinceUtc, batchSize));
            if (_throwOnSite.TryGetValue(siteId, out var ex))
            {
                throw ex;
            }
            if (_scripted.TryGetValue(siteId, out var queue) && queue.Count > 0)
            {
                return Task.FromResult(queue.Dequeue());
            }
            return Task.FromResult(
                new PullAuditEventsResponse(Array.Empty<AuditEvent>(), MoreAvailable: false));
        }
    }

    private IServiceProvider BuildScopedProvider(IAuditLogRepository repo)
    {
        var services = new ServiceCollection();
        // The actor opens a scope per tick and resolves IAuditLogRepository
        // from that scope; registering as scoped mirrors how
        // AddConfigurationDatabase wires the real repository.
        services.AddScoped(_ => repo);
        return services.BuildServiceProvider();
    }

    private IActorRef CreateActor(
        ISiteEnumerator sites,
        IPullAuditEventsClient client,
        IAuditLogRepository repo,
        SiteAuditReconciliationOptions options)
    {
        var sp = BuildScopedProvider(repo);
        return Sys.ActorOf(Props.Create(() => new SiteAuditReconciliationActor(
            sites,
            client,
            sp,
            Options.Create(options),
            NullLogger<SiteAuditReconciliationActor>.Instance)));
    }

    /// <summary>
    /// Subscribes to the EventStream and collects every
    /// <see cref="SiteAuditTelemetryStalledChanged"/> publication into a list
    /// the test can assert on. Uses a probe actor so the stream's
    /// fire-and-forget delivery is observable from the test thread.
    /// </summary>
    private (Akka.TestKit.TestProbe Probe, List<SiteAuditTelemetryStalledChanged> Captured) SubscribeStalled()
    {
        var probe = CreateTestProbe();
        Sys.EventStream.Subscribe(probe.Ref, typeof(SiteAuditTelemetryStalledChanged));
        var captured = new List<SiteAuditTelemetryStalledChanged>();
        return (probe, captured);
    }

    // ---------------------------------------------------------------------
    // 1. Timer_Fires_OnConfiguredInterval
    // ---------------------------------------------------------------------

    [Fact]
    public void Timer_Fires_OnConfiguredInterval()
    {
        var sites = new StaticEnumerator(new SiteEntry("siteA", "http://siteA:8083"));
        var client = new ScriptedPullClient();
        var repo = new RecordingRepo();
        var opts = FastTickOptions();

        CreateActor(sites, client, repo, opts);

        // The first scheduled tick fires after `ReconciliationIntervalSeconds`,
        // which is 0 for the test — Akka's scheduler still respects the
        // ScheduleTellRepeatedlyCancelable contract that issues a Tell on the
        // scheduler thread, so we await visible side effects (a PullAsync call)
        // rather than racing on internal state.
        AwaitAssert(
            () => Assert.True(client.Calls.Count >= 1, $"expected >= 1 pull call, got {client.Calls.Count}"),
            duration: TimeSpan.FromSeconds(3),
            interval: TimeSpan.FromMilliseconds(50));
    }

    // ---------------------------------------------------------------------
    // 2. Tick_PullsFromEachKnownSite
    // ---------------------------------------------------------------------

    [Fact]
    public void Tick_PullsFromEachKnownSite()
    {
        var sites = new StaticEnumerator(
            new SiteEntry("siteA", "http://siteA:8083"),
            new SiteEntry("siteB", "http://siteB:8083"));
        var client = new ScriptedPullClient();
        var repo = new RecordingRepo();

        CreateActor(sites, client, repo, FastTickOptions());

        AwaitAssert(() =>
            {
                Assert.Contains(client.Calls, c => c.SiteId == "siteA");
                Assert.Contains(client.Calls, c => c.SiteId == "siteB");
            },
            duration: TimeSpan.FromSeconds(3),
            interval: TimeSpan.FromMilliseconds(50));
    }

    // ---------------------------------------------------------------------
    // 3. Tick_IngestEvents_ViaInsertIfNotExistsAsync
    // ---------------------------------------------------------------------

    [Fact]
    public void Tick_IngestEvents_ViaInsertIfNotExistsAsync()
    {
        var sites = new StaticEnumerator(new SiteEntry("siteA", "http://siteA:8083"));
        var e1 = NewEvent("siteA");
        var e2 = NewEvent("siteA");
        var client = new ScriptedPullClient().Script("siteA",
            new PullAuditEventsResponse(new[] { e1, e2 }, MoreAvailable: false));
        var repo = new RecordingRepo();

        CreateActor(sites, client, repo, FastTickOptions());

        AwaitAssert(() => Assert.Equal(2, repo.InsertCallCount),
            duration: TimeSpan.FromSeconds(3),
            interval: TimeSpan.FromMilliseconds(50));
        Assert.Contains(repo.Inserted, e => e.EventId == e1.EventId);
        Assert.Contains(repo.Inserted, e => e.EventId == e2.EventId);
    }

    // ---------------------------------------------------------------------
    // 4. Tick_Duplicates_NotDoubleInserted (real MSSQL idempotency)
    // ---------------------------------------------------------------------

    private ScadaLinkDbContext CreateContext() =>
        new(new DbContextOptionsBuilder<ScadaLinkDbContext>()
            .UseSqlServer(_fixture.ConnectionString).Options);

    [SkippableFact]
    public async Task Tick_Duplicates_NotDoubleInserted()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var siteId = "bundle-b-" + Guid.NewGuid().ToString("N").Substring(0, 8);
        var pre = NewEvent(siteId);

        // Seed the row directly so the actor sees it already present when the
        // pull returns it.
        await using (var seedContext = CreateContext())
        {
            await new AuditLogRepository(seedContext).InsertIfNotExistsAsync(pre);
        }

        // Stack one new and the pre-existing row in the pull response. The
        // second-pull script returns empty so the actor settles.
        var fresh = NewEvent(siteId);
        var sites = new StaticEnumerator(new SiteEntry(siteId, "http://x:8083"));
        var client = new ScriptedPullClient().Script(siteId,
            new PullAuditEventsResponse(new[] { pre, fresh }, MoreAvailable: false));

        await using var context = CreateContext();
        var repo = new AuditLogRepository(context);

        CreateActor(sites, client, repo, FastTickOptions());

        // Wait for the actor to ingest both rows.
        await Task.Delay(TimeSpan.FromSeconds(1));
        AwaitAssert(() => Assert.True(client.Calls.Count >= 1),
            duration: TimeSpan.FromSeconds(3));

        // Even though the pull returned 2 events, only 1 fresh row should
        // exist in MSSQL alongside the pre-existing one — InsertIfNotExistsAsync
        // is first-write-wins on EventId.
        await using var read = CreateContext();
        var rows = await read.Set<AuditEvent>()
            .Where(e => e.SourceSiteId == siteId)
            .ToListAsync();
        Assert.Equal(2, rows.Count);
        Assert.Contains(rows, r => r.EventId == pre.EventId);
        Assert.Contains(rows, r => r.EventId == fresh.EventId);
    }

    // ---------------------------------------------------------------------
    // 5. Cursor_Advances_ToMaxOccurredAtUtc
    // ---------------------------------------------------------------------

    [Fact]
    public void Cursor_Advances_ToMaxOccurredAtUtc()
    {
        var sites = new StaticEnumerator(new SiteEntry("siteA", "http://siteA:8083"));

        var t1 = new DateTime(2026, 5, 20, 10, 0, 0, DateTimeKind.Utc);
        var t2 = new DateTime(2026, 5, 20, 10, 1, 0, DateTimeKind.Utc);
        var t3 = new DateTime(2026, 5, 20, 10, 2, 0, DateTimeKind.Utc);
        var e1 = NewEvent("siteA", t1);
        var e2 = NewEvent("siteA", t2);
        var e3 = NewEvent("siteA", t3);

        // First pull returns three events with t1, t2, t3. Subsequent pulls
        // return empty — but the test asserts the SECOND pull's since argument
        // is t3 (the max OccurredAtUtc from the first pull).
        var client = new ScriptedPullClient().Script("siteA",
            new PullAuditEventsResponse(new[] { e1, e2, e3 }, MoreAvailable: false));
        var repo = new RecordingRepo();

        CreateActor(sites, client, repo, FastTickOptions());

        // Wait until we have at least two pulls — the second one must use t3
        // as its `since` argument because that was the max OccurredAtUtc in
        // the first response.
        AwaitAssert(() => Assert.True(client.Calls.Count >= 2,
            $"need at least 2 pulls to assert cursor advancement, got {client.Calls.Count}"),
            duration: TimeSpan.FromSeconds(5),
            interval: TimeSpan.FromMilliseconds(50));

        Assert.Equal(DateTime.MinValue, client.Calls[0].SinceUtc);
        Assert.Equal(t3, client.Calls[1].SinceUtc);
    }

    // ---------------------------------------------------------------------
    // 6. Tick_OneSiteThrows_OtherSitesStillProcessed
    // ---------------------------------------------------------------------

    [Fact]
    public void Tick_OneSiteThrows_OtherSitesStillProcessed()
    {
        var sites = new StaticEnumerator(
            new SiteEntry("siteA", "http://siteA:8083"),
            new SiteEntry("siteB", "http://siteB:8083"));

        var bEvent = NewEvent("siteB");
        var client = new ScriptedPullClient()
            .ThrowFor("siteA", new InvalidOperationException("simulated transport failure"))
            .Script("siteB",
                new PullAuditEventsResponse(new[] { bEvent }, MoreAvailable: false));
        var repo = new RecordingRepo();

        CreateActor(sites, client, repo, FastTickOptions());

        AwaitAssert(() =>
            {
                Assert.Contains(client.Calls, c => c.SiteId == "siteA");
                Assert.Contains(repo.Inserted, e => e.EventId == bEvent.EventId);
            },
            duration: TimeSpan.FromSeconds(3),
            interval: TimeSpan.FromMilliseconds(50));
    }

    // ---------------------------------------------------------------------
    // 7. StalledDetection_TwoConsecutiveNonDrainingCycles_PublishesStalledTrue
    // ---------------------------------------------------------------------

    [Fact]
    public void StalledDetection_TwoConsecutiveNonDrainingCycles_PublishesStalledTrue()
    {
        var sites = new StaticEnumerator(new SiteEntry("siteA", "http://siteA:8083"));

        // Two scripted responses that each return events AND MoreAvailable=true
        // — the second pull triggers the stalled transition.
        var batch1 = Enumerable.Range(0, 3).Select(_ => NewEvent("siteA")).ToArray();
        var batch2 = Enumerable.Range(0, 3).Select(_ => NewEvent("siteA")).ToArray();
        var client = new ScriptedPullClient().Script("siteA",
            new PullAuditEventsResponse(batch1, MoreAvailable: true),
            new PullAuditEventsResponse(batch2, MoreAvailable: true));

        var repo = new RecordingRepo();
        var (probe, _) = SubscribeStalled();

        CreateActor(sites, client, repo, FastTickOptions(stalledAfter: 2));

        // Expect Stalled=true after the second non-draining tick. The probe
        // waits with its own timeout (a few seconds gives the 0 s repeat
        // interval ample slack).
        var msg = probe.ExpectMsg<SiteAuditTelemetryStalledChanged>(TimeSpan.FromSeconds(5));
        Assert.Equal("siteA", msg.SiteId);
        Assert.True(msg.Stalled);
    }

    // ---------------------------------------------------------------------
    // 8. StalledDetection_DrainingCycle_PublishesStalledFalse
    // ---------------------------------------------------------------------

    [Fact]
    public void StalledDetection_DrainingCycle_PublishesStalledFalse()
    {
        var sites = new StaticEnumerator(new SiteEntry("siteA", "http://siteA:8083"));

        // Two non-draining responses get the actor into Stalled=true, then a
        // draining response (events but MoreAvailable=false) flips it back.
        var batch1 = Enumerable.Range(0, 3).Select(_ => NewEvent("siteA")).ToArray();
        var batch2 = Enumerable.Range(0, 3).Select(_ => NewEvent("siteA")).ToArray();
        var batch3 = Enumerable.Range(0, 3).Select(_ => NewEvent("siteA")).ToArray();
        var client = new ScriptedPullClient().Script("siteA",
            new PullAuditEventsResponse(batch1, MoreAvailable: true),
            new PullAuditEventsResponse(batch2, MoreAvailable: true),
            new PullAuditEventsResponse(batch3, MoreAvailable: false));

        var repo = new RecordingRepo();
        var (probe, _) = SubscribeStalled();

        CreateActor(sites, client, repo, FastTickOptions(stalledAfter: 2));

        // First publication is the stalled=true transition; second is the
        // back-to-draining flip. The actor publishes ONLY on transitions so we
        // expect exactly these two messages in order.
        var first = probe.ExpectMsg<SiteAuditTelemetryStalledChanged>(TimeSpan.FromSeconds(5));
        Assert.True(first.Stalled);

        var second = probe.ExpectMsg<SiteAuditTelemetryStalledChanged>(TimeSpan.FromSeconds(5));
        Assert.False(second.Stalled);
        Assert.Equal("siteA", second.SiteId);
    }
}