kopano-ol-extension/src/AcaciaZPushPlugin/AcaciaZPushPlugin/Utils/CompletionTracker.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace Acacia.Utils
{
    public class CompletionTracker
    {
        public class Step : IDisposable
        {
            private readonly CompletionTracker _tracker;

            public Step(CompletionTracker tracker)
            {
                this._tracker = tracker;
            }

            public void Dispose()
            {
                _tracker.End();
            }
        }

        private readonly List<Action> _completions = new List<Action>();
        private int steps = 0;

        public CompletionTracker(Action completion)
        {
            if (completion != null)
                _completions.Add(completion);
        }

        /// <summary>
        /// Begins a sub-step.
        /// </summary>
        /// <returns>A step. This may be disposed, or End may be used</returns>
        public Step Begin()
        {
            Interlocked.Increment(ref steps);
            return new Step(this);
        }

        public void End()
        {
            if (Interlocked.Decrement(ref steps) == 0)
            {
                // Done
                foreach(Action completion in _completions)
                    completion();
            }
        }

        public void AddCompletion(Action completion)
        {
            _completions.Add(completion);
        }
    }
}