osu-lazer/osu.Game/Screens/Select/Carousel/CarouselBeatmapSet.cs

// 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.Linq;
using osu.Framework.Bindables;
using osu.Framework.Extensions.IEnumerableExtensions;
using osu.Game.Beatmaps;
using osu.Game.Screens.Select.Filter;

namespace osu.Game.Screens.Select.Carousel
{
    public class CarouselBeatmapSet : CarouselGroupEagerSelect
    {
        private readonly Bindable<double> recommendedStarDifficulty = new Bindable<double>();

        public IEnumerable<CarouselBeatmap> Beatmaps => InternalChildren.OfType<CarouselBeatmap>();

        public BeatmapSetInfo BeatmapSet;

        public CarouselBeatmapSet(BeatmapSetInfo beatmapSet, Bindable<double> recommendedStarDifficulty)
        {
            BeatmapSet = beatmapSet ?? throw new ArgumentNullException(nameof(beatmapSet));

            beatmapSet.Beatmaps
                      .Where(b => !b.Hidden)
                      .Select(b => new CarouselBeatmap(b))
                      .ForEach(AddChild);

            this.recommendedStarDifficulty.BindTo(recommendedStarDifficulty);
        }

        protected override DrawableCarouselItem CreateDrawableRepresentation() => new DrawableCarouselBeatmapSet(this);

        protected override CarouselItem GetNextToSelect()
        {
            if (LastSelected == null)
            {
                return Children.OfType<CarouselBeatmap>()
                               .Where(b => !b.Filtered.Value)
                               .OrderBy(b =>
                               {
                                   var difference = b.Beatmap.StarDifficulty - recommendedStarDifficulty.Value;
                                   return difference >= 0 ? difference * 2 : difference * -1; // prefer easier over harder
                               })
                               .FirstOrDefault();
            }

            return base.GetNextToSelect();
        }

        public override int CompareTo(FilterCriteria criteria, CarouselItem other)
        {
            if (!(other is CarouselBeatmapSet otherSet))
                return base.CompareTo(criteria, other);

            switch (criteria.Sort)
            {
                default:
                case SortMode.Artist:
                    return string.Compare(BeatmapSet.Metadata.Artist, otherSet.BeatmapSet.Metadata.Artist, StringComparison.OrdinalIgnoreCase);

                case SortMode.Title:
                    return string.Compare(BeatmapSet.Metadata.Title, otherSet.BeatmapSet.Metadata.Title, StringComparison.OrdinalIgnoreCase);

                case SortMode.Author:
                    return string.Compare(BeatmapSet.Metadata.Author.Username, otherSet.BeatmapSet.Metadata.Author.Username, StringComparison.OrdinalIgnoreCase);

                case SortMode.DateAdded:
                    return otherSet.BeatmapSet.DateAdded.CompareTo(BeatmapSet.DateAdded);

                case SortMode.BPM:
                    return compareUsingAggregateMax(otherSet, b => b.BPM);

                case SortMode.Length:
                    return compareUsingAggregateMax(otherSet, b => b.Length);

                case SortMode.Difficulty:
                    return compareUsingAggregateMax(otherSet, b => b.StarDifficulty);
            }
        }

        /// <summary>
        /// All beatmaps which are not filtered and valid for display.
        /// </summary>
        protected IEnumerable<BeatmapInfo> ValidBeatmaps => Beatmaps.Where(b => !b.Filtered.Value || b.State.Value == CarouselItemState.Selected).Select(b => b.Beatmap);

        private int compareUsingAggregateMax(CarouselBeatmapSet other, Func<BeatmapInfo, double> func)
        {
            var ourBeatmaps = ValidBeatmaps.Any();
            var otherBeatmaps = other.ValidBeatmaps.Any();

            if (!ourBeatmaps && !otherBeatmaps) return 0;
            if (!ourBeatmaps) return -1;
            if (!otherBeatmaps) return 1;

            return ValidBeatmaps.Max(func).CompareTo(other.ValidBeatmaps.Max(func));
        }

        public override void Filter(FilterCriteria criteria)
        {
            base.Filter(criteria);
            Filtered.Value = InternalChildren.All(i => i.Filtered.Value);
        }

        public override string ToString() => BeatmapSet.ToString();
    }
}