// 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.Threading;
using System.Threading.Tasks;
 
namespace Microsoft.CodeAnalysis.Shared.Utilities
{
    /// <summary>
    /// Utility class that can be used to track the progress of an operation in a threadsafe manner.
    /// </summary>
    internal sealed class StreamingProgressTracker : IStreamingProgressTracker
    {
        private int _completedItems;
        private int _totalItems;
 
        private readonly Func<int, int, CancellationToken, ValueTask>? _updateAction;
 
        public StreamingProgressTracker(Func<int, int, CancellationToken, ValueTask>? updateAction = null)
            => _updateAction = updateAction;
 
        public ValueTask AddItemsAsync(int count, CancellationToken cancellationToken)
        {
            Interlocked.Add(ref _totalItems, count);
            return UpdateAsync(cancellationToken);
        }
 
        public ValueTask ItemsCompletedAsync(int count, CancellationToken cancellationToken)
        {
            Interlocked.Add(ref _completedItems, count);
            return UpdateAsync(cancellationToken);
        }
 
        private ValueTask UpdateAsync(CancellationToken cancellationToken)
            => _updateAction?.Invoke(Volatile.Read(ref _completedItems), Volatile.Read(ref _totalItems), cancellationToken) ?? default;
    }
}