#define PIN_DIN1 2
#define PIN_DIN2 3
#define PIN_DIN3 4
#define PIN_DIN4 5


void setup()
{
  Serial.begin(9600);
  pinMode (PIN_DIN1, INPUT_PULLUP);
  pinMode (PIN_DIN2, INPUT_PULLUP);
  pinMode (PIN_DIN3, INPUT_PULLUP);
  pinMode (PIN_DIN4, INPUT_PULLUP);
}
void loop()
{
  const byte numInputs = 4;
  static unsigned long debounceTime;
  static unsigned long clickTime[numInputs];
  static bool stateOld[numInputs];
  bool stateNew[numInputs];
  static bool press[numInputs]; // long press



  if (millis() - debounceTime >= 50)
  {
    debounceTime = millis(); // update every 50mS
    stateNew[0] = !digitalRead(PIN_DIN1); // true for press
    stateNew[1] = !digitalRead(PIN_DIN2); // true for press
    stateNew[2] = !digitalRead(PIN_DIN3); // true for press
    stateNew[3] = !digitalRead(PIN_DIN4); // true for press
    for (byte x = 0; x < numInputs; x++) {
      if (stateOld[x] != stateNew[x]) // press or release
      {
        stateOld[x] = stateNew[x];
        if (stateNew[x] == true) // if new state is pressed
        {
          clickTime[x] = millis();
          press[x] = true;
        } else if (press[x] == true) // 50mS later, released
        {
          press[x] = false;
          Serial.print("pressed short ");
          Serial.println(x);
        }
      }
      // 1000mS after press
      if (press[x] == true && millis() - clickTime[x] >= 1000 )
      {
        press[x] = false;
        Serial.print("pressed long ");
        Serial.println(x);
      }

    }
  }

}