#include<iostream>
using namespace std;
#include<easyx.h>       //包含图形库头文件
#include<stdlib.h>      
#include<time.h>       

#define WIDTH 1040  //定义场景大小   
#define HEIGHT 640    
#define SIZE  20   //定义食物以及蛇的大小   一个格子的大小
#define UP 1    //定义蛇的朝向
#define DOWN -1
#define LEFT 2
#define RIGHT -2
#define MAX 2000   //蛇的最大长度


typedef struct
{
    int x;
    int y;
}SnakeNode;

SnakeNode temp[MAX];    //用另外一个数组来存储蛇原来的位置
int speed = 150;        //蛇的速度

//创建蛇的类
class Snake
{
    friend class Food;
public:
    Snake();                    //初始化
    void Move();                //移动
    void Draw();                //绘制蛇
    bool Eat(Food food);        //吃食物
    bool Defeat();              //失败判定
private:
    int dirt;                   //朝向
    int length;                 //长度
    SnakeNode node[MAX];        //蛇的坐标
};

//创建食物的类
class Food
{
    friend class Snake;
public:
    Food(Snake snake);          //食物初始化
    void Draw();                //绘制食物
private:
    int x, y;                   //坐标
};

//蛇的初始化
Snake::Snake()
{
    dirt = RIGHT;
    length = 3;
    //下标是0的位置为蛇的头部
    for (int i = 0; i < length; i++)
    {
        node[i].x = 60 - ((i + 1) * SIZE);//坐标带上20
        node[i].y = 0;
    }    //固定刚开始蛇的位置
    //蛇一开始从屏幕的左上角出现
}

//移动
void Snake::Move()
{
    for (int i = 0; i < length; i++)    //将原来的蛇结点拷贝一份
    {
        temp[i].x = node[i].x;
        temp[i].y = node[i].y;
    }
    int status = 0;    //用来判断是否点击了转向按键
    if (dirt == RIGHT) //四个方向，讨论现在的方向，分别判断是否转向，不能反向。
    {
        //判断是否转向
        if (GetAsyncKeyState('W') && status == 0) //捕捉键盘输入为w，easyx 判断转向
        {
            dirt = UP;  //去了if(dirt==up)的else
            status = 1;
        }
        else if (GetAsyncKeyState('S') && status == 0)
        {
            dirt = DOWN;
            status = 1;
        }
        else
        {
            node[0].x = node[0].x + SIZE;
        }
    }
    if (dirt == DOWN)
    {
        //判断是否转向
        if (GetAsyncKeyState('A') && status == 0)
        {
            dirt = LEFT;
            status = 1;
        }
        else if (GetAsyncKeyState('D') && status == 0)
        {
            node[0].x = node[0].x + SIZE;
            dirt = RIGHT;
            status = 1;
        }
        else
        {
            node[0].y = node[0].y + SIZE;
        }
    }
    if (dirt == LEFT)
    {
        //判断是否转向
        if (GetAsyncKeyState('W') && status == 0)
        {
            dirt = UP;
            status = 1;
        }
        else if (GetAsyncKeyState('S') && status == 0)
        {
            node[0].y = node[0].y + SIZE;
            dirt = DOWN;
            status = 1;
        }
        else
        {
            node[0].x -= SIZE;
        }
    }
    if (dirt == UP)
    {
        //判断是否转向
        if (GetAsyncKeyState('A') && status == 0)
        {
            node[0].x = node[0].x - SIZE;
            dirt = LEFT;
            status = 1;
        }
        else if (GetAsyncKeyState('D') && status == 0)
        {
            node[0].x = node[0].x + SIZE;
            dirt = RIGHT;
            status = 1;
        }
        else
        {
            node[0].y = node[0].y - SIZE;
            //改变坐标
        }
    }

    //移动
    for (int i = 1; i < length; i++)
    {
        node[i].x = temp[i - 1].x;
        node[i].y = temp[i - 1].y;
    }
    Sleep(speed);   //休眠这么长时间，停顿一下
}

//绘制蛇
void Snake::Draw()
{
    cleardevice();   //清空原先的绘图
    srand((unsigned)time(NULL));   //设置颜色随机数（setfillcolor)时用
    for (int i = 0; i < length; i++)
    {
        setfillcolor(RGB(rand() % 256, rand() % 256, rand() % 256));  //五颜六色的蛇
        fillrectangle(node[i].x, node[i].y, node[i].x + SIZE, node[i].y + SIZE);
    }
}

//吃食物
bool Snake::Eat(Food food)
{
    if (food.x == node[0].x && food.y == node[0].y) //头有没有碰到食物
    {
        if (node[length - 1].x - node[length - 2].x == 0 && node[length - 1].y - node[length - 2].y == -20)
        {   
            //判断蛇尾巴的方向（数组最后两个点的位置关系），新点加在尾巴后面
            length++;
            node[length - 1].x = node[length - 2].x;
            node[length - 1].y = node[length - 2].y - SIZE;
        }
        else if (node[length - 1].x - node[length - 2].x == 0 && node[length - 1].y - node[length - 2].y == 20)
        {
            length++;
            node[length - 1].x = node[length - 2].x;
            node[length - 1].y = node[length - 2].y + SIZE;
        }
        else if (node[length - 1].x - node[length - 2].x == 20 && node[length - 1].y - node[length - 2].y == 0)
        {
            length++;
            node[length - 1].x = node[length - 2].x + SIZE;
            node[length - 1].y = node[length - 2].y;
        }
        else if (node[length - 1].x - node[length - 2].x == -20 && node[length - 1].y - node[length - 2].y == 0)
        {
            length++;
            node[length - 1].x = node[length - 2].x - SIZE;
            node[length - 1].y = node[length - 2].y;
        }

        return true;
    }
    return false;
}

//失败判定
bool Snake::Defeat()
{
    //碰到边界
    if (node[0].x < 0 || node[0].x >= WIDTH || node[0].y < 0 || node[0].y >= HEIGHT)
        return true;

    //碰到自己的身体
    for (int i = 1; i < length; i++)
    {
        if (node[0].x == node[i].x && node[0].y == node[i].y)
            return true;
    }
    return false;
}

//食物的初始化
Food::Food(Snake snake)
{
table:
    srand((unsigned)time(NULL));     //设计随机种子，产生随机数
    x = (rand() % (WIDTH / SIZE)) * SIZE;
    y = (rand() % (HEIGHT / SIZE)) * SIZE;

    for (int i = 0; i < snake.length; i++)
    {
        if (snake.node[i].x == x && snake.node[i].y == y)
            goto table;   //如果食物在蛇身上，则重新初始化
    }
}

//绘制食物
void Food::Draw()
{
    setfillcolor(GREEN);   //食物是绿色
    fillrectangle(x, y, x + SIZE, y + SIZE); //绘制食物为矩形，四个顶点坐标。
}

int main()
{
    initgraph(WIDTH, HEIGHT);
    Snake snake;

table:
    Food food(snake);
    while (1)
    {
        BeginBatchDraw();
        FlushBatchDraw();   //双缓冲，防止屏幕一闪一闪的
        snake.Draw();
        food.Draw();
        FlushBatchDraw();   //双缓冲，防止屏幕一闪一闪的
        EndBatchDraw();      
        /*双缓冲，防止屏幕一闪一闪的*/
        if (snake.Eat(food))
        {
            goto table;  //如果吃到食物，就再设置一个食物
        }
        if (snake.Defeat())
        {
            break;
        }
        snake.Move();
    }

    HWND window = GetHWnd();   //弹窗，提示游戏失败
    SetWindowText(window, L"提示");     //修改窗口标题，设置成提示
    MessageBox(window, L"游戏失败", L"提示", MB_OKCANCEL);   
    //提示失败信息  MB_OKCANCEL：下面有两个按键，确定或取消

    return 0;
}