const int button = 4;         // connected to trigger button
const int doorSensor = 5;     // connected to door sensor switch (HIGH is closed, LOW is open)
const int doorLock =  6;      // connected to door lock relay trigger input (HIGH is unlocked, LOW is locked)

int buttonState = 0;          // variable for reading the pushbutton status
int doorState = 0;            // variable for reading the door status (open/closed)

void setup(){
  pinMode (doorSensor, INPUT);     // set pin to input
  pinMode (button, INPUT);         // set pin to input     
  pinMode (doorLock, OUTPUT);      // set pin to output
}

void loop(){
  doorState = digitalRead(doorSensor);    // read state of door sensor
  buttonState = digitalRead(button);      // read state of button
   
  if (buttonState == HIGH) {              // if button is pressed
    unlockDoor();                         // perform unlock function    
  }else{                                  // if button is not pressed
    digitalWrite(doorLock, LOW);          // keep door locked
  }
}

void unlockDoor(){  
  digitalWrite(doorLock,HIGH);                // unlock door
  delay(2000);                                // wait 2 seconds
    
  if (doorState == LOW){                      // if door is open after 2 second delay 
  
    do {
       doorState = digitalRead(doorSensor);   // Re-check sensor
       digitalWrite(doorLock,HIGH);           // keep door unlocked
    }while (doorState == LOW);                // while door is open
    
                                              // when doorState == HIGH
    delay(500);                               // wait 1/2 second 
    digitalWrite(doorLock, LOW);              // lock door
    
  }else if (doorState == HIGH){               // if door is closed after 2 second delay
    digitalWrite(doorLock,LOW);               // lock door
  }
}