using System.Collections;
using System.Collections.Generic;
using System.Text;
using UnityEngine;
using static Gameplay.Map;

namespace Gameplay
{

    public static class PathFinder
    {

        public static List<int> FindPath(Map map,
            int from,
            int to,
            int moveLevel)
        {
            var result = new List<int>();
            if (from == to)
            {
                // 同一个格子
                result.Add(to);
                return result;
            }

            var canReach = true;
            var mapData = map.GetBlockData(to);
            if (mapData == null)
            {
                canReach = false;
                return result;
            }
            if (!MapUtils.CanPass(moveLevel, mapData.GetTerrainTypeProperty()))
            {
                // 如果终点不可通行,直接走无法走通的逻辑
                canReach = false;
            }

            var toData = default(RuntimeBlockProperty);
            var oldCrossLevelTo = 0;


            // 将自己所在点和目标所在点临时设置为可通行
            map.GetRuntimeBlockProperty(from, out RuntimeBlockProperty fromData);
            var oldCrossLevelFrom = fromData.crossLevel;
            MapUtils.ForceSetCanCross(true, ref fromData);
            map.SetRuntimeBlockProperty(from, fromData);

            if (canReach)
            {
                map.GetRuntimeBlockProperty(to, out toData);
                oldCrossLevelTo = toData.crossLevel;
                MapUtils.ForceSetCanCross(true, ref toData);
                map.SetRuntimeBlockProperty(to, toData);
                result = map.TerrainGridSystem.FindPath(from, to, moveLevel);
            }


            // 无法直接走通
            if (!_IsFathExist(result))
            {
                var cacheFrom = from;
                var deepSearch = _ProcessCannotFindPath(map, cacheFrom, to, result);
                while (deepSearch)
                {
                    cacheFrom = result[^1];
                    deepSearch = _ProcessCannotFindPath(map, cacheFrom, to, result);
                }
            }

            fromData.crossLevel = oldCrossLevelFrom;

            map.SetRuntimeBlockProperty(from, fromData);

            if (canReach)
            {
                // 再设置回去
                toData.crossLevel = oldCrossLevelTo;
                map.SetRuntimeBlockProperty(to, toData);
            }

            if (result.Count == 1 && !MapUtils.CanPass(moveLevel, toData))
            {
                // 只有一格 且下一格子不可通行,则无法到达
                result.Clear();
            }

            if (DebugUtil.LogEnable)
            {
                var stringBuilder = new StringBuilder();
                stringBuilder.Append("FindPath: ");
                stringBuilder.Append(from);
                stringBuilder.Append(" -> ");
                stringBuilder.Append(to);
                stringBuilder.Append(" : ");
                for (int i = 0; i < result.Count; i++)
                {
                    stringBuilder.Append(result[i]);
                    stringBuilder.Append(" ");
                }
                DebugUtil.Log(stringBuilder);
            }


            return result;
        }

        private static bool _ProcessCannotFindPath(Map map,
            int from,
            int to,
            ICollection<int> pathList)
        {
            // 无法到达
            // 获得附近一圈的格子
            var nearByCells = map.TerrainGridSystem.CellGetNeighboursWithinRange(from, 1, 1);
            if (nearByCells == null || nearByCells.Count <= 0) return false;
            // 取最近的格子
            int closestCell = -1;
            var selfPos = map.TGSCellIndex2WorldPosition(from);
            var targetPos = map.TGSCellIndex2WorldPosition(to);
            var minDistance = Vector3.Distance(selfPos, targetPos);
            for (int i = 0; i < nearByCells.Count; i++)
            {
                var cellIndex = nearByCells[i];
                var newPos = map.TGSCellIndex2WorldPosition(cellIndex);
                var distance = Vector3.Distance(targetPos, newPos);

                if (distance < minDistance)
                {
                    minDistance = distance;
                    closestCell = cellIndex;
                }
            }
            if (closestCell != -1)
            {
                pathList.Add(closestCell);
                return true;
            }
            return false;
        }

        private static bool _IsFathExist(ICollection pathList)
        {
            return !(pathList == null || pathList.Count <= 0);
        }

    }
}