#include <avr/sleep.h>//this AVR library contains the methods that controls the sleep modes
#include <avr/wdt.h>
#define interruptPin 2 //Pin we are going to use to wake up the Arduino
int lspwr = 3; //to power the light sensor
int lsoutput = 4; //digital 1/0 output of the sensor
int relay = 5; // the relay that is the work of the code
int relaypwr = 6; 
void setup() {
  pinMode(interruptPin,INPUT_PULLUP);//Set pin d2 to input using the buildin pullup resistor
  pinMode(lspwr, OUTPUT);
  pinMode(lsoutput, INPUT);
  pinMode(relay, OUTPUT);
  pinMode(relaypwr, OUTPUT);
}

void loop() {
 delay(5000);//wait 5 seconds before going to sleep
 Going_To_Sleep();
}

void Going_To_Sleep(){
    sleep_enable();//Enabling sleep mode
    attachInterrupt(0, wakeUp, CHANGE);//attaching a interrupt to pin d2
    set_sleep_mode(SLEEP_MODE_PWR_DOWN);//Setting the sleep mode, in our case full sleep
    delay(1000); //wait a second to allow the led to be turned off before going to sleep
    sleep_cpu();//activating sleep mode
  }

void wakeUp(){
   sleep_disable();//Disable sleep mode
  detachInterrupt(0); //Removes the interrupt from pin 2;
 sleep_enable(); // Enable sleep mode
  set_sleep_mode(SLEEP_MODE_PWR_DOWN); // Set sleep mode to power down

  while (digitalRead(lsoutput)==LOW) {
    digitalWrite(lspwr, LOW);
    for (int i = 0; i < 8; i++) {
    sleep_cpu(); // activate sleep mode for 8 seconds
    };
    digitalWrite(lspwr, HIGH); 
    delay(50); // give ls time to pwr up
  };
  sleep_disable();//Disable sleep mode
  digitalWrite(relaypwr, HIGH);
  delay(50);
  digitalWrite(relay, HIGH);
  delay(2000); //open relay for 2 seconds
  digitalWrite(relay, LOW);
  digitalWrite(relaypwr, LOW);

 }