using System.Text;
using Akka.Actor;
using Microsoft.EntityFrameworkCore;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.AdminUI.Clients;
using ZB.MOM.WW.OtOpcUa.Commons.Interfaces;
using ZB.MOM.WW.OtOpcUa.Commons.Types;
using ZB.MOM.WW.OtOpcUa.Configuration;
using ZB.MOM.WW.OtOpcUa.Configuration.Entities;

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

/// <summary>
///     #786: the <c>/fleet/diagnostics</c> "Faulted devices" tile counts DISTINCT faulted devices across a
///     cluster's nodes (a device faulted on both nodes of a redundant pair counts once), Faulted only.
/// </summary>
[Trait("Category", "Unit")]
public sealed class FleetDiagnosticsAggregationTests
{
    private static readonly DateTime Now = DateTime.UtcNow;

    private static DriverInstanceDiagnostics Driver(
        string name, int faulted, IReadOnlyList<string>? faultedHosts, int stopped = 0) =>
        new(Guid.NewGuid(), name, "Degraded", 0, faulted, Now, stopped, faultedHosts);

    private static NodeDiagnosticsSnapshot Node(string nodeId, params DriverInstanceDiagnostics[] drivers) =>
        new(NodeId.Parse(nodeId), null, drivers, Now);

    [Fact]
    public void The_same_device_faulted_on_both_nodes_of_a_pair_counts_once()
    {
        var a = Node("node-a:4053", Driver("drv-modbus", 2, new[] { "plc-1:502", "plc-2:502" }));
        var b = Node("node-b:4053", Driver("drv-modbus", 1, new[] { "PLC-1:502" })); // host names compare case-insensitively

        FleetDiagnosticsAggregation.DistinctFaultedDevices(new[] { a, b }).ShouldBe(2);
    }

    [Fact]
    public void Different_devices_faulted_on_each_node_are_unioned()
    {
        var a = Node("node-a:4053", Driver("drv-modbus", 1, new[] { "plc-1:502" }));
        var b = Node("node-b:4053", Driver("drv-modbus", 1, new[] { "plc-2:502" }));

        FleetDiagnosticsAggregation.DistinctFaultedDevices(new[] { a, b }).ShouldBe(2);
    }

    [Fact]
    public void The_same_host_name_under_two_drivers_is_two_devices()
    {
        var a = Node("node-a:4053",
            Driver("drv-modbus", 1, new[] { "10.0.0.5" }),
            Driver("drv-s7", 1, new[] { "10.0.0.5" }));

        FleetDiagnosticsAggregation.DistinctFaultedDevices(new[] { a }).ShouldBe(2);
    }

    [Fact]
    public void A_faulted_single_host_driver_on_both_nodes_counts_once()
    {
        // No IHostConnectivityProbe: the driver itself is the device and carries no host name.
        var a = Node("node-a:4053", Driver("drv-galaxy", 1, Array.Empty<string>()));
        var b = Node("node-b:4053", Driver("drv-galaxy", 1, Array.Empty<string>()));

        FleetDiagnosticsAggregation.DistinctFaultedDevices(new[] { a, b }).ShouldBe(1);
    }

    [Fact]
    public void Stopped_devices_are_not_counted()
    {
        var a = Node("node-a:4053", Driver("drv-galaxy", 0, Array.Empty<string>(), stopped: 3));

        FleetDiagnosticsAggregation.DistinctFaultedDevices(new[] { a }).ShouldBe(0);
    }

    [Fact]
    public void A_pre_786_sender_without_host_names_is_combined_by_max_not_sum()
    {
        var oldSender = Node("node-a:4053", Driver("drv-modbus", 3, faultedHosts: null));
        var newSender = Node("node-b:4053", Driver("drv-modbus", 2, new[] { "plc-1:502", "plc-2:502" }));

        // Unnamed 3 (max over nodes) + named 2: the old sender's devices cannot be matched by name, so the
        // figure is the best the wire can prove, never a doubled sum of the same unnamed devices.
        FleetDiagnosticsAggregation.DistinctFaultedDevices(new[] { oldSender, oldSender }).ShouldBe(3);
        FleetDiagnosticsAggregation.DistinctFaultedDevices(new[] { oldSender, newSender }).ShouldBe(5);
    }

    [Fact]
    public void An_unreachable_node_empty_snapshot_contributes_nothing()
    {
        var a = Node("node-a:4053", Driver("drv-modbus", 1, new[] { "plc-1:502" }));
        var unreachable = Node("node-b:4053");

        FleetDiagnosticsAggregation.DistinctFaultedDevices(new[] { a, unreachable }).ShouldBe(1);
        FleetDiagnosticsAggregation.DistinctFaultedDevices(Array.Empty<NodeDiagnosticsSnapshot>()).ShouldBe(0);
    }

    [Fact]
    public async Task Cluster_node_ids_are_the_enabled_rows_of_the_selected_nodes_cluster_self_first()
    {
        var options = new DbContextOptionsBuilder<OtOpcUaConfigDbContext>()
            .UseInMemoryDatabase(Guid.NewGuid().ToString("N")).Options;
        await using (var seed = new OtOpcUaConfigDbContext(options))
        {
            seed.ClusterNodes.AddRange(
                Row("site-a-2:4053", "SITE-A"),
                Row("site-a-1:4053", "SITE-A"),
                Row("site-a-3:4053", "SITE-A", enabled: false),
                Row("site-b-1:4053", "SITE-B"));
            await seed.SaveChangesAsync(TestContext.Current.CancellationToken);
        }

        await using var db = new OtOpcUaConfigDbContext(options);
        var (clusterId, nodeIds) = await FleetDiagnosticsAggregation.LoadClusterNodeIdsAsync(
            db, "site-a-2:4053", TestContext.Current.CancellationToken);
        clusterId.ShouldBe("SITE-A");
        nodeIds.ShouldBe(new[] { "site-a-2:4053", "site-a-1:4053" });

        var (unknownCluster, alone) = await FleetDiagnosticsAggregation.LoadClusterNodeIdsAsync(
            db, "stray:4053", TestContext.Current.CancellationToken);
        unknownCluster.ShouldBeNull();
        alone.ShouldBe(new[] { "stray:4053" });
    }

    [Fact]
    public async Task A_snapshot_from_a_pre_786_sender_still_deserializes_over_the_akka_wire()
    {
        // The snapshot crosses Akka remoting with the default (Newtonsoft JSON) serializer. Strip the #786
        // members from a serialized snapshot to reproduce an older sender's bytes.
        using var system = ActorSystem.Create("diag-compat");
        try
        {
            var snapshot = Node("node-a:4053", Driver("drv-modbus", 1, new[] { "plc-1:502" }, stopped: 2));
            var serializer = system.Serialization.FindSerializerFor(snapshot);
            var json = Encoding.UTF8.GetString(serializer.ToBinary(snapshot));
            json.ShouldContain("StoppedDevices");

            var tree = JObject.Parse(json);
            foreach (var prop in tree.Descendants().OfType<JProperty>()
                         .Where(p => p.Name is "StoppedDevices" or "FaultedHostNames").ToList())
                prop.Remove();
            var oldJson = tree.ToString(Formatting.None);
            oldJson.ShouldNotContain("StoppedDevices");
            oldJson.ShouldNotContain("FaultedHostNames");

            var back = (NodeDiagnosticsSnapshot)serializer.FromBinary(Encoding.UTF8.GetBytes(oldJson), typeof(NodeDiagnosticsSnapshot));
            var driver = back.Drivers.ShouldHaveSingleItem();
            driver.FaultedDevices.ShouldBe(1);
            driver.StoppedDevices.ShouldBe(0);
            driver.FaultedHostNames.ShouldBeNull();
        }
        finally
        {
            await system.Terminate();
        }
    }

    private static ClusterNode Row(string nodeId, string clusterId, bool enabled = true) => new()
    {
        NodeId = nodeId, ClusterId = clusterId, Host = nodeId.Split(':')[0],
        ApplicationUri = "urn:" + nodeId, CreatedBy = "test", Enabled = enabled,
    };
}