// final Seat Occupancy Switch project, i.e. reading lamp
// uses 5v buck converter attached to 12v input from 12v ad/dc converter to power Nano at 5v and LED light panel at 12 volts
// and MOSFET attached to car seat pressure switch to trigger on/off lights when chair is occupied

const byte SwitchPin = 3;    // now just a momentary switch that'll be replaced with the seat occupany sensor
const byte LedReadingLightPin = A0;       // This triggers the Mosfet to turn on the reading light
const int NanoLed = 13;  // this is the builtin LED on the Arduino Nano board

const byte seatOccupied = LOW;
const byte seatFree     = HIGH;

const byte OFF = LOW;
const byte ON  = HIGH;

unsigned long firstClosing = 0;

byte SwitchState = seatFree;  // variable for reading the pushbutton status

void setup() {
  pinMode(LedReadingLightPin, OUTPUT);
  pinMode(SwitchPin, INPUT_PULLUP);
}

void loop() {
  SwitchState = digitalRead(SwitchPin);

  if (SwitchState == seatOccupied) {
    if (firstClosing == 0) {  // if no time is stored yet indicated through value 0
      firstClosing = millis(); // store snapshot of time in the moment of first close
    }
    digitalWrite(LedReadingLightPin, ON);
  }

  // check if more than 3 seconds have passed by since the moment 
  // the contact was closed for the first time 
  if (millis() - firstClosing > 3000) { 
    if (SwitchState == seatFree) {
      digitalWrite(LedReadingLightPin, OFF);
      firstClosing = 0; // reset timing variable to zero
    }
  }
}