using System;
using System.Buffers;
using System.Collections.Concurrent;
using Unity.Mathematics;
using System.Collections.Generic;
#if UNITY_5_3_OR_NEWER
using Unity.Burst;
#endif

namespace Net.BITKit.Quadtree
{
    public struct QuadtreeNode
    {
        private readonly Quadtree _root;

        public int Depth;
        
        public float2 Center; // 节点中心
        public float2 Size;   // 节点大小

        public readonly QuadtreeNode[] Children; // 子节点
        public readonly HashSet<int> Objects;       // 存储的对象ID

        public bool IsLeaf;
        public QuadtreeNode(Quadtree root,float2 center, float2 size)
        {
            _root = root;
            Center = center;
            Size = size;
            
            Children = new QuadtreeNode[4];

            Objects = new HashSet<int>();
            //Objects = root.HashSetPool.Take();
            //Objects.Clear();

            IsLeaf = true;
            Depth = 0;
        }
        #if UNITY_5_3_OR_NEWER
        [BurstCompile]
        #endif
        public readonly bool Contains(float2 point)
        {
            var min = Center - Size * 0.5f;
            var max = Center + Size * 0.5f;
    
            return math.all(point >= min & point <= max);
        }

        public void Split()
        {
            if (IsLeaf is false)
            {
                throw new InvalidOperationException("Node has already been split.");
            }
            
            var childSize = Size / 2;
            var offset = childSize / 2;

            Children[0] = new QuadtreeNode(_root, Center + new float2(-offset.x, offset.y), childSize)
            {
                Depth = Depth + 1,
            };
            Children[1] = new QuadtreeNode(_root, Center + new float2(offset.x, offset.y), childSize)
            {
                Depth = Depth + 1,
            };
            Children[2] = new QuadtreeNode(_root, Center + new float2(-offset.x, -offset.y), childSize)
            {
                Depth = Depth + 1,
            };
            Children[3] = new QuadtreeNode(_root, Center + new float2(offset.x, -offset.y), childSize)
            {
                Depth = Depth + 1,
            };
            
            IsLeaf = false;


            foreach (var id in Objects)
            {
                var pos = _root.Positions[id];
                for (var i = 0; i < Children.Length; i++)
                {
                    ref var node =ref Children[i];
                    if (!node.Contains(pos)) continue;
                    node.Objects.Add(id);
                    break;
                }
            }
            Objects.Clear();
        }
    }
}