/*
  Forum: https://forum.arduino.cc/t/help-beginner-with-led-flash-for-specified-time/1337748
  Wokwi: https://wokwi.com/projects/418890592487643137
*/

const byte buttonPin = 2;
const byte ledPin = 5;
boolean flashing = false;
byte currentButtonState = HIGH;
byte previousButtonState = HIGH;
unsigned long currentTime;
unsigned long onoffStarted;
long flashPeriod = 1000;

void setup()
{
  pinMode(buttonPin, INPUT_PULLUP);
  pinMode(ledPin, OUTPUT);
}

void loop()
{
  currentButtonState = digitalRead(buttonPin);
  if (currentButtonState != previousButtonState)  //buttonstate has changed
  {
    delay(30);                                         // Poor man's debouncing ... ;-)
    previousButtonState = currentButtonState;          //save the button state for the next check
    if (currentButtonState == LOW) {                   // Change the flash state only if the change was from HIGH to LOW
      flashing = !flashing;
      if (!flashing) {                                 // We only need to do this once when going to "not flashing"
        digitalWrite(ledPin, LOW);                     //force the LED off if not flashing
      }
    }
  }

  if (flashing)
  {
    currentTime = millis();
    if (currentTime - onoffStarted > flashPeriod)  //if the flash period ended ?
    {
      digitalWrite(ledPin, !digitalRead(ledPin));  //flip the state of the LED
      onoffStarted = currentTime;                  //save the time when it occured
    }
  }
}