#include <LCD_I2C.h>
LCD_I2C lcd(0x27, 20, 4);

const byte echoPin = 15;
const byte trigPin = 2;

const byte startButtonPin = 0;
const byte resetButtonPin = 4;

float initialDepth;
float currentDepth;
float finalDepth;

void setup() {
  Serial.begin(115200);

  pinMode(echoPin, INPUT);
  pinMode(trigPin, OUTPUT);

  pinMode(startButtonPin, INPUT_PULLUP);
  pinMode(resetButtonPin, INPUT_PULLUP);

  lcd.begin();
  lcd.clear();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Initial : ");
  lcd.setCursor(0, 1);
  lcd.print("Current : ");
  lcd.setCursor(0, 2);
  lcd.print("Final   : ");
}

void loop() {
  delay(100);

  if(!digitalRead(startButtonPin)) {
    initialDepth = readDistance();
    lcd.setCursor(10, 0);
    lcd.print(initialDepth);
  }

  currentDepth = readDistance();
  lcd.setCursor(10, 1);
  lcd.print(currentDepth);
  // Serial.println("start button: " + String(!digitalRead(startButtonPin)));
  // Serial.println("reset button: " + String(!digitalRead(resetButtonPin)));
}

float readDistance() {
  digitalWrite(trigPin, HIGH);
  digitalWrite(trigPin, LOW);
  return mapIntFloat(pulseIn(echoPin, HIGH), 117, 23527, 2.0, 400.0);
}

float mapIntFloat(int x, int in_min, int in_max, float out_min, float out_max) {
    return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}