/* Medicine Temperature Control - ESP32 + DHT + LCD + SD + RTC
   Updated 2025-11-07
   Features:
   - Fully offline (no Wi-Fi/Blynk)
   - DHT, LCD, SD logging, control every 2 seconds
   - Relays active HIGH
   - Continuous buzzer while fan/heater ON
   - Professional SD log format using "|"
*/

#define DHTPIN 4
#define DHTTYPE DHT22   // or DHT11
#define RELAY_FAN 16
#define RELAY_HEATER 17
#define GREEN_LED 26
#define RED_LED 27
#define BUZZER 23
#define SD_CS 5

// Relays are active HIGH
#define RELAY_ACTIVE_HIGH true
#define LCD_I2C_ADDR 0x27
#define UPDATE_INTERVAL_MS 2000UL  // 2 seconds

#include <DHT.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <SD.h>
#include <RTClib.h>

DHT dht(DHTPIN, DHTTYPE);
LiquidCrystal_I2C lcd(LCD_I2C_ADDR, 16, 2);
RTC_DS3231 rtc;

float lastTempC = NAN;
float lastHum = NAN;

bool fanOn = false;
bool heaterOn = false;

unsigned long lastUpdate = 0;

void setup() {
  Serial.begin(115200);
  delay(200);

  pinMode(RELAY_FAN, OUTPUT);
  pinMode(RELAY_HEATER, OUTPUT);
  pinMode(GREEN_LED, OUTPUT);
  pinMode(RED_LED, OUTPUT);
  pinMode(BUZZER, OUTPUT);

  // Initial states
  digitalWrite(RELAY_FAN, LOW);
  digitalWrite(RELAY_HEATER, LOW);
  digitalWrite(GREEN_LED, LOW);
  digitalWrite(RED_LED, LOW);
  digitalWrite(BUZZER, LOW);

  Wire.begin();
  lcd.init();
  lcd.backlight();
  dht.begin();

  // --- RTC Setup ---
  if (!rtc.begin()) {
    Serial.println("RTC not found!");
    lcd.setCursor(0, 0);
    lcd.print("RTC not found!");
  } else if (rtc.lostPower()) {
    Serial.println("RTC lost power, setting time...");
    rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
  }

  // --- SD Setup ---
  if (!SD.begin(SD_CS)) {
    Serial.println("SD init failed!");
    lcd.setCursor(0, 1);
    lcd.print("SD init failed!");
  } else {
    Serial.println("SD initialized.");
  }

  lcd.clear();
  lcd.print("System Ready");
  delay(1000);
  lcd.clear();
}

void loop() {
  unsigned long now = millis();
  if (now - lastUpdate >= UPDATE_INTERVAL_MS) {
    lastUpdate = now;
    updateSystem();
  }
}

void updateSystem() {
  // --- Read DHT Sensor ---
  float t = dht.readTemperature();
  if (!isnan(t)) lastTempC = t;

  // --- Control Logic ---
  if (!isnan(lastTempC)) {
    if (lastTempC >= 26.0) {  // too warm
      fanOn = true;
      heaterOn = false;
    } else if (lastTempC <= 25.0) {
      fanOn = false;
    }

    if (lastTempC <= 19.0) {  // too cold
      heaterOn = true;
      fanOn = false;
    } else if (lastTempC >= 20.0) {
      heaterOn = false;
    }

    if (fanOn && heaterOn) heaterOn = false; // safety
  }

  // --- Relay Outputs ---
  digitalWrite(RELAY_FAN, fanOn ? HIGH : LOW);
  digitalWrite(RELAY_HEATER, heaterOn ? HIGH : LOW);

  // --- LEDs & Buzzer ---
  if (!isnan(lastTempC) && lastTempC >= 20 && lastTempC <= 25) {
    digitalWrite(GREEN_LED, HIGH);
  } else {
    digitalWrite(GREEN_LED, LOW);
  }

  if (fanOn || heaterOn) {
    digitalWrite(RED_LED, HIGH);
    digitalWrite(BUZZER, HIGH); // continuous tone
  } else {
    digitalWrite(RED_LED, LOW);
    digitalWrite(BUZZER, LOW);
  }

  // --- LCD Display ---
  lcd.clear();
  lcd.setCursor(0, 0);
  if (!isnan(lastTempC))
    lcd.printf("Temp: %.2f C", lastTempC);
  else
    lcd.print("Temp: --.- C");

  lcd.setCursor(0, 1);
  lcd.printf("Fan:%s Heat:%s", fanOn ? "ON " : "OFF", heaterOn ? "ON" : "OFF");

  // --- Logging (SD + Serial) ---
  DateTime nowTime;
  String timestamp;
  if (rtc.begin()) {
    nowTime = rtc.now();
    timestamp = String(nowTime.year()) + "-" + twoDigits(nowTime.month()) + "-" +
                twoDigits(nowTime.day()) + " " + twoDigits(nowTime.hour()) + ":" +
                twoDigits(nowTime.minute()) + ":" + twoDigits(nowTime.second());
  } else {
    timestamp = String(millis() / 1000) + "s";
  }

  String tempStr = isnan(lastTempC) ? "NaN" : String(lastTempC, 2);
  String fanStr = fanOn ? "FAN ON" : "FAN OFF";
  String heatStr = heaterOn ? "HEATER ON" : "HEATER OFF";

  String logLine = timestamp + " | " + tempStr + "°C | " + fanStr + " | " + heatStr + "\n";

  // Print to Serial
  Serial.print(logLine);

  // --- SD Logging ---
  if (SD.begin(SD_CS)) {
    File logFile = SD.open("/templog.txt", FILE_APPEND);
    if (logFile) {
      logFile.print(logLine);
      logFile.close();
    } else {
      Serial.println("SD write failed!");
    }
  } else {
    Serial.println("SD not ready.");
  }
}

String twoDigits(int v) {
  if (v < 10) return "0" + String(v);
  return String(v);
}