osu-lazer/osu.Game/Beatmaps/Beatmap.cs

// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE

using System.Collections.Generic;
using System.Linq;
using OpenTK.Graphics;
using osu.Game.Beatmaps.Timing;
using osu.Game.Database;
using osu.Game.Modes.Objects;
using osu.Game.Modes;

namespace osu.Game.Beatmaps
{
    public class Beatmap
    {
        public BeatmapInfo BeatmapInfo { get; set; }
        public BeatmapMetadata Metadata => BeatmapInfo?.Metadata ?? BeatmapInfo?.BeatmapSet?.Metadata;
        public List<HitObject> HitObjects { get; set; }
        public List<ControlPoint> ControlPoints { get; set; }
        public List<Color4> ComboColors { get; set; }
        public double BPMMaximum => 60000 / ControlPoints.Where(c => c.BeatLength != 0).OrderBy(c => c.BeatLength).First().BeatLength;
        public double BPMMinimum => 60000 / ControlPoints.Where(c => c.BeatLength != 0).OrderByDescending(c => c.BeatLength).First().BeatLength;
        public double BPMMode => BPMAt(ControlPoints.Where(c => c.BeatLength != 0).GroupBy(c => c.BeatLength).OrderByDescending(grp => grp.Count()).First().First().Time);

        public double BPMAt(double time)
        {
            return 60000 / BeatLengthAt(time);
        }

        public double BeatLengthAt(double time)
        {
            ControlPoint overridePoint;
            ControlPoint timingPoint = TimingPointAt(time, out overridePoint);
            return timingPoint.BeatLength;
        }

        public ControlPoint TimingPointAt(double time, out ControlPoint overridePoint)
        {
            overridePoint = null;

            ControlPoint timingPoint = null;
            foreach (var controlPoint in ControlPoints)
            {
                // Some beatmaps have the first timingPoint (accidentally) start after the first HitObject(s).
                // This null check makes it so that the first ControlPoint that makes a timing change is used as
                // the timingPoint for those HitObject(s).
                if (controlPoint.Time <= time || timingPoint == null)
                {
                    if (controlPoint.TimingChange)
                    {
                        timingPoint = controlPoint;
                        overridePoint = null;
                    }
                    else overridePoint = controlPoint;
                }
                else break;
            }

            return timingPoint ?? ControlPoint.Default;
        }

        public double CalculateStarDifficulty() => Ruleset.GetRuleset(BeatmapInfo.Mode).CreateDifficultyCalculator(this).Calculate();
    }
}