// 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.Game.Online.API;
using osu.Game.Scoring;

#nullable enable

namespace osu.Game.Online
{
    public class ScoreDownloadTracker : DownloadTracker<ScoreInfo>
    {
        [Resolved(CanBeNull = true)]
        protected ScoreManager? Manager { get; private set; }

        private ArchiveDownloadRequest<ScoreInfo>? attachedRequest;

        public ScoreDownloadTracker(ScoreInfo trackedItem)
            : base(trackedItem)
        {
        }

        private IBindable<WeakReference<ScoreInfo>>? managerUpdated;
        private IBindable<WeakReference<ScoreInfo>>? managerRemoved;
        private IBindable<WeakReference<ArchiveDownloadRequest<ScoreInfo>>>? managerDownloadBegan;
        private IBindable<WeakReference<ArchiveDownloadRequest<ScoreInfo>>>? managerDownloadFailed;

        [BackgroundDependencyLoader(true)]
        private void load()
        {
            // Used to interact with manager classes that don't support interface types. Will eventually be replaced.
            var beatmapSetInfo = new ScoreInfo { OnlineScoreID = TrackedItem.OnlineScoreID };

            if (TrackedItem.ID > 0 || Manager?.IsAvailableLocally(beatmapSetInfo) == true)
                UpdateState(DownloadState.LocallyAvailable);
            else if (Manager != null)
                attachDownload(Manager.GetExistingDownload(beatmapSetInfo));

            if (Manager != null)
            {
                managerDownloadBegan = Manager.DownloadBegan.GetBoundCopy();
                managerDownloadBegan.BindValueChanged(downloadBegan);
                managerDownloadFailed = Manager.DownloadFailed.GetBoundCopy();
                managerDownloadFailed.BindValueChanged(downloadFailed);
                managerUpdated = Manager.ItemUpdated.GetBoundCopy();
                managerUpdated.BindValueChanged(itemUpdated);
                managerRemoved = Manager.ItemRemoved.GetBoundCopy();
                managerRemoved.BindValueChanged(itemRemoved);
            }
        }

        /// <summary>
        /// Checks that a database model matches the one expected to be downloaded.
        /// </summary>
        /// <example>
        /// For online play, this could be used to check that the databased model matches the online beatmap.
        /// </example>
        /// <param name="databasedModel">The model in database.</param>
        protected virtual bool VerifyDatabasedModel(ScoreInfo databasedModel) => true; // TODO: do we still need this?

        private void downloadBegan(ValueChangedEvent<WeakReference<ArchiveDownloadRequest<ScoreInfo>>> weakRequest)
        {
            if (weakRequest.NewValue.TryGetTarget(out var request))
            {
                Schedule(() =>
                {
                    if (checkEquality(request.Model, TrackedItem))
                        attachDownload(request);
                });
            }
        }

        private void downloadFailed(ValueChangedEvent<WeakReference<ArchiveDownloadRequest<ScoreInfo>>> weakRequest)
        {
            if (weakRequest.NewValue.TryGetTarget(out var request))
            {
                Schedule(() =>
                {
                    if (checkEquality(request.Model, TrackedItem))
                        attachDownload(null);
                });
            }
        }

        private void attachDownload(ArchiveDownloadRequest<ScoreInfo>? request)
        {
            if (attachedRequest != null)
            {
                attachedRequest.Failure -= onRequestFailure;
                attachedRequest.DownloadProgressed -= onRequestProgress;
                attachedRequest.Success -= onRequestSuccess;
            }

            attachedRequest = request;

            if (attachedRequest != null)
            {
                if (attachedRequest.Progress == 1)
                {
                    UpdateProgress(1);
                    UpdateState(DownloadState.Importing);
                }
                else
                {
                    UpdateProgress(attachedRequest.Progress);
                    UpdateState(DownloadState.Downloading);

                    attachedRequest.Failure += onRequestFailure;
                    attachedRequest.DownloadProgressed += onRequestProgress;
                    attachedRequest.Success += onRequestSuccess;
                }
            }
            else
            {
                UpdateState(DownloadState.NotDownloaded);
            }
        }

        private void onRequestSuccess(string _) => Schedule(() => UpdateState(DownloadState.Importing));

        private void onRequestProgress(float progress) => Schedule(() => UpdateProgress(progress));

        private void onRequestFailure(Exception e) => Schedule(() => attachDownload(null));

        private void itemUpdated(ValueChangedEvent<WeakReference<ScoreInfo>> weakItem)
        {
            if (weakItem.NewValue.TryGetTarget(out var item))
            {
                Schedule(() =>
                {
                    if (!checkEquality(item, TrackedItem))
                        return;

                    if (!VerifyDatabasedModel(item))
                    {
                        UpdateState(DownloadState.NotDownloaded);
                        return;
                    }

                    UpdateState(DownloadState.LocallyAvailable);
                });
            }
        }

        private void itemRemoved(ValueChangedEvent<WeakReference<ScoreInfo>> weakItem)
        {
            if (weakItem.NewValue.TryGetTarget(out var item))
            {
                Schedule(() =>
                {
                    if (checkEquality(item, TrackedItem))
                        UpdateState(DownloadState.NotDownloaded);
                });
            }
        }

        private bool checkEquality(ScoreInfo x, ScoreInfo y) => x.OnlineScoreID == y.OnlineScoreID;

        #region Disposal

        protected override void Dispose(bool isDisposing)
        {
            base.Dispose(isDisposing);
            attachDownload(null);
        }

        #endregion
    }
}