// 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.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using NUnit.Framework;
using osu.Framework.Allocation;
using osu.Framework.Audio;
using osu.Framework.Bindables;
using osu.Framework.Graphics;
using osu.Framework.Graphics.Containers;
using osu.Framework.Platform;
using osu.Framework.Testing;
using osu.Game.Beatmaps;
using osu.Game.Database;
using osu.Game.Online.Multiplayer;
using osu.Game.Online.Rooms;
using osu.Game.Rulesets;
using osu.Game.Screens.OnlinePlay;
using osu.Game.Screens.OnlinePlay.Multiplayer;
using osu.Game.Tests.Resources;
using osuTK;

namespace osu.Game.Tests.Visual.Multiplayer
{
    public class TestSceneMultiplayerPlaylist : MultiplayerTestScene
    {
        private BeatmapManager beatmaps;
        private RulesetStore rulesets;
        private BeatmapSetInfo importedSet;
        private BeatmapInfo importedBeatmap;

        [Cached(typeof(UserLookupCache))]
        private UserLookupCache lookupCache = new TestUserLookupCache();

        [BackgroundDependencyLoader]
        private void load(GameHost host, AudioManager audio)
        {
            Dependencies.Cache(rulesets = new RulesetStore(ContextFactory));
            Dependencies.Cache(beatmaps = new BeatmapManager(LocalStorage, ContextFactory, rulesets, null, audio, Resources, host, Beatmap.Default));
        }

        [SetUp]
        public new void Setup() => Schedule(() =>
        {
            Child = new MultiplayerPlaylist
            {
                Anchor = Anchor.Centre,
                Origin = Anchor.Centre,
                RelativeSizeAxes = Axes.Both,
                Size = new Vector2(0.4f, 0.8f)
            };
        });

        [SetUpSteps]
        public new void SetUpSteps()
        {
            AddStep("import beatmap", () =>
            {
                beatmaps.Import(TestResources.GetQuickTestBeatmapForImport()).Wait();
                importedSet = beatmaps.GetAllUsableBeatmapSetsEnumerable(IncludedDetails.All).First();
                importedBeatmap = importedSet.Beatmaps.First(b => b.RulesetID == 0);
            });
        }

        [Test]
        public void DoTest()
        {
            AddStep("change to round robin mode", () => Client.ChangeSettings(new MultiplayerRoomSettings { QueueMode = QueueMode.AllPlayersRoundRobin }));
            AddStep("add playlist item for user 1", () => Client.AddPlaylistItem(new MultiplayerPlaylistItem
            {
                BeatmapID = importedBeatmap.OnlineID!.Value
            }));
        }

        public class MultiplayerPlaylist : MultiplayerRoomComposite
        {
            private QueueList queueList;
            private DrawableRoomPlaylist historyList;
            private bool firstPopulation = true;

            [BackgroundDependencyLoader]
            private void load()
            {
                InternalChild = new GridContainer
                {
                    RelativeSizeAxes = Axes.Both,
                    Content = new[]
                    {
                        new Drawable[]
                        {
                            queueList = new QueueList(false, false, true)
                            {
                                RelativeSizeAxes = Axes.Both
                            },
                            historyList = new DrawableRoomPlaylist(false, false, true)
                            {
                                RelativeSizeAxes = Axes.Both
                            }
                        }
                    }
                };
            }

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

                if (Room == null)
                    return;

                if (!firstPopulation) return;

                foreach (var item in Room.Playlist)
                    PlaylistItemAdded(item);

                firstPopulation = false;
            }

            protected override void PlaylistItemAdded(MultiplayerPlaylistItem item)
            {
                base.PlaylistItemAdded(item);

                if (item.Expired)
                    historyList.Items.Add(getPlaylistItem(item));
                else
                    queueList.Items.Add(getPlaylistItem(item));
            }

            protected override void PlaylistItemRemoved(long item)
            {
                base.PlaylistItemRemoved(item);

                queueList.Items.RemoveAll(i => i.ID == item);
            }

            protected override void PlaylistItemChanged(MultiplayerPlaylistItem item)
            {
                base.PlaylistItemChanged(item);

                PlaylistItemRemoved(item.ID);
                PlaylistItemAdded(item);
            }

            private PlaylistItem getPlaylistItem(MultiplayerPlaylistItem item) => Playlist.Single(i => i.ID == item.ID);
        }

        public class QueueList : DrawableRoomPlaylist
        {
            public readonly IBindable<QueueMode> QueueMode = new Bindable<QueueMode>();

            public QueueList(bool allowEdit, bool allowSelection, bool reverse = false)
                : base(allowEdit, allowSelection, reverse)
            {
            }

            protected override FillFlowContainer<RearrangeableListItem<PlaylistItem>> CreateListFillFlowContainer() => new QueueFillFlowContainer
            {
                QueueMode = { BindTarget = QueueMode },
                Spacing = new Vector2(0, 2)
            };

            private class QueueFillFlowContainer : FillFlowContainer<RearrangeableListItem<PlaylistItem>>
            {
                public readonly IBindable<QueueMode> QueueMode = new Bindable<QueueMode>();

                protected override void LoadComplete()
                {
                    base.LoadComplete();
                    QueueMode.BindValueChanged(_ => InvalidateLayout());
                }

                public override IEnumerable<Drawable> FlowingChildren
                {
                    get
                    {
                        switch (QueueMode.Value)
                        {
                            default:
                                return AliveInternalChildren.Where(d => d.IsPresent)
                                                            .OfType<RearrangeableListItem<PlaylistItem>>()
                                                            .OrderBy(item => item.Model.ID);

                            case Game.Online.Multiplayer.QueueMode.AllPlayersRoundRobin:
                                // TODO: THIS IS SO INEFFICIENT, can it be done any better?

                                // Group all items by their owners.
                                var groups = AliveInternalChildren.Where(d => d.IsPresent)
                                                                  .OfType<RearrangeableListItem<PlaylistItem>>()
                                                                  .GroupBy(item => item.Model.OwnerID)
                                                                  .Select(g => g.ToArray())
                                                                  .ToArray();

                                if (groups.Length == 0)
                                    return Enumerable.Empty<Drawable>();

                                // Find the initial picking order for the groups. The group with the smallest 'weight' picks first.
                                int[] groupWeights = new int[groups.Length];

                                for (int i = 0; i < groups.Length; i++)
                                {
                                    groupWeights[i] = groups[i].Count(item => item.Model.Expired);
                                    groups[i] = groups[i].Where(item => !item.Model.Expired).ToArray();
                                }

                                var result = new List<Drawable>();

                                // Simulate the playlist by picking in order from the smallest-weighted room each time until no longer able to.
                                while (true)
                                {
                                    var candidateGroup = groups
                                                         // Map each group to an index.
                                                         .Select((items, index) => new { index, items })
                                                         // Order groups by their weights.
                                                         .OrderBy(group => groupWeights[group.index])
                                                         // Select the first group with remaining items (null is set from previous iterations).
                                                         .FirstOrDefault(group => group.items.Any(i => i != null));

                                    // Iteration ends when all groups have been exhausted of items.
                                    if (candidateGroup == null)
                                        break;

                                    // Find the index of the first non-null (i.e. unused) item in the group.
                                    int candidateItemIndex = 0;
                                    RearrangeableListItem<PlaylistItem> candidateItem = null;

                                    for (int i = 0; i < candidateGroup.items.Length; i++)
                                    {
                                        if (candidateGroup.items[i] != null)
                                        {
                                            candidateItemIndex = i;
                                            candidateItem = candidateGroup.items[i];
                                        }
                                    }

                                    // The item is guaranteed to not be expired, since we've previously removed all expired items.
                                    Debug.Assert(candidateItem?.Model.Expired == false);

                                    // Add the item to the result set.
                                    result.Add(candidateItem);

                                    // Update the group for the next iteration.
                                    candidateGroup.items[candidateItemIndex] = null;
                                    groupWeights[candidateGroup.index]++;
                                }

                                return result;
                        }
                    }
                }
            }
        }
    }
}