#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Keypad.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET    -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// 键盘配置
const byte ROWS = 4;
const byte COLS = 4;
char keys[ROWS][COLS] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};
byte rowPins[ROWS] = {9,8,7,6};  // 连接行引脚
byte colPins[COLS] = {5,4,3,2};  // 连接列引脚
Keypad customKeypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

// 游戏区域参数
#define SCORE_AREA_HEIGHT 12    // 分数栏高度
#define OFFSET_Y SCORE_AREA_HEIGHT
#define CELL_SIZE 4             // 网格单元尺寸
#define GAME_WIDTH SCREEN_WIDTH
#define GAME_HEIGHT (SCREEN_HEIGHT - SCORE_AREA_HEIGHT)
#define GRID_WIDTH (GAME_WIDTH / CELL_SIZE)     // 32
#define GRID_HEIGHT (GAME_HEIGHT / CELL_SIZE)   // 13
#define SNAKE_MAX_LENGTH 30     // 最大蛇长

// 游戏数据结构
struct GameObject {
  int8_t x;
  int8_t y;
};

GameObject snake[SNAKE_MAX_LENGTH];
GameObject food;
uint8_t snakeLength = 3;
int8_t dir = 0;        // 0-right,1-down,2-left,3-up
bool gameOver = false;
uint16_t score = 0;

void setup() {
  // 初始化显示
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    while(1);
  }
  // 初始化键盘（启用内部上拉）
  for(int i=0; i<ROWS; i++) pinMode(rowPins[i], INPUT_PULLUP);
  for(int j=0; j<COLS; j++) pinMode(colPins[j], INPUT_PULLUP);

  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);

  initializeGame();
}

void loop() {
  static uint32_t lastUpdate = 0;
  handleInput();  
  
  if (millis() - lastUpdate >= 150) {  // 游戏速度控制
    if (!gameOver) {
      updateGame();
      checkCollisions();
      checkFood();
      drawGame();
    } else {
      showGameOver();
    }
    lastUpdate = millis(); //millis()返回从程序启动到当前时间的毫秒数
  }
}

/*********************
 * 游戏核心逻辑 *
 *********************/
void initializeGame() {
  // 初始化蛇位置（游戏区中心）
  snake[0] = {GRID_WIDTH/2, GRID_HEIGHT/2};
  snakeLength=3;
  for(uint8_t i=1; i<snakeLength; i++){
    snake[i] = {snake[i-1].x-1, snake[i-1].y};
  }
  dir = 0;
  gameOver = false;
  score = 0;
  generateFood();
}

void handleInput() {
  static int8_t lastDir = dir;
  char key = customKeypad.getKey();
  
  if (key) {
    switch(key) {
      case '2': if(lastDir != 1) dir = 3; break; // 上
      case '8': if(lastDir != 3) dir = 1; break; // 下
      case '4': if(lastDir != 0) dir = 2; break; // 左
      case '6': if(lastDir != 2) dir = 0; break; // 右
    }
    lastDir = dir;
  }
}

void updateGame() {
  // 移动身体
  for(int i=snakeLength-1; i>0; i--){
    snake[i] = snake[i-1];
  }
  
  // 移动头部
  switch(dir) {
    case 0: snake[0].x++; break; // 右
    case 1: snake[0].y++; break; // 下
    case 2: snake[0].x--; break; // 左
    case 3: snake[0].y--; break; // 上
  }
}

void checkCollisions() {
  // 游戏区边界检测
  if(snake[0].x < 0 || snake[0].x >= GRID_WIDTH ||
     snake[0].y < 0 || snake[0].y >= GRID_HEIGHT) {
    gameOver = true;
    return;
  }
  
  // 自碰撞检测
  for(uint8_t i=1; i<snakeLength; i++){
    if(snake[0].x == snake[i].x && snake[0].y == snake[i].y){
      gameOver = true;
      return;
    }
  }
}

void checkFood() {
  if(snake[0].x == food.x && snake[0].y == food.y){
    if(snakeLength < SNAKE_MAX_LENGTH) snakeLength++;
    score += 10;
    generateFood();
  }
}

void generateFood() {
  bool valid;
  do {
    valid = true;
    food.x = random(0, GRID_WIDTH);
    food.y = random(0, GRID_HEIGHT);
    
    for(uint8_t i=0; i<snakeLength; i++){
      if(food.x == snake[i].x && food.y == snake[i].y){
        valid = false;
        break;
      }
    }
  } while(!valid);
}

/*********************
 * 显示功能 *
 *********************/
void drawGame() {
  display.clearDisplay();
  
  // 绘制分数栏
  display.fillRect(0, 0, SCREEN_WIDTH, SCORE_AREA_HEIGHT, SSD1306_WHITE);
  display.setTextColor(SSD1306_BLACK);
  display.setCursor(SCREEN_WIDTH/2 - 24, 2);
  display.print("SCORE: ");
  display.print(score);
  
  // 绘制游戏区边框
  display.drawRect(0, OFFSET_Y-1, SCREEN_WIDTH, GAME_HEIGHT+1, SSD1306_WHITE);

  // 绘制蛇身
  for(uint8_t i=0; i<snakeLength; i++){
    display.fillRect(
      snake[i].x * CELL_SIZE,
      OFFSET_Y + snake[i].y * CELL_SIZE,
      CELL_SIZE-1,
      CELL_SIZE-1,
      SSD1306_WHITE
    );
  }
  
  // 绘制闪烁食物
  static bool blink = false;
  blink = !blink;
  if(blink){
    display.drawRect(
      food.x * CELL_SIZE,
      OFFSET_Y + food.y * CELL_SIZE,
      CELL_SIZE-1,
      CELL_SIZE-1,
      SSD1306_WHITE
    );
  }
  
  display.display();
}

void showGameOver() {
  display.clearDisplay();
  
  // 绘制分数栏
  display.fillRect(0, 0, SCREEN_WIDTH, SCORE_AREA_HEIGHT, SSD1306_WHITE);
  display.setTextColor(SSD1306_BLACK);
  display.setCursor(SCREEN_WIDTH/2 - 24, 2);
  display.print("SCORE: ");
  display.print(score);
  
  // 游戏结束信息
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(SCREEN_WIDTH/2 - 30, OFFSET_Y + 10);
  display.print("GAME OVER");
  display.setCursor(SCREEN_WIDTH/2 - 20, OFFSET_Y + 25);
  display.print("Final: ");
  display.print(score);
  display.setCursor(SCREEN_WIDTH/2 - 40, OFFSET_Y + 40);
  display.print("PRESS ANY KEY");
  
  display.display();

  // 等待按键重启
  if(customKeypad.getKey()){
    
    delay(500);
    initializeGame();
  }
}