using System;
using System.Threading;
using Preparation.Interface;
using Preparation.Utility;
using Timothy.FrameRateTask;
using Preparation.GameData;

namespace GameEngine
{
    public class MoveEngine
    {
        /// <summary>
        /// 碰撞结束后要做的事情
        /// </summary>
        public enum AfterCollision
        {
            ContinueCheck = 0,  // 碰撞后继续检查其他碰撞
            MoveMax = 1,        // 行走最远距离
            Destroyed = 2       // 物体已经毁坏
        }

        private readonly ITimer gameTimer;
        private readonly Action<IMoveable> EndMove;
        private readonly CollisionChecker collisionChecker;
        private readonly Func<IMoveable, IGameObj, XY, AfterCollision> OnCollision;
        /// <summary>
        /// Constrctor
        /// </summary>
        /// <param name="gameMap">游戏地图</param>
        /// <param name="OnCollision">发生碰撞时要做的事情，第一个参数为移动的物体，第二个参数为撞到的物体，第三个参数为移动的位移向量，返回值见AfterCollision的定义</param>
        /// <param name="EndMove">结束碰撞时要做的事情</param>
        public MoveEngine(
            IMap gameMap,
            Func<IMoveable, IGameObj, XY, AfterCollision> OnCollision,
            Action<IMoveable> EndMove
        )
        {
            this.gameTimer = gameMap.Timer;
            this.EndMove = EndMove;
            this.OnCollision = OnCollision;
            this.collisionChecker = new CollisionChecker(gameMap);
        }

        /// <summary>
        /// 在无碰撞的前提下行走最远的距离
        /// </summary>
        /// <param name="obj">移动物体，默认obj.Rigid为true</param>
        /// <param name="moveVec">移动的位移向量</param>
        private void MoveMax(IMoveable obj, XY moveVec)
        {

            /*由于四周是墙，所以人物永远不可能与越界方块碰撞*/
            XY nextPos = obj.Position + XY.VectorToXY(moveVec);
            double maxLen = collisionChecker.FindMax(obj, nextPos, moveVec);
            maxLen = Math.Min(maxLen, obj.MoveSpeed / GameData.numOfStepPerSecond);
            _ = obj.Move(new Vector(moveVec.angle, maxLen));
        }

        public void MoveObj(IMoveable obj, int moveTime, double direction)
        {
            if (obj.IsMoving)  // 已经移动的物体不能再移动
                return;
            new Thread
            (
                ()=>
                {
                    if (!obj.IsAvailable&&gameTimer.IsGaming) //不能动就直接return，后面都是能动的情况
                            return;
            lock (obj.MoveLock)
                obj.IsMoving = true;

            XY moveVec = new(direction, 0.0);
            double deltaLen = moveVec.length - Math.Sqrt(obj.Move(moveVec));  // 转向，并用deltaLen存储行走的误差
            IGameObj? collisionObj = null;
            bool isDestroyed = false;
            new FrameRateTaskExecutor<int>(
                () => gameTimer.IsGaming && obj.CanMove && !obj.IsResetting,
                () =>
                {
                    moveVec.length = obj.MoveSpeed / GameData.numOfStepPerSecond;

                    // 越界情况处理：如果越界，则与越界方块碰撞
                    bool flag;  // 循环标志
                    do
                    {
                        flag = false;
                        collisionObj = collisionChecker.CheckCollision(obj, moveVec);
                        if (collisionObj == null)
                            break;

                        switch (OnCollision(obj, collisionObj, moveVec))
                        {
                            case AfterCollision.ContinueCheck:
                                flag = true;
                                break;
                            case AfterCollision.Destroyed:
                                Debugger.Output(obj, " collide with " + collisionObj.ToString() + " and has been removed from the game.");
                                isDestroyed = true;
                                return false;
                            case AfterCollision.MoveMax:
                                MoveMax(obj, moveVec);
                                moveVec.length = 0;
                                break;
                        }
                    } while (flag);

                    deltaLen += moveVec.length - Math.Sqrt(obj.Move(moveVec));

                    return true;
                },
                GameData.numOfPosGridPerCell / GameData.numOfStepPerSecond,
                () =>
                {
                    int leftTime = moveTime % (GameData.numOfPosGridPerCell / GameData.numOfStepPerSecond);
                    bool flag;
                    do
                    {
                        flag = false;
                        if (!isDestroyed)
                        {
                            moveVec.length = deltaLen + leftTime * obj.MoveSpeed / GameData.numOfPosGridPerCell;
                            if ((collisionObj = collisionChecker.CheckCollision(obj, moveVec)) == null)
                            {
                                obj.Move(moveVec);
                            }
                            else
                            {
                                switch (OnCollision(obj, collisionObj, moveVec))
                                {
                                    case AfterCollision.ContinueCheck:
                                        flag = true;
                                        break;
                                    case AfterCollision.Destroyed:
                                        Debugger.Output(obj, " collide with " + collisionObj.ToString() + " and has been removed from the game.");
                                        isDestroyed = true;
                                        break;
                                    case AfterCollision.MoveMax:
                                        MoveMax(obj, moveVec);
                                        moveVec.length = 0;
                                        break;
                                }
                            }
                        }
                    } while (flag);
                    if (leftTime > 0)
                    {
                        Thread.Sleep(leftTime);  // 多移动的在这里补回来
                    }
                    lock (obj.MoveLock)
                        obj.IsMoving = false;  // 结束移动
                    EndMove(obj);
                    return 0;
                },
                maxTotalDuration: moveTime
            ) {
                AllowTimeExceed = true,
                MaxTolerantTimeExceedCount = ulong.MaxValue,
                TimeExceedAction = b =>
                {
                    if (b)
                        Console.WriteLine("Fatal Error: The computer runs so slow that the object cannot finish moving during this time!!!!!!");

#if DEBUG
                    else
                    {
                        Console.WriteLine("Debug info: Object moving time exceed for once.");
                    }
#endif
                }
            }.Start();
        }
            ).Start();
    }
}
}