// Setup libraries and variables
#include <U8glib.h>
#include <RTClib.h>

U8GLIB_SSD1306_128X64 u8g;
RTC_DS1307 rtc;

void setup() {
  // Setup serial and check for rtc
  u8g.setFont(u8g_font_7x13);
  Serial.begin(115200);

  if (! rtc.begin()) { 
    Serial.println("Couldn't find RTC"); 
    Serial.flush(); 
    abort(); 
  }
}

void loop() {
  // Get current time and use it as input 
  // to analogClock and digitalClock function
  DateTime now = rtc.now();

  u8g.firstPage();
  do { 
    u8g.setColorIndex(1);
    u8g.drawCircle(30,30,21);

    // Show hour mark for every hour
    for(int i =0; i<12; i++){
      mark(i);
    }
    analogClock(now.second(), now.minute(), now.hour());
    digitalClock(now.second(), now.minute(), now.hour());

  } while ( u8g.nextPage() );
}

// Show hour marks on analog clock
void mark(int h){
  float x1, y1, x2, y2;
  float center = 30;
  float convertToDeg = 0.0175; // 3.141 / 180

  h=h*30;
  h=h+270;

  x1=16*cos(h*convertToDeg);
  y1=16*sin(h*convertToDeg);
  x2=21*cos(h*convertToDeg);
  y2=21*sin(h*convertToDeg);
  
  u8g.drawLine(center+x1, center+y1, center+x2, center+y2);
}

// Show second hand on analog clock
void drawSec(int secs){
  int x1, y1;
  float center = 30;
  float convertToDeg = 0.0175; // 3.141 / 180

  secs=(secs*6) + 270;

  x1=18*cos(secs * convertToDeg);
  y1=18*sin(secs * convertToDeg);

  u8g.drawLine(center, center, center+x1, center+y1);
}

// Show minute hand on analog clock
void drawMin(int mins){
  int x1, y1;
  float center = 30;
  float convertToDeg = 0.0175; // 3.141 / 180

  mins=(mins * 6) + 270;
  
  x1=18*cos(mins * convertToDeg);
  y1=18*sin(mins * convertToDeg);

  u8g.drawLine(center, center, center+x1, center+y1);
}

// Show hour hand on analog clock
void drawHour(int hours, int mins){
  float x1, y1;
  float center = 30;
  float convertToDeg = 0.0175; // 3.141 / 180

  hours=((hours*30)+(mins/2)) + 270;

  x1=10*cos(hours * convertToDeg);
  y1=10*sin(hours * convertToDeg);

  u8g.drawLine(center, center, center+x1, center+y1);
}

// Show current time in digital clock format
void digitalClock(int sec, int minute, int hour){
  char time[10];

  String hours = String(hour);
  String mins = String(minute);
  String secs = String(sec);

  if(hour<10) hours = "0" + hours;
  if(minute<10) mins = "0" + mins;
  if(sec<10) secs = "0" + secs;

  strcpy(time, hours.c_str());
  strcat(time, ":");
  strcat(time, mins.c_str());
  strcat(time, ":");
  strcat(time, secs.c_str());

  u8g.drawStr(60, 30, time);
}

// Putting drawSec, drawMin and drawHour 
// together to show analog clock
void analogClock(int sec, int minute, int hour){
  drawSec(sec);
  drawMin(minute);
  drawHour(hour, minute);
}