#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// Initialize LCD (Address 0x27 is standard for Wokwi I2C LCDs)
LiquidCrystal_I2C lcd(0x27, 16, 2);

// --- Pin Definitions ---
// Lane 1
const int green1 = 2, yellow1 = 3, red1 = 4;
const int trig1 = 8, echo1 = 9;

// Lane 2
const int green2 = 5, yellow2 = 6, red2 = 7;
const int trig2 = 10, echo2 = 11;

// Base timing
const int baseGreenTime = 10; 
const int yellowTime = 3;

void setup() {
  Serial.begin(9600);
  
  // Setup LCD
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Smart Traffic");
  lcd.setCursor(0, 1);
  lcd.print("System Loading..");
  delay(2000);

  // Setup LED Pins
  pinMode(green1, OUTPUT); pinMode(yellow1, OUTPUT); pinMode(red1, OUTPUT);
  pinMode(green2, OUTPUT); pinMode(yellow2, OUTPUT); pinMode(red2, OUTPUT);

  // Setup Ultrasonic Pins
  pinMode(trig1, OUTPUT); pinMode(echo1, INPUT);
  pinMode(trig2, OUTPUT); pinMode(echo2, INPUT);

  // Initial State: Both Red momentarily
  digitalWrite(red1, HIGH);
  digitalWrite(red2, HIGH);
}

// Function to read distance from ultrasonic sensor
long readDistance(int trigPin, int echoPin) {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  
  // Timeout of 30ms to prevent code freezing if no echo is received
  long duration = pulseIn(echoPin, HIGH, 30000); 
  if (duration == 0) return 999; // Return high distance if no ping
  
  long distance = duration * 0.034 / 2; // Convert to cm
  return distance;
}

// Function to run a traffic cycle with countdown display
void runCycle(int grnPin, int ylwPin, int rdPin, int otherRdPin, int duration, String lane) {
  digitalWrite(otherRdPin, HIGH); // Ensure other lane is stopped
  digitalWrite(rdPin, LOW);
  digitalWrite(grnPin, HIGH);

  // Green Light Countdown
  for (int i = duration; i > 0; i--) {
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print(lane + " GO: " + String(i) + "s");
    lcd.setCursor(0, 1);
    lcd.print("Traffic Flowing ");
    delay(1000);
  }

  // Yellow Light Transition
  digitalWrite(grnPin, LOW);
  digitalWrite(ylwPin, HIGH);
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print(lane + " SLOW DOWN");
  
  for (int i = yellowTime; i > 0; i--) {
    lcd.setCursor(0, 1);
    lcd.print("Wait: " + String(i) + "s    ");
    delay(1000);
  }

  digitalWrite(ylwPin, LOW);
  digitalWrite(rdPin, HIGH);
}

void loop() {
  // 1. Read real-time traffic presence
  long dist1 = readDistance(trig1, echo1);
  long dist2 = readDistance(trig2, echo2);
  
  int time1 = baseGreenTime;
  int time2 = baseGreenTime;

  // 2. Prioritize lanes with higher traffic 
  // (In this logic, if a vehicle is within 100cm, it's considered heavy traffic)
  bool trafficLane1 = (dist1 < 100);
  bool trafficLane2 = (dist2 < 100);

  if (trafficLane1 && !trafficLane2) {
    time1 = 15; // Extend Lane 1 time
    time2 = 5;  // Shorten Lane 2 time
  } 
  else if (!trafficLane1 && trafficLane2) {
    time1 = 5;  // Shorten Lane 1 time
    time2 = 15; // Extend Lane 2 time
  }
  else if (trafficLane1 && trafficLane2) {
    // Both lanes busy, give equal extended time
    time1 = 12;
    time2 = 12;
  }

  // 3. Execute Traffic Lights
  runCycle(green1, yellow1, red1, red2, time1, "Lane 1");
  runCycle(green2, yellow2, red2, red1, time2, "Lane 2");
}