// 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 System.Threading.Tasks;
using JetBrains.Annotations;
using osu.Framework.Allocation;
using osu.Framework.Graphics;
using osu.Framework.Graphics.Containers;
using osu.Framework.Graphics.Cursor;
using osu.Framework.Graphics.UserInterface;
using osu.Framework.Utils;
using osu.Game.Beatmaps;
using osu.Game.Collections;
using osu.Game.Graphics.UserInterface;
using osu.Game.Overlays;

namespace osu.Game.Screens.Select.Carousel
{
    public class DrawableCarouselBeatmapSet : DrawableCarouselItem, IHasContextMenu
    {
        public const float HEIGHT = MAX_HEIGHT;

        private Action<BeatmapSetInfo> restoreHiddenRequested;
        private Action<int> viewDetails;

        [Resolved(CanBeNull = true)]
        private DialogOverlay dialogOverlay { get; set; }

        [Resolved(CanBeNull = true)]
        private CollectionManager collectionManager { get; set; }

        [Resolved(CanBeNull = true)]
        private ManageCollectionsDialog manageCollectionsDialog { get; set; }

        public IEnumerable<DrawableCarouselItem> DrawableBeatmaps => beatmapContainer?.IsLoaded != true ? Enumerable.Empty<DrawableCarouselItem>() : beatmapContainer.AliveChildren;

        [CanBeNull]
        private Container<DrawableCarouselItem> beatmapContainer;

        private BeatmapSetInfo beatmapSet;

        [CanBeNull]
        private Task beatmapsLoadTask;

        [Resolved]
        private BeatmapManager manager { get; set; }

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

            Item = null;

            ClearTransforms();
        }

        [BackgroundDependencyLoader(true)]
        private void load(BeatmapSetOverlay beatmapOverlay)
        {
            restoreHiddenRequested = s => s.Beatmaps.ForEach(manager.Restore);

            if (beatmapOverlay != null)
                viewDetails = beatmapOverlay.FetchAndShowBeatmapSet;
        }

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

            // position updates should not occur if the item is filtered away.
            // this avoids panels flying across the screen only to be eventually off-screen or faded out.
            if (!Item.Visible)
                return;

            float targetY = Item.CarouselYPosition;

            if (Precision.AlmostEquals(targetY, Y))
                Y = targetY;
            else
                // algorithm for this is taken from ScrollContainer.
                // while it doesn't necessarily need to match 1:1, as we are emulating scroll in some cases this feels most correct.
                Y = (float)Interpolation.Lerp(targetY, Y, Math.Exp(-0.01 * Time.Elapsed));
        }

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

            Content.Clear();

            beatmapContainer = null;
            beatmapsLoadTask = null;

            if (Item == null)
                return;

            beatmapSet = ((CarouselBeatmapSet)Item).BeatmapSet;

            DelayedLoadWrapper background;
            DelayedLoadWrapper mainFlow;

            Header.Children = new Drawable[]
            {
                background = new DelayedLoadWrapper(() => new SetPanelBackground(manager.GetWorkingBeatmap(beatmapSet.Beatmaps.FirstOrDefault()))
                {
                    RelativeSizeAxes = Axes.Both,
                }, 300)
                {
                    RelativeSizeAxes = Axes.Both
                },
                mainFlow = new DelayedLoadWrapper(() => new SetPanelContent((CarouselBeatmapSet)Item), 100)
                {
                    RelativeSizeAxes = Axes.Both
                },
            };

            background.DelayedLoadComplete += fadeContentIn;
            mainFlow.DelayedLoadComplete += fadeContentIn;
        }

        private void fadeContentIn(Drawable d) => d.FadeInFromZero(750, Easing.OutQuint);

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

            MovementContainer.MoveToX(0, 500, Easing.OutExpo);

            updateBeatmapYPositions();
        }

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

            MovementContainer.MoveToX(-100, 500, Easing.OutExpo);

            updateBeatmapDifficulties();
        }

        private void updateBeatmapDifficulties()
        {
            var carouselBeatmapSet = (CarouselBeatmapSet)Item;

            var visibleBeatmaps = carouselBeatmapSet.Children.Where(c => c.Visible).ToArray();

            // if we are already displaying all the correct beatmaps, only run animation updates.
            // note that the displayed beatmaps may change due to the applied filter.
            // a future optimisation could add/remove only changed difficulties rather than reinitialise.
            if (beatmapContainer != null && visibleBeatmaps.Length == beatmapContainer.Count && visibleBeatmaps.All(b => beatmapContainer.Any(c => c.Item == b)))
            {
                updateBeatmapYPositions();
            }
            else
            {
                // on selection we show our child beatmaps.
                // for now this is a simple drawable construction each selection.
                // can be improved in the future.
                beatmapContainer = new Container<DrawableCarouselItem>
                {
                    X = 100,
                    RelativeSizeAxes = Axes.Both,
                    ChildrenEnumerable = visibleBeatmaps.Select(c => c.CreateDrawableRepresentation())
                };

                beatmapsLoadTask = LoadComponentAsync(beatmapContainer, loaded =>
                {
                    // make sure the pooled target hasn't changed.
                    if (beatmapContainer != loaded)
                        return;

                    Content.Child = loaded;
                    updateBeatmapYPositions();
                });
            }
        }

        private void updateBeatmapYPositions()
        {
            if (beatmapContainer == null)
                return;

            if (beatmapsLoadTask == null || !beatmapsLoadTask.IsCompleted)
                return;

            float yPos = DrawableCarouselBeatmap.CAROUSEL_BEATMAP_SPACING;

            bool isSelected = Item.State.Value == CarouselItemState.Selected;

            foreach (var panel in beatmapContainer.Children)
            {
                if (isSelected)
                {
                    panel.MoveToY(yPos, 800, Easing.OutQuint);
                    yPos += panel.Item.TotalHeight;
                }
                else
                    panel.MoveToY(0, 800, Easing.OutQuint);
            }
        }

        public MenuItem[] ContextMenuItems
        {
            get
            {
                Debug.Assert(beatmapSet != null);

                List<MenuItem> items = new List<MenuItem>();

                if (Item.State.Value == CarouselItemState.NotSelected)
                    items.Add(new OsuMenuItem("Expand", MenuItemType.Highlighted, () => Item.State.Value = CarouselItemState.Selected));

                if (beatmapSet.OnlineBeatmapSetID != null && viewDetails != null)
                    items.Add(new OsuMenuItem("Details...", MenuItemType.Standard, () => viewDetails(beatmapSet.OnlineBeatmapSetID.Value)));

                if (collectionManager != null)
                {
                    var collectionItems = collectionManager.Collections.Select(createCollectionMenuItem).ToList();
                    if (manageCollectionsDialog != null)
                        collectionItems.Add(new OsuMenuItem("Manage...", MenuItemType.Standard, manageCollectionsDialog.Show));

                    items.Add(new OsuMenuItem("Collections") { Items = collectionItems });
                }

                if (beatmapSet.Beatmaps.Any(b => b.Hidden))
                    items.Add(new OsuMenuItem("Restore all hidden", MenuItemType.Standard, () => restoreHiddenRequested(beatmapSet)));

                if (dialogOverlay != null)
                    items.Add(new OsuMenuItem("Delete...", MenuItemType.Destructive, () => dialogOverlay.Push(new BeatmapDeleteDialog(beatmapSet))));
                return items.ToArray();
            }
        }

        private MenuItem createCollectionMenuItem(BeatmapCollection collection)
        {
            Debug.Assert(beatmapSet != null);

            TernaryState state;

            var countExisting = beatmapSet.Beatmaps.Count(b => collection.Beatmaps.Contains(b));

            if (countExisting == beatmapSet.Beatmaps.Count)
                state = TernaryState.True;
            else if (countExisting > 0)
                state = TernaryState.Indeterminate;
            else
                state = TernaryState.False;

            return new TernaryStateToggleMenuItem(collection.Name.Value, MenuItemType.Standard, s =>
            {
                foreach (var b in beatmapSet.Beatmaps)
                {
                    switch (s)
                    {
                        case TernaryState.True:
                            if (collection.Beatmaps.Contains(b))
                                continue;

                            collection.Beatmaps.Add(b);
                            break;

                        case TernaryState.False:
                            collection.Beatmaps.Remove(b);
                            break;
                    }
                }
            })
            {
                State = { Value = state }
            };
        }
    }
}