#include <LiquidCrystal.h> // 初始化LiquidCrystal库，指定接口引脚

LiquidCrystal lcd(12, 11, 10, 9, 8, 7); // 创建一个LiquidCrystal对象

const int buttonStart = 2;     // 开始按钮引脚
const int buttonAdd = 3;       // 增加时间按钮引脚
const int buttonSubtract = 4;  // 减少时间按钮引脚
const int buzzer = 5;          // 蜂鸣器引脚

unsigned long timer = 0;       // 定时器时长（以秒为单位）
unsigned long currentTime = 0; // 当前时间戳
bool timerStarted = false;     // 定时器是否已启动

void setup() {
  // 初始化串行通信
  Serial.begin(9600);
  
  // 初始化LCD显示器
  lcd.begin(16, 2);
  lcd.setCursor(0, 0);
  lcd.print("Set timer: 0 s");

  // 配置按钮为输入模式，启用内置上拉电阻
  pinMode(buttonStart, INPUT_PULLUP);
  pinMode(buttonAdd, INPUT_PULLUP);
  pinMode(buttonSubtract, INPUT_PULLUP);

  // 设置蜂鸣器引脚为输出
  pinMode(buzzer, OUTPUT);

  // 将A0~A5设置为LED控制的输出引脚
  for (int pin = A0; pin <= A5; ++pin) {
    pinMode(pin, OUTPUT);
  }
}

void loop() {
  // 检查增加时间按钮
  if (digitalRead(buttonAdd) == LOW) {
    while (digitalRead(buttonAdd) == LOW); // 简单防抖处理
    timer += 10; // 增加1分钟
  }

  // 检查减少时间按钮
  if (digitalRead(buttonSubtract) == LOW) {
    while (digitalRead(buttonSubtract) == LOW); // 简单防抖处理
    if (timer > 10) {
      timer -= 10; // 减少1分钟
    }
  }

  // 检查开始按钮
  if (digitalRead(buttonStart) == LOW) {
    while (digitalRead(buttonStart) == LOW); // 简单防抖处理
    timerStarted = !timerStarted; // 启动或暂停定时器
    if (timerStarted) {
      currentTime = millis();
    }
  }

  // 定时器逻辑处理
  if (timerStarted && (millis() - currentTime >= timer * 1000)) {
    playMusic();
    lcd.clear();
    lcd.print("Time's up!");
    delay(2000); // 显示消息2秒
    timerStarted = false; // 停止定时器
    timer = 0; // 重置定时器
  } else if (timerStarted) {
    lcd.clear();
    unsigned long remainingTime = timer - ((millis() - currentTime) / 1000);
    lcd.setCursor(0, 0);
    lcd.print("Time left: ");
    lcd.print(remainingTime);
    lcd.print(" s");
  } else {
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Set timer: ");
    lcd.print(timer);
    lcd.print(" s");
  }
}

void playMusic() {
  // 演奏“Twinkle Twinkle Little Star”
  int melody[] = {
    262, 262, 392, 392, 440, 440, 392,
    349, 349, 330, 330, 294, 294, 262
  };

  // 每个音符的时长：4 = 四分音符, 2 = 二分音符，等等
  int noteDurations[] = {
    4, 4, 4, 4, 4, 4, 2,
    4, 4, 4, 4, 4, 4, 2
  };

  int notes = sizeof(melody) / sizeof(melody[0]);

  for (int thisNote = 0; thisNote < notes; thisNote++) {
    // 计算音符时长
    int noteDuration = 1000 / noteDurations[thisNote];
    tone(buzzer, melody[thisNote], noteDuration);

    // 控制A0~A5实现流水灯效果
    for (int pin = A0; pin <= A5; ++pin) {
      digitalWrite(pin, HIGH);
      delay(noteDuration / 6);
      digitalWrite(pin, LOW);
    }

    // 音符之间的暂停
    int pauseBetweenNotes = noteDuration * 1.30;
    delay(pauseBetweenNotes);
    noTone(buzzer); // 停止当前音符
  }
}