#include <DHT.h>

#define DHTPIN 2        // Pin where DHT22 is connected
#define DHTTYPE DHT22   // DHT22 sensor type
#define HEATER_PIN 3    // Pin for heater (LED simulation)
#define BUZZER_PIN 4    // Pin for buzzer

DHT dht(DHTPIN, DHTTYPE);

// Define state machine states
enum State {
  IDLE,
  HEATING,
  STABILIZING,
  TARGET_REACHED,
  OVERHEAT
};

State currentState = IDLE;  // Initial state
float targetTemp = 23.0;    // Target temperature in Celsius
float hysteresis = 0.5;     // Hysteresis to prevent rapid switching
float overheatTemp = 40.0;  // Overheat threshold temperature

void setup() {
  Serial.begin(9600);  // Start serial communication
  dht.begin();         // Initialize DHT22 sensor
  pinMode(HEATER_PIN, OUTPUT);  // Set heater pin (LED) as output
  pinMode(BUZZER_PIN, OUTPUT);  // Set buzzer pin as output
}

void loop() {
  float temp = dht.readTemperature();  // Read temperature from DHT22
  if (isnan(temp)) {
    Serial.println("Failed to read temperature");
    return;
  }

  updateState(temp);  // Update state based on temperature
  logStatus(temp);    // Log status and temperature to Serial

  delay(4000);        // Delay between temperature checks
}

void updateState(float temp) {
  switch (currentState) {
    case IDLE:
      if (temp < targetTemp - hysteresis) {
        currentState = HEATING;
      }
      break;

    case HEATING:
      if (temp >= targetTemp - hysteresis) {
        currentState = STABILIZING;
      }
      break;

    case STABILIZING:
      if (temp >= targetTemp) {
        currentState = TARGET_REACHED;
      }
      break;

    case TARGET_REACHED:
      if (temp > overheatTemp) {
        currentState = OVERHEAT;
      } else if (temp < targetTemp - hysteresis) {
        currentState = HEATING;
      }
      break;

    case OVERHEAT:
      if (temp < targetTemp) {
        currentState = HEATING;
      }
      break;
  }

  // Control heater (LED) and buzzer based on state
  if (currentState == HEATING || currentState == STABILIZING) {
    digitalWrite(HEATER_PIN, HIGH);  // Turn heater ON (LED simulation)
    digitalWrite(BUZZER_PIN, LOW);   // Turn buzzer OFF
  } else {
    digitalWrite(HEATER_PIN, LOW);   // Turn heater OFF
    if (currentState == OVERHEAT) {
      digitalWrite(BUZZER_PIN, HIGH); // Turn buzzer ON for overheat
    } else {
      digitalWrite(BUZZER_PIN, LOW);  // Turn buzzer OFF
    }
  }
}

void logStatus(float temp) {
  Serial.print("[Temp: ");
  Serial.print(temp);
  Serial.print("°C] State: ");

  switch (currentState) {
    case IDLE: Serial.print("IDLE"); break;
    case HEATING: Serial.print("HEATING"); break;
    case STABILIZING: Serial.print("STABILIZING"); break;
    case TARGET_REACHED: Serial.print("TARGET_REACHED"); break;
    case OVERHEAT: Serial.print("OVERHEAT"); break;
  }

  Serial.print(" | Heater: ");
  Serial.println(digitalRead(HEATER_PIN) ? "ON" : "OFF");
}