// =====================================
// PIN DEFINITIONS
// =====================================
#define TRIG_PIN 5
#define ECHO_PIN 18

#define GREEN_LED 14
#define YELLOW_LED 27
#define RED_LED 26

// =====================================
// SCALED PHYSICAL MODEL (SMALL CONTAINER)
// =====================================
const float SENSOR_HEIGHT = 20.0;   // cm (sensor above container bottom)

// Flood thresholds (cm)
const float SAFE_LEVEL = 8.0;
const float DANGER_LEVEL = 14.0;

// =====================================
// STATE VARIABLES (FOR MODELING)
// =====================================
float prevWaterLevel = 0.0;
unsigned long prevTime = 0;

// =====================================
// SETUP
// =====================================
void setup() {
  Serial.begin(115200);

  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);

  pinMode(GREEN_LED, OUTPUT);
  pinMode(YELLOW_LED, OUTPUT);
  pinMode(RED_LED, OUTPUT);

  Serial.println("ESP32 Flood Prediction Simulation Started");
}

// =====================================
// ULTRASONIC DISTANCE FUNCTION
// =====================================
long getDistance() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);

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

  long duration = pulseIn(ECHO_PIN, HIGH, 30000); // 30 ms timeout
  long distance = duration * 0.034 / 2;

  return distance;
}

// =====================================
// MAIN LOOP
// =====================================
void loop() {
  unsigned long currentTime = millis();
  float deltaTime = (currentTime - prevTime) / 1000.0; // seconds

  long distance = getDistance();

  // Convert distance to water level
  float waterLevel = SENSOR_HEIGHT - distance;

  // Clamp to physical limits
  if (waterLevel < 0) waterLevel = 0;
  if (waterLevel > SENSOR_HEIGHT) waterLevel = SENSOR_HEIGHT;

  // ===============================
  // RATE OF RISE (cm/s)
  // ===============================
  float rate = 0.0;
  if (deltaTime > 0) {
    rate = (waterLevel - prevWaterLevel) / deltaTime;
  }

  // ===============================
  // TIME-TO-DANGER PREDICTION
  // ===============================
  float timeToDanger = -1; // invalid by default

  if (rate > 0 && waterLevel < DANGER_LEVEL) {
    timeToDanger = (DANGER_LEVEL - waterLevel) / rate;
  }

  // ===============================
  // SERIAL OUTPUT (SIMULATION VIEW)
  // ===============================
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.print(" cm | Water Level: ");
  Serial.print(waterLevel);
  Serial.print(" cm | Rate: ");
  Serial.print(rate);
  Serial.print(" cm/s | ");

  if (timeToDanger > 0) {
    Serial.print("Time to danger: ");
    Serial.print(timeToDanger);
    Serial.println(" s");
  } else {
    Serial.println("Time to danger: N/A");
  }

  // ===============================
  // LED FLOOD STATUS LOGIC
  // ===============================
  if (waterLevel < SAFE_LEVEL) {
    // SAFE
    digitalWrite(GREEN_LED, HIGH);
    digitalWrite(YELLOW_LED, LOW);
    digitalWrite(RED_LED, LOW);
  }
  else if (waterLevel < DANGER_LEVEL) {
    // WARNING
    digitalWrite(GREEN_LED, LOW);
    digitalWrite(YELLOW_LED, HIGH);
    digitalWrite(RED_LED, LOW);
  }
  else {
    // DANGER
    digitalWrite(GREEN_LED, LOW);
    digitalWrite(YELLOW_LED, LOW);
    digitalWrite(RED_LED, HIGH);
  }

  // ===============================
  // STORE PREVIOUS VALUES
  // ===============================
  prevWaterLevel = waterLevel;
  prevTime = currentTime;

  delay(1000); // 1 second update interval
}