const int ledRedPin = 4;
const int ledYellowPin = 5;
const int ledGreenPin = 18;
const int buttonPin = 13;
int mode = 0;

const unsigned long longtime = 3000;
const unsigned long shorttime = 1000;



// 記錄按鈕上一個狀態
int lastButtonState = LOW;


// 燈光目前第幾個步驟
int lightStep = 0;


// 上一次切換燈光的時間
unsigned long previousMillis = 0;


// 控制三顆 LED
void light(int red, int yellow, int green) {

  digitalWrite(ledRedPin, red);
  digitalWrite(ledYellowPin, yellow);
  digitalWrite(ledGreenPin, green);
}


void loopLight() {

  unsigned long currentMillis = millis();

  unsigned long waitTime;


  // 根據「目前正在亮的燈」決定持續時間
  if (lightStep == 0) {

    // 🔴 紅燈 3 秒
    waitTime = longtime;

  }
  else if (lightStep == 1) {

    // 🔴🟡 紅＋黃 1 秒
    waitTime = shorttime;

  }
  else if (lightStep == 2) {

    // 🟢 綠燈 3 秒
    waitTime = longtime;

  }
  else {

    // 🟡 黃燈 1 秒
    waitTime = shorttime;
  }


  // 還沒到切換時間
  if (currentMillis - previousMillis < waitTime) {
    return;
  }


  // 到時間了，切換到下一個燈
  previousMillis = currentMillis;

  lightStep++;


  // 超過最後一個步驟，回到紅燈
  if (lightStep >= 4) {
    lightStep = 0;
  }


  // 顯示新的燈光
  if (lightStep == 0) {

    // 🔴
    light(HIGH, LOW, LOW);

  }
  else if (lightStep == 1) {

    // 🔴🟡
    light(HIGH, HIGH, LOW);

  }
  else if (lightStep == 2) {

    // 🟢
    light(LOW, LOW, HIGH);

  }
  else if (lightStep == 3) {

    // 🟡
    light(LOW, HIGH, LOW);
  }
}

void yellowBlink() {

  unsigned long currentMillis = millis();

  if (currentMillis - previousMillis < 500) {
    return;
  }

  previousMillis = currentMillis;

  if (lightStep == 0) {

    light(LOW, HIGH, LOW);
    lightStep = 1;

  }
  else {

    light(LOW, LOW, LOW);
    lightStep = 0;
  }
}

void setup() {

  pinMode(ledRedPin, OUTPUT);
  pinMode(ledYellowPin, OUTPUT);
  pinMode(ledGreenPin, OUTPUT);

  pinMode(buttonPin, INPUT);

  Serial.begin(115200);


  // 開機直接亮紅燈
  light(HIGH, LOW, LOW);

  // 從現在開始計時
  previousMillis = millis();
}


void loop() {

  int buttonState = digitalRead(buttonPin);


  // 偵測按鈕按下
  if (buttonState == HIGH && lastButtonState == LOW) {

    mode++;

    // 0 → 1
    // 1 → 0
    if (mode >= 2) {
      mode = 0;
    }


    if (mode == 0) {

      // 交通燈模式
      lightStep = 0;
      light(HIGH, LOW, LOW);
      previousMillis = millis();

      Serial.println("TRAFFIC");

    }
    else if (mode == 1) {

      // 黃燈閃爍模式
      lightStep = 0;
      light(LOW, HIGH, LOW);
      previousMillis = millis();

      Serial.println("YELLOW BLINK");
    }
  }


  // 根據模式執行不同程式
  if (mode == 0) {

    loopLight();

  }
  else if (mode == 1) {

    yellowBlink();
  }


  lastButtonState = buttonState;
}