using System.Collections.Generic;
using JNGame.Math;

namespace JNGame.PathFinding
{
    /// <summary>
    /// 二叉空间分割树
    /// </summary>
    public partial class BspTree
    {
        private readonly List<TriangleRef> m_AllTriangle = new List<TriangleRef>();

        /// <summary>
        /// 根节点
        /// </summary>
        private BspTreeNode m_RootNode;

        /// <summary>
        /// 查找点邻接三角形的缓存，每次查找都会清理，外部不可缓存此列表，只可一次性使用
        /// </summary>
        private readonly List<int> m_TempNeareastTrianges = new List<int>(16);

        /// <summary>
        /// 构造二叉空间分割树
        /// </summary>
        /// <param name="rawTriangles">原始的三角形数据</param>
        public void Init(List<NavTriangle> rawTriangles)
        {
            foreach (var tri in rawTriangles)
            {
                m_AllTriangle.Add(new TriangleRef(tri));
            }

            m_RootNode = new BspTreeNode();
            m_RootNode.Init(m_AllTriangle);
        }

        /// <summary>
        /// 根据位置检索BSP树，快速定位点所在三角形区域
        /// </summary>
        /// <param name="pos"></param>
        /// <param name="nearTriangleIndices"></param>
        /// <returns></returns>
        public int GetTriangle(in LVector3 pos, out List<int> nearTriangleIndices)
        {
            m_TempNeareastTrianges.Clear();
            var pos2d = pos.ToLVector2XZ();
            int triangleIndex = m_RootNode.GetTriangle(pos2d, out _, out List<TriangleRef> nearTriangles);
            if (triangleIndex == -1)
            { // 未找到落位的三角形，说明在阻挡内，获取阻挡周边的一些三角形
                for (int i = 0; i < nearTriangles.Count; ++i)
                {
                    if (!m_TempNeareastTrianges.Contains(nearTriangles[i].index))
                    {
                        m_TempNeareastTrianges.Add(nearTriangles[i].index);
                    }
                }
            }
            nearTriangleIndices = m_TempNeareastTrianges;
            return triangleIndex;
        }
    }
}