using System.Collections.Concurrent;
using System.Diagnostics;
using Microsoft.Extensions.Logging.Abstractions;
using Microsoft.Extensions.Options;
using ZB.MOM.WW.ScadaBridge.AuditLog.Site;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Services;
using ZB.MOM.WW.ScadaBridge.Commons.Types;
using AuditEvent = ZB.MOM.WW.Audit.AuditEvent;

namespace ZB.MOM.WW.ScadaBridge.AuditLog.Tests.Site;

/// <summary>
/// Tests for <see cref="SiteAuditRetentionService"/> (PLAN-04 Task 3). The hosted
/// service runs the site SQLite retention purge on a timer: first tick after
/// <see cref="SiteAuditRetentionOptions.InitialDelay"/>, then every
/// <see cref="SiteAuditRetentionOptions.ResolvedPurgeInterval"/>, passing a cutoff of
/// <c>UtcNow - ResolvedRetentionDays</c>. Per-tick failures are swallowed so a
/// transient SQLite error never tears the service down.
/// </summary>
public class SiteAuditRetentionServiceTests
{
    [Fact]
    public async Task Tick_Purges_With_RetentionCutoff()
    {
        var queue = new RecordingSiteAuditQueue();
        var options = Options.Create(new SiteAuditRetentionOptions
        {
            RetentionDays = 7,
            // Override bypasses the 1-min production clamp so the loop ticks in ms.
            PurgeIntervalOverride = TimeSpan.FromMilliseconds(50),
            InitialDelay = TimeSpan.Zero,
        });
        using var svc = new SiteAuditRetentionService(queue, options, NullLogger<SiteAuditRetentionService>.Instance);

        await svc.StartAsync(CancellationToken.None);
        await WaitUntilAsync(() => queue.PurgeCalls.Count >= 1, TimeSpan.FromSeconds(5));
        await svc.StopAsync(CancellationToken.None);

        var cutoff = queue.PurgeCalls.First();
        Assert.InRange(cutoff,
            DateTime.UtcNow.AddDays(-7).AddMinutes(-1),
            DateTime.UtcNow.AddDays(-7).AddMinutes(1));
    }

    [Fact]
    public async Task Tick_SwallowsExceptions_AndKeepsTicking()
    {
        var queue = new RecordingSiteAuditQueue { ThrowOnFirstCall = true };
        var options = Options.Create(new SiteAuditRetentionOptions
        {
            RetentionDays = 7,
            // Override bypasses the 1-min production clamp so the loop ticks in ms.
            PurgeIntervalOverride = TimeSpan.FromMilliseconds(50),
            InitialDelay = TimeSpan.Zero,
        });
        using var svc = new SiteAuditRetentionService(queue, options, NullLogger<SiteAuditRetentionService>.Instance);

        await svc.StartAsync(CancellationToken.None);
        // The first tick throws; a second tick must still arrive (service survives).
        await WaitUntilAsync(() => queue.PurgeCalls.Count >= 2, TimeSpan.FromSeconds(5));
        await svc.StopAsync(CancellationToken.None);

        Assert.True(queue.PurgeCalls.Count >= 2);
    }

    private static async Task WaitUntilAsync(Func<bool> condition, TimeSpan timeout)
    {
        var sw = Stopwatch.StartNew();
        while (!condition())
        {
            if (sw.Elapsed > timeout)
            {
                throw new TimeoutException("Condition was not met within the timeout.");
            }

            await Task.Delay(10);
        }
    }

    /// <summary>Stub queue that records purge cutoffs and can throw on the first tick.</summary>
    private sealed class RecordingSiteAuditQueue : ISiteAuditQueue
    {
        private readonly ConcurrentQueue<DateTime> _purgeCalls = new();
        private int _calls;

        public IReadOnlyCollection<DateTime> PurgeCalls => _purgeCalls;
        public bool ThrowOnFirstCall { get; init; }

        public Task<int> PurgeExpiredAsync(DateTime olderThanUtc, CancellationToken ct = default)
        {
            var n = Interlocked.Increment(ref _calls);
            _purgeCalls.Enqueue(olderThanUtc);
            if (ThrowOnFirstCall && n == 1)
            {
                throw new InvalidOperationException("Simulated transient purge failure.");
            }

            return Task.FromResult(0);
        }

        public Task<IReadOnlyList<AuditEvent>> ReadPendingAsync(int limit, CancellationToken ct = default)
            => throw new NotSupportedException();
        public Task<IReadOnlyList<AuditEvent>> ReadPendingCachedTelemetryAsync(int limit, CancellationToken ct = default)
            => throw new NotSupportedException();
        public Task MarkForwardedAsync(IReadOnlyList<Guid> eventIds, CancellationToken ct = default)
            => throw new NotSupportedException();
        public Task<IReadOnlyList<AuditEvent>> ReadPendingSinceAsync(DateTime sinceUtc, int batchSize, CancellationToken ct = default)
            => throw new NotSupportedException();
        public Task MarkReconciledAsync(IReadOnlyList<Guid> eventIds, CancellationToken ct = default)
            => throw new NotSupportedException();
        public Task<SiteAuditBacklogSnapshot> GetBacklogStatsAsync(CancellationToken ct = default)
            => throw new NotSupportedException();
    }
}