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using System.Collections.Generic;
using NUnit.Framework;
using Opc.Ua.Server.NodeManager;

namespace Opc.Ua.Server.Tests
{
    /// <summary>
    /// Tests for the <c>NodeState</c> extension helpers that support
    /// Part 5 §9.32.2 NodeVersion correlation
    /// (<see cref="NodeStateModelChangeExtensions"/>).
    /// </summary>
    [TestFixture]
    [Category("NodeState")]
    [SetCulture("en-us")]
    [SetUICulture("en-us")]
    [Parallelizable]
    public class NodeStateModelChangeExtensionsTests
    {
        /// <summary>
        /// <see cref="NodeStateModelChangeExtensions.EnableModelChangeTracking"/>
        /// is idempotent — invoking it again on a node that already has a
        /// NodeVersion property must not attach a second copy.
        /// </summary>
        [Test]
        public void EnableModelChangeTracking_IsIdempotent()
        {
            var node = new BaseObjectState(null)
            {
                NodeId = new NodeId("X", 1),
                BrowseName = new QualifiedName("X", 1)
            };

            PropertyState<string> first = node.EnableModelChangeTracking(1);
            PropertyState<string> second = node.EnableModelChangeTracking(1);

            Assert.That(second, Is.SameAs(first));

            int matches = 0;
            var children = new List<BaseInstanceState>();
            node.GetChildren(null!, children);
            foreach (BaseInstanceState child in children)
            {
                if (child.BrowseName == new QualifiedName(BrowseNames.NodeVersion, 0))
                {
                    matches++;
                }
            }
            Assert.That(matches, Is.EqualTo(1));
        }

        /// <summary>
        /// <see cref="NodeStateModelChangeExtensions.HasNodeVersion"/>
        /// reflects the presence of the NodeVersion property.
        /// </summary>
        [Test]
        public void HasNodeVersion_TrueOnlyAfterEnableTracking()
        {
            var node = new BaseObjectState(null)
            {
                NodeId = new NodeId("X", 1),
                BrowseName = new QualifiedName("X", 1)
            };

            Assert.That(node.HasNodeVersion(), Is.False);

            node.EnableModelChangeTracking(1);
            Assert.That(node.HasNodeVersion(), Is.True);
        }

        /// <summary>
        /// <see cref="NodeStateModelChangeExtensions.BumpNodeVersion"/>
        /// increments the value monotonically and is a no-op on nodes
        /// that don't have a NodeVersion property.
        /// </summary>
        [Test]
        public void BumpNodeVersion_IncrementsOnTrackedNode_NoOpOnUntrackedNode()
        {
            var untracked = new BaseObjectState(null) { BrowseName = new QualifiedName("U", 1) };
            untracked.BumpNodeVersion(null!);
            Assert.That(untracked.HasNodeVersion(), Is.False);

            var tracked = new BaseObjectState(null) { BrowseName = new QualifiedName("T", 1) };
            PropertyState<string> v = tracked.EnableModelChangeTracking(1);
            Assert.That(v.Value, Is.EqualTo("1"));

            tracked.BumpNodeVersion(null!);
            Assert.That(v.Value, Is.EqualTo("2"));

            tracked.BumpNodeVersion(null!);
            Assert.That(v.Value, Is.EqualTo("3"));
        }
    }
}