#include <Wire.h>
#include <RTClib.h>  // Include the RTClib library

const int clock = 3;  // Clock pin for the 7-segment display
const int data = 2;   // Data pin for the 7-segment display

// 7-segment display digit encoding (0-9)
uint8_t digits[] = { 0x3f, 0x06, 0x5b, 0x4f, 0x66, 0x6d, 0x7d, 0x07, 0x7f, 0x6f };

RTC_DS3231 rtc;  // Create an RTC object for DS3231

void setup() {
  pinMode(clock, OUTPUT);
  pinMode(data, OUTPUT);

  // Start the Serial Monitor for debugging
  Serial.begin(9600);

  // Initialize the RTC
  if (!rtc.begin()) {
    Serial.println("Couldn't find RTC");
    while (1);
  }

  // Check if the RTC lost power
  if (rtc.lostPower()) {
    Serial.println("RTC lost power, setting the time!");
    // Set the RTC to the compile time (this is for the first time setting)
    rtc.adjust(DateTime(F(_DATE), F(TIME_)));
  }

  // Initialize the display
  start();
  writeValue(0x8c);  // Set brightness
  stop();
  clearDisplay();
}

void loop() {
  // Get the current time from the RTC
  DateTime now = rtc.now();

  // Add 36 seconds to the current time
  now = now + TimeSpan(0, 0, 0, 36);  // Add 36 seconds (TimeSpan(hours, minutes, seconds, days))

  // Extract hours, minutes, and seconds
  uint8_t hours = now.hour();
  uint8_t minutes = now.minute();
  uint8_t seconds = now.second();

  // Update display every second
  writeDigits(hours, minutes, seconds);
  
  // Delay for 1 second to simulate real-time updates
  delay(1000);  // Delay for 1 second before the next loop
}

// Write digits to the 7-segment display
void writeDigits(uint8_t hours, uint8_t minutes, uint8_t seconds) {
  uint8_t first = digits[hours / 10];
  uint8_t second = digits[hours % 10] | 0x80;  // Keep colon always on
  uint8_t third = digits[minutes / 10];
  uint8_t fourth = digits[minutes % 10];
  write(first, second, third, fourth);
}

// Clear the display
void clearDisplay() {
  write(0x00, 0x00, 0x00, 0x00);
}

// Write data to the display
void write(uint8_t first, uint8_t second, uint8_t third, uint8_t fourth) {
  start();
  writeValue(0x40);  // Set to auto-increment mode
  stop();
  start();
  writeValue(0xc0);  // Address command
  writeValue(first);
  writeValue(second);
  writeValue(third);
  writeValue(fourth);
  stop();
}

// Send start signal
void start() {
  digitalWrite(clock, HIGH);
  digitalWrite(data, HIGH);
  delayMicroseconds(5);
  digitalWrite(data, LOW);
  digitalWrite(clock, LOW);
  delayMicroseconds(5);
}

// Send stop signal
void stop() {
  digitalWrite(clock, LOW);
  digitalWrite(data, LOW);
  delayMicroseconds(5);
  digitalWrite(clock, HIGH);
  digitalWrite(data, HIGH);
  delayMicroseconds(5);
}

// Write a single byte to the display
bool writeValue(uint8_t value) {
  for (uint8_t i = 0; i < 8; i++) {
    digitalWrite(clock, LOW);
    delayMicroseconds(5);
    digitalWrite(data, (value & (1 << i)) >> i);
    delayMicroseconds(5);
    digitalWrite(clock, HIGH);
    delayMicroseconds(5);
  }
  digitalWrite(clock, LOW);
  delayMicroseconds(5);
  pinMode(data, INPUT);
  digitalWrite(clock, HIGH);
  delayMicroseconds(5);
  bool ack = digitalRead(data) == 0;
  pinMode(data, OUTPUT);
  return ack;
}