#include <OneWire.h>
#include <DallasTemperature.h>
#include <Ticker.h> // Built-in ESP32/ESP8266 timer library

#define ONE_WIRE_BUS 21
#define HEATER_PIN 2

// Temperature thresholds
const float TARGET_TEMP = 30.0;
const float STABILIZE_MARGIN = 1.0;
const float OVERHEAT_TEMP = 40.0;
const float IDLE_TEMP = 20.0;

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

OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);

volatile bool tempCheckFlag = false; // Set by timer ISR

Ticker tempTimer; // Timer object

const char* stateToStr(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";
  }
}

// Timer ISR runs every second
void IRAM_ATTR onTempTimer() {
  tempCheckFlag = true; // Set flag for main loop
}

void setup() {
  Serial.begin(115200);
  sensors.begin();
  pinMode(HEATER_PIN, OUTPUT);
  digitalWrite(HEATER_PIN, LOW);

  // Start timer interrupt every 1 second
  tempTimer.attach_ms(1000, onTempTimer);
}

void loop() {
  if (tempCheckFlag) {
    tempCheckFlag = false; // Reset flag

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

    if (lastTempC >= OVERHEAT_TEMP) {
    currentState = OVERHEAT;
    digitalWrite(HEATER_PIN, LOW);
} else {
    // State machine logic
    switch (currentState) {
      case IDLE:
        if (lastTempC < IDLE_TEMP) {
          currentState = HEATING;
          digitalWrite(HEATER_PIN, HIGH);
        }
        break;

      case HEATING:
        if (lastTempC >= TARGET_TEMP - STABILIZE_MARGIN) {
          currentState = STABILIZING;
        }
        break;

      case STABILIZING:
        if (lastTempC >= TARGET_TEMP) {
          currentState = TARGET_REACHED;
          digitalWrite(HEATER_PIN, LOW);
        }
        break;

      case TARGET_REACHED:
        if (lastTempC < TARGET_TEMP - STABILIZE_MARGIN) {
          currentState = HEATING;
          digitalWrite(HEATER_PIN, HIGH);
        }
        break;

      case OVERHEAT:
        if (lastTempC < IDLE_TEMP) {
          currentState = HEATING;
          digitalWrite(HEATER_PIN, HIGH);
        }
        break;
    }
}
// Serial log
    Serial.printf("Temp: %.2f°C | State: %s | Heater: %s\n",
                  lastTempC, stateToStr(currentState),
                  digitalRead(HEATER_PIN) ? "ON" : "OFF");
  }
}