using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace 贪吃蛇
{
    enum E_MoveDirection
    {
        Up,
        Down,
        Left,
        Right
    }
    class Snake : IDraw
    {
        E_MoveDirection moveDirection;//记录蛇当前的移动方向
        SnakeBody[] bodies; //存放蛇身体的数组
        int nowNum;//用一个变量记录蛇的长度
        public Snake(int x, int y)
        {
            moveDirection = E_MoveDirection.Right;
            bodies = new SnakeBody[200];
            bodies[0] = new SnakeBody(x, y, E_BodyType.Head);
            nowNum = 1;
        }
        public void Draw()
        {
            //只画出当前的蛇身
            for (int i = 0; i < nowNum; i++)
            {
                bodies[i].Draw();
            }

        }

        #region Lesson7
        //蛇的移动
        public void Move()
        {
            //移动前擦除前一个位置
            SnakeBody lastBody = bodies[nowNum - 1];
            Console.SetCursorPosition(lastBody.pos.x, lastBody.pos.y);
            Console.Write("  ");

            for(int i = nowNum - 1; i > 0; i--)
            {
                bodies[i].pos = bodies[i - 1].pos;
            }
            switch (moveDirection)
            {
                case E_MoveDirection.Up:
                    bodies[0].pos.y--;
                    break;
                case E_MoveDirection.Down:
                    bodies[0].pos.y++;
                    break;
                case E_MoveDirection.Left:
                    bodies[0].pos.x -= 2;
                    break;
                case E_MoveDirection.Right:
                    bodies[0].pos.x += 2;
                    break;
            }
        }
        #endregion

        #region Lesson8
        public void ChangeDirection(E_MoveDirection newDirection)
        {
            //不能直接掉头
            if ( newDirection == moveDirection || 
                nowNum > 1 && (moveDirection == E_MoveDirection.Right && newDirection == E_MoveDirection.Left ) ||
                nowNum > 1 && (moveDirection == E_MoveDirection.Left && newDirection == E_MoveDirection.Right) ||
                nowNum > 1 && (moveDirection == E_MoveDirection.Up && newDirection == E_MoveDirection.Down) ||
                nowNum > 1 && (moveDirection == E_MoveDirection.Down && newDirection == E_MoveDirection.Up) )
            {
                return;
            }
            moveDirection = newDirection;
        }
        #endregion

        #region Lesson9
        //碰撞检测
        public bool CheckEnd(Map map)
        {
            //是否和墙体位置重合
            for(int i = 0; i < map.walls.Length; i++)
            {
                if (bodies[0].pos == map.walls[i].pos)
                {
                    return true;
                }
            }
            //是否和自己身体位置重合
            for(int i = 1; i < nowNum; i++)
            {
                if (bodies[0].pos == bodies[i].pos)
                {
                    return true;
                }
            }
            return false;
        }
        #endregion

        #region Lesson10    
        public bool CheckSamePos(Position p)
        {
            for(int i = 0; i < nowNum; i++)
            {
                if (bodies[i].pos == p)
                {
                    return true;
                }
            }
            return false;
        }
        public void CheckEat(Food food)
        {
            if (bodies[0].pos == food.pos)
            {
                //吃到了就再次随机生成食物，并且让蛇变长
                food.RandomPos(this);
                GrowUp();
            }
        }
        #endregion

        #region Lesson11
        private void GrowUp()
        {
            SnakeBody lastBody = bodies[nowNum - 1];
            bodies[nowNum] = new SnakeBody(lastBody.pos.x, lastBody.pos.y, E_BodyType.Body);
            nowNum++;
        }
        #endregion
    }
}