// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
// See the LICENCE file in the repository root for full licence text.

using System;
using osu.Framework.Allocation;
using osu.Framework.Bindables;
using osu.Framework.Graphics;

namespace osu.Game.Screens.OnlinePlay
{
    /// <summary>
    /// Utility class to track ongoing online operations' progress.
    /// Can be used to disable interactivity while waiting for a response from online sources.
    /// </summary>
    public class OngoingOperationTracker : Component
    {
        /// <summary>
        /// Whether there is an online operation in progress.
        /// </summary>
        public IBindable<bool> InProgress => inProgress;

        private readonly Bindable<bool> inProgress = new BindableBool();

        private LeasedBindable<bool> leasedInProgress;

        public OngoingOperationTracker()
        {
            AlwaysPresent = true;
        }

        /// <summary>
        /// Begins tracking a new online operation.
        /// </summary>
        /// <returns>
        /// An <see cref="IDisposable"/> that will automatically mark the operation as ended on disposal.
        /// </returns>
        /// <exception cref="InvalidOperationException">An operation has already been started.</exception>
        public IDisposable BeginOperation()
        {
            if (leasedInProgress != null)
                throw new InvalidOperationException("Cannot begin operation while another is in progress.");

            leasedInProgress = inProgress.BeginLease(true);
            leasedInProgress.Value = true;

            // for extra safety, marshal the end of operation back to the update thread if necessary.
            return new InvokeOnDisposal(() => Scheduler.Add(endOperation, false));
        }

        private void endOperation()
        {
            if (leasedInProgress == null)
                throw new InvalidOperationException("Cannot end operation multiple times.");

            leasedInProgress.Return();
            leasedInProgress = null;
        }
    }
}