using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.AdminUI.Hosts;
using ZB.MOM.WW.OtOpcUa.Commons.Messages.Drivers;
using ZB.MOM.WW.OtOpcUa.Core.Abstractions;

namespace ZB.MOM.WW.OtOpcUa.AdminUI.Tests.Hosts;

/// <summary>
///     Covers <see cref="HostsDriverView.Build"/>: the pure, DB-agnostic view-model builder that
///     groups driver-health snapshots by cluster, attaches each cluster's nodes, and enriches each
///     driver row with the configured name + type. The builder is null-safe and stable-ordered so
///     the (later) <c>/hosts</c> Razor section renders deterministically.
/// </summary>
public sealed class HostsDriverViewTests
{
    private static readonly DateTime When = new(2026, 6, 18, 0, 0, 0, DateTimeKind.Utc);

    private static DriverHealthChanged Snap(string cluster, string instance, string state = "Healthy") =>
        new(cluster, instance, state, null, null, 0, When);

    private static HostsNodeInfo Node(string cluster, string node, string host = "h", int port = 4840) =>
        new(cluster, node, host, port);

    private static HostsDriverInstanceInfo Instance(string instance, string cluster, string name, string type) =>
        new(instance, cluster, name, type);

    [Fact]
    public void Build_groups_two_clusters_with_their_nodes_and_snapshots()
    {
        var snaps = new[]
        {
            Snap("MAIN", "drv-a"),
            Snap("EDGE", "drv-b"),
        };
        var nodes = new[]
        {
            Node("MAIN", "MAIN-1"),
            Node("EDGE", "EDGE-1"),
        };

        var groups = HostsDriverView.Build(snaps, nodes, instances: null);

        groups.Count.ShouldBe(2);
        var main = groups.Single(g => g.ClusterId == "MAIN");
        var edge = groups.Single(g => g.ClusterId == "EDGE");

        main.Nodes.Select(n => n.NodeId).ShouldBe(new[] { "MAIN-1" });
        main.Drivers.Select(d => d.DriverInstanceId).ShouldBe(new[] { "drv-a" });
        edge.Nodes.Select(n => n.NodeId).ShouldBe(new[] { "EDGE-1" });
        edge.Drivers.Select(d => d.DriverInstanceId).ShouldBe(new[] { "drv-b" });
    }

    [Fact]
    public void Build_enriches_driver_row_from_matching_instance()
    {
        var groups = HostsDriverView.Build(
            new[] { Snap("MAIN", "drv-a", "Faulted") },
            nodes: null,
            new[] { Instance("drv-a", "MAIN", "Pump House Modbus", "Modbus") });

        var row = groups.Single().Drivers.Single();
        row.DriverInstanceId.ShouldBe("drv-a");
        row.Name.ShouldBe("Pump House Modbus");
        row.DriverType.ShouldBe("Modbus");
        row.State.ShouldBe("Faulted");
    }

    [Fact]
    public void Build_leaves_name_and_type_null_for_unknown_driver()
    {
        var groups = HostsDriverView.Build(
            new[] { Snap("MAIN", "orphan") },
            nodes: null,
            new[] { Instance("drv-a", "MAIN", "Known", "Modbus") });

        var row = groups.Single().Drivers.Single(d => d.DriverInstanceId == "orphan");
        row.Name.ShouldBeNull();
        row.DriverType.ShouldBeNull();
    }

    [Fact]
    public void Build_includes_cluster_with_nodes_but_no_snapshots()
    {
        var groups = HostsDriverView.Build(
            snapshots: null,
            new[] { Node("MAIN", "MAIN-1") },
            instances: null);

        var group = groups.Single();
        group.ClusterId.ShouldBe("MAIN");
        group.Nodes.Count.ShouldBe(1);
        group.Drivers.ShouldBeEmpty();
    }

    [Fact]
    public void Build_with_empty_inputs_returns_empty_list()
    {
        HostsDriverView.Build(
            Array.Empty<DriverHealthChanged>(),
            Array.Empty<HostsNodeInfo>(),
            Array.Empty<HostsDriverInstanceInfo>()).ShouldBeEmpty();
    }

    [Fact]
    public void Build_with_all_null_inputs_returns_empty_list_without_throwing()
    {
        HostsDriverView.Build(snapshots: null, nodes: null, instances: null).ShouldBeEmpty();
    }

    [Fact]
    public void Build_orders_drivers_by_name_then_instance_id()
    {
        var snaps = new[]
        {
            Snap("MAIN", "drv-z"),  // no instance -> null name -> sorts by id "drv-z"
            Snap("MAIN", "drv-a"),  // no instance -> null name -> sorts by id "drv-a"
            Snap("MAIN", "drv-m"),  // named "Alpha"
        };
        var instances = new[]
        {
            Instance("drv-m", "MAIN", "Alpha", "Modbus"),
        };

        var drivers = HostsDriverView.Build(snaps, nodes: null, instances).Single().Drivers;

        // Sort key is (Name ?? DriverInstanceId): "Alpha"(drv-m), "drv-a", "drv-z".
        drivers.Select(d => d.DriverInstanceId).ShouldBe(new[] { "drv-m", "drv-a", "drv-z" });
    }

    [Fact]
    public void Build_takes_first_when_instance_id_appears_twice()
    {
        var groups = HostsDriverView.Build(
            new[] { Snap("MAIN", "drv-a") },
            nodes: null,
            new[]
            {
                Instance("drv-a", "MAIN", "First", "Modbus"),
                Instance("drv-a", "MAIN", "Second", "S7"),
            });

        var row = groups.Single().Drivers.Single();
        row.Name.ShouldBe("First");
        row.DriverType.ShouldBe("Modbus");
    }

    [Fact]
    public void Build_orders_clusters_case_insensitively()
    {
        var groups = HostsDriverView.Build(
            new[] { Snap("zeta", "d1"), Snap("Alpha", "d2") },
            new[] { Node("Beta", "b1") },
            instances: null);

        groups.Select(g => g.ClusterId).ShouldBe(new[] { "Alpha", "Beta", "zeta" });
    }

    /// <summary>
    ///     Per-host connectivity flows through to the row (Gitea #521), and <c>DegradedHosts</c> picks out
    ///     exactly the hosts an operator needs to look at. This is the case the driver-level Status chip
    ///     cannot express: the driver is Healthy and one of its devices is not.
    /// </summary>
    [Fact]
    public void Build_carries_host_statuses_and_flags_only_the_degraded_ones()
    {
        var snapshot = Snap("MAIN", "drv-a") with
        {
            HostStatuses =
            [
                new HostConnectivityStatus("plc-a", HostState.Running, When),
                new HostConnectivityStatus("plc-b", HostState.Stopped, When),
                new HostConnectivityStatus("plc-c", HostState.Faulted, When),
            ],
        };

        var row = HostsDriverView.Build([snapshot], nodes: null, instances: null).Single().Drivers.Single();

        row.State.ShouldBe("Healthy");
        row.HostStatuses!.Count.ShouldBe(3);
        row.DegradedHosts.Select(h => h.HostName).ShouldBe(["plc-b", "plc-c"]);
    }

    /// <summary>
    ///     <see cref="HostState.Unknown"/> counts as degraded. A probe that has not completed its first tick
    ///     — or one a driver failed to start at all, which AbCip logs explicitly — reports Unknown, and
    ///     rendering that as healthy is how an unstarted probe stays invisible.
    /// </summary>
    [Fact]
    public void Unknown_host_state_counts_as_degraded()
    {
        var snapshot = Snap("MAIN", "drv-a") with
        {
            HostStatuses = [new HostConnectivityStatus("plc-a", HostState.Unknown, When)],
        };

        var row = HostsDriverView.Build([snapshot], nodes: null, instances: null).Single().Drivers.Single();

        row.DegradedHosts.ShouldHaveSingleItem().HostName.ShouldBe("plc-a");
    }

    /// <summary>
    ///     A driver with no probe keeps a null host list — distinct from a probe reporting zero hosts. The
    ///     /hosts column renders "—" for the former and "0 hosts" for the latter, and collapsing them would
    ///     claim every probe-less driver's devices are fine.
    /// </summary>
    [Fact]
    public void A_driver_without_host_statuses_keeps_null_and_reports_no_degraded_hosts()
    {
        var row = HostsDriverView.Build([Snap("MAIN", "drv-a")], nodes: null, instances: null)
            .Single().Drivers.Single();

        row.HostStatuses.ShouldBeNull();
        row.DegradedHosts.ShouldBeEmpty();
    }
}