//initializes the libraries that are required
#include "RTClib.h"
#include <Adafruit_SSD1306.h>
#include <Adafruit_GFX.h>

//the screen dimensions are specified
#define OLED_WIDTH 128
#define OLED_HEIGHT 64
#define OLED_ADDR   0x3C

//appropriate variables are defined below
char userChoiceMem = '1';
char userChoice;
byte clockCentreX = 63;
byte clockCentreY = 31;
int hour, second, minute;
int x;
int y;
int x1;
int y1;

//stopwatch variables
int timerState = 0; // 0 = clock, 1 = timer, 2 = stopwatch running
String timeCount;
int timeStart;
int timeCurrent;
int secondRunning;

//objects are initialized so that functions from adafruit and RTC can be obtained
Adafruit_SSD1306 display(OLED_WIDTH, OLED_HEIGHT);
RTC_DS1307 rtc;
DateTime currentTime;

void setup() {
  Serial.begin(9600);

  pinMode(10, INPUT_PULLUP);
  //check rtc connection
  if (! rtc.begin()) {
    Serial.println("Couldn't find RTC");
    Serial.flush();
    abort();
  }
  //display is connected and started
  display.begin(SSD1306_SWITCHCAPVCC, OLED_ADDR);
  display.clearDisplay();
  display.display();

  //user prompt is displayed
  Serial.println("Press 1: Digital Clock");
  Serial.println("Press 2: Analog Clock");

}

void loop() {
  //user choice is read from the serial monitor
  userChoice = Serial.read();

  //if the userchoice is 1 (digital time), it stores into the user choice memory, this applies for analog clock(2)
  if (userChoice == '1')
  {
    //timer state is set to 0 
    timerState = 0;
    userChoiceMem = '1';
  }
  else if (userChoice == '2')
  {
    //timer state is set to 0
    timerState = 0;
    userChoiceMem = '2';
  }
  //depending on the userchoice, digital clock and analog clock are displayed on the screen
  if (userChoiceMem == '1')
  {
    //clears the display
    display.clearDisplay();
    //current time is obtained from the RTC
    currentTime = rtc.now();

    //heading for digital time is printed
    display.setTextSize(1);
    display.setTextColor(WHITE);
    display.setCursor(0, 0);
    display.print("Digital time: ");

    //position for the digital time is set
    display.setTextSize(2);
    display.setTextColor(WHITE);
    display.setCursor(15, 32);
    String hour = String(currentTime.hour(), DEC);
    String minute = String(currentTime.minute(), DEC);
    String second = String(currentTime.second(), DEC);
    String timeDisplay = hour + ":" + minute + ":" + second;
    display.print(timeDisplay);
    display.display();
    delay(1000);
  }
  if (userChoiceMem == '2')
  {
    //current time is obtained from RTC
    currentTime = rtc.now();
    //hour, minute and second is obtained individually
    hour = currentTime.hour();
    minute = currentTime.minute();
    second = currentTime.second();

    //clears the display
    display.clearDisplay();
    //the border of the clock is drawn on the display screen
    display.drawCircle(63, 31, 31, WHITE);
    //functions are called to draw second, minute and hour hand
    drawSecond(second);
    drawMinute(minute);
    drawHour(hour, minute);
    //the display screen is updated
    display.display();
    //given a delay of 1 second
    delay(1000);
  }
  //timer state validation is occured to change the state
  if (timerState == 1) {
    timer(timeCount);
  } else if (timerState == 2) {
    DateTime now = rtc.now();
    //converting hour, minute, second to string
    String strHourStart = String(now.hour(), DEC);
    String strMinuteStart = String(now.minute(), DEC);
    String strSecondStart = String(now.second(), DEC);

    //converting the string start hour to integer
    int hourStart = strHourStart.toInt();

    //running function is called 
    timeCount = running(timeStart);
  }

//when the button is pressed - theres few delays to check if the button is held and not just pressed
  if (digitalRead(10) == LOW) {
    userChoiceMem = 0;
    delay(200);
    if (digitalRead(10) == LOW) {
      delay(500);
      //when timer state = 0, it prints 00:00:00
      if (timerState == 0) {
        timerState = 1;
        timeCount = "00:00:00";
        //if the timer state = 1 or 2, reset it to 0 so it loops through the 3 states (0,1,2)
      } else if (timerState == 1 || timerState == 2) {
        timerState = 0;
      }
    }
    //after a short delay, if the timer state = 1, change it to 2 and start the timer and display it on the OLED
    delay(500);
    if (timerState == 1) {
      timerState = 2;

      DateTime now = rtc.now();

      String strHourStart = String(now.hour(), DEC);
      String strMinuteStart = String(now.minute(), DEC);
      String strSecondStart = String(now.second(), DEC);

      int hourStart = strHourStart.toInt();
      int minuteStart = strMinuteStart.toInt();
      int secondStart = strSecondStart.toInt();

      //setting start time is set 
      timeStart = ((hourStart * 60) + minuteStart) * 60 + secondStart;

      String timeDisplay = strHourStart + ":" + strHourStart + ":" + strHourStart;
      //when the timer state = 2, go back to 1 or 0 and if 0 depending on the user Choice print digital/analog clock
    } else if (timerState == 2) {
      timerState = 1;
    } else {
      timerState = 0;
      if (userChoiceMem == '1') {
        display.clearDisplay();
        currentTime = rtc.now();

        display.setTextSize(1);
        display.setTextColor(WHITE);
        display.setCursor(0, 0);
        display.print("Digital time: ");

        display.setTextSize(2);
        display.setTextColor(WHITE);
        display.setCursor(15, 32);
        String hour = String(currentTime.hour(), DEC);
        String minute = String(currentTime.minute(), DEC);
        String second = String(currentTime.second(), DEC);
        String timeDisplay = hour + ":" + minute + ":" + second;
        display.print(timeDisplay);
        display.display();
        delay(1000);
      }
      else if (userChoiceMem == '2') {
        currentTime = rtc.now();
        hour = currentTime.hour();
        minute = currentTime.minute();
        second = currentTime.second();

        display.clearDisplay();
        display.drawCircle(63, 31, 31, WHITE);
        drawSecond(second);
        drawMinute(minute);
        drawHour(hour, minute);
        display.display();
        delay(1000);
      }
    }
  }
}

//function that draws the minute hand with the argument of minutes
void drawMinute(int minute)
{
  //the formula for x and y position of the minute hand is given below using trig and centre positions of initial x and inital y
  y = (24*cos(PI-(2*PI)/60*minute)) + clockCentreY;
  x = (24*sin(PI-(2*PI)/60*minute)) + clockCentreX;
  display.drawLine(clockCentreX,clockCentreY,x,y,WHITE);
}

//function that draws the hour hand with the argument of hour and minutes
void drawHour(int hour, int minute)
{
  //the formula for x and y position of the hour hand is given below using trig and centre positions of initial x and inital y
  y = (18*cos(PI-(2*PI)/12*hour-(2*PI)/720*minute))+clockCentreY;
  x =(18*sin(PI-(2*PI)/12*hour-(2*PI)/720*minute))+clockCentreX;
  //the hour hand is made a bit thicker to display that its hour hand
  y1=(18*cos(PI-(2*PI)/12*hour-(2*PI)/720*minute))+clockCentreY;
  x1=(18*sin(PI-(2*PI)/12*hour-(2*PI)/720*minute))+clockCentreX;
  display.drawLine(clockCentreX,clockCentreY,x,y,WHITE);
  display.drawLine(clockCentreX+1,clockCentreY+1,x1,y1,WHITE);
}

//function that draws the second hand with the argument of seconds
void drawSecond(int second)
{
  //the formula for x and y position of the second hand (which is a circle) is given below using trig and centre positions of initial x and inital y
  y= (24*cos(PI-(2*PI)/60*second))+clockCentreY;
  x =(24*sin(PI-(2*PI)/60*second))+clockCentreX;
  display.drawCircle(x, y, 2, WHITE);
}

//function for timer to print the 00:00:00
void timer (String timerValue) {
  display.clearDisplay();

  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.setCursor(15, 25);

  display.print(timerValue);
  display.display();
}

//function that starts the stopwatch and formats it accordingly
String running (int timeStart) {

  DateTime now = rtc.now();
  //converting hour, minute, second to string 
  String strHourCurrent = String(now.hour(), DEC);
  String strMinuteCurrent = String(now.minute(), DEC);
  String strSecondCurrent = String(now.second(), DEC);

  //getting the current time in hour, minute and second
  int hourCurrent = strHourCurrent.toInt();
  int minuteCurrent = strMinuteCurrent.toInt();
  int secondCurrent = strSecondCurrent.toInt();

  timeCurrent = ((hourCurrent * 60) + minuteCurrent) * 60 + secondCurrent;
  secondRunning = timeCurrent - timeStart;

  //converting integer time to appropriate parameter as minutes cant go above 59 etc.
  int intMinute = secondRunning / 60;
  int intSecond = secondRunning - intMinute * 60;
  int intHour = intMinute / 60;
  intMinute = intMinute - intHour * 60;

  String hour = String(intHour);

  if (hour == "0" || hour == "1" || hour == "2" || hour == "3" || hour == "4" || hour == "5" || hour == "6" || hour == "7" || hour == "8" || hour == "9") {
    hour = "0" + hour;
  }
  String minute = String(intMinute);
  if (minute == "0" || minute == "1" || minute == "2" || minute == "3" || minute == "4" || minute == "5" || minute == "6" || minute == "7" || minute == "8" || minute == "9") {
    minute = "0" + minute;
  }
  String second = String(intSecond);
  if (second == "0" || second == "1" || second == "2" || second == "3" || second == "4" || second == "5" || second == "6" || second == "7" || second == "8" || second == "9" ) {
    second = "0" + second;
  }

  String timerValue = hour + ":" + minute + ":" + second;

  //prints the time and updates the stopwatch
  display.clearDisplay();

  display.setTextSize(2);
  display.setTextColor(WHITE);
  display.setCursor(15, 25);

  display.print(timerValue);
  display.display();
  return (timerValue);
}