// 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 System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using JetBrains.Annotations;
using osu.Framework.Allocation;
using osu.Framework.Graphics;
using osu.Framework.Graphics.Containers;
using osu.Game.Graphics.UserInterface;
using osu.Game.Online.API;
using osu.Game.Online.Multiplayer;
using osu.Game.Scoring;
using osu.Game.Screens.Ranking;

namespace osu.Game.Screens.Multi.Ranking
{
    public class TimeshiftResultsScreen : ResultsScreen
    {
        private readonly int roomId;
        private readonly PlaylistItem playlistItem;

        private LoadingSpinner leftLoadingLayer;
        private LoadingSpinner centreLoadingLayer;
        private LoadingSpinner rightLoadingLayer;
        private MultiplayerScores higherScores;
        private MultiplayerScores lowerScores;

        [Resolved]
        private IAPIProvider api { get; set; }

        public TimeshiftResultsScreen(ScoreInfo score, int roomId, PlaylistItem playlistItem, bool allowRetry = true)
            : base(score, allowRetry)
        {
            this.roomId = roomId;
            this.playlistItem = playlistItem;
        }

        [BackgroundDependencyLoader]
        private void load()
        {
            AddInternal(new Container
            {
                RelativeSizeAxes = Axes.Both,
                Padding = new MarginPadding { Bottom = TwoLayerButton.SIZE_EXTENDED.Y },
                Children = new Drawable[]
                {
                    leftLoadingLayer = new PanelListLoadingSpinner(ScorePanelList)
                    {
                        Anchor = Anchor.CentreLeft,
                        Origin = Anchor.Centre,
                    },
                    centreLoadingLayer = new PanelListLoadingSpinner(ScorePanelList)
                    {
                        Anchor = Anchor.Centre,
                        Origin = Anchor.Centre,
                        State = { Value = Score == null ? Visibility.Visible : Visibility.Hidden },
                    },
                    rightLoadingLayer = new PanelListLoadingSpinner(ScorePanelList)
                    {
                        Anchor = Anchor.CentreRight,
                        Origin = Anchor.Centre,
                    },
                }
            });
        }

        protected override APIRequest FetchScores(Action<IEnumerable<ScoreInfo>> scoresCallback)
        {
            // This performs two requests:
            // 1. A request to show the user's score (and scores around).
            // 2. If that fails, a request to index the room starting from the highest score.

            var userScoreReq = new ShowPlaylistUserScoreRequest(roomId, playlistItem.ID, api.LocalUser.Value.Id);

            userScoreReq.Success += userScore =>
            {
                var allScores = new List<MultiplayerScore> { userScore };

                if (userScore.ScoresAround?.Higher != null)
                {
                    allScores.AddRange(userScore.ScoresAround.Higher.Scores);
                    higherScores = userScore.ScoresAround.Higher;
                }

                if (userScore.ScoresAround?.Lower != null)
                {
                    allScores.AddRange(userScore.ScoresAround.Lower.Scores);
                    lowerScores = userScore.ScoresAround.Lower;
                }

                performSuccessCallback(scoresCallback, allScores);
            };

            // On failure, fallback to a normal index.
            userScoreReq.Failure += _ => api.Queue(createIndexRequest(scoresCallback));

            return userScoreReq;
        }

        protected override APIRequest FetchNextPage(int direction, Action<IEnumerable<ScoreInfo>> scoresCallback)
        {
            Debug.Assert(direction == 1 || direction == -1);

            MultiplayerScores pivot = direction == -1 ? higherScores : lowerScores;

            if (pivot?.Cursor == null)
                return null;

            if (pivot == higherScores)
                leftLoadingLayer.Show();
            else
                rightLoadingLayer.Show();

            return createIndexRequest(scoresCallback, pivot);
        }

        /// <summary>
        /// Creates a <see cref="IndexPlaylistScoresRequest"/> with an optional score pivot.
        /// </summary>
        /// <remarks>Does not queue the request.</remarks>
        /// <param name="scoresCallback">The callback to perform with the resulting scores.</param>
        /// <param name="pivot">An optional score pivot to retrieve scores around. Can be null to retrieve scores from the highest score.</param>
        /// <returns>The indexing <see cref="APIRequest"/>.</returns>
        private APIRequest createIndexRequest(Action<IEnumerable<ScoreInfo>> scoresCallback, [CanBeNull] MultiplayerScores pivot = null)
        {
            var indexReq = pivot != null
                ? new IndexPlaylistScoresRequest(roomId, playlistItem.ID, pivot.Cursor, pivot.Params)
                : new IndexPlaylistScoresRequest(roomId, playlistItem.ID);

            indexReq.Success += r =>
            {
                if (pivot == lowerScores)
                    lowerScores = r;
                else
                    higherScores = r;

                performSuccessCallback(scoresCallback, r.Scores, r);
            };

            indexReq.Failure += _ => hideLoadingSpinners(pivot);

            return indexReq;
        }

        /// <summary>
        /// Transforms returned <see cref="MultiplayerScores"/> into <see cref="ScoreInfo"/>s, ensure the <see cref="ScorePanelList"/> is put into a sane state, and invokes a given success callback.
        /// </summary>
        /// <param name="callback">The callback to invoke with the final <see cref="ScoreInfo"/>s.</param>
        /// <param name="scores">The <see cref="MultiplayerScore"/>s that were retrieved from <see cref="APIRequest"/>s.</param>
        /// <param name="pivot">An optional pivot around which the scores were retrieved.</param>
        private void performSuccessCallback([NotNull] Action<IEnumerable<ScoreInfo>> callback, [NotNull] List<MultiplayerScore> scores, [CanBeNull] MultiplayerScores pivot = null)
        {
            var scoreInfos = new List<ScoreInfo>(scores.Select(s => s.CreateScoreInfo(playlistItem)));

            // Select a score if we don't already have one selected.
            // Note: This is done before the callback so that the panel list centres on the selected score before panels are added (eliminating initial scroll).
            if (SelectedScore.Value == null)
            {
                Schedule(() =>
                {
                    // Prefer selecting the local user's score, or otherwise default to the first visible score.
                    SelectedScore.Value = scoreInfos.FirstOrDefault(s => s.User.Id == api.LocalUser.Value.Id) ?? scoreInfos.FirstOrDefault();
                });
            }

            // Invoke callback to add the scores. Exclude the user's current score which was added previously.
            callback.Invoke(scoreInfos.Where(s => s.OnlineScoreID != Score?.OnlineScoreID));

            hideLoadingSpinners(pivot);
        }

        private void hideLoadingSpinners([CanBeNull] MultiplayerScores pivot = null)
        {
            centreLoadingLayer.Hide();

            if (pivot == lowerScores)
                rightLoadingLayer.Hide();
            else if (pivot == higherScores)
                leftLoadingLayer.Hide();
        }

        private class PanelListLoadingSpinner : LoadingSpinner
        {
            private readonly ScorePanelList list;

            /// <summary>
            /// Creates a new <see cref="PanelListLoadingSpinner"/>.
            /// </summary>
            /// <param name="list">The list to track.</param>
            /// <param name="withBox">Whether the spinner should have a surrounding black box for visibility.</param>
            public PanelListLoadingSpinner(ScorePanelList list, bool withBox = true)
                : base(withBox)
            {
                this.list = list;
            }

            protected override void Update()
            {
                base.Update();

                float panelOffset = list.DrawWidth / 2 - ScorePanel.EXPANDED_WIDTH;

                if ((Anchor & Anchor.x0) > 0)
                    X = (float)(panelOffset - list.Current);
                else if ((Anchor & Anchor.x2) > 0)
                    X = (float)(list.ScrollableExtent - list.Current - panelOffset);
            }
        }
    }
}