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using System;
using System.Collections.Generic;
using System.Linq;
using NUnit.Framework;
using NUnit.Framework.Interfaces;
using Opc.Ua.Security.Certificates;
using Opc.Ua.Tests;

// Apply leak tracking action to all test fixtures in the assembly.
[assembly: Opc.Ua.Core.Tests.CoreLeakDetectionFixtureAction]

namespace Opc.Ua.Core.Tests
{
    /// <summary>
    /// Assembly-level setup/teardown that verifies no Certificate
    /// instances are leaked during the test run.
    /// </summary>
    [SetUpFixture]
    public class CoreLeakDetectionSetup
    {
        private static readonly System.Collections.Concurrent.ConcurrentDictionary<string, (long created, long disposed)>
            s_fixtureLeaks = new();

        [OneTimeSetUp]
        public void GlobalSetup()
        {
            Certificate.ResetLeakCounters();
        }

        [OneTimeTearDown]
        public void GlobalTeardown()
        {
            // Force GC to finalize any abandoned certificates. Multiple
            // cycles ensure that finalizable objects whose finalizer
            // creates new garbage are themselves collected. The sweep is
            // bounded by a watchdog so a stuck finalizer cannot hang the
            // test host indefinitely during assembly teardown.
            if (!LeakDetectionHelpers.TryRunFinalizerSweep())
            {
                Assert.Warn(
                    $"Finalizer sweep exceeded {LeakDetectionHelpers.DefaultFinalizerSweepTimeout.TotalSeconds:0}s " +
                    "watchdog; at least one finalizer is stuck. Leak counts below may be inaccurate.");
            }

            long leaked = Certificate.InstancesLeaked;
            string summary = $"CoreLeakDetectionSetup: tracked {s_fixtureLeaks.Count} fixtures, " +
                $"created={Certificate.InstancesCreated}, " +
                $"disposed={Certificate.InstancesDisposed}, leaked={leaked}";
            Console.WriteLine(summary);
            try
            {
                string path = System.IO.Path.Combine(System.IO.Path.GetTempPath(), "core-leak-summary.txt");
                System.IO.File.AppendAllText(path, summary + "\n");
                // Dump ALL fixtures sorted by net delta (positive first, negative last).
                System.IO.File.AppendAllText(path, "\nALL FIXTURES (positive net first):\n");
                foreach (KeyValuePair<string, (long created, long disposed)> kv in s_fixtureLeaks
                    .OrderByDescending(kv => kv.Value.created - kv.Value.disposed))
                {
                    long net = kv.Value.created - kv.Value.disposed;
                    System.IO.File.AppendAllText(path,
                        $"  net={net,4} created={kv.Value.created,4} disposed={kv.Value.disposed,4}  {kv.Key}\n");
                }
#if DEBUG
                // In Debug builds, also dump the allocation stack of any
                // live (reachable) certificate that still has a positive
                // refcount. These are the actual leaks.
                System.IO.File.AppendAllText(path, "\nLIVE LEAKED CERTIFICATES (DEBUG):\n");
                foreach ((string thumbprint, int refCount, DateTime createdAt, string stackTrace) in
                    Certificate.EnumerateLiveCertificates())
                {
                    System.IO.File.AppendAllText(path,
                        $"\n  Thumbprint={thumbprint}, RefCount={refCount}, " +
                        $"CreatedAt={createdAt:O}\n  StackTrace:\n{stackTrace}\n");
                }
                // Certificates whose finaliser ran while their refcount was
                // still > 0 (AddRef without matching Dispose).
                System.IO.File.AppendAllText(path, "\nFINALIZED-WITH-LEAKED-REF CERTIFICATES (DEBUG):\n");
                foreach ((string thumbprint, DateTime createdAt, string stackTrace) in
                    Certificate.EnumerateFinalizedLeakedCertificates())
                {
                    System.IO.File.AppendAllText(path,
                        $"\n  Thumbprint={thumbprint}, " +
                        $"CreatedAt={createdAt:O}\n  StackTrace:\n{stackTrace}\n");
                }
#endif
            }
            catch
            {
                // ignore
            }
            if (leaked > 0)
            {
                string details = string.Join("\n",
                    s_fixtureLeaks
                        .Where(kv => kv.Value.created > kv.Value.disposed)
                        .OrderByDescending(kv => kv.Value.created - kv.Value.disposed)
                        .Select(kv => $"  {kv.Key}: leaked={kv.Value.created - kv.Value.disposed} (created={kv.Value.created}, disposed={kv.Value.disposed})"));

                Assert.Warn(
                    $"Certificate leak detected: {leaked} instance(s) created " +
                    $"but not disposed (created={Certificate.InstancesCreated}, " +
                    $"disposed={Certificate.InstancesDisposed}).\n" +
                    $"Per-fixture breakdown:\n{details}");
            }
        }

        /// <summary>
        /// Records the certificate creation/disposal delta for a fixture.
        /// </summary>
        public static void RecordFixture(string fixtureName, long created, long disposed)
        {
            s_fixtureLeaks.AddOrUpdate(
                fixtureName,
                (created, disposed),
                (_, prev) => (prev.created + created, prev.disposed + disposed));
        }
    }

    /// <summary>
    /// Records Certificate counter deltas per individual test so leaks can
    /// be attributed to a specific fixture or test. Lightweight: no per-
    /// test GC; the global teardown is responsible for the final GC.
    /// </summary>
    [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class | AttributeTargets.Method)]
    public sealed class CoreLeakDetectionFixtureActionAttribute : Attribute, ITestAction
    {
        private static readonly System.Threading.AsyncLocal<(long created, long disposed, string name)> s_baseline
            = new();

        public ActionTargets Targets => ActionTargets.Test;

        public void BeforeTest(ITest test)
        {
            if (!test.IsSuite)
            {
                string parent = test.Parent?.FullName ?? test.FullName;
                s_baseline.Value = (
                    Certificate.InstancesCreated,
                    Certificate.InstancesDisposed,
                    parent);
            }
        }

        public void AfterTest(ITest test)
        {
            if (!test.IsSuite)
            {
                long createdDelta = Certificate.InstancesCreated - s_baseline.Value.created;
                long disposedDelta = Certificate.InstancesDisposed - s_baseline.Value.disposed;
                if (createdDelta > 0 || disposedDelta > 0)
                {
                    CoreLeakDetectionSetup.RecordFixture(
                        s_baseline.Value.name,
                        createdDelta,
                        disposedDelta);
                }
            }
        }
    }
}