#include "DHT.h"
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <Stepper.h>

// Pins
#define DHTPIN 2
#define DHTTYPE DHT22
#define POT_PIN A0

// Stepper Motor Pins (4-wire connection)
const int stepsPerRevolution = 200;
Stepper myStepper(stepsPerRevolution, 8, 9, 10, 11);

// Constants
#define TEMP_LOW 25
#define TEMP_HIGH 30
#define MANUAL_THRESHOLD 15 // Change in pot value to trigger manual mode

// Objects
DHT dht(DHTPIN, DHTTYPE);
LiquidCrystal_I2C lcd(0x27, 16, 2);

// States
float temperature = 0;
int motorRPM = 0;
bool isManualMode = false;
int lastPotValue = 0;

// Timing (Soft Real-Time)
unsigned long lastSensorRead = 0;
const unsigned long sensorInterval = 2000; // Read DHT every 2s

void setup() {
  Serial.begin(9600);
  dht.begin();
  lcd.init();
  lcd.backlight();
  
  pinMode(POT_PIN, INPUT);

  lcd.setCursor(0, 0);
  lcd.print("Fan Control Sys");
  lcd.setCursor(0, 1);
  lcd.print("Initializing...");
  delay(2000);
  lcd.clear();
}

void loop() {
  unsigned long currentMillis = millis();

  // 1. Read Potentiometer (Manual Override Detection)
  int currentPotValue = analogRead(POT_PIN);
  if (abs(currentPotValue - lastPotValue) > MANUAL_THRESHOLD) {
    isManualMode = true;
  }
  lastPotValue = currentPotValue;

  // 2. Periodic Sensor Reading (Automatic Mode Logic)
  if (currentMillis - lastSensorRead >= sensorInterval) {
    lastSensorRead = currentMillis;
    float tempRead = dht.readTemperature();
    
    if (!isnan(tempRead)) {
      temperature = tempRead;
    } else {
      Serial.println("Sensor Error");
    }

    // Auto Logic (only updates speed if not in manual override)
    if (!isManualMode) {
      if (temperature < TEMP_LOW) {
        motorRPM = 0;
      } else if (temperature >= TEMP_LOW && temperature < TEMP_HIGH) {
        motorRPM = 30; // Medium RPM
      } else {
        motorRPM = 100; // High RPM
      }
    }
  }

  // 3. Manual Speed Control
  if (isManualMode) {
    motorRPM = map(currentPotValue, 0, 1023, 0, 100);
  }

  // 4. Actuator Control (Stepper)
  if (motorRPM > 0) {
    myStepper.setSpeed(motorRPM);
    myStepper.step(stepsPerRevolution / 10); // Step a small fraction each loop iteration
  }

  // 5. Update Display
  updateDisplay();
}

void updateDisplay() {
  static unsigned long lastDisplayUpdate = 0;
  if (millis() - lastDisplayUpdate < 500) return; // Update LCD every 500ms
  lastDisplayUpdate = millis();

  lcd.setCursor(0, 0);
  lcd.print("T:");
  lcd.print(temperature, 1);
  lcd.print("C ");
  
  lcd.setCursor(9, 0);
  lcd.print(isManualMode ? "MOD:MAN" : "MOD:AUT");

  lcd.setCursor(0, 1);
  lcd.print("Spd: ");
  lcd.print(motorRPM);
  lcd.print(" RPM");
}