/*
   Arduino Interrupt Demonstration

   Features:
   - External interrupt on pin 2
   - ISR execution counting
   - Debounce handling
   - Event timestamping
   - Main loop communication via volatile variables
   - Interrupt mode switching
*/

const byte BUTTON_PIN = 2;
const byte LED_PIN = 13;

// Variables shared between ISR and main code
volatile unsigned long interruptCount = 0;
volatile unsigned long lastInterruptTime = 0;
volatile bool eventOccurred = false;

unsigned long lastReportTime = 0;
unsigned long modeChangeTime = 0;

enum InterruptMode {
  MODE_RISING,
  MODE_FALLING,
  MODE_CHANGE
};

InterruptMode currentMode = MODE_FALLING;

// ISR
void buttonISR()
{
  unsigned long now = millis();

  // Simple debounce (50 ms)
  if (now - lastInterruptTime < 50)
    return;

  interruptCount++;
  lastInterruptTime = now;
  eventOccurred = true;
}

void setup()
{
  Serial.begin(115200);

  pinMode(BUTTON_PIN, INPUT_PULLUP);
  pinMode(LED_PIN, OUTPUT);

  attachInterrupt(
    digitalPinToInterrupt(BUTTON_PIN),
    buttonISR,
    FALLING
  );

  Serial.println("Interrupt Demo Started");
  Serial.println("Press the button connected to pin 2");
}

void loop()
{
  // Process interrupt events safely
  if (eventOccurred)
  {
    noInterrupts();

    unsigned long count = interruptCount;
    unsigned long timestamp = lastInterruptTime;

    eventOccurred = false;

    interrupts();

    digitalWrite(LED_PIN, !digitalRead(LED_PIN));

    Serial.print("Interrupt detected. Count = ");
    Serial.print(count);
    Serial.print("  Time = ");
    Serial.print(timestamp);
    Serial.println(" ms");
  }

  // Print status every 5 seconds
  if (millis() - lastReportTime >= 5000)
  {
    lastReportTime = millis();

    noInterrupts();
    unsigned long count = interruptCount;
    interrupts();

    Serial.println("\n--- Status Report ---");
    Serial.print("Total interrupts: ");
    Serial.println(count);

    Serial.print("Current mode: ");

    switch (currentMode)
    {
      case MODE_RISING:
        Serial.println("RISING");
        break;

      case MODE_FALLING:
        Serial.println("FALLING");
        break;

      case MODE_CHANGE:
        Serial.println("CHANGE");
        break;
    }

    Serial.println("---------------------");
  }

  // Demonstrate changing interrupt modes every 15 seconds
  if (millis() - modeChangeTime >= 15000)
  {
    modeChangeTime = millis();

    detachInterrupt(digitalPinToInterrupt(BUTTON_PIN));

    switch (currentMode)
    {
      case MODE_FALLING:
        currentMode = MODE_RISING;
        attachInterrupt(
          digitalPinToInterrupt(BUTTON_PIN),
          buttonISR,
          RISING
        );
        Serial.println("Switched to RISING mode");
        break;

      case MODE_RISING:
        currentMode = MODE_CHANGE;
        attachInterrupt(
          digitalPinToInterrupt(BUTTON_PIN),
          buttonISR,
          CHANGE
        );
        Serial.println("Switched to CHANGE mode");
        break;

      case MODE_CHANGE:
        currentMode = MODE_FALLING;
        attachInterrupt(
          digitalPinToInterrupt(BUTTON_PIN),
          buttonISR,
          FALLING
        );
        Serial.println("Switched to FALLING mode");
        break;
    }
  }
}