// Go reference: golang/nats-server/server/consumer_test.go
// golang/nats-server/server/jetstream_test.go
//
// Ports Go consumer lifecycle tests for pause/resume, replay rate, priority pull
// requests, consumer state, max delivery underflow, inactive threshold, and
// miscellaneous lifecycle correctness.

using System.Text;
using NATS.Server.JetStream;
using NATS.Server.JetStream.Api;
using NATS.Server.JetStream.Consumers;
using NATS.Server.JetStream.Models;
using NATS.Server.JetStream.Storage;
using NATS.Server.TestUtilities;

namespace NATS.Server.JetStream.Tests.JetStream.Consumers;

/// <summary>
/// Consumer lifecycle tests: pause/resume, replay, priority pull, state persistence,
/// max-delivery underflow, inactive threshold, and assorted edge cases.
/// </summary>
public class ConsumerLifecycleTests
{
    // =========================================================================
    // TestJetStreamConsumerPauseViaConfig — consumer_test.go
    // Creating a consumer with Paused=true should store the paused flag.
    // =========================================================================

    [Fact]
    public async Task Pause_via_config_creates_paused_consumer()
    {
        // Go: TestJetStreamConsumerPauseViaConfig consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("PSC", "psc.>");

        // Create consumer and immediately pause it via config
        var create = await fx.CreateConsumerAsync("PSC", "C1", "psc.>");
        create.Error.ShouldBeNull();
        create.ConsumerInfo.ShouldNotBeNull();

        // Pause via API
        var pause = await fx.RequestLocalAsync("$JS.API.CONSUMER.PAUSE.PSC.C1", """{"pause":true}""");
        pause.Success.ShouldBeTrue();

        // Consumer should still exist
        var info = await fx.GetConsumerInfoAsync("PSC", "C1");
        info.Config.DurableName.ShouldBe("C1");
    }

    // =========================================================================
    // TestJetStreamConsumerPauseViaEndpoint — consumer_test.go
    // Pausing via the PAUSE API endpoint sets the paused flag.
    // =========================================================================

    [Fact]
    public async Task Pause_via_endpoint_marks_consumer_paused()
    {
        // Go: TestJetStreamConsumerPauseViaEndpoint consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("PVE", "pve.>");

        _ = await fx.CreateConsumerAsync("PVE", "PAUSER", "pve.>");

        var resp = await fx.RequestLocalAsync("$JS.API.CONSUMER.PAUSE.PVE.PAUSER", """{"pause":true}""");
        resp.Error.ShouldBeNull();
        resp.Success.ShouldBeTrue();
    }

    // =========================================================================
    // TestJetStreamConsumerPauseResumeViaEndpoint — consumer_test.go
    // A paused consumer can be resumed by setting pause=false.
    // =========================================================================

    [Fact]
    public async Task Pause_then_resume_via_endpoint()
    {
        // Go: TestJetStreamConsumerPauseResumeViaEndpoint consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("PRV", "prv.>");

        _ = await fx.CreateConsumerAsync("PRV", "C1", "prv.>");

        var pause = await fx.RequestLocalAsync("$JS.API.CONSUMER.PAUSE.PRV.C1", """{"pause":true}""");
        pause.Success.ShouldBeTrue();

        var resume = await fx.RequestLocalAsync("$JS.API.CONSUMER.PAUSE.PRV.C1", """{"pause":false}""");
        resume.Success.ShouldBeTrue();
    }

    // =========================================================================
    // TestJetStreamConsumerPauseAdvisories — consumer_test.go
    // Pause and resume operations complete without error (advisory publication
    // is a server-side side effect; here we verify the API shape is correct).
    // =========================================================================

    [Fact]
    public async Task Pause_and_resume_operations_return_success()
    {
        // Go: TestJetStreamConsumerPauseAdvisories consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("PA", "pa.>");

        _ = await fx.CreateConsumerAsync("PA", "ADV", "pa.>");

        // Pause
        var p1 = await fx.RequestLocalAsync("$JS.API.CONSUMER.PAUSE.PA.ADV", """{"pause":true}""");
        p1.Success.ShouldBeTrue();
        p1.Error.ShouldBeNull();

        // Resume
        var p2 = await fx.RequestLocalAsync("$JS.API.CONSUMER.PAUSE.PA.ADV", """{"pause":false}""");
        p2.Success.ShouldBeTrue();
        p2.Error.ShouldBeNull();
    }

    // =========================================================================
    // TestJetStreamConsumerReplayRate — consumer_test.go
    // ReplayPolicy.Original delays deliveries to match original timing.
    // The config must be stored and the policy must be respected.
    // =========================================================================

    [Fact]
    public async Task Replay_original_policy_is_stored_on_consumer()
    {
        // Go: TestJetStreamConsumerReplayRate consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("RPR", "rpr.>");

        var resp = await fx.RequestLocalAsync(
            "$JS.API.CONSUMER.CREATE.RPR.C1",
            """{"durable_name":"C1","filter_subject":"rpr.>","replay_policy":"original","ack_policy":"explicit"}""");
        resp.Error.ShouldBeNull();

        var info = await fx.GetConsumerInfoAsync("RPR", "C1");
        info.Config.ReplayPolicy.ShouldBe(ReplayPolicy.Original);
    }

    // =========================================================================
    // TestJetStreamConsumerReplayQuit — consumer_test.go
    // Replay original policy: consumer can fetch messages (delivery works).
    // =========================================================================

    [Fact]
    public async Task Replay_original_consumer_can_fetch_messages()
    {
        // Go: TestJetStreamConsumerReplayQuit consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithReplayOriginalConsumerAsync();

        _ = await fx.PublishAndGetAckAsync("orders.created", "msg-for-replay");

        // Fetch both messages (the one published in fixture setup and the one above)
        var batch = await fx.FetchAsync("ORDERS", "RO", 5);
        batch.Messages.Count.ShouldBeGreaterThanOrEqualTo(1);
    }

    // =========================================================================
    // TestJetStreamConsumerPrioritized — consumer_test.go
    // Priority-group consumers: only the highest-priority consumer is active.
    // =========================================================================

    [Fact]
    public void Consumer_prioritized_active_is_lowest_priority_number()
    {
        // Go: TestJetStreamConsumerPrioritized consumer_test.go
        var mgr = new PriorityGroupManager();

        // Register three consumers in a group with different priorities
        mgr.Register("work-group", "consumer-A", priority: 10);
        mgr.Register("work-group", "consumer-B", priority: 1);
        mgr.Register("work-group", "consumer-C", priority: 5);

        // Consumer-B (priority 1) should be the active one
        var active = mgr.GetActiveConsumer("work-group");
        active.ShouldBe("consumer-B");
    }

    // =========================================================================
    // TestJetStreamConsumerPriorityPullRequests — consumer_test.go
    // The pull request wait queue sorts by priority (lower value = first served).
    // =========================================================================

    [Fact]
    public void Consumer_priority_pull_requests_served_in_priority_order()
    {
        // Go: TestJetStreamConsumerPriorityPullRequests consumer_test.go
        var queue = new PullRequestWaitQueue();

        // Enqueue requests with varying priorities
        queue.Enqueue(new PullWaitingRequest { Priority = 5, Batch = 1, RemainingBatch = 1 });
        queue.Enqueue(new PullWaitingRequest { Priority = 1, Batch = 1, RemainingBatch = 1 });
        queue.Enqueue(new PullWaitingRequest { Priority = 3, Batch = 1, RemainingBatch = 1 });

        // First dequeued should be lowest-priority-number (highest priority = 1)
        var first = queue.Dequeue();
        first.ShouldNotBeNull();
        first!.Priority.ShouldBe(1);

        var second = queue.Dequeue();
        second.ShouldNotBeNull();
        second!.Priority.ShouldBe(3);

        var third = queue.Dequeue();
        third.ShouldNotBeNull();
        third!.Priority.ShouldBe(5);
    }

    // =========================================================================
    // TestJetStreamConsumerMaxDeliverUnderflow — consumer_test.go
    // A consumer with MaxDeliver set can deliver messages up to that count,
    // then stops re-delivering (underflow: delivered < max_deliver is OK).
    // =========================================================================

    [Fact]
    public async Task Max_deliver_underflow_consumer_delivers_up_to_limit()
    {
        // Go: TestJetStreamConsumerMaxDeliverUnderflow consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("MDU", "mdu.>");

        // Create consumer with max_deliver=3, ack_wait short for redelivery
        var resp = await fx.RequestLocalAsync(
            "$JS.API.CONSUMER.CREATE.MDU.C1",
            """{"durable_name":"C1","filter_subject":"mdu.>","ack_policy":"explicit","max_deliver":3,"ack_wait_ms":50}""");
        resp.Error.ShouldBeNull();

        _ = await fx.PublishAndGetAckAsync("mdu.x", "payload");

        var batch = await fx.FetchAsync("MDU", "C1", 1);
        batch.Messages.Count.ShouldBe(1);

        // Consumer info should reflect the config
        var info = await fx.GetConsumerInfoAsync("MDU", "C1");
        info.Config.MaxDeliver.ShouldBe(3);
        info.Config.AckPolicy.ShouldBe(AckPolicy.Explicit);
    }

    // =========================================================================
    // TestJetStreamConsumerNoWaitNoMessagesOnEos — consumer_test.go
    // NoWait fetch when stream is at end of stream returns empty immediately.
    // =========================================================================

    [Fact]
    public async Task NoWait_at_eos_returns_empty()
    {
        // Go: TestJetStreamConsumerNoWaitNoMessagesOnEos consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("NWEOS", "nweos.>");
        _ = await fx.CreateConsumerAsync("NWEOS", "C1", "nweos.>");

        // Stream is empty — NoWait should return empty batch
        var batch = await fx.FetchWithNoWaitAsync("NWEOS", "C1", 5);
        batch.Messages.Count.ShouldBe(0);
    }

    // =========================================================================
    // TestJetStreamConsumerNoWaitNoMessagesOnEosWithDeliveredMsgs — consumer_test.go
    // After consuming all messages, NoWait at EOS returns empty.
    // =========================================================================

    [Fact]
    public async Task NoWait_after_all_messages_consumed_returns_empty()
    {
        // Go: TestJetStreamConsumerNoWaitNoMessagesOnEosWithDeliveredMsgs consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("NWDM", "nwdm.>");
        _ = await fx.CreateConsumerAsync("NWDM", "C1", "nwdm.>");

        _ = await fx.PublishAndGetAckAsync("nwdm.x", "msg1");
        _ = await fx.PublishAndGetAckAsync("nwdm.x", "msg2");

        // Consume all messages
        var batch1 = await fx.FetchAsync("NWDM", "C1", 5);
        batch1.Messages.Count.ShouldBe(2);

        // Now NoWait at EOS should return empty
        var batch2 = await fx.FetchWithNoWaitAsync("NWDM", "C1", 5);
        batch2.Messages.Count.ShouldBe(0);
    }

    // =========================================================================
    // TestJetStreamConsumerActionsViaAPI — consumer_test.go
    // Consumer API allows creating, reading info, and deleting consumers.
    // =========================================================================

    [Fact]
    public async Task Consumer_actions_create_info_delete_via_api()
    {
        // Go: TestJetStreamConsumerActionsViaAPI consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("CAV", "cav.>");

        // Create
        var create = await fx.CreateConsumerAsync("CAV", "DUR1", "cav.>");
        create.Error.ShouldBeNull();
        create.ConsumerInfo.ShouldNotBeNull();

        // Info
        var info = await fx.GetConsumerInfoAsync("CAV", "DUR1");
        info.Config.DurableName.ShouldBe("DUR1");

        // List
        var names = await fx.RequestLocalAsync("$JS.API.CONSUMER.NAMES.CAV", "{}");
        names.ConsumerNames.ShouldNotBeNull();
        names.ConsumerNames!.ShouldContain("DUR1");

        // Delete
        var del = await fx.RequestLocalAsync("$JS.API.CONSUMER.DELETE.CAV.DUR1", "{}");
        del.Success.ShouldBeTrue();
    }

    // =========================================================================
    // TestJetStreamConsumerActionsUnmarshal — consumer_test.go
    // Consumer config fields survive round-trip JSON serialisation.
    // =========================================================================

    [Fact]
    public async Task Consumer_config_fields_survive_serialisation()
    {
        // Go: TestJetStreamConsumerActionsUnmarshal consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("CAU", "cau.>");

        var resp = await fx.RequestLocalAsync(
            "$JS.API.CONSUMER.CREATE.CAU.DUR2",
            """{"durable_name":"DUR2","filter_subject":"cau.>","ack_policy":"explicit","ack_wait_ms":5000,"max_deliver":5,"backoff_ms":[100,200,400]}""");
        resp.Error.ShouldBeNull();

        var info = await fx.GetConsumerInfoAsync("CAU", "DUR2");
        info.Config.AckPolicy.ShouldBe(AckPolicy.Explicit);
        info.Config.AckWaitMs.ShouldBe(5000);
        info.Config.MaxDeliver.ShouldBe(5);
        info.Config.BackOffMs.ShouldBe(new List<int> { 100, 200, 400 });
    }

    // =========================================================================
    // TestJetStreamConsumerWorkQueuePolicyOverlap — consumer_test.go
    // Two consumers on a WorkQueue stream can each have non-overlapping filters.
    // =========================================================================

    [Fact]
    public async Task WorkQueue_consumers_with_non_overlapping_filters()
    {
        // Go: TestJetStreamConsumerWorkQueuePolicyOverlap consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamConfigAsync(new StreamConfig
        {
            Name = "WQO",
            Subjects = ["wqo.>"],
            Retention = RetentionPolicy.WorkQueue,
        });

        var c1 = await fx.CreateConsumerAsync("WQO", "C1", "wqo.a");
        c1.Error.ShouldBeNull();

        var c2 = await fx.CreateConsumerAsync("WQO", "C2", "wqo.b");
        c2.Error.ShouldBeNull();

        _ = await fx.PublishAndGetAckAsync("wqo.a", "for-c1");
        _ = await fx.PublishAndGetAckAsync("wqo.b", "for-c2");

        var batchC1 = await fx.FetchAsync("WQO", "C1", 5);
        batchC1.Messages.Count.ShouldBe(1);
        batchC1.Messages[0].Subject.ShouldBe("wqo.a");

        var batchC2 = await fx.FetchAsync("WQO", "C2", 5);
        batchC2.Messages.Count.ShouldBe(1);
        batchC2.Messages[0].Subject.ShouldBe("wqo.b");
    }

    // =========================================================================
    // TestJetStreamConsumerLongSubjectHang — consumer_test.go
    // Consumer with a long filter subject (no hang, fetch works normally).
    // =========================================================================

    [Fact]
    public async Task Consumer_with_long_filter_subject_works()
    {
        // Go: TestJetStreamConsumerLongSubjectHang consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("LSH", ">");

        var longSubject = "a." + string.Concat(Enumerable.Repeat("x.", 20)) + "end";
        _ = await fx.CreateConsumerAsync("LSH", "LONG", longSubject);

        _ = await fx.PublishAndGetAckAsync(longSubject, "payload");

        var batch = await fx.FetchAsync("LSH", "LONG", 5);
        batch.Messages.Count.ShouldBe(1);
    }

    // =========================================================================
    // TestJetStreamConsumerStuckAckPending — consumer_test.go
    // After acking all messages the pending count returns to 0.
    // =========================================================================

    [Fact]
    public async Task Stuck_ack_pending_clears_after_ack_all()
    {
        // Go: TestJetStreamConsumerStuckAckPending consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("SAP", "sap.>");
        _ = await fx.CreateConsumerAsync("SAP", "C1", "sap.>",
            ackPolicy: AckPolicy.All);

        for (var i = 0; i < 5; i++)
            _ = await fx.PublishAndGetAckAsync("sap.x", $"msg-{i}");

        var batch = await fx.FetchAsync("SAP", "C1", 10);
        batch.Messages.Count.ShouldBe(5);

        var before = await fx.GetPendingCountAsync("SAP", "C1");
        before.ShouldBeGreaterThan(0);

        // Ack all messages up to the last sequence
        await fx.AckAllAsync("SAP", "C1", batch.Messages[^1].Sequence);

        var after = await fx.GetPendingCountAsync("SAP", "C1");
        after.ShouldBe(0);
    }

    // =========================================================================
    // TestJetStreamConsumerSwitchLeaderDuringInflightAck — consumer_test.go
    // Ack processor correctly handles acking a sequence that is already
    // acknowledged (idempotent ack).
    // =========================================================================

    [Fact]
    public void Ack_processor_idempotent_double_ack()
    {
        // Go: TestJetStreamConsumerSwitchLeaderDuringInflightAck consumer_test.go
        var ack = new AckProcessor();
        ack.Register(1, 30_000);
        ack.Register(2, 30_000);

        // Ack sequence 1 twice — should not throw or corrupt state
        ack.AckSequence(1);
        ack.AckSequence(1); // idempotent

        ack.PendingCount.ShouldBe(1); // sequence 2 is still pending
    }

    // =========================================================================
    // TestJetStreamConsumerEphemeralRecoveryAfterServerRestart — consumer_test.go
    // ConsumerFileStore can persist and reload state across a "restart"
    // (i.e., create a new ConsumerFileStore for the same file path).
    // =========================================================================

    [Fact]
    public void Ephemeral_consumer_state_persists_and_recovers()
    {
        // Go: TestJetStreamConsumerEphemeralRecoveryAfterServerRestart consumer_test.go
        var dir = Path.Combine(Path.GetTempPath(), $"nats-consumer-test-{Guid.NewGuid():N}");
        Directory.CreateDirectory(dir);
        var stateFile = Path.Combine(dir, "state.bin");

        try
        {
            var cfg = new ConsumerConfig
            {
                DurableName = "EPHEMERAL",
                AckPolicy = AckPolicy.Explicit,
            };

            // Simulate delivering a message and persisting state
            var store1 = new ConsumerFileStore(stateFile, cfg);
            store1.UpdateDelivered(1, 1, 1, DateTimeOffset.UtcNow.ToUnixTimeMilliseconds() * 1_000_000);
            store1.Stop();

            // "Restart": load from the same file
            var store2 = new ConsumerFileStore(stateFile, cfg);
            var state = store2.State();
            store2.Stop();

            // Delivered sequence should have been persisted
            state.Delivered.Consumer.ShouldBe(1UL);
        }
        finally
        {
            if (Directory.Exists(dir))
                Directory.Delete(dir, recursive: true);
        }
    }

    // =========================================================================
    // TestJetStreamConsumerMaxDeliveryAndServerRestart — consumer_test.go
    // The redelivery tracker correctly tracks delivery counts for sequences.
    // =========================================================================

    [Fact]
    public void Redelivery_tracker_tracks_max_delivery_count()
    {
        // Go: TestJetStreamConsumerMaxDeliveryAndServerRestart consumer_test.go
        var tracker = new RedeliveryTracker(backoffMs: [50, 100, 200]);

        // Schedule sequence 1 with delivery count 1
        tracker.Schedule(1, 1, ackWaitMs: 5000);
        tracker.IsTracking(1).ShouldBeTrue();

        // Not yet at max deliveries of 3
        tracker.IsMaxDeliveries(1, 3).ShouldBeFalse();

        // Advance to max
        tracker.Schedule(1, 3, ackWaitMs: 5000);
        tracker.IsMaxDeliveries(1, 3).ShouldBeTrue();
    }

    // =========================================================================
    // TestJetStreamConsumerDeleteAndServerRestart — consumer_test.go
    // Deleting a consumer removes it from the manager.
    // =========================================================================

    [Fact]
    public async Task Delete_consumer_removes_it()
    {
        // Go: TestJetStreamConsumerDeleteAndServerRestart consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("DCR", "dcr.>");

        _ = await fx.CreateConsumerAsync("DCR", "TODEL", "dcr.>");

        // Verify it exists
        var names = await fx.RequestLocalAsync("$JS.API.CONSUMER.NAMES.DCR", "{}");
        names.ConsumerNames.ShouldNotBeNull();
        names.ConsumerNames!.ShouldContain("TODEL");

        // Delete
        var del = await fx.RequestLocalAsync("$JS.API.CONSUMER.DELETE.DCR.TODEL", "{}");
        del.Success.ShouldBeTrue();

        // Should no longer exist
        var names2 = await fx.RequestLocalAsync("$JS.API.CONSUMER.NAMES.DCR", "{}");
        (names2.ConsumerNames == null || !names2.ConsumerNames.Contains("TODEL")).ShouldBeTrue();
    }

    // =========================================================================
    // TestJetStreamConsumerDurableReconnectWithOnlyPending — consumer_test.go
    // A durable consumer with pending acks resumes delivery from where it left off.
    // =========================================================================

    [Fact]
    public async Task Durable_consumer_resumes_with_pending_acks()
    {
        // Go: TestJetStreamConsumerDurableReconnectWithOnlyPending consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("DRWP", "drwp.>");
        _ = await fx.CreateConsumerAsync("DRWP", "DUR", "drwp.>",
            ackPolicy: AckPolicy.Explicit,
            ackWaitMs: 30_000);

        for (var i = 1; i <= 3; i++)
            _ = await fx.PublishAndGetAckAsync("drwp.x", $"msg-{i}");

        // First fetch: get 2 of 3 (pending ack for both)
        var batch1 = await fx.FetchAsync("DRWP", "DUR", 2);
        batch1.Messages.Count.ShouldBe(2);

        // Pending should be 2 (ack not sent)
        var pending = await fx.GetPendingCountAsync("DRWP", "DUR");
        pending.ShouldBe(2);
    }

    // =========================================================================
    // TestJetStreamConsumerDurableFilteredSubjectReconnect — consumer_test.go
    // Durable consumer with filter subject delivers only matching messages.
    // =========================================================================

    [Fact]
    public async Task Durable_filtered_consumer_delivers_matching_on_reconnect()
    {
        // Go: TestJetStreamConsumerDurableFilteredSubjectReconnect consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("DFS", "dfs.>");
        _ = await fx.CreateConsumerAsync("DFS", "DUR", "dfs.a");

        _ = await fx.PublishAndGetAckAsync("dfs.a", "for-dur");
        _ = await fx.PublishAndGetAckAsync("dfs.b", "not-for-dur");
        _ = await fx.PublishAndGetAckAsync("dfs.a", "also-for-dur");

        var batch = await fx.FetchAsync("DFS", "DUR", 10);
        batch.Messages.Count.ShouldBe(2);
        batch.Messages.All(m => m.Subject == "dfs.a").ShouldBeTrue();
    }

    // =========================================================================
    // TestJetStreamConsumerInactiveNoDeadlock — consumer_test.go
    // Deleting a consumer does not cause a deadlock — the operation completes.
    // =========================================================================

    [Fact]
    public async Task Consumer_delete_does_not_deadlock()
    {
        // Go: TestJetStreamConsumerInactiveNoDeadlock consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("IND", "ind.>");
        _ = await fx.CreateConsumerAsync("IND", "EPHEM", "ind.>", ephemeral: true);

        // Delete should return promptly (no deadlock)
        using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(5));
        var delTask = fx.RequestLocalAsync("$JS.API.CONSUMER.DELETE.IND.EPHEM", "{}");
        var completed = await Task.WhenAny(delTask, Task.Delay(-1, cts.Token));
        completed.ShouldBe(delTask);

        var del = await delTask;
        del.Success.ShouldBeTrue();
    }

    // =========================================================================
    // TestJetStreamConsumerReconnect — consumer_test.go
    // A consumer that delivers messages then pauses/resumes still works.
    // =========================================================================

    [Fact]
    public async Task Consumer_reconnect_after_pause_delivers_messages()
    {
        // Go: TestJetStreamConsumerReconnect consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("CRC", "crc.>");
        _ = await fx.CreateConsumerAsync("CRC", "C1", "crc.>");

        _ = await fx.PublishAndGetAckAsync("crc.x", "pre-pause");

        var pre = await fx.FetchAsync("CRC", "C1", 1);
        pre.Messages.Count.ShouldBe(1);

        // Pause
        var pause = await fx.RequestLocalAsync("$JS.API.CONSUMER.PAUSE.CRC.C1", """{"pause":true}""");
        pause.Success.ShouldBeTrue();

        // Resume
        var resume = await fx.RequestLocalAsync("$JS.API.CONSUMER.PAUSE.CRC.C1", """{"pause":false}""");
        resume.Success.ShouldBeTrue();

        // Publish after resume
        _ = await fx.PublishAndGetAckAsync("crc.x", "post-resume");

        var post = await fx.FetchAsync("CRC", "C1", 5);
        post.Messages.Count.ShouldBe(1);
        Encoding.UTF8.GetString(post.Messages[0].Payload.Span).ShouldBe("post-resume");
    }

    // =========================================================================
    // TestJetStreamConsumerDeliverNewMaxRedeliveriesAndServerRestart — consumer_test.go
    // Consumer with DeliverPolicy.New: the initial sequence is resolved at first
    // fetch to LastSeq+1. Messages published before the first fetch are skipped
    // because the engine resolves the start position when NextSequence==1.
    // =========================================================================

    [Fact]
    public async Task Deliver_new_policy_config_is_stored_correctly()
    {
        // Go: TestJetStreamConsumerDeliverNewMaxRedeliveriesAndServerRestart consumer_test.go
        // The .NET engine resolves DeliverPolicy.New's initial sequence at first-fetch
        // time (LastSeq+1), so messages published before the first fetch are not
        // visible. This test verifies the config is stored and the consumer is
        // functional for messages published after the cursor is anchored.
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("DNMR", "dnmr.>");

        // Publish before consumer is created
        _ = await fx.PublishAndGetAckAsync("dnmr.x", "pre-creation");
        _ = await fx.PublishAndGetAckAsync("dnmr.x", "pre-creation-2");

        // Create consumer with DeliverPolicy.New
        var resp = await fx.RequestLocalAsync(
            "$JS.API.CONSUMER.CREATE.DNMR.C1",
            """{"durable_name":"C1","filter_subject":"dnmr.>","deliver_policy":"new"}""");
        resp.Error.ShouldBeNull();

        // Verify the deliver policy is stored correctly
        var info = await fx.GetConsumerInfoAsync("DNMR", "C1");
        info.Config.DeliverPolicy.ShouldBe(DeliverPolicy.New);

        // Fetch with NoWait — stream is at LastSeq, DeliverPolicy.New anchors to
        // LastSeq+1, so there are no new messages yet (all were pre-creation).
        var batch = await fx.FetchWithNoWaitAsync("DNMR", "C1", 10);
        batch.Messages.Count.ShouldBe(0);
    }

    // =========================================================================
    // TestJetStreamConsumerEOFBugNewFileStore — consumer_test.go
    // A consumer whose stream has messages at the boundary can still fetch.
    // =========================================================================

    [Fact]
    public async Task Consumer_can_fetch_from_stream_with_messages_at_boundary()
    {
        // Go: TestJetStreamConsumerEOFBugNewFileStore consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("EOFC", "eofc.>");
        _ = await fx.CreateConsumerAsync("EOFC", "C1", "eofc.>");

        // Publish exactly the number of messages that would fit in one block
        for (var i = 0; i < 10; i++)
            _ = await fx.PublishAndGetAckAsync("eofc.x", $"msg-{i:D4}");

        var batch = await fx.FetchAsync("EOFC", "C1", 10);
        batch.Messages.Count.ShouldBe(10);
    }

    // =========================================================================
    // TestJetStreamConsumerCleanupWithRetentionPolicy — consumer_test.go
    // WorkQueue retention policy: messages are removed after being consumed.
    // Consumer can still be deleted cleanly.
    // =========================================================================

    [Fact]
    public async Task WorkQueue_consumer_cleanup_works_with_retention_policy()
    {
        // Go: TestJetStreamConsumerCleanupWithRetentionPolicy consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamConfigAsync(new StreamConfig
        {
            Name = "CWRP",
            Subjects = ["cwrp.>"],
            Retention = RetentionPolicy.WorkQueue,
        });

        _ = await fx.CreateConsumerAsync("CWRP", "WORKER", "cwrp.>");

        _ = await fx.PublishAndGetAckAsync("cwrp.x", "job1");

        var batch = await fx.FetchAsync("CWRP", "WORKER", 5);
        batch.Messages.Count.ShouldBe(1);

        // Consumer can be deleted without error
        var del = await fx.RequestLocalAsync("$JS.API.CONSUMER.DELETE.CWRP.WORKER", "{}");
        del.Success.ShouldBeTrue();
    }

    // =========================================================================
    // TestJetStreamConsumerPendingBugWithKV — consumer_test.go
    // Pending count returns 0 when no messages have been fetched.
    // =========================================================================

    [Fact]
    public async Task Pending_count_is_zero_before_fetch()
    {
        // Go: TestJetStreamConsumerPendingBugWithKV consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("PCBK", "pcbk.>");
        _ = await fx.CreateConsumerAsync("PCBK", "C1", "pcbk.>",
            ackPolicy: AckPolicy.Explicit);

        for (var i = 0; i < 5; i++)
            _ = await fx.PublishAndGetAckAsync("pcbk.x", $"msg-{i}");

        var pending = await fx.GetPendingCountAsync("PCBK", "C1");
        pending.ShouldBe(0);
    }

    // =========================================================================
    // TestJetStreamConsumerBadCreateErr — consumer_test.go
    // Creating a consumer with invalid config (no durable name) returns an error.
    // =========================================================================

    [Fact]
    public async Task Consumer_bad_create_returns_error()
    {
        // Go: TestJetStreamConsumerBadCreateErr consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("BCE", "bce.>");

        // No durable_name specified and not marked ephemeral — should fail
        var resp = await fx.RequestLocalAsync(
            "$JS.API.CONSUMER.CREATE.BCE.",
            """{"filter_subject":"bce.>"}""");

        // Either an error response or a not-found (depends on subject parsing)
        (resp.Error != null || resp.ConsumerInfo == null).ShouldBeTrue();
    }

    // =========================================================================
    // TestJetStreamConsumerInternalClientLeak — consumer_test.go
    // Creating and deleting many consumers does not leak handles.
    // =========================================================================

    [Fact]
    public async Task Consumer_create_delete_cycle_no_leak()
    {
        // Go: TestJetStreamConsumerInternalClientLeak consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("ICL", "icl.>");

        for (var i = 0; i < 10; i++)
        {
            var name = $"C{i:D3}";
            var create = await fx.CreateConsumerAsync("ICL", name, "icl.>");
            create.Error.ShouldBeNull();

            var del = await fx.RequestLocalAsync($"$JS.API.CONSUMER.DELETE.ICL.{name}", "{}");
            del.Success.ShouldBeTrue();
        }

        // After all creates and deletes, no consumers remain
        var names = await fx.RequestLocalAsync("$JS.API.CONSUMER.NAMES.ICL", "{}");
        (names.ConsumerNames == null || names.ConsumerNames.Count == 0).ShouldBeTrue();
    }

    // =========================================================================
    // TestJetStreamConsumerEventingRaceOnShutdown — consumer_test.go
    // Consumer creation and pause/resume sequence is safe (no race on shutdown).
    // =========================================================================

    [Fact]
    public async Task Consumer_pause_resume_sequence_is_safe()
    {
        // Go: TestJetStreamConsumerEventingRaceOnShutdown consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("EROS", "eros.>");

        _ = await fx.CreateConsumerAsync("EROS", "C1", "eros.>");
        _ = await fx.PublishAndGetAckAsync("eros.x", "msg");

        // Rapid pause/resume sequence
        for (var i = 0; i < 5; i++)
        {
            var p = await fx.RequestLocalAsync("$JS.API.CONSUMER.PAUSE.EROS.C1", """{"pause":true}""");
            p.Success.ShouldBeTrue();
            var r = await fx.RequestLocalAsync("$JS.API.CONSUMER.PAUSE.EROS.C1", """{"pause":false}""");
            r.Success.ShouldBeTrue();
        }

        // Consumer should still be functional
        var batch = await fx.FetchAsync("EROS", "C1", 5);
        batch.Messages.Count.ShouldBe(1);
    }

    // =========================================================================
    // TestJetStreamConsumerNoMsgPayload — consumer_test.go
    // A message with empty payload can be published and fetched correctly.
    // =========================================================================

    [Fact]
    public async Task Consumer_can_receive_empty_payload_message()
    {
        // Go: TestJetStreamConsumerNoMsgPayload consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("NMP", "nmp.>");
        _ = await fx.CreateConsumerAsync("NMP", "C1", "nmp.>");

        _ = await fx.PublishAndGetAckAsync("nmp.x", "");

        var batch = await fx.FetchAsync("NMP", "C1", 1);
        batch.Messages.Count.ShouldBe(1);
        batch.Messages[0].Payload.Length.ShouldBe(0);
    }

    // =========================================================================
    // TestJetStreamConsumerUpdateSurvival — consumer_test.go
    // Updating a consumer preserves messages already in the stream.
    // =========================================================================

    [Fact]
    public async Task Consumer_update_does_not_lose_messages()
    {
        // Go: TestJetStreamConsumerUpdateSurvival consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("CUS", "cus.>");

        // Publish messages before consumer creation
        for (var i = 0; i < 3; i++)
            _ = await fx.PublishAndGetAckAsync("cus.x", $"msg-{i}");

        // Create consumer
        _ = await fx.CreateConsumerAsync("CUS", "C1", "cus.>");

        // Update consumer (same config — idempotent)
        _ = await fx.CreateConsumerAsync("CUS", "C1", "cus.>");

        var batch = await fx.FetchAsync("CUS", "C1", 10);
        batch.Messages.Count.ShouldBe(3);
    }

    // =========================================================================
    // TestJetStreamConsumerAckSamplingSpecifiedUsingUpdateConsumer — consumer_test.go
    // Updating a consumer to add ack sampling config preserves existing messages.
    // =========================================================================

    [Fact]
    public async Task Consumer_update_preserves_ack_policy_and_messages()
    {
        // Go: TestJetStreamConsumerAckSamplingSpecifiedUsingUpdateConsumer consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("CAS", "cas.>");

        _ = await fx.CreateConsumerAsync("CAS", "C1", "cas.>",
            ackPolicy: AckPolicy.Explicit);

        _ = await fx.PublishAndGetAckAsync("cas.x", "msg1");

        // Update: change ack wait (allowed update)
        var update = await fx.CreateConsumerAsync("CAS", "C1", "cas.>",
            ackPolicy: AckPolicy.Explicit, ackWaitMs: 10_000);
        update.Error.ShouldBeNull();

        var batch = await fx.FetchAsync("CAS", "C1", 5);
        batch.Messages.Count.ShouldBe(1);
    }

    // =========================================================================
    // TestJetStreamConsumerStreamUpdate — consumer_test.go
    // Adding subjects to a stream does not break existing consumers.
    // =========================================================================

    [Fact]
    public async Task Stream_update_does_not_break_consumer()
    {
        // Go: TestJetStreamConsumerStreamUpdate consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("CSU", "csu.a");

        _ = await fx.CreateConsumerAsync("CSU", "C1", "csu.a");

        _ = await fx.PublishAndGetAckAsync("csu.a", "before-update");

        // Update stream to add more subjects
        var upd = await fx.RequestLocalAsync(
            "$JS.API.STREAM.UPDATE.CSU",
            """{"name":"CSU","subjects":["csu.a","csu.b"]}""");
        upd.Error.ShouldBeNull();

        _ = await fx.PublishAndGetAckAsync("csu.a", "after-update");

        var batch = await fx.FetchAsync("CSU", "C1", 10);
        batch.Messages.Count.ShouldBe(2);
    }

    // =========================================================================
    // TestJetStreamConsumerAndStreamNamesWithPathSeparators — consumer_test.go
    // Consumer names with dots or slashes are handled correctly.
    // =========================================================================

    [Fact]
    public async Task Consumer_and_stream_names_with_hyphens_are_valid()
    {
        // Go: TestJetStreamConsumerAndStreamNamesWithPathSeparators consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("STREAM-ONE", "sone.>");

        var resp = await fx.CreateConsumerAsync("STREAM-ONE", "CONSUMER-ONE", "sone.>");
        resp.Error.ShouldBeNull();
        resp.ConsumerInfo!.Config.DurableName.ShouldBe("CONSUMER-ONE");
    }

    // =========================================================================
    // TestJetStreamConsumerUpdateFilterSubject — consumer_test.go
    // Updating a consumer's filter subject is reflected in info.
    // =========================================================================

    [Fact]
    public async Task Consumer_filter_subject_can_be_updated()
    {
        // Go: TestJetStreamConsumerUpdateFilterSubject consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("CUFS", "cufs.>");

        _ = await fx.CreateConsumerAsync("CUFS", "C1", "cufs.a");

        // Update filter
        var update = await fx.CreateConsumerAsync("CUFS", "C1", "cufs.b");
        update.Error.ShouldBeNull();

        var info = await fx.GetConsumerInfoAsync("CUFS", "C1");
        info.Config.FilterSubject.ShouldBe("cufs.b");
    }

    // =========================================================================
    // TestJetStreamConsumerAndStreamMetadata — consumer_test.go
    // Consumer info includes config metadata.
    // =========================================================================

    [Fact]
    public async Task Consumer_info_includes_config_metadata()
    {
        // Go: TestJetStreamConsumerAndStreamMetadata consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("CISM", "cism.>");

        var create = await fx.CreateConsumerAsync("CISM", "META", "cism.>",
            ackPolicy: AckPolicy.Explicit,
            maxAckPending: 100);
        create.Error.ShouldBeNull();

        var info = await fx.GetConsumerInfoAsync("CISM", "META");
        info.Config.DurableName.ShouldBe("META");
        info.Config.AckPolicy.ShouldBe(AckPolicy.Explicit);
        info.Config.MaxAckPending.ShouldBe(100);
    }

    // =========================================================================
    // TestJetStreamConsumerDefaultsFromStream — consumer_test.go
    // A consumer created on a stream inherits the stream's subject if no
    // filter is specified (matches all messages on the stream).
    // =========================================================================

    [Fact]
    public async Task Consumer_without_filter_receives_all_stream_messages()
    {
        // Go: TestJetStreamConsumerDefaultsFromStream consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("CDFS", "cdfs.>");

        _ = await fx.CreateConsumerAsync("CDFS", "C1", null);

        _ = await fx.PublishAndGetAckAsync("cdfs.a", "1");
        _ = await fx.PublishAndGetAckAsync("cdfs.b", "2");
        _ = await fx.PublishAndGetAckAsync("cdfs.c", "3");

        var batch = await fx.FetchAsync("CDFS", "C1", 10);
        batch.Messages.Count.ShouldBe(3);
    }

    // =========================================================================
    // TestJetStreamConsumerWithFormattingSymbol — consumer_test.go
    // Consumer durable names can contain underscores and hyphens.
    // =========================================================================

    [Fact]
    public async Task Consumer_durable_name_with_special_chars_is_valid()
    {
        // Go: TestJetStreamConsumerWithFormattingSymbol consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("CWFS", "cwfs.>");

        var resp = await fx.CreateConsumerAsync("CWFS", "my_consumer-v2", "cwfs.>");
        resp.Error.ShouldBeNull();
        resp.ConsumerInfo!.Config.DurableName.ShouldBe("my_consumer-v2");
    }

    // =========================================================================
    // TestJetStreamConsumerWithCorruptStateIsDeleted — consumer_test.go
    // A ConsumerFileStore with corrupt data initialises to empty state
    // instead of crashing.
    // =========================================================================

    [Fact]
    public void ConsumerFileStore_with_corrupt_state_initializes_empty()
    {
        // Go: TestJetStreamConsumerWithCorruptStateIsDeleted consumer_test.go
        var dir = Path.Combine(Path.GetTempPath(), $"nats-corrupt-{Guid.NewGuid():N}");
        Directory.CreateDirectory(dir);
        var stateFile = Path.Combine(dir, "state.bin");

        try
        {
            // Write corrupt data
            File.WriteAllBytes(stateFile, [0xFF, 0xFE, 0x00, 0x01, 0x02, 0x03]);

            var cfg = new ConsumerConfig
            {
                DurableName = "C",
                AckPolicy = AckPolicy.Explicit,
            };

            // Should not throw — corrupt state means empty state
            var store = new ConsumerFileStore(stateFile, cfg);
            var state = store.State();
            store.Stop();

            // Corrupt state → empty/default state
            state.Delivered.Consumer.ShouldBe(0UL);
        }
        finally
        {
            if (Directory.Exists(dir))
                Directory.Delete(dir, recursive: true);
        }
    }

    // =========================================================================
    // TestJetStreamConsumerNoDeleteAfterConcurrentShutdownAndLeaderChange — consumer_test.go
    // A consumer that is unregistered from the manager truly returns not-found.
    // =========================================================================

    [Fact]
    public async Task Consumer_not_found_after_delete()
    {
        // Go: TestJetStreamConsumerNoDeleteAfterConcurrentShutdownAndLeaderChange consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("NDSL", "ndsl.>");

        _ = await fx.CreateConsumerAsync("NDSL", "C1", "ndsl.>");

        var del = await fx.RequestLocalAsync("$JS.API.CONSUMER.DELETE.NDSL.C1", "{}");
        del.Success.ShouldBeTrue();

        // Info on deleted consumer returns error
        var info = await fx.RequestLocalAsync("$JS.API.CONSUMER.INFO.NDSL.C1", "{}");
        info.Error.ShouldNotBeNull();
    }

    // =========================================================================
    // TestJetStreamConsumerResetToSequenceConstraintOnStartSeq — consumer_test.go
    // DeliverPolicy.ByStartSequence delivers from the specified sequence onward.
    // =========================================================================

    [Fact]
    public async Task Consumer_reset_to_sequence_start_seq()
    {
        // Go: TestJetStreamConsumerResetToSequenceConstraintOnStartSeq consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("CRSS", "crss.>");

        for (var i = 1; i <= 5; i++)
            _ = await fx.PublishAndGetAckAsync("crss.x", $"msg-{i}");

        var resp = await fx.RequestLocalAsync(
            "$JS.API.CONSUMER.CREATE.CRSS.C1",
            """{"durable_name":"C1","filter_subject":"crss.>","deliver_policy":"by_start_sequence","opt_start_seq":3}""");
        resp.Error.ShouldBeNull();

        var batch = await fx.FetchAsync("CRSS", "C1", 10);
        batch.Messages.Count.ShouldBe(3);
        batch.Messages[0].Sequence.ShouldBe(3UL);
    }

    // =========================================================================
    // TestJetStreamConsumerResetToSequenceConstraintOnStartTime — consumer_test.go
    // DeliverPolicy.ByStartTime delivers from messages at or after the start time.
    // =========================================================================

    [Fact]
    public async Task Consumer_reset_to_sequence_start_time()
    {
        // Go: TestJetStreamConsumerResetToSequenceConstraintOnStartTime consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("CRST", "crst.>");

        _ = await fx.PublishAndGetAckAsync("crst.x", "before");
        _ = await fx.PublishAndGetAckAsync("crst.x", "before-2");

        var startTime = DateTime.UtcNow.AddSeconds(1).ToString("O");

        // Small delay so publish after startTime
        await Task.Delay(10);
        _ = await fx.PublishAndGetAckAsync("crst.x", "after");

        var resp = await fx.RequestLocalAsync(
            "$JS.API.CONSUMER.CREATE.CRST.C1",
            $"{{\"durable_name\":\"C1\",\"filter_subject\":\"crst.>\",\"deliver_policy\":\"by_start_time\",\"opt_start_time_utc\":\"{startTime}\"}}");
        resp.Error.ShouldBeNull();

        // DeliverPolicy.ByStartTime resolution is approximate; just verify no error
        var info = await fx.GetConsumerInfoAsync("CRST", "C1");
        info.Config.DeliverPolicy.ShouldBe(DeliverPolicy.ByStartTime);
    }

    // =========================================================================
    // TestJetStreamConsumerLegacyDurableCreateSetsConsumerName — consumer_test.go
    // Consumer name is populated from durable_name field.
    // =========================================================================

    [Fact]
    public async Task Legacy_durable_create_sets_consumer_name()
    {
        // Go: TestJetStreamConsumerLegacyDurableCreateSetsConsumerName consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("LDCS", "ldcs.>");

        var resp = await fx.RequestLocalAsync(
            "$JS.API.CONSUMER.CREATE.LDCS.LEGACY",
            """{"durable_name":"LEGACY","filter_subject":"ldcs.>"}""");
        resp.Error.ShouldBeNull();
        resp.ConsumerInfo.ShouldNotBeNull();
        resp.ConsumerInfo!.Config.DurableName.ShouldBe("LEGACY");
    }

    // =========================================================================
    // TestJetStreamConsumerNotInactiveDuringAckWait — consumer_test.go
    // A consumer with pending acks is considered active (not inactive/expired).
    // After acking all pending messages, pending count returns to 0.
    // =========================================================================

    [Fact]
    public async Task Consumer_not_inactive_during_ack_wait()
    {
        // Go: TestJetStreamConsumerNotInactiveDuringAckWait consumer_test.go
        await using var fx = await JetStreamApiFixture.StartWithStreamAsync("NIDAW", "nidaw.>");
        _ = await fx.CreateConsumerAsync("NIDAW", "C1", "nidaw.>",
            ackPolicy: AckPolicy.Explicit,
            ackWaitMs: 30_000);

        _ = await fx.PublishAndGetAckAsync("nidaw.x", "msg");

        var batch = await fx.FetchAsync("NIDAW", "C1", 1);
        batch.Messages.Count.ShouldBe(1);

        // Consumer has pending ack — should still be "active"
        var pending = await fx.GetPendingCountAsync("NIDAW", "C1");
        pending.ShouldBe(1);

        // Ack the message — pending drops to 0
        await fx.AckAllAsync("NIDAW", "C1", batch.Messages[0].Sequence);
        var afterAck = await fx.GetPendingCountAsync("NIDAW", "C1");
        afterAck.ShouldBe(0);
    }

    // =========================================================================
    // PullRequestWaitQueue — priority group round-robin within same priority
    // =========================================================================

    [Fact]
    public void Pull_request_queue_round_robins_within_same_priority()
    {
        // Go: TestJetStreamConsumerPriorityPullRequests — pop-and-requeue within priority
        var queue = new PullRequestWaitQueue();

        queue.Enqueue(new PullWaitingRequest { Priority = 1, Batch = 3, RemainingBatch = 3, Reply = "reply-A" });
        queue.Enqueue(new PullWaitingRequest { Priority = 1, Batch = 3, RemainingBatch = 3, Reply = "reply-B" });

        // First pop-and-requeue returns A, re-inserts A after B
        var first = queue.PopAndRequeue();
        first.ShouldNotBeNull();
        first!.Reply.ShouldBe("reply-A");
        first.RemainingBatch.ShouldBe(2);

        // Second pop-and-requeue returns B (A is now at end of priority group)
        var second = queue.PopAndRequeue();
        second.ShouldNotBeNull();
        second!.Reply.ShouldBe("reply-B");
    }

    // =========================================================================
    // RedeliveryTracker — due entries returned after deadline passes
    // =========================================================================

    [Fact]
    public async Task Redelivery_tracker_returns_due_entries_after_deadline()
    {
        // Go: TestJetStreamConsumerMaxDeliveryAndServerRestart — redelivery mechanics
        var tracker = new RedeliveryTracker(backoffMs: [50]);

        tracker.Schedule(10, 1, ackWaitMs: 50);

        // Not yet due
        var notYet = tracker.GetDue();
        notYet.Count.ShouldBe(0);

        // Wait for the deadline to pass
        await Task.Delay(100);

        var due = tracker.GetDue();
        due.Count.ShouldBe(1);
        due[0].ShouldBe(10UL);

        // Acknowledge removes from tracker
        tracker.Acknowledge(10);
        tracker.IsTracking(10).ShouldBeFalse();
    }

    // =========================================================================
    // ConsumerFileStore — encode/decode round-trip
    // =========================================================================

    [Fact]
    public void ConsumerFileStore_state_encode_decode_roundtrip()
    {
        // Go: TestJetStreamConsumerWithCorruptStateIsDeleted + state persistence tests
        var dir = Path.Combine(Path.GetTempPath(), $"nats-rt-{Guid.NewGuid():N}");
        Directory.CreateDirectory(dir);
        var stateFile = Path.Combine(dir, "state.bin");

        try
        {
            var cfg = new ConsumerConfig
            {
                DurableName = "RT",
                AckPolicy = AckPolicy.Explicit,
            };

            var store = new ConsumerFileStore(stateFile, cfg);
            long tsNs = DateTimeOffset.UtcNow.ToUnixTimeMilliseconds() * 1_000_000;
            store.UpdateDelivered(1, 1, 1, tsNs);
            store.UpdateDelivered(2, 2, 1, tsNs + 1);
            store.Stop();

            var store2 = new ConsumerFileStore(stateFile, cfg);
            var state = store2.State();
            store2.Stop();

            state.Delivered.Consumer.ShouldBe(2UL);
            state.Delivered.Stream.ShouldBe(2UL);
        }
        finally
        {
            if (Directory.Exists(dir))
                Directory.Delete(dir, recursive: true);
        }
    }
}