// Go parity: golang/nats-server/server/jetstream_cluster_1_test.go
// Covers: cluster metadata operations, asset placement planner,
// replica group management, stream scaling, config validation,
// cluster expand, account info in cluster, max streams.
using System.Text;
using NATS.Server.Configuration;
using NATS.Server.JetStream;
using NATS.Server.JetStream.Api;
using NATS.Server.JetStream.Cluster;
using NATS.Server.JetStream.Models;
using NATS.Server.JetStream.Publish;
using NATS.Server.JetStream.Validation;

namespace NATS.Server.JetStream.Tests.JetStream.Cluster;

/// <summary>
/// Tests covering JetStream cluster metadata operations: asset placement,
/// replica group management, config validation, scaling, and account operations.
/// Ported from Go jetstream_cluster_1_test.go.
/// </summary>
public class JetStreamClusterMetaTests
{
    // ---------------------------------------------------------------
    // Go: TestJetStreamClusterConfig server/jetstream_cluster_1_test.go:43
    // ---------------------------------------------------------------

    [Fact]
    public void Config_requires_server_name_for_jetstream_cluster()
    {
        var options = new NatsOptions
        {
            ServerName = null,
            JetStream = new JetStreamOptions { StoreDir = "/tmp/js" },
            Cluster = new ClusterOptions { Port = 6222 },
        };
        var result = JetStreamConfigValidator.ValidateClusterConfig(options);
        result.IsValid.ShouldBeFalse();
        result.Message.ShouldContain("server_name");
    }

    [Fact]
    public void Config_requires_cluster_name_for_jetstream_cluster()
    {
        var options = new NatsOptions
        {
            ServerName = "S1",
            JetStream = new JetStreamOptions { StoreDir = "/tmp/js" },
            Cluster = new ClusterOptions { Name = null, Port = 6222 },
        };
        var result = JetStreamConfigValidator.ValidateClusterConfig(options);
        result.IsValid.ShouldBeFalse();
        result.Message.ShouldContain("cluster.name");
    }

    [Fact]
    public void Config_valid_when_server_and_cluster_names_set()
    {
        var options = new NatsOptions
        {
            ServerName = "S1",
            JetStream = new JetStreamOptions { StoreDir = "/tmp/js" },
            Cluster = new ClusterOptions { Name = "JSC", Port = 6222 },
        };
        var result = JetStreamConfigValidator.ValidateClusterConfig(options);
        result.IsValid.ShouldBeTrue();
    }

    [Fact]
    public void Config_skips_cluster_checks_when_no_cluster_configured()
    {
        var options = new NatsOptions
        {
            JetStream = new JetStreamOptions { StoreDir = "/tmp/js" },
        };
        var result = JetStreamConfigValidator.ValidateClusterConfig(options);
        result.IsValid.ShouldBeTrue();
    }

    [Fact]
    public void Config_skips_cluster_checks_when_no_jetstream_configured()
    {
        var options = new NatsOptions
        {
            Cluster = new ClusterOptions { Port = 6222 },
        };
        var result = JetStreamConfigValidator.ValidateClusterConfig(options);
        result.IsValid.ShouldBeTrue();
    }

    // ---------------------------------------------------------------
    // Placement planner tests
    // ---------------------------------------------------------------

    [Fact]
    public void Placement_planner_returns_requested_replica_count()
    {
        var planner = new AssetPlacementPlanner(nodes: 5);
        var placement = planner.PlanReplicas(replicas: 3);
        placement.Count.ShouldBe(3);
    }

    [Fact]
    public void Placement_planner_caps_at_cluster_size()
    {
        var planner = new AssetPlacementPlanner(nodes: 3);
        var placement = planner.PlanReplicas(replicas: 5);
        placement.Count.ShouldBe(3);
    }

    [Fact]
    public void Placement_planner_minimum_is_one_replica()
    {
        var planner = new AssetPlacementPlanner(nodes: 3);
        var placement = planner.PlanReplicas(replicas: 0);
        placement.Count.ShouldBe(1);
    }

    [Fact]
    public void Placement_planner_handles_single_node_cluster()
    {
        var planner = new AssetPlacementPlanner(nodes: 1);
        var placement = planner.PlanReplicas(replicas: 3);
        placement.Count.ShouldBe(1);
    }

    // ---------------------------------------------------------------
    // Meta group lifecycle tests
    // ---------------------------------------------------------------

    [Fact]
    public void Meta_group_initial_state_is_correct()
    {
        var meta = new JetStreamMetaGroup(3);
        var state = meta.GetState();

        state.ClusterSize.ShouldBe(3);
        state.LeaderId.ShouldNotBeNullOrWhiteSpace();
        state.LeadershipVersion.ShouldBe(1);
        state.Streams.Count.ShouldBe(0);
    }

    [Fact]
    public async Task Meta_group_tracks_stream_proposals()
    {
        var meta = new JetStreamMetaGroup(3);

        await meta.ProposeCreateStreamAsync(new StreamConfig { Name = "S1" }, default);
        await meta.ProposeCreateStreamAsync(new StreamConfig { Name = "S2" }, default);

        var state = meta.GetState();
        state.Streams.Count.ShouldBe(2);
        state.Streams.ShouldContain("S1");
        state.Streams.ShouldContain("S2");
    }

    [Fact]
    public void Meta_group_stepdown_cycles_leader()
    {
        var meta = new JetStreamMetaGroup(3);
        var leader1 = meta.GetState().LeaderId;

        meta.StepDown();
        var leader2 = meta.GetState().LeaderId;
        leader2.ShouldNotBe(leader1);

        meta.StepDown();
        var leader3 = meta.GetState().LeaderId;
        leader3.ShouldNotBe(leader2);
    }

    [Fact]
    public void Meta_group_stepdown_wraps_around()
    {
        var meta = new JetStreamMetaGroup(2);
        var leaders = new HashSet<string>();

        for (var i = 0; i < 5; i++)
        {
            leaders.Add(meta.GetState().LeaderId);
            meta.StepDown();
        }

        // Should cycle between 2 leaders
        leaders.Count.ShouldBe(2);
    }

    [Fact]
    public void Meta_group_leadership_version_increments()
    {
        var meta = new JetStreamMetaGroup(3);
        meta.GetState().LeadershipVersion.ShouldBe(1);

        meta.StepDown();
        meta.GetState().LeadershipVersion.ShouldBe(2);

        meta.StepDown();
        meta.GetState().LeadershipVersion.ShouldBe(3);
    }

    // ---------------------------------------------------------------
    // Replica group tests
    // ---------------------------------------------------------------

    [Fact]
    public void Replica_group_creates_correct_node_count()
    {
        var group = new StreamReplicaGroup("TEST", replicas: 3);
        group.Nodes.Count.ShouldBe(3);
        group.StreamName.ShouldBe("TEST");
    }

    [Fact]
    public void Replica_group_elects_initial_leader()
    {
        var group = new StreamReplicaGroup("TEST", replicas: 3);
        group.Leader.ShouldNotBeNull();
        group.Leader.IsLeader.ShouldBeTrue();
    }

    [Fact]
    public async Task Replica_group_stepdown_changes_leader()
    {
        var group = new StreamReplicaGroup("TEST", replicas: 3);
        var leaderBefore = group.Leader.Id;

        await group.StepDownAsync(default);
        var leaderAfter = group.Leader.Id;

        leaderAfter.ShouldNotBe(leaderBefore);
        group.Leader.IsLeader.ShouldBeTrue();
    }

    [Fact]
    public async Task Replica_group_leader_accepts_proposals()
    {
        var group = new StreamReplicaGroup("TEST", replicas: 3);

        var index = await group.ProposeAsync("PUB test.1", default);
        index.ShouldBeGreaterThan(0);
    }

    [Fact]
    public async Task Replica_group_apply_placement_scales_up()
    {
        var group = new StreamReplicaGroup("TEST", replicas: 1);
        group.Nodes.Count.ShouldBe(1);

        await group.ApplyPlacementAsync([1, 2, 3], default);
        group.Nodes.Count.ShouldBe(3);
    }

    [Fact]
    public async Task Replica_group_apply_placement_scales_down()
    {
        var group = new StreamReplicaGroup("TEST", replicas: 5);
        group.Nodes.Count.ShouldBe(5);

        await group.ApplyPlacementAsync([1, 2], default);
        group.Nodes.Count.ShouldBe(2);
    }

    [Fact]
    public async Task Replica_group_apply_same_size_is_noop()
    {
        var group = new StreamReplicaGroup("TEST", replicas: 3);
        var leaderBefore = group.Leader.Id;

        await group.ApplyPlacementAsync([1, 2, 3], default);
        group.Nodes.Count.ShouldBe(3);
    }

    // ---------------------------------------------------------------
    // Go: TestJetStreamClusterAccountInfo server/jetstream_cluster_1_test.go:94
    // ---------------------------------------------------------------

    [Fact]
    public async Task Account_info_tracks_streams_and_consumers_in_cluster()
    {
        await using var fx = await ClusterMetaFixture.StartAsync(nodes: 3);

        await fx.CreateStreamAsync("ACCT1", ["a1.>"], replicas: 3);
        await fx.CreateStreamAsync("ACCT2", ["a2.>"], replicas: 3);
        await fx.CreateConsumerAsync("ACCT1", "c1");
        await fx.CreateConsumerAsync("ACCT1", "c2");

        var resp = await fx.RequestAsync(JetStreamApiSubjects.Info, "{}");
        resp.AccountInfo.ShouldNotBeNull();
        resp.AccountInfo!.Streams.ShouldBe(2);
        resp.AccountInfo.Consumers.ShouldBe(2);
    }

    // ---------------------------------------------------------------
    // Go: TestJetStreamClusterExtendedAccountInfo server/jetstream_cluster_1_test.go:3389
    // ---------------------------------------------------------------

    [Fact]
    public async Task Account_info_after_stream_delete_reflects_removal()
    {
        await using var fx = await ClusterMetaFixture.StartAsync(nodes: 3);

        await fx.CreateStreamAsync("DEL1", ["d1.>"], replicas: 3);
        await fx.CreateStreamAsync("DEL2", ["d2.>"], replicas: 3);

        (await fx.RequestAsync($"{JetStreamApiSubjects.StreamDelete}DEL1", "{}")).Success.ShouldBeTrue();

        var resp = await fx.RequestAsync(JetStreamApiSubjects.Info, "{}");
        resp.AccountInfo!.Streams.ShouldBe(1);
    }

    // ---------------------------------------------------------------
    // Go: TestJetStreamClusterAccountPurge server/jetstream_cluster_1_test.go:3891
    // ---------------------------------------------------------------

    [Fact]
    public async Task Account_purge_returns_success()
    {
        await using var fx = await ClusterMetaFixture.StartAsync(nodes: 3);
        await fx.CreateStreamAsync("PURGE1", ["pur.>"], replicas: 3);

        var resp = await fx.RequestAsync($"{JetStreamApiSubjects.AccountPurge}GLOBAL", "{}");
        resp.Success.ShouldBeTrue();
    }

    // ---------------------------------------------------------------
    // Go: TestJetStreamClusterStreamLimitWithAccountDefaults server/jetstream_cluster_1_test.go:124
    // ---------------------------------------------------------------

    [Fact]
    public async Task Stream_with_max_bytes_and_replicas_created_successfully()
    {
        await using var fx = await ClusterMetaFixture.StartAsync(nodes: 3);

        var cfg = new StreamConfig
        {
            Name = "MBLIMIT",
            Subjects = ["mbl.>"],
            Replicas = 2,
            MaxBytes = 4 * 1024 * 1024,
        };
        var resp = fx.CreateStreamDirect(cfg);
        resp.Error.ShouldBeNull();
        resp.StreamInfo!.Config.MaxBytes.ShouldBe(4 * 1024 * 1024);
    }

    // ---------------------------------------------------------------
    // Go: TestJetStreamClusterMaxStreamsReached server/jetstream_cluster_1_test.go:3177
    // ---------------------------------------------------------------

    [Fact]
    public async Task Multiple_streams_tracked_correctly_in_meta()
    {
        await using var fx = await ClusterMetaFixture.StartAsync(nodes: 3);

        for (var i = 0; i < 10; i++)
            await fx.CreateStreamAsync($"MS{i}", [$"ms{i}.>"], replicas: 3);

        var names = await fx.RequestAsync(JetStreamApiSubjects.StreamNames, "{}");
        names.StreamNames!.Count.ShouldBe(10);

        var meta = fx.GetMetaState();
        meta.Streams.Count.ShouldBe(10);
    }

    // ---------------------------------------------------------------
    // Direct API tests (DirectGet)
    // ---------------------------------------------------------------

    [Fact]
    public async Task Direct_get_returns_message_by_sequence()
    {
        await using var fx = await ClusterMetaFixture.StartAsync(nodes: 3);

        var cfg = new StreamConfig
        {
            Name = "DIRECT",
            Subjects = ["dir.>"],
            Replicas = 3,
            AllowDirect = true,
        };
        fx.CreateStreamDirect(cfg);

        for (var i = 0; i < 5; i++)
            await fx.PublishAsync("dir.event", $"msg-{i}");

        var resp = await fx.RequestAsync($"{JetStreamApiSubjects.DirectGet}DIRECT", """{"seq":3}""");
        resp.DirectMessage.ShouldNotBeNull();
        resp.DirectMessage!.Sequence.ShouldBe(3UL);
        resp.DirectMessage.Subject.ShouldBe("dir.event");
    }

    // ---------------------------------------------------------------
    // Stream message get
    // ---------------------------------------------------------------

    [Fact]
    public async Task Stream_message_get_returns_correct_payload()
    {
        await using var fx = await ClusterMetaFixture.StartAsync(nodes: 3);

        await fx.CreateStreamAsync("MSGGET", ["mg.>"], replicas: 3);

        await fx.PublishAsync("mg.event", "payload-1");
        await fx.PublishAsync("mg.event", "payload-2");

        var resp = await fx.RequestAsync($"{JetStreamApiSubjects.StreamMessageGet}MSGGET", """{"seq":2}""");
        resp.StreamMessage.ShouldNotBeNull();
        resp.StreamMessage!.Sequence.ShouldBe(2UL);
        resp.StreamMessage.Payload.ShouldBe("payload-2");
    }

    // ---------------------------------------------------------------
    // Consumer list and names
    // ---------------------------------------------------------------

    [Fact]
    public async Task Consumer_list_via_api_router()
    {
        await using var fx = await ClusterMetaFixture.StartAsync(nodes: 3);

        await fx.CreateStreamAsync("CLISTM", ["clm.>"], replicas: 3);
        await fx.CreateConsumerAsync("CLISTM", "d1");
        await fx.CreateConsumerAsync("CLISTM", "d2");

        var names = await fx.RequestAsync($"{JetStreamApiSubjects.ConsumerNames}CLISTM", "{}");
        names.ConsumerNames.ShouldNotBeNull();
        names.ConsumerNames!.Count.ShouldBe(2);

        var list = await fx.RequestAsync($"{JetStreamApiSubjects.ConsumerList}CLISTM", "{}");
        list.ConsumerNames.ShouldNotBeNull();
        list.ConsumerNames!.Count.ShouldBe(2);
    }

    // ---------------------------------------------------------------
    // Account stream move returns success shape
    // ---------------------------------------------------------------

    [Fact]
    public async Task Account_stream_move_api_returns_success()
    {
        await using var fx = await ClusterMetaFixture.StartAsync(nodes: 3);

        var resp = await fx.RequestAsync($"{JetStreamApiSubjects.AccountStreamMove}TEST", "{}");
        resp.Success.ShouldBeTrue();
    }

    // ---------------------------------------------------------------
    // Account stream move cancel returns success shape
    // ---------------------------------------------------------------

    [Fact]
    public async Task Account_stream_move_cancel_api_returns_success()
    {
        await using var fx = await ClusterMetaFixture.StartAsync(nodes: 3);

        var resp = await fx.RequestAsync($"{JetStreamApiSubjects.AccountStreamMoveCancel}TEST", "{}");
        resp.Success.ShouldBeTrue();
    }

    // ---------------------------------------------------------------
    // Stream create requires name
    // ---------------------------------------------------------------

    [Fact]
    public void Stream_create_without_name_returns_error()
    {
        var streamManager = new StreamManager();
        var resp = streamManager.CreateOrUpdate(new StreamConfig { Name = "" });
        resp.Error.ShouldNotBeNull();
        resp.Error!.Description.ShouldContain("name");
    }

    // ---------------------------------------------------------------
    // NotFound for unknown API subject
    // ---------------------------------------------------------------

    [Fact]
    public async Task Unknown_api_subject_returns_not_found()
    {
        await using var fx = await ClusterMetaFixture.StartAsync(nodes: 3);

        var resp = await fx.RequestAsync("$JS.API.UNKNOWN.SUBJECT", "{}");
        resp.Error.ShouldNotBeNull();
        resp.Error!.Code.ShouldBe(404);
    }

    // ---------------------------------------------------------------
    // Stream info for non-existent stream returns 404
    // ---------------------------------------------------------------

    [Fact]
    public async Task Stream_info_nonexistent_returns_not_found()
    {
        await using var fx = await ClusterMetaFixture.StartAsync(nodes: 3);

        var resp = await fx.RequestAsync($"{JetStreamApiSubjects.StreamInfo}NOSTREAM", "{}");
        resp.Error.ShouldNotBeNull();
        resp.Error!.Code.ShouldBe(404);
    }

    // ---------------------------------------------------------------
    // Consumer info for non-existent consumer returns 404
    // ---------------------------------------------------------------

    [Fact]
    public async Task Consumer_info_nonexistent_returns_not_found()
    {
        await using var fx = await ClusterMetaFixture.StartAsync(nodes: 3);
        await fx.CreateStreamAsync("NOCONS", ["nc.>"], replicas: 3);

        var resp = await fx.RequestAsync($"{JetStreamApiSubjects.ConsumerInfo}NOCONS.MISSING", "{}");
        resp.Error.ShouldNotBeNull();
        resp.Error!.Code.ShouldBe(404);
    }

    // ---------------------------------------------------------------
    // Delete non-existent stream returns 404
    // ---------------------------------------------------------------

    [Fact]
    public async Task Delete_nonexistent_stream_returns_not_found()
    {
        await using var fx = await ClusterMetaFixture.StartAsync(nodes: 3);

        var resp = await fx.RequestAsync($"{JetStreamApiSubjects.StreamDelete}GONE", "{}");
        resp.Error.ShouldNotBeNull();
        resp.Error!.Code.ShouldBe(404);
    }

    // ---------------------------------------------------------------
    // Delete non-existent consumer returns 404
    // ---------------------------------------------------------------

    [Fact]
    public async Task Delete_nonexistent_consumer_returns_not_found()
    {
        await using var fx = await ClusterMetaFixture.StartAsync(nodes: 3);
        await fx.CreateStreamAsync("NODEL", ["nd.>"], replicas: 3);

        var resp = await fx.RequestAsync($"{JetStreamApiSubjects.ConsumerDelete}NODEL.MISSING", "{}");
        resp.Error.ShouldNotBeNull();
        resp.Error!.Code.ShouldBe(404);
    }
}

/// <summary>
/// Self-contained fixture for JetStream cluster meta tests.
/// </summary>
internal sealed class ClusterMetaFixture : IAsyncDisposable
{
    private readonly JetStreamMetaGroup _metaGroup;
    private readonly StreamManager _streamManager;
    private readonly ConsumerManager _consumerManager;
    private readonly JetStreamApiRouter _router;
    private readonly JetStreamPublisher _publisher;

    private ClusterMetaFixture(
        JetStreamMetaGroup metaGroup,
        StreamManager streamManager,
        ConsumerManager consumerManager,
        JetStreamApiRouter router,
        JetStreamPublisher publisher)
    {
        _metaGroup = metaGroup;
        _streamManager = streamManager;
        _consumerManager = consumerManager;
        _router = router;
        _publisher = publisher;
    }

    public static Task<ClusterMetaFixture> StartAsync(int nodes)
    {
        var meta = new JetStreamMetaGroup(nodes);
        var consumerManager = new ConsumerManager(meta);
        var streamManager = new StreamManager(meta, consumerManager: consumerManager);
        var router = new JetStreamApiRouter(streamManager, consumerManager, meta);
        var publisher = new JetStreamPublisher(streamManager);
        return Task.FromResult(new ClusterMetaFixture(meta, streamManager, consumerManager, router, publisher));
    }

    public Task CreateStreamAsync(string name, string[] subjects, int replicas)
    {
        var response = _streamManager.CreateOrUpdate(new StreamConfig
        {
            Name = name,
            Subjects = [.. subjects],
            Replicas = replicas,
        });
        if (response.Error is not null)
            throw new InvalidOperationException(response.Error.Description);
        return Task.CompletedTask;
    }

    public JetStreamApiResponse CreateStreamDirect(StreamConfig config)
        => _streamManager.CreateOrUpdate(config);

    public Task<JetStreamApiResponse> CreateConsumerAsync(string stream, string durableName)
    {
        return Task.FromResult(_consumerManager.CreateOrUpdate(stream, new ConsumerConfig
        {
            DurableName = durableName,
        }));
    }

    public Task<PubAck> PublishAsync(string subject, string payload)
    {
        if (_publisher.TryCapture(subject, Encoding.UTF8.GetBytes(payload), null, out var ack))
            return Task.FromResult(ack);
        throw new InvalidOperationException($"Publish to '{subject}' did not match a stream.");
    }

    public MetaGroupState GetMetaState() => _metaGroup.GetState();

    public Task<JetStreamApiResponse> RequestAsync(string subject, string payload)
        => Task.FromResult(_router.Route(subject, Encoding.UTF8.GetBytes(payload)));

    public ValueTask DisposeAsync() => ValueTask.CompletedTask;
}