// === Pin Definitions ===
#define TRIG_PIN 23
#define ECHO_PIN 22
#define BUZZER_PIN 2
#define RED_LED 25
#define ORANGE_LED 26
#define GREEN_LED 27

// === Tank height (cm) ===
const float TANK_HEIGHT = 17.0;

// === Distance thresholds (from sensor to water surface) ===
// Note: smaller distance = higher water level
const float TOO_HIGH_MIN = 0.0;   
const float TOO_HIGH_MAX = 5.0;   
const float NORMAL_MIN   = 5.0;  
const float NORMAL_MAX   = 11.0;  
const float TOO_LOW_MIN  = 11.0;  
const float TOO_LOW_MAX  = 17.0;  

// === Variables ===
String lastStatus = "";

// === Measure distance (cm) ===
float measureDistanceCM() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  long duration = pulseIn(ECHO_PIN, HIGH, 40000); // timeout 40ms
  if (duration == 0) return -1; 
  return duration * 0.0343 / 2.0; 
}

// === Beep twice (danger alert) ===
void beepTwice() {
  for (int i = 0; i < 2; i++) {
    digitalWrite(BUZZER_PIN, HIGH);
    delay(150);
    digitalWrite(BUZZER_PIN, LOW);
    delay(150);
  }
}

void setup() {
  Serial.begin(115200);
  Serial.println("💧 WATER LEVEL MONITOR STARTING...");

  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(BUZZER_PIN, OUTPUT);
  pinMode(RED_LED, OUTPUT);
  pinMode(ORANGE_LED, OUTPUT);
  pinMode(GREEN_LED, OUTPUT);

  digitalWrite(RED_LED, LOW);
  digitalWrite(ORANGE_LED, LOW);
  digitalWrite(GREEN_LED, LOW);
  digitalWrite(BUZZER_PIN, LOW);

  delay(1000);
  Serial.println("✅ System Ready.\n");
}

void loop() {
  float distance = measureDistanceCM();

  if (distance < 0) {
    Serial.println("⚠️ STATUS: NO ECHO | DISTANCE: ----");
    digitalWrite(RED_LED, LOW);
    digitalWrite(ORANGE_LED, LOW);
    digitalWrite(GREEN_LED, LOW);
    digitalWrite(BUZZER_PIN, LOW);
    return;
  }

  // Compute actual water height (cm)
  float waterLevel = TANK_HEIGHT - distance;
  if (waterLevel < 0) waterLevel = 0;

  // Display readings on Serial Monitor
  Serial.print("Distance to water: ");
  Serial.print(distance, 1);
  Serial.print(" cm  |  Water Level: ");
  Serial.print(waterLevel, 1);
  Serial.println(" cm");

  // === TOO HIGH ===
  if (distance >= TOO_HIGH_MIN && distance <= TOO_HIGH_MAX) {
    Serial.println("STATUS: TOO HIGH (⚠️ Water Level DANGER - HIGH)");
    digitalWrite(RED_LED, LOW);
    digitalWrite(ORANGE_LED, HIGH);
    digitalWrite(GREEN_LED, LOW);

    if (lastStatus != "HIGH") {
      beepTwice();
      lastStatus = "HIGH";
    }
  }

  // === NORMAL ===
  else if (distance >= NORMAL_MIN && distance <= NORMAL_MAX) {
    Serial.println("STATUS: NORMAL (✅ Water Level SAFE)");
    digitalWrite(RED_LED, LOW);
    digitalWrite(ORANGE_LED, LOW);
    digitalWrite(GREEN_LED, HIGH);
    digitalWrite(BUZZER_PIN, LOW);
    lastStatus = "NORMAL";
  }

  // === TOO LOW ===
  else if (distance >= TOO_LOW_MIN && distance <= TOO_LOW_MAX) {
    Serial.println("STATUS: TOO LOW (⚠️ Water Level DANGER - LOW)");
    digitalWrite(RED_LED, HIGH);
    digitalWrite(ORANGE_LED, LOW);
    digitalWrite(GREEN_LED, LOW);

    if (lastStatus != "LOW") {
      beepTwice();
      lastStatus = "LOW";
    }
  }

  // === OUT OF RANGE ===
  else {
    Serial.println("STATUS: OUT OF RANGE (Check sensor alignment or tank level)");
    digitalWrite(RED_LED, LOW);
    digitalWrite(ORANGE_LED, LOW);
    digitalWrite(GREEN_LED, LOW);
    digitalWrite(BUZZER_PIN, LOW);
    lastStatus = "OUT OF RANGE";
  }

  Serial.println("------------------------------------");
  delay(1000);
}