const int RED = 4;
const int YELLOW = 3;
const int GREEN = 2;

const int DELAY_RED = 9;
const int DELAY_YELLOW = 3;
const int DELAY_GREEN = 9;

const int a = 12;
const int b = 13;
const int c = 5;
const int d = 6;
const int e = 7;
const int f = 11;
const int g = 10;

const bool digitMap[10][7] = {
  {1, 1, 1, 1, 1, 1, 0}, // 0
  {0, 1, 1, 0, 0, 0, 0}, // 1
  {1, 1, 0, 1, 1, 0, 1}, // 2
  {1, 1, 1, 1, 0, 0, 1}, // 3
  {0, 1, 1, 0, 0, 1, 1}, // 4
  {1, 0, 1, 1, 0, 1, 1}, // 5
  {1, 0, 1, 1, 1, 1, 1}, // 6
  {1, 1, 1, 0, 0, 0, 0}, // 7
  {1, 1, 1, 1, 1, 1, 1}, // 8
  {1, 1, 1, 0, 0, 1, 1}  // 9
};

const int segmentPins[7] = {a, b, c, d, e, f, g};

void setup() {
  // Traffic lights
  pinMode(RED, OUTPUT);
  pinMode(YELLOW, OUTPUT);
  pinMode(GREEN, OUTPUT);

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

  Serial.begin(9600);
}

void loop() {
  // STOP PHASE
  for (int i = DELAY_RED; i > 0; i--) {
    if (i <= DELAY_YELLOW) {
      // RED/YELLOW TRANSITION
      red_yellow_light();
      display(i);
    } else {
      // RED LIGHT
      red_light();
      display(i);
    }
    delay(1000);
  }

  // GO PHASE
  for (int i = DELAY_GREEN; i > 0; i--) {
    if (i <= DELAY_YELLOW) {
      // YELLOW TRANSITION
      yellow_light();
      display(i);
    } else {
      // GREEN LIGHT
      green_light();
      display(i);
    }
    delay(1000);
  }
}

void red_light() {
  digitalWrite(RED, HIGH);
  digitalWrite(YELLOW, LOW);
  digitalWrite(GREEN, LOW);
}

void red_yellow_light() {
  digitalWrite(RED, HIGH);
  digitalWrite(YELLOW, HIGH);
  digitalWrite(GREEN, LOW);
}

void yellow_light() {
  digitalWrite(RED, LOW);
  digitalWrite(YELLOW, HIGH);
  digitalWrite(GREEN, LOW);
}

void green_light() {
  digitalWrite(RED, LOW);
  digitalWrite(YELLOW, LOW);
  digitalWrite(GREEN, HIGH);
}

void display(int num) {
  if (num < 0 || num > 9) {
    clearDisplay();
    return;
  }

  for (int i = 0; i < 7; i++) {
    digitalWrite(segmentPins[i], digitMap[num][i] ? HIGH : LOW);
  }

  Serial.print("Countdown: ");
  Serial.println(num);
}

void clearDisplay() {
  for (int i = 0; i < 7; i++) {
    digitalWrite(segmentPins[i], LOW);
  }
}