using Unity.Entities;
using Unity.Jobs;
using Unity.Mathematics;
using Unity.Transforms;
using UnityEngine;

namespace Samples.Boids
{
    public class SampledAnimationClipPlaybackSystem : JobComponentSystem
    {
        protected override JobHandle OnUpdate(JobHandle inputDeps)
        {
            var deltaTime = math.min(0.05f,Time.DeltaTime);
            
            var transformJobHandle = Entities.ForEach((ref Translation translation, ref Rotation rotation, in SampledAnimationClip sampledAnimationClip) =>
            {
                var frameIndex = sampledAnimationClip.FrameIndex;
                var timeOffset = sampledAnimationClip.TimeOffset;
                
                // Be careful not to cache Value (or any field in Value like Samples) inside of blob asset.
                var prevTranslation = sampledAnimationClip.TransformSamplesBlob.Value.TranslationSamples[frameIndex];
                var nextTranslation = sampledAnimationClip.TransformSamplesBlob.Value.TranslationSamples[frameIndex+1];
                var prevRotation    = sampledAnimationClip.TransformSamplesBlob.Value.RotationSamples[frameIndex];
                var nextRotation    = sampledAnimationClip.TransformSamplesBlob.Value.RotationSamples[frameIndex+1];
                
                translation.Value = math.lerp(prevTranslation, nextTranslation, timeOffset);
                rotation.Value = math.slerp(prevRotation, nextRotation, timeOffset);
            }).Schedule(inputDeps);

            var clipJobHandle = Entities.ForEach((ref SampledAnimationClip sampledAnimationClip) =>
            {
                var currentTime = sampledAnimationClip.CurrentTime + deltaTime;
                var sampleRate = sampledAnimationClip.SampleRate;
                var frameIndex = (int)(currentTime / sampledAnimationClip.SampleRate);
                var timeOffset = (currentTime - (frameIndex * sampleRate)) * (1.0f / sampleRate);

                // Just restart loop when over end:
                //   - Don't interpolate between last and first frame.
                //   - Don't worry about interpolating time into the start of the loop.
                //   - Don't worry too much about exactly what the last frame even means.
                if (frameIndex >= (sampledAnimationClip.FrameCount - 2))
                {
                    currentTime = 0.0f;
                    frameIndex = 0;
                    timeOffset = 0.0f;
                }

                sampledAnimationClip.CurrentTime = currentTime;
                sampledAnimationClip.FrameIndex = frameIndex;
                sampledAnimationClip.TimeOffset = timeOffset;
            }).Schedule(transformJobHandle);

            return clipJobHandle;
        }
    }
}