namespace LibMMD.Motion
{
    internal sealed class MmdGrooveFallback
    {
        private readonly MmdMotion _motion;
        private readonly Poser _poser;
        private readonly MmdMotionTranslationScaler _scaler;
        private readonly int _centerIndex;

        internal MmdGrooveFallback(MmdMotion motion, Poser poser,
            MmdMotionTranslationScaler scaler, int centerIndex)
        {
            _motion = motion;
            _poser = poser;
            _scaler = scaler;
            _centerIndex = centerIndex;
        }

        internal void ApplyFrame(int frame)
        {
            if (_centerIndex < 0) return;
            Apply(_motion.GetBonePose("センター", frame), _motion.GetBonePose("グルーブ", frame));
        }

        internal void ApplyTime(double time)
        {
            if (_centerIndex < 0) return;
            Apply(_motion.GetBonePose("センター", time), _motion.GetBonePose("グルーブ", time));
        }

        private void Apply(BonePose center, BonePose groove)
        {
            _poser.SetBonePose(_centerIndex, _scaler.Apply(_centerIndex, new BonePose
            {
                Translation = center.Translation + groove.Translation,
                Rotation = center.Rotation * groove.Rotation
            }));
        }
    }
}