// Task 4: Interrupt Handling using a Button Press

const int buttonPin = 2;    // Interrupt pin (INT0)
const int ledInterrupt = 12; // LED toggled by interrupt
const int ledMain = 13;      // LED blinking in main loop

volatile bool ledState = false; // Must be volatile since used in ISR
unsigned long previousMillis = 0;
const long interval = 500;      // Blink interval for main LED (in ms)

// Interrupt Service Routine (ISR)
void toggleLED() {
  ledState = !ledState; // Toggle LED state
  digitalWrite(ledInterrupt, ledState);
}

void setup() {
  pinMode(buttonPin, INPUT_PULLUP);  // Internal pull-up resistor
  pinMode(ledInterrupt, OUTPUT);
  pinMode(ledMain, OUTPUT);

  attachInterrupt(digitalPinToInterrupt(buttonPin), toggleLED, FALLING);
  Serial.begin(9600);
  Serial.println("Interrupt test started...");
}

void loop() {
  // Main loop LED blink using millis() (non-blocking)
  unsigned long currentMillis = millis();

  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;
    digitalWrite(ledMain, !digitalRead(ledMain));  // Toggle LED
  }

  // Print status (optional)
  Serial.print("Main LED: ");
  Serial.print(digitalRead(ledMain));
  Serial.print(" | Interrupt LED: ");
  Serial.println(digitalRead(ledInterrupt));
}