#include <LiquidCrystal.h>

// Smart Water Tank Management System
// STM32 Nucleo-C031C6

const int TRIG_PIN = 2;
const int ECHO_PIN = 3;
const int PUMP_LED = 4;

// LCD pins: RS, E, D4, D5, D6, D7
LiquidCrystal lcd(12, 11, 10, 9, 8, 7);

// Distance from sensor to water surface
const float EMPTY_DISTANCE = 100.0; // Tank empty
const float FULL_DISTANCE = 20.0;   // Tank full

bool pumpOn = false;

// Update LCD with water level and pump status
void showOnLCD(float waterLevel) {
  int level = (int)(waterLevel + 0.5);

  // First row: water level
  lcd.setCursor(0, 0);
  lcd.print("Water: ");
  lcd.print(level);
  lcd.print("%    ");

  // Second row: pump state and level bar
  lcd.setCursor(0, 1);

  if (pumpOn) {
    lcd.print("ON  [");
  } else {
    lcd.print("OFF [");
  }

  // Eight blocks represent the water level
  int filledBlocks = (int)((waterLevel * 8.0 / 100.0) + 0.5);

  for (int i = 0; i < 8; i++) {
    if (i < filledBlocks) {
      lcd.write((uint8_t)255); // Filled block
    } else {
      lcd.print(" ");
    }
  }

  lcd.print("]  ");
}

void setup() {
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(PUMP_LED, OUTPUT);

  digitalWrite(TRIG_PIN, LOW);
  digitalWrite(PUMP_LED, LOW);

  Serial.begin(115200);

  lcd.begin(16, 2);
  lcd.setCursor(0, 0);
  lcd.print("  SMART WATER");
  lcd.setCursor(0, 1);
  lcd.print("  TANK SYSTEM");

  Serial.println("Smart Water Tank Management System");
  Serial.println("----------------------------------");

  delay(2000);
  lcd.clear();
}

void loop() {
  // Send ultrasonic pulse
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);

  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);

  digitalWrite(TRIG_PIN, LOW);

  // Read echo with timeout
  unsigned long duration = pulseIn(ECHO_PIN, HIGH, 30000);

  if (duration == 0) {
    // Stop the pump if the sensor gives no reading
    pumpOn = false;
    digitalWrite(PUMP_LED, LOW);

    lcd.setCursor(0, 0);
    lcd.print("Sensor error    ");
    lcd.setCursor(0, 1);
    lcd.print("Pump: OFF       ");

    Serial.println("Sensor reading unavailable. Pump OFF.");

    delay(1000);
    return;
  }

  // Convert echo time into distance in cm
  float distance = duration / 58.0;

  // Convert distance into water-level percentage
  float waterLevel =
    (EMPTY_DISTANCE - distance) * 100.0 /
    (EMPTY_DISTANCE - FULL_DISTANCE);

  if (waterLevel < 0) waterLevel = 0;
  if (waterLevel > 100) waterLevel = 100;

  // Pump control: ON at 20%, OFF at 80%
  if (waterLevel <= 20) {
    pumpOn = true;
  } else if (waterLevel >= 80) {
    pumpOn = false;
  }

  digitalWrite(PUMP_LED, pumpOn ? HIGH : LOW);

  // Update the LCD
  showOnLCD(waterLevel);

  // Keep the existing Serial Monitor readings
  Serial.print("Distance: ");
  Serial.print(distance, 1);
  Serial.print(" cm  |  Water level: ");
  Serial.print(waterLevel, 0);
  Serial.print("%  |  Pump: ");
  Serial.println(pumpOn ? "ON" : "OFF");

  delay(1000);
}