#include "snake.h"




//创建一个贪吃蛇类
snak_struct *snake_creat(void)
{
	snak_struct *s=mymalloc(sizeof(snak_struct));
	snake_init(s);
	return s;
}


//初始化
void snake_init(snak_struct *s)
{
	mymemset(s,0,sizeof(snak_struct));
	for(int i=0;i<MAP_X_SIZE*MAP_Y_SIZE;i++)
	{
		cell_struct *cell=&s->map[i];
		cell->next_x=0xff;
		cell->next_y=0xff;
	}
	
	//贪吃蛇从左上角出现
	cell_struct *cell=&s->map[0];
	cell->next_x=0;cell->next_y=0;cell->type=CELL_TYPE_BODY;
	cell=&s->map[1];
	cell->next_x=0;cell->next_y=0;cell->type=CELL_TYPE_HEAD;
	s->head_x=1;s->head_y=0;
	s->tail_x=0;s->tail_y=0;
	s->dir=DIR_RIGHT;
	
	snake_food(s);
}





//删除一个贪吃蛇类
void snake_delete(snak_struct *s)
{
	if(s)
	{
		myfree(s);
	}
}



//找到新的尾部,返回1，成功，0，失败
int snake_find_tail_new(snak_struct *s)
{
	u8 x=s->tail_x;
	u8 y=s->tail_y;
	
	cell_struct *tail=&s->map[y*MAP_X_SIZE+x];
	tail->type=CELL_TYPE_AIR;
	tail->next_x=0xff;
	tail->next_y=0xff;
	
	cell_struct *cell=0;
	
	if(y<MAP_Y_SIZE-1)
	{
		cell=&s->map[(y+1)*MAP_X_SIZE+x];
		if(cell->next_x==x&&cell->next_y==y)
		{
			s->tail_x=x;
			s->tail_y=y+1;
			return 1;
		}
	}
	if(y>0)
	{
		cell=&s->map[(y-1)*MAP_X_SIZE+x];
		if(cell->next_x==x&&cell->next_y==y)
		{
			s->tail_x=x;
			s->tail_y=y-1;
			return 1;
		}
	}
	if(x>0)
	{
		cell=&s->map[y*MAP_X_SIZE+(x-1)];
		if(cell->next_x==x&&cell->next_y==y)
		{
			s->tail_x=x-1;
			s->tail_y=y;
			return 1;
		}
	}
	if(x<MAP_X_SIZE-1)
	{
		cell=&s->map[y*MAP_X_SIZE+(x+1)];
		if(cell->next_x==x&&cell->next_y==y)
		{
			s->tail_x=x+1;
			s->tail_y=y;
			return 1;
		}
	}
	return 0;
}


//蛇生长，吃到了食物，返回1，成功
int snake_grow(snak_struct *s)
{
	u8 x=s->tail_x;
	u8 y=s->tail_y;
	
	cell_struct *tail=&s->map[y*MAP_X_SIZE+x];
	x=tail->next_x;
	y=tail->next_y;
	
	//除非连续生长两次，这不可能
	if(x>=MAP_X_SIZE||y>=MAP_Y_SIZE) return 0;
	
	tail=&s->map[y*MAP_X_SIZE+x];
	tail->type=CELL_TYPE_BODY;
	s->tail_x=x;
	s->tail_y=y;
	return 1;
}




//贪吃蛇前进一步,1,成功，0，失败
int snake_forward(snak_struct *s)
{
	u8 x=s->head_x;
	u8 y=s->head_y;
	cell_struct *cell=&s->map[y*MAP_X_SIZE+x];
	
	//把当前头部设置为身体
	cell->type=CELL_TYPE_BODY;
	
	//没找到新的尾部，正常情况是不可能发生的
	if(snake_find_tail_new(s)==0) return 0;
	
	//头部向前走
	u8 x_old=x;
	u8 y_old=y;
	if(s->dir==DIR_RIGHT) x++;
	else if(s->dir==DIR_LEFT) x--;
	else if(s->dir==DIR_UP) y--;
	else if(s->dir==DIR_DOWN)	y++;
	
	//超出边界
	if(x>=MAP_X_SIZE||y>=MAP_Y_SIZE)
		return 0;
	
	cell_struct *head=&s->map[y*MAP_X_SIZE+x];
	if(head->type!=CELL_TYPE_AIR)
	{
		//头部撞到了东西
		if(head->type==CELL_TYPE_FOOD)
		{
			s->mark++;
			head->type=CELL_TYPE_HEAD;
			head->next_x=x_old;
			head->next_y=y_old;
			snake_grow(s);
			snake_food(s);
		}
		else
		{
			//撞到了其他东西，游戏失败
			return 0;
		}
	}
	else
	{
		head->type=CELL_TYPE_HEAD;
		head->next_x=x_old;
		head->next_y=y_old;
	}
	s->head_x=x;
	s->head_y=y;
	return 1;
	
	
}


//生成新的食物,返回1，生成了食物，0，找不到地方生成食物了，游戏结束
int snake_food(snak_struct *s)
{
	if(s->mark>(MAP_X_SIZE*MAP_Y_SIZE-s->wall_num-10))
		return 0;
	
	//使用硬件随机数发生器生成随机数
	do{
		u8 x=((u32)rand())%MAP_X_SIZE;
		u8 y=((u32)rand())%MAP_Y_SIZE;
		cell_struct *cell=&s->map[y*MAP_X_SIZE+x];
		
		if(cell->type==CELL_TYPE_AIR)
		{
			cell->type=CELL_TYPE_FOOD;
			return 1;
		}
		
	} while(1);
	
}

//运行,返回0，游戏结束
int snake_run(snak_struct *s)
{
	if(snake_forward(s)==0) return 0;
	return 1;
	
}

//设置前进方向
int snake_set_dir(snak_struct *s,int dir)
{
	if(s==0) return 0;
	if(dir>=1&&dir<=4)
	{
		s->dir=dir;
		return 1;
	}
	return 0;
}