#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

// ---------------- LED PINS ----------------
#define GREEN_LED 27
#define YELLOW_LED 26
#define RED_LED 25

// ---------------- ULTRASONIC ----------------
#define TRIG_PIN 5
#define ECHO_PIN 18

// ---------------- BUZZER ----------------
#define BUZZER 4

// ---------------- OLED ----------------
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);


// =================================================
// SETUP
// =================================================
void setup() {

  // LED pins
  pinMode(GREEN_LED, OUTPUT);
  pinMode(YELLOW_LED, OUTPUT);
  pinMode(RED_LED, OUTPUT);

  // Ultrasonic pins
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);

  // Buzzer
  pinMode(BUZZER, OUTPUT);

  // Serial Monitor
  Serial.begin(115200);

  // OLED
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println("OLED not found!");
    while (1);
  }

  // Initial OLED message
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);
  display.setCursor(25, 25);
  display.println("Traffic System");
  display.display();

  delay(2000);
}


// =================================================
// GET DISTANCE
// =================================================
float getDistance() {

  // Send ultrasonic pulse
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);

  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);

  digitalWrite(TRIG_PIN, LOW);

  // Receive echo
  long duration = pulseIn(ECHO_PIN, HIGH);

  // Calculate distance in cm
  float distance = duration * 0.034 / 2;

  return distance;
}


// =================================================
// MAIN LOOP
// =================================================
void loop() {

  // =================================================
  // GREEN LIGHT
  // =================================================

  digitalWrite(GREEN_LED, HIGH);
  digitalWrite(YELLOW_LED, LOW);
  digitalWrite(RED_LED, LOW);

  noTone(BUZZER);

  // OLED
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(2);
  display.setCursor(25, 25);
  display.println("GREEN");
  display.display();

  delay(10000);


  // =================================================
  // YELLOW LIGHT
  // =================================================

  digitalWrite(GREEN_LED, LOW);
  digitalWrite(YELLOW_LED, HIGH);
  digitalWrite(RED_LED, LOW);

  noTone(BUZZER);

  // OLED
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(2);
  display.setCursor(25, 25);
  display.println("YELLOW");
  display.display();

  delay(10000);


  // =================================================
  // RED LIGHT
  // =================================================

  digitalWrite(GREEN_LED, LOW);
  digitalWrite(YELLOW_LED, LOW);
  digitalWrite(RED_LED, HIGH);

  // OLED
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(2);
  display.setCursor(40, 25);
  display.println("RED");
  display.display();


  // Start 10-second red timer
  unsigned long startTime = millis();


  // =================================================
  // CHECK VEHICLE DURING RED
  // =================================================

  while (millis() - startTime < 10000) {

    float distance = getDistance();

    // Print distance
    Serial.print("Distance: ");
    Serial.print(distance);
    Serial.println(" cm");


    // -----------------------------------------------
    // VEHICLE CROSSED RED LIGHT
    // -----------------------------------------------

    if (distance < 10) {

      // Buzzer ON
      tone(BUZZER, 1000);


      // OLED MESSAGE
      display.clearDisplay();

      display.setTextColor(SSD1306_WHITE);

      display.setTextSize(2);
      display.setCursor(0, 5);
      display.println("Red Light");

      display.setCursor(15, 35);
      display.println("Crossed");

      display.display();

    }


    // -----------------------------------------------
    // NO VEHICLE
    // -----------------------------------------------

    else {

      // Buzzer OFF
      noTone(BUZZER);


      // OLED continues showing RED
      display.clearDisplay();

      display.setTextColor(SSD1306_WHITE);

      display.setTextSize(2);
      display.setCursor(40, 25);
      display.println("RED");

      display.display();
    }


    delay(100);
  }


  // =================================================
  // END OF RED LIGHT
  // =================================================

  noTone(BUZZER);

}