// ---------------- LED PINS ----------------
#define R1 23
#define Y1 22
#define G1 21

#define R2 19
#define Y2 18
#define G2 5

#define R3 17
#define Y3 16
#define G3 4

// ---------------- SENSOR PINS ----------------
#define TRIG1 13
#define ECHO1 12

#define TRIG2 14
#define ECHO2 27

#define TRIG3 26
#define ECHO3 25

#define YELLOW_TIME 4000

long duration;
float distance;

// -------- Function to Measure Distance --------
float getDistance(int trigPin, int echoPin) {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);

  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH);
  float dist = duration * 0.034 / 2;
  return dist;
}

// -------- Set All Red --------
void allRed() {
  digitalWrite(R1, HIGH);
  digitalWrite(R2, HIGH);
  digitalWrite(R3, HIGH);

  digitalWrite(G1, LOW);
  digitalWrite(G2, LOW);
  digitalWrite(G3, LOW);

  digitalWrite(Y1, LOW);
  digitalWrite(Y2, LOW);
  digitalWrite(Y3, LOW);
}

// -------- Road Control Function --------
void operateRoad(int R, int Y, int G, float distance) {

  int greenTime;

  if (distance < 20) {
    greenTime = 40000;   // Heavy traffic
  } else {
    greenTime = 15000;   // Low traffic
  }

  digitalWrite(R, LOW);
  digitalWrite(G, HIGH);
  delay(greenTime);

  digitalWrite(G, LOW);
  digitalWrite(Y, HIGH);
  delay(YELLOW_TIME);

  digitalWrite(Y, LOW);
  digitalWrite(R, HIGH);
}

void setup() {

  pinMode(R1, OUTPUT); pinMode(Y1, OUTPUT); pinMode(G1, OUTPUT);
  pinMode(R2, OUTPUT); pinMode(Y2, OUTPUT); pinMode(G2, OUTPUT);
  pinMode(R3, OUTPUT); pinMode(Y3, OUTPUT); pinMode(G3, OUTPUT);

  pinMode(TRIG1, OUTPUT); pinMode(ECHO1, INPUT);
  pinMode(TRIG2, OUTPUT); pinMode(ECHO2, INPUT);
  pinMode(TRIG3, OUTPUT); pinMode(ECHO3, INPUT);

  allRed();
}

void loop() {

  float d1 = getDistance(TRIG1, ECHO1);
  float d2 = getDistance(TRIG2, ECHO2);
  float d3 = getDistance(TRIG3, ECHO3);

  allRed();
  operateRoad(R1, Y1, G1, d1);

  allRed();
  operateRoad(R2, Y2, G2, d2);

  allRed();
  operateRoad(R3, Y3, G3, d3);
}