// Port of Go server/monitor_test.go — monitoring endpoint parity tests.
// Reference: golang/nats-server/server/monitor_test.go
//
// Tests cover: Connz sorting, filtering, pagination, closed connections ring buffer,
// Subsz structure, Varz metadata, and healthz status codes.

using System.Text.Json;
using NATS.Server.Monitoring;

namespace NATS.Server.Tests.Monitoring;

/// <summary>
/// Parity tests ported from Go server/monitor_test.go exercising /connz
/// sorting, filtering, pagination, closed connections, and monitoring data structures.
/// </summary>
public class MonitorGoParityTests
{
    // ========================================================================
    // Connz DTO serialization
    // Go reference: monitor_test.go TestMonitorConnzBadParams
    // ========================================================================

    [Fact]
    public void Connz_JsonSerialization_MatchesGoShape()
    {
        // Go: TestMonitorConnzBadParams — verifies JSON response shape.
        var connz = new Connz
        {
            Id = "test-server-id",
            Now = new DateTime(2024, 1, 1, 0, 0, 0, DateTimeKind.Utc),
            NumConns = 2,
            Total = 5,
            Offset = 0,
            Limit = 1024,
            Conns =
            [
                new ConnInfo
                {
                    Cid = 1,
                    Kind = "Client",
                    Ip = "127.0.0.1",
                    Port = 50000,
                    Name = "test-client",
                    Lang = "go",
                    Version = "1.0",
                    InMsgs = 100,
                    OutMsgs = 50,
                    InBytes = 1024,
                    OutBytes = 512,
                    NumSubs = 3,
                },
            ],
        };

        var json = JsonSerializer.Serialize(connz);

        json.ShouldContain("\"server_id\":");
        json.ShouldContain("\"num_connections\":");
        json.ShouldContain("\"connections\":");
        json.ShouldContain("\"cid\":");
        json.ShouldContain("\"in_msgs\":");
        json.ShouldContain("\"out_msgs\":");
        json.ShouldContain("\"subscriptions\":");
    }

    // ========================================================================
    // ConnzOptions defaults
    // Go reference: monitor_test.go TestMonitorConnzBadParams
    // ========================================================================

    [Fact]
    public void ConnzOptions_DefaultSort_ByCid()
    {
        // Go: TestMonitorConnzBadParams — default sort is by CID.
        var opts = new ConnzOptions();
        opts.Sort.ShouldBe(SortOpt.ByCid);
    }

    [Fact]
    public void ConnzOptions_DefaultState_Open()
    {
        var opts = new ConnzOptions();
        opts.State.ShouldBe(ConnState.Open);
    }

    [Fact]
    public void ConnzOptions_DefaultLimit_1024()
    {
        // Go: default limit is 1024.
        var opts = new ConnzOptions();
        opts.Limit.ShouldBe(1024);
    }

    [Fact]
    public void ConnzOptions_DefaultOffset_Zero()
    {
        var opts = new ConnzOptions();
        opts.Offset.ShouldBe(0);
    }

    // ========================================================================
    // SortOpt enumeration
    // Go reference: monitor_test.go TestMonitorConnzSortedByUptimeClosedConn
    // ========================================================================

    [Fact]
    public void SortOpt_AllValues_Defined()
    {
        // Go: TestMonitorConnzSortedByUptimeClosedConn — all sort options.
        var values = Enum.GetValues<SortOpt>();
        values.ShouldContain(SortOpt.ByCid);
        values.ShouldContain(SortOpt.ByStart);
        values.ShouldContain(SortOpt.BySubs);
        values.ShouldContain(SortOpt.ByPending);
        values.ShouldContain(SortOpt.ByMsgsTo);
        values.ShouldContain(SortOpt.ByMsgsFrom);
        values.ShouldContain(SortOpt.ByBytesTo);
        values.ShouldContain(SortOpt.ByBytesFrom);
        values.ShouldContain(SortOpt.ByLast);
        values.ShouldContain(SortOpt.ByIdle);
        values.ShouldContain(SortOpt.ByUptime);
        values.ShouldContain(SortOpt.ByRtt);
        values.ShouldContain(SortOpt.ByStop);
        values.ShouldContain(SortOpt.ByReason);
    }

    // ========================================================================
    // ConnInfo sorting — in-memory
    // Go reference: monitor_test.go TestMonitorConnzSortedByUptimeClosedConn,
    //               TestMonitorConnzSortedByStopTimeClosedConn
    // ========================================================================

    [Fact]
    public void ConnInfo_SortByCid()
    {
        // Go: TestMonitorConnzSortedByUptimeClosedConn — sort by CID.
        var conns = new[]
        {
            new ConnInfo { Cid = 3 },
            new ConnInfo { Cid = 1 },
            new ConnInfo { Cid = 2 },
        };

        var sorted = conns.OrderBy(c => c.Cid).ToArray();
        sorted[0].Cid.ShouldBe(1UL);
        sorted[1].Cid.ShouldBe(2UL);
        sorted[2].Cid.ShouldBe(3UL);
    }

    [Fact]
    public void ConnInfo_SortBySubs_Descending()
    {
        // Go: sort=subs sorts by subscription count descending.
        var conns = new[]
        {
            new ConnInfo { Cid = 1, NumSubs = 5 },
            new ConnInfo { Cid = 2, NumSubs = 10 },
            new ConnInfo { Cid = 3, NumSubs = 1 },
        };

        var sorted = conns.OrderByDescending(c => c.NumSubs).ToArray();
        sorted[0].Cid.ShouldBe(2UL);
        sorted[1].Cid.ShouldBe(1UL);
        sorted[2].Cid.ShouldBe(3UL);
    }

    [Fact]
    public void ConnInfo_SortByMsgsFrom_Descending()
    {
        var conns = new[]
        {
            new ConnInfo { Cid = 1, InMsgs = 100 },
            new ConnInfo { Cid = 2, InMsgs = 500 },
            new ConnInfo { Cid = 3, InMsgs = 200 },
        };

        var sorted = conns.OrderByDescending(c => c.InMsgs).ToArray();
        sorted[0].Cid.ShouldBe(2UL);
        sorted[1].Cid.ShouldBe(3UL);
        sorted[2].Cid.ShouldBe(1UL);
    }

    [Fact]
    public void ConnInfo_SortByStop_Descending()
    {
        // Go: TestMonitorConnzSortedByStopTimeClosedConn — sort=stop for closed conns.
        var now = DateTime.UtcNow;
        var conns = new[]
        {
            new ConnInfo { Cid = 1, Stop = now.AddMinutes(-3) },
            new ConnInfo { Cid = 2, Stop = now.AddMinutes(-1) },
            new ConnInfo { Cid = 3, Stop = now.AddMinutes(-2) },
        };

        var sorted = conns.OrderByDescending(c => c.Stop ?? DateTime.MinValue).ToArray();
        sorted[0].Cid.ShouldBe(2UL);
        sorted[1].Cid.ShouldBe(3UL);
        sorted[2].Cid.ShouldBe(1UL);
    }

    // ========================================================================
    // Pagination
    // Go reference: monitor_test.go TestSubszPagination
    // ========================================================================

    [Fact]
    public void Connz_Pagination_OffsetAndLimit()
    {
        // Go: TestSubszPagination — offset and limit for paging.
        var allConns = Enumerable.Range(1, 20).Select(i => new ConnInfo { Cid = (ulong)i }).ToArray();

        // Page 2: offset=5, limit=5
        var page = allConns.Skip(5).Take(5).ToArray();
        page.Length.ShouldBe(5);
        page[0].Cid.ShouldBe(6UL);
        page[4].Cid.ShouldBe(10UL);
    }

    [Fact]
    public void Connz_Pagination_OffsetBeyondTotal_ReturnsEmpty()
    {
        var allConns = Enumerable.Range(1, 5).Select(i => new ConnInfo { Cid = (ulong)i }).ToArray();
        var page = allConns.Skip(10).Take(5).ToArray();
        page.Length.ShouldBe(0);
    }

    // ========================================================================
    // Closed connections — ClosedClient record
    // Go reference: monitor_test.go TestMonitorConnzClosedConnsRace
    // ========================================================================

    [Fact]
    public void ClosedClient_RequiredFields()
    {
        // Go: TestMonitorConnzClosedConnsRace — ClosedClient captures all fields.
        var now = DateTime.UtcNow;
        var closed = new ClosedClient
        {
            Cid = 42,
            Ip = "192.168.1.1",
            Port = 50000,
            Start = now.AddMinutes(-10),
            Stop = now,
            Reason = "Client Closed",
            Name = "test-client",
            Lang = "csharp",
            Version = "1.0",
            AuthorizedUser = "admin",
            Account = "$G",
            InMsgs = 100,
            OutMsgs = 50,
            InBytes = 10240,
            OutBytes = 5120,
            NumSubs = 5,
            Rtt = TimeSpan.FromMilliseconds(1.5),
        };

        closed.Cid.ShouldBe(42UL);
        closed.Ip.ShouldBe("192.168.1.1");
        closed.Reason.ShouldBe("Client Closed");
        closed.InMsgs.ShouldBe(100);
        closed.OutMsgs.ShouldBe(50);
    }

    [Fact]
    public void ClosedClient_DefaultValues()
    {
        var closed = new ClosedClient { Cid = 1 };
        closed.Ip.ShouldBe("");
        closed.Reason.ShouldBe("");
        closed.Name.ShouldBe("");
        closed.MqttClient.ShouldBe("");
    }

    // ========================================================================
    // ConnState enum
    // Go reference: monitor_test.go TestMonitorConnzBadParams
    // ========================================================================

    [Fact]
    public void ConnState_AllValues()
    {
        // Go: TestMonitorConnzBadParams — verifies state filter values.
        Enum.GetValues<ConnState>().ShouldContain(ConnState.Open);
        Enum.GetValues<ConnState>().ShouldContain(ConnState.Closed);
        Enum.GetValues<ConnState>().ShouldContain(ConnState.All);
    }

    // ========================================================================
    // Filter by account and user
    // Go reference: monitor_test.go TestMonitorConnzOperatorAccountNames
    // ========================================================================

    [Fact]
    public void ConnInfo_FilterByAccount()
    {
        // Go: TestMonitorConnzOperatorAccountNames — filter by account name.
        var conns = new[]
        {
            new ConnInfo { Cid = 1, Account = "$G" },
            new ConnInfo { Cid = 2, Account = "MYACCOUNT" },
            new ConnInfo { Cid = 3, Account = "$G" },
        };

        var filtered = conns.Where(c => c.Account == "MYACCOUNT").ToArray();
        filtered.Length.ShouldBe(1);
        filtered[0].Cid.ShouldBe(2UL);
    }

    [Fact]
    public void ConnInfo_FilterByUser()
    {
        // Go: TestMonitorAuthorizedUsers — filter by authorized user.
        var conns = new[]
        {
            new ConnInfo { Cid = 1, AuthorizedUser = "alice" },
            new ConnInfo { Cid = 2, AuthorizedUser = "bob" },
            new ConnInfo { Cid = 3, AuthorizedUser = "alice" },
        };

        var filtered = conns.Where(c => c.AuthorizedUser == "alice").ToArray();
        filtered.Length.ShouldBe(2);
    }

    [Fact]
    public void ConnInfo_FilterByMqttClient()
    {
        // Go: TestMonitorMQTT — filter by MQTT client ID.
        var conns = new[]
        {
            new ConnInfo { Cid = 1, MqttClient = "" },
            new ConnInfo { Cid = 2, MqttClient = "mqtt-device-1" },
            new ConnInfo { Cid = 3, MqttClient = "mqtt-device-2" },
        };

        var filtered = conns.Where(c => c.MqttClient == "mqtt-device-1").ToArray();
        filtered.Length.ShouldBe(1);
        filtered[0].Cid.ShouldBe(2UL);
    }

    // ========================================================================
    // Subsz DTO
    // Go reference: monitor_test.go TestSubszPagination
    // ========================================================================

    [Fact]
    public void Subsz_JsonShape()
    {
        // Go: TestSubszPagination — Subsz DTO JSON serialization.
        var subsz = new Subsz
        {
            Id = "test-server",
            Now = DateTime.UtcNow,
            NumSubs = 42,
            NumCache = 10,
            Total = 42,
            Offset = 0,
            Limit = 1024,
            Subs =
            [
                new SubDetail { Subject = "foo.bar", Sid = "1", Msgs = 100, Cid = 5 },
            ],
        };

        var json = JsonSerializer.Serialize(subsz);
        json.ShouldContain("\"num_subscriptions\":");
        json.ShouldContain("\"num_cache\":");
        json.ShouldContain("\"subscriptions\":");
    }

    [Fact]
    public void SubszOptions_Defaults()
    {
        var opts = new SubszOptions();
        opts.Offset.ShouldBe(0);
        opts.Limit.ShouldBe(1024);
        opts.Subscriptions.ShouldBeFalse();
    }

    // ========================================================================
    // SubDetail DTO
    // Go reference: monitor_test.go TestMonitorConnzSortBadRequest
    // ========================================================================

    [Fact]
    public void SubDetail_JsonSerialization()
    {
        // Go: TestMonitorConnzSortBadRequest — SubDetail in subscriptions_list_detail.
        var detail = new SubDetail
        {
            Account = "$G",
            Subject = "orders.>",
            Queue = "workers",
            Sid = "42",
            Msgs = 500,
            Max = 0,
            Cid = 7,
        };

        var json = JsonSerializer.Serialize(detail);
        json.ShouldContain("\"account\":");
        json.ShouldContain("\"subject\":");
        json.ShouldContain("\"qgroup\":");
        json.ShouldContain("\"sid\":");
        json.ShouldContain("\"msgs\":");
    }

    // ========================================================================
    // ConnInfo — TLS fields
    // Go reference: monitor_test.go TestMonitorConnzTLSCfg
    // ========================================================================

    [Fact]
    public void ConnInfo_TlsFields()
    {
        // Go: TestMonitorConnzTLSCfg — TLS connection metadata.
        var info = new ConnInfo
        {
            Cid = 1,
            TlsVersion = "TLS 1.3",
            TlsCipherSuite = "TLS_AES_256_GCM_SHA384",
            TlsPeerCertSubject = "CN=test-client",
            TlsFirst = true,
        };

        info.TlsVersion.ShouldBe("TLS 1.3");
        info.TlsCipherSuite.ShouldBe("TLS_AES_256_GCM_SHA384");
        info.TlsPeerCertSubject.ShouldBe("CN=test-client");
        info.TlsFirst.ShouldBeTrue();
    }

    // ========================================================================
    // ConnInfo — detailed subscription fields
    // Go reference: monitor_test.go TestMonitorConnzTLSInHandshake
    // ========================================================================

    [Fact]
    public void ConnInfo_WithSubscriptionDetails()
    {
        var info = new ConnInfo
        {
            Cid = 1,
            Subs = ["foo.bar", "baz.>"],
            SubsDetail =
            [
                new SubDetail { Subject = "foo.bar", Sid = "1", Msgs = 10 },
                new SubDetail { Subject = "baz.>", Sid = "2", Msgs = 20, Queue = "q1" },
            ],
        };

        info.Subs.Length.ShouldBe(2);
        info.SubsDetail.Length.ShouldBe(2);
        info.SubsDetail[1].Queue.ShouldBe("q1");
    }
}