// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
using System;
using System.Diagnostics;
using System.Threading;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.Editor.Tagging;
 
internal partial class AbstractAsynchronousTaggerProvider<TTag>
{
    private partial class TagSource
    {
        /// <summary>How many taggers are currently using us.</summary>
        private int _taggers = 0;
 
        ~TagSource()
        {
            if (!Environment.HasShutdownStarted)
            {
#if DEBUG
                Contract.Fail($@"Should have been disposed!
DataSource-StackTrace:
{_dataSource.StackTrace}
 
StackTrace:
{_stackTrace}");
#else
                Contract.Fail($@"Should have been disposed! Try running in Debug to get the allocation callstack");
#endif
            }
        }
 
        internal void OnTaggerAdded(Tagger _)
        {
            // this should be only called from UI thread. 
            // in unit test, must be called from same thread as OnTaggerDisposed
            Contract.ThrowIfFalse(_taggers >= 0);
 
            _taggers++;
 
            DebugRecordCurrentThread();
        }
 
        internal void OnTaggerDisposed(Tagger _)
        {
            // this should be only called from UI thread.
            // in unit test, must be called from same thread as OnTaggerAdded
            Contract.ThrowIfFalse(_taggers > 0);
 
            _taggers--;
 
            if (_taggers == 0)
            {
                this.Dispose();
 
                DebugVerifyThread();
            }
        }
 
        internal void TestOnly_Dispose()
            => Dispose();
 
#if DEBUG
        private Thread? _thread;
        private string? _stackTrace;
 
        private void DebugRecordInitialStackTrace()
            => _stackTrace = new StackTrace().ToString();
 
        private void DebugRecordCurrentThread()
        {
            if (_taggers != 1)
            {
                return;
            }
 
            _thread = Thread.CurrentThread;
        }
 
        private void DebugVerifyThread()
            => Contract.ThrowIfFalse(Thread.CurrentThread == _thread);
#else
        private static void DebugRecordInitialStackTrace()
        {
        }
 
        private static void DebugRecordCurrentThread()
        {
        }
 
        private static void DebugVerifyThread()
        {
        }
#endif
    }
}