// Variable Definitions
#define buttonPin         12    // The Push-Button pin.
#define relayPin        13    // The relay pin (Light-Emitting Diode).


// Constants
const unsigned long debounceTime = 20; // Th Debounce time for the Push-Button.

// Variables
bool relayState = HIGH;       // The variable for the current state of the relay with an initial state.
bool buttonState;           // The variable for current reading value from the Push-Button pin.
bool prevButtonState = LOW; // The variable for previous reading value from the Push-Button pin.

unsigned long prevDebounceTime = 0; // The variable for the previous time Push-Button change.


void setup() {
  pinMode(buttonPin, INPUT);          // Set the Push-Button pin mode as an input.
  pinMode(relayPin, OUTPUT);        // Set the relay pin mode as an output.

  digitalWrite(relayPin, relayState); // Write the relay with an initial state.
}

void loop() {
  bool currButtonState = digitalRead(buttonPin);  // Read the current Push-Button state.

  // Read a Push-Button value and compare the current value with the previous value.
  // If the Push-Button value is different, reset the debounce time.
  if (currButtonState != prevButtonState) {
    prevDebounceTime = millis();    // Reset the debounce time
  }

  // If the Push-Button state is different from the current value, continue to debounce the Push-Button
  if (buttonState != currButtonState) {
    // If the current value is stable, fully debounce time.
    // Set the push-button state with the current value
    if ((millis() - prevDebounceTime) >= debounceTime) {

      buttonState = currButtonState;  //Set the push-button state with the current value

      // In PULL-DOWN mode, the push-button pressed state is HIGH.
      // If the push-button state is HIGH, toggle the relay state.
      if (buttonState == HIGH) {
        relayState = !relayState; // Toggle the relay state
      }
    }
  }

  digitalWrite(relayPin, relayState);     // Write the relay with an initial state.
  prevButtonState = currButtonState;  // Set the previous push-button state with the current push-button state.
}