osu-lazer/osu.Game/Beatmaps/BeatmapUpdater.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.

#nullable enable

using System.Linq;
using System.Threading.Tasks;
using osu.Framework.Extensions;
using osu.Game.Database;
using osu.Game.Rulesets.Objects;

namespace osu.Game.Beatmaps
{
    /// <summary>
    /// Handles all processing required to ensure a local beatmap is in a consistent state with any changes.
    /// </summary>
    public class BeatmapUpdater
    {
        private readonly BeatmapManager beatmapManager;
        private readonly BeatmapOnlineLookupQueue onlineLookupQueue;
        private readonly BeatmapDifficultyCache difficultyCache;

        public BeatmapUpdater(BeatmapManager beatmapManager, BeatmapOnlineLookupQueue onlineLookupQueue, BeatmapDifficultyCache difficultyCache)
        {
            this.beatmapManager = beatmapManager;
            this.onlineLookupQueue = onlineLookupQueue;
            this.difficultyCache = difficultyCache;
        }

        /// <summary>
        /// Queue a beatmap for background processing.
        /// </summary>
        public void Queue(Live<BeatmapSetInfo> beatmap)
        {
            // For now, just fire off a task.
            // TODO: Add actual queueing probably.
            Task.Factory.StartNew(() => beatmap.PerformRead(Process));
        }

        /// <summary>
        /// Run all processing on a beatmap immediately.
        /// </summary>
        public void Process(BeatmapSetInfo beatmapSet)
        {
            beatmapSet.Realm.Write(() =>
            {
                onlineLookupQueue.Update(beatmapSet);

                foreach (var beatmap in beatmapSet.Beatmaps)
                {
                    var working = beatmapManager.GetWorkingBeatmap(beatmap);

                    // Because we aren't guaranteed all processing will happen on this thread, it's very hard to use the live realm object.
                    // This can be fixed by adding a synchronous flow to `BeatmapDifficultyCache`.
                    var detachedBeatmap = beatmap.Detach();

                    beatmap.StarRating = difficultyCache.GetDifficultyAsync(detachedBeatmap).GetResultSafely()?.Stars ?? 0;
                    beatmap.Length = calculateLength(working.Beatmap);
                    beatmap.BPM = 60000 / working.Beatmap.GetMostCommonBeatLength();
                }
            });
        }

        private double calculateLength(IBeatmap b)
        {
            if (!b.HitObjects.Any())
                return 0;

            var lastObject = b.HitObjects.Last();

            //TODO: this isn't always correct (consider mania where a non-last object may last for longer than the last in the list).
            double endTime = lastObject.GetEndTime();
            double startTime = b.HitObjects.First().StartTime;

            return endTime - startTime;
        }
    }
}