#include <LiquidCrystal_I2C.h>

// LCD
LiquidCrystal_I2C lcd(0x27,16,2);

// Ultrasonic sensor
const int trigPin = 5;
const int echoPin = 18;

// TDS potentiometer
const int tdsPin = 34;

// Tank height in cm
const float tankHeight = 400.0;

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

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

  lcd.init();
  lcd.backlight();
  lcd.setCursor(0,0);
  lcd.print("Ground Tank ESP");
  delay(2000);
  lcd.clear();
}

float getWaterLevel() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  long duration = pulseIn(echoPin, HIGH);
  float distance = duration * 0.034 / 2.0; // cm
  float levelPercent = constrain(100 - ((distance / tankHeight) * 100), 0, 100);
  return levelPercent;
}

float getTDS() {
  int val = analogRead(tdsPin);
  return map(val, 0, 4095, 0, 1000); // ppm
}

void loop() {
  float level = getWaterLevel();
  float tds = getTDS();

  // Display on LCD
  lcd.setCursor(0,0);
  lcd.print("Lvl: ");
  lcd.print(level,1);
  lcd.print("%   ");
  lcd.setCursor(0,1);
  lcd.print("TDS: ");
  lcd.print(tds,0);
  lcd.print("ppm  ");

  // Serial output
  Serial.print("Ground Tank Level: ");
  Serial.print(level,1);
  Serial.print("%, TDS: ");
  Serial.println(tds,0);

  delay(2000);
}