using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using ZB.MOM.WW.Secrets.Abstractions;

namespace ZB.MOM.WW.Secrets.Replicator.Grpc.Tests;

/// <summary>
/// Covers the hub follower's sweep-outcome observability: the Debug-per-sweep / Information-
/// heartbeat-once-per-interval pair for an in-sync sweep (EventId 4/5), the recovered line the
/// first success after a run of failures logs (EventId 6), and <see cref="ISecretsHubSyncStatus"/>
/// tracking the same outcomes.
/// </summary>
public sealed class GrpcSecretSyncServiceLoggingTests
{
    [Fact]
    public async Task InSyncSweep_LogsDebugEveryTime_AndInformationHeartbeatOncePerInterval()
    {
        var time = new FakeTimeProvider(DateTimeOffset.Parse("2026-09-28T00:00:00Z"));
        (GrpcSecretSyncService svc, RecordingListLogger logs, _) = Harness.Create(
            time, inSyncLogInterval: TimeSpan.FromHours(1), manifestUnchanged: true);

        await svc.SweepForTestAsync(CancellationToken.None);
        time.Advance(TimeSpan.FromMinutes(30));
        await svc.SweepForTestAsync(CancellationToken.None);
        time.Advance(TimeSpan.FromMinutes(31));
        await svc.SweepForTestAsync(CancellationToken.None);

        Assert.Equal(3, logs.Entries.Count(l => l.EventId.Id == 4 && l.Level == LogLevel.Debug));
        Assert.Equal(2, logs.Entries.Count(l => l.EventId.Id == 5 && l.Level == LogLevel.Information));
    }

    [Fact]
    public async Task FirstSuccessAfterFailures_LogsRecovered_AndStatusResets()
    {
        var time = new FakeTimeProvider();
        (GrpcSecretSyncService svc, RecordingListLogger logs, ISecretsHubSyncStatus status) =
            Harness.Create(time, failFirst: 2);

        await svc.SweepForTestAsync(default);
        await svc.SweepForTestAsync(default);

        Assert.Equal(2, status.ConsecutiveFailures);

        await svc.SweepForTestAsync(default);

        Assert.Contains(logs.Entries, l => l.EventId.Id == 6 && l.Message.Contains("after 2 failed"));
        Assert.Equal(0, status.ConsecutiveFailures);
        Assert.NotNull(status.LastSuccessUtc);
    }

    [Fact]
    public async Task A_failed_sweep_never_logs_EventId6_and_status_records_the_error()
    {
        var time = new FakeTimeProvider();
        (GrpcSecretSyncService svc, RecordingListLogger logs, ISecretsHubSyncStatus status) =
            Harness.Create(time, failFirst: 1);

        await svc.SweepForTestAsync(default);

        Assert.DoesNotContain(logs.Entries, l => l.EventId.Id == 6);
        Assert.Equal(1, status.ConsecutiveFailures);
        Assert.NotNull(status.LastError);
        Assert.Null(status.LastSuccessUtc);
    }

    [Fact]
    public async Task An_in_sync_sweep_never_logs_the_recovered_line()
    {
        var time = new FakeTimeProvider();
        (GrpcSecretSyncService svc, RecordingListLogger logs, ISecretsHubSyncStatus status) =
            Harness.Create(time, manifestUnchanged: true);

        await svc.SweepForTestAsync(default);
        await svc.SweepForTestAsync(default);

        Assert.DoesNotContain(logs.Entries, l => l.EventId.Id == 6);
        Assert.Equal(0, status.ConsecutiveFailures);
        Assert.NotNull(status.LastSweepUtc);
    }

    // Assembles a GrpcSecretSyncService wired to a controllable fake hub, a no-op local store (the
    // scenarios here never actually apply a row — an empty hub manifest means the reconciler's pull
    // set is always empty), a log-capturing logger, and the internal status tracker the service
    // writes to — so a test can both drive sweeps and observe everything they produced.
    private static class Harness
    {
        public static (GrpcSecretSyncService Service, RecordingListLogger Logs, ISecretsHubSyncStatus Status) Create(
            FakeTimeProvider time,
            TimeSpan? inSyncLogInterval = null,
            bool manifestUnchanged = false,
            int failFirst = 0)
        {
            var logger = new RecordingListLogger();
            var status = new SecretsHubSyncStatus();

            ISecretsHubReader hub = failFirst > 0
                ? new SequencedFailThenEmptyHubReader(failFirst)
                : new EmptyHubReader();

            IOptions<SecretsGrpcHubClientOptions> options = Options.Create(new SecretsGrpcHubClientOptions
            {
                Endpoint = "https://central:5001",
                BearerToken = "unused-by-the-fake",
                SyncInterval = TimeSpan.FromHours(1),
                InSyncLogInterval = inSyncLogInterval ?? TimeSpan.FromHours(1),
            });

            // manifestUnchanged has no separate fake to select: both readers above always answer an
            // empty (therefore unchanged, nothing-to-pull) manifest once they are done failing, so
            // the parameter exists to make each call site self-documenting rather than to branch on.
            var svc = new GrpcSecretSyncService(
                new NoOpLocalStore(),
                hub,
                cacheInvalidator: null,
                options,
                logger,
                time,
                status);

            return (svc, logger, status);
        }
    }

    /// <summary>A hub with nothing in it — every sweep is in-sync with zero rows to pull.</summary>
    private sealed class EmptyHubReader : ISecretsHubReader
    {
        public Task<IReadOnlyList<SecretManifestEntry>> GetManifestAsync(CancellationToken ct) =>
            Task.FromResult<IReadOnlyList<SecretManifestEntry>>([]);

        public Task<IReadOnlyList<StoredSecret>> GetManyAsync(
            IReadOnlyList<SecretName> names, CancellationToken ct) =>
            Task.FromResult<IReadOnlyList<StoredSecret>>([]);
    }

    /// <summary>
    /// Fails the manifest call with a transport-shaped exception for the first
    /// <paramref name="failuresBeforeSuccess"/> calls, then behaves exactly like
    /// <see cref="EmptyHubReader"/> forever after.
    /// </summary>
    private sealed class SequencedFailThenEmptyHubReader(int failuresBeforeSuccess) : ISecretsHubReader
    {
        private int _remaining = failuresBeforeSuccess;

        public Task<IReadOnlyList<SecretManifestEntry>> GetManifestAsync(CancellationToken ct)
        {
            if (_remaining > 0)
            {
                _remaining--;
                return Task.FromException<IReadOnlyList<SecretManifestEntry>>(
                    new InvalidOperationException("hub unreachable"));
            }

            return Task.FromResult<IReadOnlyList<SecretManifestEntry>>([]);
        }

        public Task<IReadOnlyList<StoredSecret>> GetManyAsync(
            IReadOnlyList<SecretName> names, CancellationToken ct) =>
            Task.FromResult<IReadOnlyList<StoredSecret>>([]);
    }

    /// <summary>
    /// A local store that is never actually exercised by these scenarios (the hub manifest is
    /// always empty, so the reconciler's pull set is always empty and none of these members are
    /// called) beyond <see cref="GetManifestAsync"/>, which the reconciler always calls to compute
    /// the pull set.
    /// </summary>
    private sealed class NoOpLocalStore : ISecretStore
    {
        public Task<StoredSecret?> GetAsync(SecretName name, CancellationToken ct) =>
            throw new NotSupportedException("not exercised by the logging test scenarios.");

        public Task UpsertAsync(StoredSecret row, CancellationToken ct) =>
            throw new NotSupportedException("not exercised by the logging test scenarios.");

        public Task<bool> DeleteAsync(SecretName name, string? actor, CancellationToken ct) =>
            throw new NotSupportedException("not exercised by the logging test scenarios.");

        public Task<IReadOnlyList<SecretMetadata>> ListAsync(bool includeDeleted, CancellationToken ct) =>
            throw new NotSupportedException("not exercised by the logging test scenarios.");

        public Task<IReadOnlyList<SecretManifestEntry>> GetManifestAsync(CancellationToken ct) =>
            Task.FromResult<IReadOnlyList<SecretManifestEntry>>([]);

        public Task ApplyReplicatedAsync(StoredSecret row, CancellationToken ct) =>
            throw new NotSupportedException("not exercised by the logging test scenarios.");

        public Task<bool> ApplyRewrapAsync(
            StoredSecret rewrappedRow, byte[] expectedCurrentWrappedDek, CancellationToken ct) =>
            throw new NotSupportedException("not exercised by the logging test scenarios.");
    }
}

/// <summary>A clock a test advances by hand, so an hourly heartbeat can be tested without waiting an hour.</summary>
/// <remarks>
/// Hand-rolled rather than taken from <c>Microsoft.Extensions.TimeProvider.Testing</c>, matching
/// this project's existing convention (see <c>HubFakeTimeProvider</c> in
/// <c>SecretsHubAuthInterceptorTests.cs</c>) of not taking that package dependency for one small type.
/// </remarks>
internal sealed class FakeTimeProvider : TimeProvider
{
    private DateTimeOffset _now;

    /// <summary>Creates a clock starting at the current wall-clock time.</summary>
    public FakeTimeProvider() : this(DateTimeOffset.UtcNow)
    {
    }

    /// <summary>Creates a clock starting at <paramref name="now"/>.</summary>
    /// <param name="now">The instant the clock starts at.</param>
    public FakeTimeProvider(DateTimeOffset now) => _now = now;

    /// <inheritdoc/>
    public override DateTimeOffset GetUtcNow() => _now;

    /// <summary>Moves the clock forward by <paramref name="delta"/>.</summary>
    /// <param name="delta">The amount of time to advance.</param>
    public void Advance(TimeSpan delta) => _now += delta;
}

/// <summary>Captures every log entry's level, event id, and formatted message, across all levels.</summary>
/// <remarks>
/// Distinct from the existing <c>RecordingLogger&lt;T&gt;</c> in <c>TestDoubles.cs</c>, which only
/// captures Information/Warning and neither type captures <see cref="EventId"/> — this suite needs
/// Debug-level entries and event-id assertions that the existing double does not support, and
/// widening it would risk the tests that already depend on its narrower shape.
/// </remarks>
internal sealed class RecordingListLogger : ILogger<GrpcSecretSyncService>
{
    /// <summary>Every entry logged, in order.</summary>
    public List<(LogLevel Level, EventId EventId, string Message)> Entries { get; } = [];

    /// <inheritdoc/>
    public IDisposable? BeginScope<TState>(TState state) where TState : notnull => null;

    /// <inheritdoc/>
    public bool IsEnabled(LogLevel logLevel) => true;

    /// <inheritdoc/>
    public void Log<TState>(
        LogLevel logLevel,
        EventId eventId,
        TState state,
        Exception? exception,
        Func<TState, Exception?, string> formatter)
    {
        ArgumentNullException.ThrowIfNull(formatter);

        Entries.Add((logLevel, eventId, formatter(state, exception)));
    }
}