#include <LiquidCrystal_I2C.h>
#include <Wire.h>

LiquidCrystal_I2C lcd(0x27,  16, 2); 

#define PIN_TRIG 13
#define PIN_ECHO 12
#define PIN_BUTTON 4
#define PIN_LED 3

int buttonLastState = HIGH;

void setup() {

  // initialize serial
  //Serial.begin(115200);

  // initialize ultrasonic
  pinMode(PIN_TRIG, OUTPUT);
  pinMode(PIN_ECHO, INPUT);  

  // initialize button
  pinMode(PIN_BUTTON, INPUT_PULLUP);
  buttonLastState = HIGH;

  // initialize LED
  pinMode(PIN_LED, OUTPUT);
  digitalWrite(PIN_LED, LOW);

  //initialize lcd screen
  lcd.begin(16,2);  
  lcd.backlight();
  lcd.print("Ultrasonic v1.0");
  delay(1000);  
  lcd.clear();
  lcd.noBacklight();
  
}

void loop() {
  // read button value
  int buttonValue = digitalRead(PIN_BUTTON);
  //Serial.println(buttonValue);
    
  // Start a new measurement:
  digitalWrite(PIN_TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(PIN_TRIG, LOW);

  int duration = pulseIn(PIN_ECHO, HIGH);
  
  // Use 343 metres per second as speed of sound
  float distance = duration * 0.034 / 2;
  
  if(distance <= 20){
    digitalWrite(PIN_LED, HIGH);
  }
  else{
    digitalWrite(PIN_LED, LOW);
  }


  if(buttonLastState != buttonValue){
    buttonLastState = buttonValue;

    if(buttonValue == HIGH){
    
      lcd.clear();
      lcd.noBacklight();
    }

    if(buttonValue == LOW){

      lcd.backlight();
      lcd.setCursor(0,0);
      lcd.print("Level: ");
      lcd.print(distance);  
      lcd.print("cm");
      
      lcd.setCursor(0,1);
      lcd.print("Remaining: ");
      lcd.print(getDays(distance));
      lcd.print(" d.");      

      delay(3000);
    }    
  }
}


int getDays(int distance)
{
    // Calculate the number of days based on the distance
    int days = distance / 5;

    return days;
}