#include <DallasTemperature.h>
#include <OneWire.h>

// Pin definitions
#define ONE_WIRE_BUS 2  // DS18B20 data pin
#define HEATER_PIN 3    // Heater (simulated by LED)
#define INDICATOR_LED 4 // Indicator LED for visual feedback

// Temperature thresholds
#define TARGET_TEMP 25.0  // Target temperature in Celsius
#define HYSTERESIS 1.0    // Hysteresis to prevent rapid switching
#define OVERHEAT_TEMP 35.0 // Overheat threshold

// State enumeration
enum State { IDLE, HEATING, STABILIZING, TARGET_REACHED, OVERHEAT };
State currentState = IDLE;

// Setup OneWire and DallasTemperature libraries
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);

void setup() {
  // Initialize serial communication
  Serial.begin(9600);
  
  // Initialize pins
  pinMode(HEATER_PIN, OUTPUT);
  pinMode(INDICATOR_LED, OUTPUT);
  digitalWrite(HEATER_PIN, LOW); // Heater off initially
  digitalWrite(INDICATOR_LED, LOW); // Indicator off
  
  // Initialize temperature sensor
  sensors.begin();
}

void loop() {
  // Read temperature
  sensors.requestTemperatures();
  float temp = sensors.getTempCByIndex(0);
  
  // Handle invalid temperature readings
  if (temp == DEVICE_DISCONNECTED_C) {
    Serial.println("Error: Temperature sensor disconnected");
    return;
  }

  // State machine logic
  switch (currentState) {
    case IDLE:
      if (temp < TARGET_TEMP - HYSTERESIS) {
        currentState = HEATING;
        digitalWrite(HEATER_PIN, HIGH);
        digitalWrite(INDICATOR_LED, HIGH); // Turn on indicator
      }
      break;

    case HEATING:
      if (temp >= TARGET_TEMP) {
        currentState = STABILIZING;
      } else if (temp >= OVERHEAT_TEMP) {
        currentState = OVERHEAT;
        digitalWrite(HEATER_PIN, LOW);
        digitalWrite(INDICATOR_LED, LOW);
      }
      break;

    case STABILIZING:
      if (temp >= TARGET_TEMP + HYSTERESIS) {
        digitalWrite(HEATER_PIN, LOW);
        digitalWrite(INDICATOR_LED, LOW);
        currentState = TARGET_REACHED;
      } else if (temp < TARGET_TEMP - HYSTERESIS) {
        currentState = HEATING;
        digitalWrite(HEATER_PIN, HIGH);
        digitalWrite(INDICATOR_LED, HIGH);
      } else if (temp >= OVERHEAT_TEMP) {
        currentState = OVERHEAT;
        digitalWrite(HEATER_PIN, LOW);
        digitalWrite(INDICATOR_LED, LOW);
      }
      break;

    case TARGET_REACHED:
      if (temp < TARGET_TEMP - HYSTERESIS) {
        currentState = HEATING;
        digitalWrite(HEATER_PIN, HIGH);
        digitalWrite(INDICATOR_LED, HIGH);
      } else if (temp >= OVERHEAT_TEMP) {
        currentState = OVERHEAT;
        digitalWrite(HEATER_PIN, LOW);
        digitalWrite(INDICATOR_LED, LOW);
      }
      break;

    case OVERHEAT:
      if (temp < OVERHEAT_TEMP - HYSTERESIS) {
        currentState = STABILIZING;
      }
      break;
  }

  // Log temperature and state
  Serial.print("Temperature: ");
  Serial.print(temp);
  Serial.print(" C, State: ");
  switch (currentState) {
    case IDLE: Serial.println("IDLE"); break;
    case HEATING: Serial.println("HEATING"); break;
    case STABILIZING: Serial.println("STABILIZING"); break;
    case TARGET_REACHED: Serial.println("TARGET_REACHED"); break;
    case OVERHEAT: Serial.println("OVERHEAT"); break;
  }

  // Delay for readability
  delay(1000);
}