using System.Collections.Concurrent;
using System.Diagnostics;
using Shouldly;
using ZB.MOM.NatsNet.Server;

namespace ZB.MOM.NatsNet.Server.Tests.ImplBacklog;

public sealed partial class ConcurrencyTests1
{
    [Fact] // T:2452
    public void NoRaceFileStoreStreamMaxAgePerformance_ShouldSucceed()
    {
        WithStore((fs, _) =>
        {
            Parallel.For(0, 200, i => fs.StoreMsg($"age.{i % 4}", null, new[] { (byte)(i % 255) }, 0));

            var state = fs.State();
            state.Msgs.ShouldBeGreaterThan(0UL);
            state.LastSeq.ShouldBeGreaterThanOrEqualTo(state.Msgs);

            var (total, validThrough, err) = fs.NumPending(1, ">", false);
            err.ShouldBeNull();
            total.ShouldBeGreaterThan(0UL);
            validThrough.ShouldBeGreaterThan(0UL);
        }, DefaultStreamConfig(maxAge: TimeSpan.FromMilliseconds(20)));
    }

    [Fact] // T:2453
    public void NoRaceFileStoreFilteredStateWithLargeDeletes_ShouldSucceed()
    {
        WithStore((fs, _) =>
        {
            for (var i = 0; i < 240; i++)
                fs.StoreMsg("fd", null, new[] { (byte)(i % 255) }, 0);

            Parallel.For(1L, 240L, i =>
            {
                if (i % 3 == 0)
                    fs.RemoveMsg((ulong)i);
            });

            var filtered = fs.FilteredState(1, "fd");
            filtered.Msgs.ShouldBeGreaterThan(0UL);
            filtered.Last.ShouldBeGreaterThanOrEqualTo(filtered.First);

            fs.SubjectsTotals(">")["fd"].ShouldBeGreaterThan(0UL);
        });
    }

    [Fact] // T:2462
    public void NoRaceFileStoreNumPending_ShouldSucceed()
    {
        WithStore((fs, _) =>
        {
            for (var i = 0; i < 100; i++)
                fs.StoreMsg($"np.{i % 5}", null, "x"u8.ToArray(), 0);

            var errors = new ConcurrentQueue<Exception>();
            var workers = Enumerable.Range(0, 8).Select(_ => Task.Run(() =>
            {
                try
                {
                    for (var i = 0; i < 40; i++)
                    {
                        var (_, _, err1) = fs.NumPending(1, ">", false);
                        if (err1 != null)
                            throw err1;

                        var (_, _, err2) = fs.NumPendingMulti(1, new[] { "np.1", "np.*" }, false);
                        if (err2 != null)
                            throw err2;
                    }
                }
                catch (Exception ex)
                {
                    errors.Enqueue(ex);
                }
            })).ToArray();

            Task.WaitAll(workers);
            errors.ShouldBeEmpty();
        });
    }

    [Fact] // T:2427
    public void NoRaceJetStreamFileStoreKeyFileCleanup_ShouldSucceed()
    {
        WithStore((_, root) =>
        {
            var msgDir = Path.Combine(root, FileStoreDefaults.MsgDir);
            Directory.CreateDirectory(msgDir);
            var perm = UnixFileMode.UserRead | UnixFileMode.UserWrite;

            var errors = new ConcurrentQueue<Exception>();
            Parallel.For(0, 300, i =>
            {
                var payload = BitConverter.GetBytes(i);
                var keyFile = Path.Combine(msgDir, string.Format(FileStoreDefaults.KeyScan, (uint)(i + 1)));
                var err = JetStreamFileStore.WriteAtomically(keyFile, payload, perm, sync: true);
                if (err != null)
                    errors.Enqueue(err);
            });

            errors.ShouldBeEmpty();
            var keyFiles = Directory.GetFiles(msgDir, "*.key");
            keyFiles.Length.ShouldBe(300);

            foreach (var key in keyFiles.Skip(1))
                File.Delete(key);

            Directory.GetFiles(msgDir, "*.key").Length.ShouldBe(1);
            Directory.GetFiles(msgDir, "*.tmp").ShouldBeEmpty();
        });
    }

    [Fact] // T:2447
    public void NoRaceEncodeConsumerStateBug_ShouldSucceed()
    {
        for (var i = 0; i < 5_000; i++)
        {
            var pending = new Pending
            {
                Sequence = 1,
                Timestamp = DateTimeOffset.UtcNow.AddSeconds(1).ToUnixTimeSeconds() * 1_000_000_000L,
            };
            var state = new ConsumerState
            {
                Delivered = new SequencePair { Consumer = 1, Stream = 1 },
                Pending = new Dictionary<ulong, Pending> { [1] = pending },
            };

            var encoded = StoreParity.EncodeConsumerState(state);
            var (_, err) = JetStreamFileStore.DecodeConsumerState(encoded);
            err.ShouldBeNull();
        }
    }

    [Fact] // T:2441
    public void NoRaceJetStreamFileStoreLargeKVAccessTiming_ShouldSucceed()
    {
        var value = Enumerable.Repeat((byte)'Z', 256).ToArray();
        const int keyCount = 5_000;

        WithStore((fs, _) =>
        {
            for (var i = 1; i <= keyCount; i++)
            {
                fs.StoreMsg($"KV.STREAM_NAME.{i}", null, value, 0).Seq.ShouldBeGreaterThan(0UL);
            }

            var sw = Stopwatch.StartNew();
            var last = fs.LoadLastMsg($"KV.STREAM_NAME.{keyCount}", null);
            sw.Stop();
            var lastLookup = sw.Elapsed;

            last.ShouldNotBeNull();
            last!.Msg.ShouldBe(value);

            sw.Restart();
            var first = fs.LoadLastMsg("KV.STREAM_NAME.1", null);
            sw.Stop();
            var firstLookup = sw.Elapsed;

            first.ShouldNotBeNull();
            first!.Msg.ShouldBe(value);

            // Keep generous bounds to avoid machine-specific flakiness while still
            // asserting access stays fast under a large key set.
            lastLookup.ShouldBeLessThan(TimeSpan.FromMilliseconds(250));
            firstLookup.ShouldBeLessThan(TimeSpan.FromMilliseconds(350));

            var firstState = fs.FilteredState(1, "KV.STREAM_NAME.1");
            var lastState = fs.FilteredState(1, $"KV.STREAM_NAME.{keyCount}");
            firstState.First.ShouldBeGreaterThan(0UL);
            lastState.First.ShouldBeGreaterThan(0UL);
        }, DefaultStreamConfig());
    }

    private static void WithStore(Action<JetStreamFileStore, string> action, StreamConfig? cfg = null)
    {
        var root = NewRoot();
        Directory.CreateDirectory(root);
        JetStreamFileStore? fs = null;

        try
        {
            fs = JetStreamFileStore.NewFileStore(new FileStoreConfig { StoreDir = root }, cfg ?? DefaultStreamConfig());
            action(fs, root);
        }
        finally
        {
            fs?.Stop();
            if (Directory.Exists(root))
                Directory.Delete(root, recursive: true);
        }
    }

    private static StreamConfig DefaultStreamConfig(TimeSpan? maxAge = null)
    {
        return new StreamConfig
        {
            Name = "TEST",
            Storage = StorageType.FileStorage,
            Subjects = ["test.>"],
            MaxMsgs = -1,
            MaxBytes = -1,
            MaxAge = maxAge ?? TimeSpan.Zero,
            MaxMsgsPer = -1,
            Discard = DiscardPolicy.DiscardOld,
            Retention = RetentionPolicy.LimitsPolicy,
        };
    }

    private static string NewRoot() => Path.Combine(Path.GetTempPath(), $"impl-fs-c1-{Guid.NewGuid():N}");
}