#include <OneWire.h>
#include <DallasTemperature.h>
#define ONE_WIRE_BUS 15
#define HEATER_PIN 4
#define BUZZER_PIN 5
#define ALERT_LED_PIN 2     
float targetTemp = 60.0;
float hysteresis = 2.0;
float overheatTemp = 70.0;
float overheatRecovery = 68.0;
enum State {IDLE, HEATING, STABILIZING, TARGET_REACHED, OVERHEAT};
State currentState = IDLE;
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);
String stateToString(State s) {
  switch (s) {
    case IDLE: return "IDLE";
    case HEATING: return "HEATING";
    case STABILIZING: return "STABILIZING";
    case TARGET_REACHED: return "TARGET_REACHED";
    case OVERHEAT: return "OVERHEAT";
    default: return "UNKNOWN";
  }
}

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

  pinMode(HEATER_PIN, OUTPUT);
  pinMode(BUZZER_PIN, OUTPUT);
  pinMode(ALERT_LED_PIN, OUTPUT);

  digitalWrite(HEATER_PIN, LOW);
  noTone(BUZZER_PIN);
  digitalWrite(ALERT_LED_PIN, LOW);
  Serial.println("ESP32 Heater Controller Started");

  sensors.requestTemperatures();
  float tempC = sensors.getTempCByIndex(0);

  if (tempC >= overheatTemp) {
    currentState = OVERHEAT;
  } 
  else if (abs(tempC - targetTemp) <= 0.5 || (tempC > targetTemp && tempC <= targetTemp + 2)) {
    currentState = TARGET_REACHED;
  } 
  else if (tempC > targetTemp + 2 && tempC < overheatTemp) {
    currentState = TARGET_REACHED; 
  } 
  else if (tempC >= targetTemp - 1.5 && tempC < targetTemp - 0.5) {
    currentState = STABILIZING;
  } 
  else if (tempC <= targetTemp - hysteresis) {
    currentState = HEATING;
    digitalWrite(HEATER_PIN, HIGH);
  } 
  else {
    currentState = IDLE;
  }

  Serial.print("Initial Temp: ");
  Serial.print(tempC);
  Serial.print("°C  Starting State: ");
  Serial.println(stateToString(currentState));
}
void loop() {
  sensors.requestTemperatures();
  float tempC = sensors.getTempCByIndex(0);
  if (tempC >= overheatTemp) {
    currentState = OVERHEAT;
  }
  switch (currentState) {

    case IDLE:
      digitalWrite(HEATER_PIN, LOW);
      digitalWrite(ALERT_LED_PIN, LOW);
      if (tempC <= targetTemp - hysteresis) {
        currentState = HEATING;
        digitalWrite(HEATER_PIN, HIGH);
      }
      break;

    case HEATING:
      digitalWrite(HEATER_PIN, HIGH);
      digitalWrite(ALERT_LED_PIN, LOW);

      if (tempC >= targetTemp - 1.5 && tempC < targetTemp - 0.5) {
        currentState = STABILIZING;
        digitalWrite(HEATER_PIN, LOW);
      }
      else if (tempC > targetTemp + 2 && tempC < overheatTemp) {
        currentState = TARGET_REACHED;
        digitalWrite(HEATER_PIN, LOW);
      }
      break;

    case STABILIZING:
      digitalWrite(HEATER_PIN, LOW);
      digitalWrite(ALERT_LED_PIN, LOW);
      if (abs(tempC - targetTemp) <= 0.5 || (tempC > targetTemp && tempC <= targetTemp + 2)) {
        currentState = TARGET_REACHED;
      }
      else if (tempC <= targetTemp - hysteresis) {
        currentState = HEATING;
        digitalWrite(HEATER_PIN, HIGH);
      }
      else if (tempC > targetTemp + 2 && tempC < overheatTemp) {
        currentState = TARGET_REACHED;
      }
      break;

    case TARGET_REACHED:
      digitalWrite(HEATER_PIN, LOW);
      digitalWrite(ALERT_LED_PIN, LOW);
      if (tempC <= targetTemp - hysteresis) {
        currentState = HEATING;
        digitalWrite(HEATER_PIN, HIGH);
      }
      break;

    case OVERHEAT:
      digitalWrite(HEATER_PIN, LOW);
      tone(BUZZER_PIN, 1000);
      digitalWrite(ALERT_LED_PIN, HIGH);
      delay(200);
      digitalWrite(ALERT_LED_PIN, LOW);
      delay(200);

      if (tempC < overheatRecovery) {
        currentState = IDLE;
        noTone(BUZZER_PIN);
      }
      break;
  }

  if (currentState != OVERHEAT) {
    noTone(BUZZER_PIN);
  }
  Serial.print("Temp: ");
  Serial.print(tempC);
  Serial.print("°C  State: ");
  Serial.println(stateToString(currentState));
  if (currentState != OVERHEAT) {
    delay(1000);
  }
}