using System;
using System.Collections.Generic;
using LibMMD.Model;
using LibMMD.Util;

namespace LibMMD.Motion
{
    internal sealed class MmdMorphWeightCalculator
    {
        private readonly MmdMotion _motion;
        private readonly List<KeyValuePair<string, int>> _morphs = new List<KeyValuePair<string, int>>();

        internal MmdMorphWeightCalculator(MmdMotion motion,
            IEnumerable<KeyValuePair<string, int>> morphs)
        {
            _motion = motion;
            _morphs.AddRange(morphs);
        }

        internal void Calculate(MmdModel model, double time, float[] output)
        {
            if (output.Length != model.Morphs.Length)
                throw new ArgumentException("model morph count not equals to output array length");
            Array.Clear(output, 0, output.Length);
            foreach (var entry in _morphs)
            {
                var pose = _motion.GetMorphPose(entry.Key, time);
                Accumulate(model, entry.Value, pose.Weight, output);
            }
        }

        private static void Accumulate(MmdModel model, int index, float rate, float[] output)
        {
            if (rate < Tools.MmdMathConstEps) return;
            var morph = model.Morphs[index];
            switch (morph.Type)
            {
                case Morph.MorphType.MorphTypeGroup:
                    foreach (var morphData in morph.MorphDatas)
                    {
                        var data = (Morph.GroupMorph) morphData;
                        Accumulate(model, data.MorphIndex, data.MorphRate * rate, output);
                    }
                    break;
                case Morph.MorphType.MorphTypeVertex:
                    output[index] += rate;
                    break;
            }
        }
    }
}