using Opc.Ua;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Commons.OpcUa;

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

/// <summary>
///     FixedTree injection — the BEHAVIOURAL half of the runtime node-add model-change announcement. When a
///     driver discovers FixedTree nodes AFTER the server is up and they are materialised into the served
///     Equipment address space, already-connected OPC UA clients won't see them unless the server emits a
///     Part 3 <c>GeneralModelChangeEvent</c> (verb <c>NodeAdded</c>) under the affected parent so subscribed
///     clients refresh their browse. <see cref="OtOpcUaNodeManager.RaiseNodesAddedModelChange"/> is that seam
///     (Tasks 4/5 call it after materialising discovered nodes); this test asserts:
///     <list type="bullet">
///         <item>the built event announces the affected parent with verb <c>NodeAdded</c> (the runtime-add
///         counterpart of <see cref="NodeManagerSurgicalShapeUpdateTests"/>'s <c>DataTypeChanged</c> case);</item>
///         <item>raising it is tolerant — callable before AND after nodes exist, and never throws even when the
///         event path is disabled / has no monitored items.</item>
///     </list>
///     <para>
///         Coverage boundary (deliberate, mirrors <see cref="NodeManagerSurgicalShapeUpdateTests"/>): the
///         model-change event is asserted via its <i>builder</i>
///         (<see cref="OtOpcUaNodeManager.BuildNodesAddedModelChange"/>) in isolation, not its end-to-end
///         <c>Server.ReportEvent</c> dispatch — observing that would require a subscribed event monitored-item.
///         The single in-lock report call-site is covered by inspection (it mirrors the shape-changed reporter).
///     </para>
/// </summary>
public sealed class NodeManagerModelChangeOnAddTests : IDisposable
{
    private static CancellationToken Ct => TestContext.Current.CancellationToken;

    private readonly string _pkiRoot = Path.Combine(
        Path.GetTempPath(),
        $"otopcua-modelchange-add-{Guid.NewGuid():N}");

    /// <summary>The built model-change event announces the affected parent with verb NodeAdded and the parent's
    /// TypeDefinition as AffectedType — what model-aware clients consume to re-browse the new children.</summary>
    [Trait("Category", "Unit")]
    [Fact]
    public async Task Built_nodes_added_event_announces_the_affected_parent_with_NodeAdded_verb()
    {
        var (host, server) = await BootAsync();
        var nm = server.NodeManager!;

        nm.EnsureFolder("eq-7", parentNodeId: null, displayName: "Equipment 7", realm: AddressSpaceRealm.Uns);
        nm.EnsureVariable("eq-7/speed", parentFolderNodeId: "eq-7", displayName: "Speed", dataType: "Float", writable: false, realm: AddressSpaceRealm.Uns);
        var parent = nm.TryGetFolder("eq-7")!;

        var e = nm.BuildNodesAddedModelChange("eq-7");

        e.ShouldNotBeNull();
        e.Changes.ShouldNotBeNull();
        var changes = e.Changes.Value;
        changes.Length.ShouldBe(1);
        changes[0].Affected.ShouldBe(parent.NodeId);
        changes[0].AffectedType.ShouldBe(ObjectTypeIds.FolderType);
        changes[0].Verb.ShouldBe((byte)ModelChangeStructureVerbMask.NodeAdded);

        await host.DisposeAsync();
    }

    /// <summary>For an affected id that is not (yet) materialised, the built event still announces NodeAdded but
    /// its AffectedType falls back to <see cref="NodeId.Null"/> (a valid Part 3 "type not applicable") — the
    /// documented fallback of <see cref="OtOpcUaNodeManager.BuildNodesAddedModelChange"/>, locked in as an
    /// invariant.</summary>
    [Trait("Category", "Unit")]
    [Fact]
    public async Task Built_event_for_unknown_id_falls_back_to_null_AffectedType()
    {
        var (host, server) = await BootAsync();
        var nm = server.NodeManager!;

        // No EnsureFolder/EnsureVariable for this id — it is not in the node maps.
        var e = nm.BuildNodesAddedModelChange("eq-unknown");

        e.ShouldNotBeNull();
        e.Changes.ShouldNotBeNull();
        var changes = e.Changes.Value;
        changes.Length.ShouldBe(1);
        changes[0].Verb.ShouldBe((byte)ModelChangeStructureVerbMask.NodeAdded);
        changes[0].AffectedType.ShouldBe(NodeId.Null);

        await host.DisposeAsync();
    }

    /// <summary>Raising the announcement is tolerant: callable before any nodes exist (unknown affected id ⇒
    /// AffectedType defaults to null, still a valid Part 3 change) AND after they are materialised, and never
    /// throws even when the event path reaches no monitored items (same tolerance as the write-revert path).</summary>
    [Trait("Category", "Unit")]
    [Fact]
    public async Task Raising_nodes_added_is_tolerant_before_and_after_nodes_exist()
    {
        var (host, server) = await BootAsync();
        var nm = server.NodeManager!;

        // Before any nodes exist under the parent — must not throw.
        Should.NotThrow(() => nm.RaiseNodesAddedModelChange("eq-9", realm: AddressSpaceRealm.Uns));

        nm.EnsureFolder("eq-9", parentNodeId: null, displayName: "Equipment 9", realm: AddressSpaceRealm.Uns);
        nm.EnsureVariable("eq-9/temp", parentFolderNodeId: "eq-9", displayName: "Temp", dataType: "Float", writable: false, realm: AddressSpaceRealm.Uns);

        // After the nodes are materialised — still must not throw.
        Should.NotThrow(() => nm.RaiseNodesAddedModelChange("eq-9", realm: AddressSpaceRealm.Uns));

        await host.DisposeAsync();
    }

    private async Task<(OpcUaApplicationHost Host, OtOpcUaSdkServer Server)> BootAsync()
    {
        var host = new OpcUaApplicationHost(
            new OpcUaApplicationHostOptions
            {
                ApplicationName = "OtOpcUa.ModelChangeOnAddTest",
                ApplicationUri = $"urn:OtOpcUa.ModelChangeOnAddTest:{Guid.NewGuid():N}",
                OpcUaPort = AllocateFreePort(),
                PublicHostname = "localhost",
                PkiStoreRoot = _pkiRoot,
            },
            Microsoft.Extensions.Logging.Abstractions.NullLogger<OpcUaApplicationHost>.Instance);

        var server = new OtOpcUaSdkServer();
        await host.StartAsync(server, Ct);
        return (host, server);
    }

    private static int AllocateFreePort()
    {
        using var listener = new System.Net.Sockets.TcpListener(System.Net.IPAddress.Loopback, 0);
        listener.Start();
        var port = ((System.Net.IPEndPoint)listener.LocalEndpoint).Port;
        listener.Stop();
        return port;
    }

    /// <summary>Cleans up the PKI root directory.</summary>
    public void Dispose()
    {
        if (Directory.Exists(_pkiRoot))
        {
            try { Directory.Delete(_pkiRoot, recursive: true); }
            catch { /* best-effort cleanup */ }
        }
    }
}
