#include <stdio.h>
#include <stdlib.h>
#include "RTClib.h"

RTC_DS1307 rtc;

const int latchPin = 11; //Pin connected to ST_CP of 74HC595
const int clockPin = 13; //Pin connected to SH_CP of 74HC595
const int dataPin = 12; //Pin connected to DS of 74HC595
const int btnDay = A3;
const int btnMonth = A2;
const int btnYear = A1;
const int btnSet = A0;
const int num_0 = 0b00111111;
const int num_1 = 0b00000110;
const int num_2 = 0b01011011;
const int num_3 = 0b01001111;
const int num_4 = 0b01100110;
const int num_5 = 0b01101101;
const int num_6 = 0b01111101;
const int num_7 = 0b00000111;
const int num_8 = 0b01111111;
const int num_9 = 0b01101111;
const int off = 0b00000000;
const int digit[11] = {num_0, num_1, num_2, num_3, num_4, num_5, num_6, num_7, num_8, num_9, off};

DateTime goalDate = DateTime(2024, 11, 3, 18, 9, 0);
unsigned long previousMillis = 0;
const long updateInterval = 1000;
const unsigned long waitBtnTime = 10000;

void formatDataWithLeadingZero(int days, int hours, int minutes, int seconds, int digDays[], int digHours[], int digMinutes[], int digSeconds[]) {
  for (int i = 3-1; i >= 0; i--) {
    digDays[i] = days % 10;
    days /= 10;
  }
  for (int i = 2-1; i >= 0; i--) {
    digHours[i] = hours % 10;
    hours /= 10;
    digMinutes[i] = minutes % 10;
    minutes /= 10;
    digSeconds[i] = seconds % 10;
    seconds /= 10;
  }
}

DateTime setGoalDate(int digDays[], int digHours[], int digMinutes[], int digSeconds[]) {
  int setDay = 0;
  int setMonth = 0;
  int setYear = 20;

  formatDataWithLeadingZero(0, 0, 0, 0, digDays, digHours, digMinutes, digSeconds);
  lightDigits(digDays, digHours, digMinutes, digSeconds);
  unsigned long startTime = millis();
  while (millis() - startTime <= waitBtnTime) {
    // set day
    if (digitalRead(btnDay) == LOW) {
      delay(50);
      if (digitalRead(btnDay) == LOW) {
        setDay++;
        if (setDay > 31) {
          setDay = 0;
        }
        formatDataWithLeadingZero(0, setDay, 0, 0, digDays, digHours, digMinutes, digSeconds);
        lightDigits(digDays, digHours, digMinutes, digSeconds);
        startTime = millis();
      }
    }
    // set month
    if (digitalRead(btnMonth) == LOW) {
      delay(50);
      if (digitalRead(btnMonth) == LOW) {
        setMonth++;
        if (setMonth > 12) {
          setMonth = 0;
        }
        formatDataWithLeadingZero(0, setDay, setMonth, 0, digDays, digHours, digMinutes, digSeconds);
        lightDigits(digDays, digHours, digMinutes, digSeconds);
        startTime = millis();
      }
    }
    // set year
    if (digitalRead(btnYear) == LOW) {
      delay(50);
      if (digitalRead(btnYear) == LOW) {
        setYear++;
        formatDataWithLeadingZero(0, setDay, setMonth, setYear, digDays, digHours, digMinutes, digSeconds);
        lightDigits(digDays, digHours, digMinutes, digSeconds);
        startTime = millis();
      }
    }

    if (digitalRead(btnSet) == LOW) {
      delay(50);
      if (digitalRead(btnSet) == LOW) {
        setDay = 0;
        setMonth = 0;
        setYear = 0;
        formatDataWithLeadingZero(0, setDay, setMonth, setYear, digDays, digHours, digMinutes, digSeconds);
        lightDigits(digDays, digHours, digMinutes, digSeconds);
        startTime = millis();
      }
    }
  }
  if (setDay != 0 && setMonth != 0 && setYear != 20) {
    return DateTime(2000+setYear, setMonth, setDay, 13, 0, 0);
  }
}

void setup() {
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  pinMode(btnDay, INPUT_PULLUP);
  pinMode(btnMonth, INPUT_PULLUP);
  pinMode(btnYear, INPUT_PULLUP);
  pinMode(btnSet, INPUT_PULLUP);

  rtc.begin();
}

void loop(){
  unsigned long currentMillis = millis();
  DateTime now = rtc.now();
  int digDays[3];
  int digHours[2];
  int digMinutes[2];
  int digSeconds[2];

  if(digitalRead(btnSet) == LOW) {
    delay(50);
    if (digitalRead(btnSet) == LOW) {
      goalDate = setGoalDate(digDays, digHours, digMinutes, digSeconds);
    }
  }
  // Check if updateInterval has elapsed since previousMillis
  if (currentMillis - previousMillis >= updateInterval) {
    previousMillis = currentMillis;
    TimeSpan remainingTime = goalDate - now;
    int days;
    int hours;
    int minutes;
    int seconds;

    if (remainingTime.totalseconds() <= 0) {
      // Goal time!
      days = 0;
      hours = 0;
      minutes = 0;
      seconds = 0;
    } else {
      days = remainingTime.days();
      hours = remainingTime.hours();
      minutes = remainingTime.minutes();
      seconds = remainingTime.seconds();
    }

    formatDataWithLeadingZero(days, hours, minutes, seconds, digDays, digHours, digMinutes, digSeconds);

    lightDigits(digDays, digHours, digMinutes, digSeconds);
  }
}

void lightDigits(int days[3], int hours[2], int minutes[2], int seconds[2]) {
  digitalWrite(latchPin, LOW);
  
  // display days DDD
  shiftOut(dataPin, clockPin, MSBFIRST, digit[days[0]]);
  shiftOut(dataPin, clockPin, MSBFIRST, digit[days[1]]);
  shiftOut(dataPin, clockPin, MSBFIRST, digit[days[2]]);

  // display hours HH
  shiftOut(dataPin, clockPin, MSBFIRST, digit[hours[0]]);
  shiftOut(dataPin, clockPin, MSBFIRST, digit[hours[1]]);

  // display minutes MM
  shiftOut(dataPin, clockPin, MSBFIRST, digit[minutes[0]]);
  shiftOut(dataPin, clockPin, MSBFIRST, digit[minutes[1]]);

  // display seconds SS
  shiftOut(dataPin, clockPin, MSBFIRST, digit[seconds[0]]);
  shiftOut(dataPin, clockPin, MSBFIRST, digit[seconds[1]]);
  digitalWrite(latchPin, HIGH);
}