const int redLed = 2;
const int yellowLed = 3;
const int greenLed = 4;
const int buttonPin = 5; // 按钮引脚

// 数码管段位定义
const int segmentPins[7] = {8, 9, 10, 11, 12, 13, 14};

// 数码管显示的数字对应的段码（共阴极）
const byte numbers[10] = {
  B00111111, // 0
  B00000110, // 1
  B01011011, // 2
  B01001111, // 3
  B01100110, // 4
  B01101101, // 5
  B01111101, // 6
  B00000111, // 7
  B01111111, // 8
  B01101111  // 9
};

int currentNumber = 30; // 初始倒计时时间（秒）
bool isCountingDown = true; // 是否在倒计时
unsigned long previousMillis = 0; // 上一次更新的时间
const long interval = 1000; // 间隔时间（毫秒）

void setup() {
  pinMode(redLed, OUTPUT);
  pinMode(yellowLed, OUTPUT);
  pinMode(greenLed, OUTPUT);
  pinMode(buttonPin, INPUT_PULLUP); // 使用内部上拉电阻

  for (int i = 0; i < 7; i++) {
    pinMode(segmentPins[i], OUTPUT);
  }
}

void loop() {
  if (digitalRead(buttonPin) == LOW) { // 如果按下按钮，重置倒计时
    currentNumber = 30;
    isCountingDown = true;
    delay(200); // 防抖处理
  }

  if (isCountingDown) {
    unsigned long currentMillis = millis();
    if (currentMillis - previousMillis >= interval) {
      previousMillis = currentMillis;
      currentNumber--;
      if (currentNumber < 0) {
        currentNumber = 30; // 重置倒计时
      }
    }
  }

  displayNumber(currentNumber);
  controlTrafficLights(currentNumber);
}

void displayNumber(int num) {
  int digits[2];
  digits[0] = num / 10; // 十位
  digits[1] = num % 10; // 个位

  for (int i = 0; i < 2; i++) {
    digitalWrite(segmentPins[i], LOW); // 关闭当前位的显示
    for (int j = 0; j < 7; j++) {
      digitalWrite(segmentPins[j], bitRead(numbers[digits[i]], j));
    }
    delay(5); // 确保显示稳定
    digitalWrite(segmentPins[i], HIGH); // 打开当前位的显示
  }
}

void controlTrafficLights(int num) {
  if (num > 25) { // 绿灯亮
    digitalWrite(greenLed, HIGH);
    digitalWrite(redLed, LOW);
    digitalWrite(yellowLed, LOW);
  } else if (num > 20) { // 黄灯亮
    digitalWrite(greenLed, LOW);
    digitalWrite(redLed, LOW);
    digitalWrite(yellowLed, HIGH);
  } else { // 红灯亮
    digitalWrite(greenLed, LOW);
    digitalWrite(redLed, HIGH);
    digitalWrite(yellowLed, LOW);
  }
}