#include <U8g2lib.h>
#include <Arduino.h>
#include <RTClib.h>
#include <Wire.h>
// Initialize the OLED display
U8G2_SSD1306_128X64_NONAME_F_HW_I2C u8g2(U8G2_R0, /* reset=*/ U8X8_PIN_NONE);
RTC_DS3231 rtc;

//Constants
char daysOfTheWeek[7][12] = {"Sunday","Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
const int btSet = 8;
const int btUp = 7;
const int btDown = 6;
const int buzzer = 9;

//Variables
int DD,MM,YY,H,M,S;
int btnCount = 0;
unsigned long previousMillis = 0;
unsigned long currentMillis; 
int set;
int up;
int down;
String sDD;
String sMM;
String sYY;
String sH;
String sM;
String sS;
float T;
boolean setupScreen = false;
boolean backlightON = true;

// Declare a variable to hold the number to be displayed
int number = 42;

void setup() {
  u8g2.begin();
  rtc.begin();
  //Serial.begin(57600);
  pinMode(btSet, INPUT_PULLUP);
  pinMode(btUp, INPUT_PULLUP);
  pinMode(btDown, INPUT_PULLUP);
  pinMode(buzzer, OUTPUT);
}

void loop() {
    
  getTime();
  readBtn();
  if (!setupScreen){
    oledPrint();
  }
  else{
    oledSetup();
  }

}

void getTime() {
  if (!setupScreen){
    DateTime now = rtc.now();
    DD = now.day();
    MM = now.month();
    YY = now.year();
    H = now.hour();
    M = now.minute();
    S = now.second();
    T = rtc.getTemperature();
  }
}

void readBtn() {
  set = digitalRead(btSet);
  up = digitalRead(btUp);
  down = digitalRead(btDown);

  if (set==LOW){
    if(btnCount<5){
      btnCount++;
      setupScreen = true;
      if(btnCount==1){
        u8g2.clearBuffer();
        u8g2.setFont(u8g2_font_ncenB08_tr);
        u8g2.setCursor(0, 10);
        u8g2.print("- - - - - - NASTAV - - - - - -");
        u8g2.setCursor(0, 25);
        u8g2.print("- - CAS A DATUM - - ");
        u8g2.sendBuffer();
        delay(1000);
        u8g2.clearBuffer();
        u8g2.sendBuffer();
      }
    }
    else {
      u8g2.clearBuffer();
      rtc.adjust(DateTime(YY, MM, DD, H, M, 0));
      u8g2.setFont(u8g2_font_ncenB08_tr);
      u8g2.setCursor(20, 10);
      u8g2.print(". . . Ukladam . . . .");
      u8g2.sendBuffer();
      delay(2000);
      setupScreen = false;
      btnCount=0;
    }
    delay(250);
  }
  
  
  if (set==LOW || up==LOW || down==LOW) {
    digitalWrite(buzzer, HIGH);
    }  
   else {
   digitalWrite(buzzer, LOW);
   }  

  if (down==LOW && btnCount==0) {
    if (backlightON==true) {
      u8g2.setPowerSave(1);
      backlightON = false;
    }
    else {
      u8g2.setPowerSave(0);
      backlightON = true;
   }
    delay(250);
  }
  
}

void oledPrint() {
  String teplota = "Teplota:  " + String(T);
 
  u8g2.clearBuffer();

  u8g2.setFont(u8g2_font_ncenB08_tr);
  u8g2.setCursor(0, 10);
  u8g2.print(teplota);
  u8g2.setCursor(80, 10);
  u8g2.print("C");

  u8g2.setFont(u8g2_font_ncenB08_tr);
  u8g2.setCursor(00, 25);
  u8g2.print("Datum -");
  u8g2.setCursor(50, 25);
  u8g2.print(DD);
  u8g2.print(" / ");
  u8g2.print(MM);
  u8g2.print(" / ");
  u8g2.print(YY);

  u8g2.setFont(u8g2_font_ncenB08_tr);
  u8g2.setCursor(45 - u8g2.getStrWidth("Cas - "), 40);
  u8g2.print("Cas - ");
  u8g2.setCursor(50, 40);
  u8g2.print(H);
  u8g2.print(" : ");
  u8g2.print(M);
  u8g2.print(" : ");
  u8g2.print(S);
 
  u8g2.sendBuffer();
  delay(500);
}

void oledSetup(){
  u8g2.setFont(u8g2_font_ncenB08_tr);
  u8g2.clearBuffer();
  if (btnCount==1){
    u8g2.setCursor(30, 40);
    u8g2.print(">"); 
    if (up == LOW){
      if (H<23){
        H++;
      }
      else {
        H=0;
      }
      delay(250);
    }
    if (down == LOW){
      if (H>0){
        H--;
      }
      else {
        H=23;
      }
      delay(250);
    }
    
  }
  else if (btnCount==2){
    u8g2.setCursor(55, 40);
    u8g2.print(">"); 
    if (up == LOW){
      if (M<59){
        M++;
      }
      else {
        M=0;
      }
      delay(250);
    }
    if (down == LOW){
      if (M>0){
        M--;
      }
      else {
        M=59;
      }
      delay(250);
    }
  }
  else if (btnCount==3){
    u8g2.setCursor(45, 25);
    u8g2.print(">"); 
    if (up == LOW){
      if (DD<31){
        DD++;
      }
      else {
        DD=1;
      }
      delay(250);
    }
    if (down == LOW){
      if (DD>1){
        DD--;
      }
      else {
        DD=31;
      }
      delay(250);
    }
  }
  else if (btnCount==4){
    u8g2.setCursor(70, 25);
    u8g2.print(">"); 
    if (up == LOW){
      if (MM<12){
        MM++;
      }
      else {
        MM=1;
      }
      delay(250);
    }
    if (down == LOW){
      if (MM>1){
        MM--;
      }
      else {
        MM=12;
      }
      delay(250);
    }
  }
  else if (btnCount==5){
    u8g2.setCursor(90, 25);
    u8g2.print(">"); 
    if (up == LOW){
      if (YY<2999){
        YY++;
      }
      else {
        YY=2000;
      }
      delay(250);
    }
    if (down == LOW){
      if (YY>2000){
        YY--;
      }
      else {
        YY=2999;
      }
      delay(250);
    }
  }
  u8g2.setFont(u8g2_font_ncenB08_tr);
  u8g2.setCursor(0, 25);
  u8g2.print("Datum - ");
  u8g2.setCursor(50, 25);
  u8g2.print(DD);
  u8g2.print(" /");
  u8g2.setCursor(75, 25);
  u8g2.print(MM);
  u8g2.print(" /");
  u8g2.setCursor(100, 25);
  u8g2.print(YY);

  u8g2.setFont(u8g2_font_ncenB08_tr);
  u8g2.setCursor(0, 40);
  u8g2.print("Cas - ");
  u8g2.setCursor(35, 40);
  u8g2.print(H);
  u8g2.setCursor(50, 40);
  u8g2.print(":");
  u8g2.setCursor(65, 40);
  u8g2.print(M);
  u8g2.print(": ");
  u8g2.print(S);
  u8g2.sendBuffer();
  delay(1000);
}