using System.Linq;

namespace JD.Serialization
{
    public partial class AlphaClip
    {
        /// <summary>
        /// Computes whether the curve is a fade in or fade out curve.
        /// </summary>
        public static bool? FadesToOpaque(BezierCurveFloat curve)
        {
            if (curve.Keys.Count == 0)
            {
                // No fading
                return null;
            }
            else if (curve.Keys.Count == 1)
            {
                return IsOpaque(curve.Keys.First());
            }

            float minFrame = curve.Keys.Min(point => point.Frame);
            var from = IsOpaque(curve.Keys.First(x => x.Frame.Equals(minFrame)));
            float maxFrame = curve.Keys.Max(point => point.Frame);
            var to = IsOpaque(curve.Keys.First(x => x.Frame.Equals(maxFrame)));
            
            if (@from != to)
            {
                return to;
            }

            // No fading, returns a normal type
            return null;
        }

        private static bool IsOpaque(KeyFloat key)
        {
            return key.Position.Y > 0.5f;
        }
    }
}