osu/osu.Game/Storyboards/CommandTimeline.cs

// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE

using osu.Framework.Caching;
using osu.Framework.Graphics;
using System;
using System.Collections.Generic;
using System.Linq;

namespace osu.Game.Storyboards
{
    public class CommandTimeline<T> : ICommandTimeline
    {
        private readonly List<TypedCommand> commands = new List<TypedCommand>();
        public IEnumerable<TypedCommand> Commands => commands.OrderBy(c => c.StartTime);
        public bool HasCommands => commands.Count > 0;

        private Cached<double> startTimeBacking;
        public double StartTime => startTimeBacking.IsValid ? startTimeBacking : startTimeBacking.Value = HasCommands ? commands.Min(c => c.StartTime) : double.MinValue;

        private Cached<double> endTimeBacking;
        public double EndTime => endTimeBacking.IsValid ? endTimeBacking : endTimeBacking.Value = HasCommands ? commands.Max(c => c.EndTime) : double.MaxValue;

        public T StartValue => HasCommands ? commands.OrderBy(c => c.StartTime).First().StartValue : default(T);
        public T EndValue => HasCommands ? commands.OrderByDescending(c => c.EndTime).First().EndValue : default(T);

        public void Add(Easing easing, double startTime, double endTime, T startValue, T endValue)
        {
            if (endTime < startTime)
                return;

            commands.Add(new TypedCommand { Easing = easing, StartTime = startTime, EndTime = endTime, StartValue = startValue, EndValue = endValue, });

            startTimeBacking.Invalidate();
            endTimeBacking.Invalidate();
        }

        public override string ToString()
            => $"{commands.Count} command(s)";

        public class TypedCommand : ICommand
        {
            public Easing Easing { get; set; }
            public double StartTime { get; set; }
            public double EndTime { get; set; }
            public double Duration => EndTime - StartTime;

            public T StartValue;
            public T EndValue;

            public int CompareTo(ICommand other)
            {
                var result = StartTime.CompareTo(other.StartTime);
                if (result != 0) return result;
                return EndTime.CompareTo(other.EndTime);
            }

            public override string ToString()
                => $"{StartTime} -> {EndTime}, {StartValue} -> {EndValue} {Easing}";
        }
    }

    public interface ICommandTimeline
    {
        double StartTime { get; }
        double EndTime { get; }
        bool HasCommands { get; }
    }

    public interface ICommand : IComparable<ICommand>
    {
        Easing Easing { get; set; }
        double StartTime { get; set; }
        double EndTime { get; set; }
        double Duration { get; }
    }
}