// January 25th, 2024

//libraries for LCD screen
#include <LiquidCrystal.h>

//servo library
#include <Servo.h>

//EEPROM library
#include <EEPROM.h>

Servo door;

//LCD setup -- pins
const int rs=12, en=11, d4=5, d5=4, d6=3, d7=2; 
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

//serial monitor
 //Serial.readStringUntil(delimiter)
 // example if we want delimiter to be enter, then we need to
 //set the delimiter to be newline char so that when 
 //user presses enter it saves the entered value in the serial

//EEPROM
//need to store user entered thresshold value using write

//pins for trig and echo
const int trig = 9;
const int echo = 8;
//variable setups for ultrasonic sensor
float duration, distance;

const int door_pin = 19;

int threshold;
int state;

void setup() {
  //trig pin
  pinMode(trig, OUTPUT);
  //echo pin
  pinMode(echo, INPUT);
  door.attach(door_pin);

  Serial.begin(9600);
  Serial.println("hello world");
  lcd.begin(16,2); //setup of lcd with rows, cols of screensize
  //reruns each power cycle


  //use eeprom read in setup so it only runs when power is lost/regained
  //eprom read should not be used in loop (slows program)
  //reading previous value stored for the threshold value
  threshold = EEPROM.read(0);
}

void loop() {
  //writing value from serial into memory, if a user enters something into the serial
  if (Serial.available() > 0){
    //reads integer from serial 
    String entered = Serial.readStringUntil('\n');
    int thresh2 = entered.toInt();
    EEPROM.write(0, thresh2);
    Serial.println(thresh2);
    threshold = thresh2;
  }




  //trig pin starts on low for 2 us
  digitalWrite(trig, LOW);
  delayMicroseconds(2);
  //then we set it to high for 10 us, so that it will then send a burst
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);

  //now we are awaiting a pulse back, so we can read the duration
  duration = pulseIn(echo, HIGH); //reads how long echo is high aka how long until the pulse returns
  
  // vsound = 0.034cm/μs
  //calculate distance
  float v = 0.034;
  distance = (duration * v)/2;
  
  lcd.setCursor(0,0);
  lcd.print("Distance: ");
  lcd.print(distance);

 if (distance < threshold){
   door.write(180);
    lcd.setCursor(0,1);
    lcd.print("State: Open");
  }
  else{
   door.write(0);
   lcd.setCursor(0,1);
   lcd.print("State: Closed");
  }

  delay(100);

   }