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

#define I2C_ADDR 0x27
#define LCD_COLUMNS 16
#define LCD_LINES 2

RTC_DS1307 rtc;
DHT dht(2, DHT22);
LiquidCrystal_I2C lcd(I2C_ADDR, LCD_COLUMNS, LCD_LINES);

char daysOfTheWeek[7][3] = {"SUN", "MON", "THU", "WED", "THU", "FRI", "SAT"};
unsigned int displayMode = 1;
unsigned long startTime = 0;
unsigned int switchPin = 4;
unsigned int prevState = 1;

void displayDateTime() {
  DateTime now = rtc.now();

  String d1 = "Date: " + String(now.year() + 543) + "-" + String(now.month()) + "-" + String(now.day());
  String d2 = " (" + String(daysOfTheWeek[now.dayOfTheWeek()]) + ")";

  String hh = String(now.hour());
  String mm = String(now.minute());
  String ss = String(now.second());

  lcd.setCursor(0, 0);
  lcd.print(d1);

  lcd.setCursor(0, 1);
  lcd.print("Time: " + hh + ":" + mm + ":" + ss);
}

void displayHumidity() {
  int t = dht.readTemperature();
  int h = dht.readHumidity();

  String message1 = "Temp: ";
  message1.concat(t);
  String message2 = "Humidity: ";
  message2.concat(h);

  lcd.setCursor(0, 0);
  lcd.print(message1 + "C       ");

  lcd.setCursor(0, 1);
  lcd.print(message2 + "%       ");
}

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

  if (! rtc.begin()) {
    Serial.println("RTC not found");
    Serial.flush();
    abort();
  }

  dht.begin();

  lcd.begin(LCD_COLUMNS, LCD_LINES);
  lcd.backlight();
}

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

  if (currentTime - startTime > 5000) {
    startTime = currentTime;

    if (displayMode == 1) {
      displayMode = 2;
    } else {
      displayMode = 1;
    }
  }

  if (displayMode == 1) {
    displayDateTime();
  } else {
    displayHumidity();
  }
}