using System.Collections;
using System.Collections.Generic;
using Unity.Burst;
using Unity.Collections;
using Unity.Collections.LowLevel.Unsafe;
using Unity.Entities;
using Unity.Jobs;
using Unity.Jobs.LowLevel.Unsafe;
using Unity.Transforms;
using UnityEngine;
using Random = Unity.Mathematics.Random;

public class SpawnEntitySystem : ComponentSystem
{
    private float _nextEntitySpawnTime = 0;

    private GameObject _ballPrefab;

    private NativeArray<Random> randoms;

    protected override void OnCreateManager()
    {
        _ballPrefab = Resources.Load<GameObject>("Cube");
        randoms = new NativeArray<Random>(JobsUtility.MaxJobThreadCount, Allocator.Persistent);
        for (var i = 0; i < JobsUtility.MaxJobThreadCount; i++)
            randoms[i] = new Random((uint)i + 1);
    }

    protected override void OnDestroyManager()
    {
        randoms.Dispose();
    }

    protected override void OnUpdate()
    {
        var state = GetSingleton<GameState>();

        switch (state.state)
        {
            case GameState.State.PLAY:
                SpawnEntity();
                break;
        }
    }

    void SpawnEntity()
    {
        if (Time.timeSinceLevelLoad < _nextEntitySpawnTime)
        {
            return;
        }

        using (var entities = new NativeArray<Entity>(6, Allocator.TempJob))
        {
            EntityManager.Instantiate(_ballPrefab, entities);
            new InitJob
            {
                Entities = entities,
                Positions = GetComponentDataFromEntity<Position>(),
                Randoms = randoms
            }.Schedule(entities.Length, 8).Complete();
        }

        _nextEntitySpawnTime = Time.timeSinceLevelLoad + 1;
    }

    //[BurstCompile]
    struct InitJob : IJobParallelFor
    {
        [ReadOnly]
        public NativeArray<Entity> Entities;

        [NativeDisableParallelForRestriction]
        public ComponentDataFromEntity<Position> Positions;

        [NativeDisableParallelForRestriction]
        public NativeArray<Random> Randoms;

        [NativeSetThreadIndex] private int ThreadIndex;

        public void Execute(int index)
        {
            var random = Randoms[ThreadIndex];
            var pos = Positions[Entities[index]];
            pos.Value.y = 15;
            pos.Value.x = random.NextFloat(-5f, 5f);
            Randoms[ThreadIndex] = random;
            Positions[Entities[index]] = pos;
        }
    }
}