MonoGame.Extended/Source/MonoGame.Extended.Tweening/TweenMember.cs

using System;
using System.Linq.Expressions;

namespace MonoGame.Extended.Tweening
{
    public abstract class TweenMember
    {
        protected TweenMember(object target)
        {
            Target = target;
        }

        public object Target { get; }
        public abstract Type Type { get; }
        public abstract string Name { get; }
    }

    public abstract class TweenMember<T> : TweenMember
        where T : struct 
    {
        static TweenMember()
        {
            var a = Expression.Parameter(typeof(T));
            var b = Expression.Parameter(typeof(T));
            var c = Expression.Parameter(typeof(float));
            Add = Expression.Lambda<Func<T, T, T>>(Expression.Add(a, b), a, b).Compile();
            Subtract = Expression.Lambda<Func<T, T, T>>(Expression.Subtract(a, b), a, b).Compile();
            Multiply = Expression.Lambda<Func<T, float, T>>(Expression.Multiply(a, c), a, c).Compile();
        }

        public static Func<T, T, T> Add { get; }
        public static Func<T, T, T> Subtract { get; }
        public static Func<T, float, T> Multiply { get; }

        protected TweenMember(object target, Func<object, object> getMethod, Action<object, object> setMethod)
            : base(target)
        {
            _getMethod = getMethod;
            _setMethod = setMethod; 
        }
        
        private readonly Func<object, object> _getMethod;
        private readonly Action<object, object> _setMethod;

        public T Value
        {
            get { return (T) _getMethod(Target); }
            set { _setMethod(Target, value); }
        }
    }
}