#include <Wire.h>
#include <RTClib.h>

RTC_DS1307 rtc;

// Shift Register Pins
const uint8_t dataPin = 8;   // D1 (GPIO8)
const uint8_t clockPin = 9;  // D2 (GPIO9)
const uint8_t latchPin = 10;  // D3 (GPIO10)

static uint8_t digits[6];

// Segment patterns (Common Cathode: 1=ON, 0=OFF)
const byte digitPattern[10] = {
  B11111100, // 0 (A-F on, G/DP off)
  B01100000, // 1
  B11011010, // 2
  B11110010, // 3
  B01100110, // 4
  B10110110, // 5
  B10111110, // 6
  B11100000, // 7
  B11111110, // 8
  B11110110  // 9
};


void setup() {
  
  Serial.begin(9600);
  
  // Initialize Shift Register Pins
  pinMode(dataPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(latchPin, OUTPUT);

  // Initialize RTC
  Wire.begin();
  if (!rtc.begin()) {
    while (1); // Halt if RTC not found
  }
  
  if (!rtc.isrunning()) {
    // Set to compile time if RTC not running
    rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
  }
  
}


void loop() {

  static uint32_t lastUpdate = 0;
  static uint8_t currentDigit = 0;
  
  // Update time every second
  if (millis() - lastUpdate >= 1000) {
    DateTime now = rtc.now();
    digits[0] = now.hour() / 10;    // Hour tens
    digits[1] = now.hour() % 10;    // Hour ones
    digits[2] = now.minute() / 10;  // Minute tens
    digits[3] = now.minute() % 10;  // Minute ones
    digits[4] = now.second() / 10;  // Second tens
    digits[5] = now.second() % 10;  // Second ones
    lastUpdate = millis();
    
    // Serial debug output
    Serial.printf("Time: %02d:%02d:%02d\n", 
                 now.hour(), now.minute(), now.second());
  }

  // Multiplex digits (100Hz refresh)
  if (millis() % 2 == 0) { // Update every 2ms
    updateDisplay(currentDigit, digits[currentDigit]);
    delay(2);
    currentDigit = (currentDigit + 1) % 6;
  }

}

void updateDisplay(uint8_t digitPos, uint8_t value) {
  // Active-LOW digit control (common cathode)
  byte digitByte = ~(1 << digitPos);  // Invert to make active digit LOW
  
  // Get segment pattern
  byte segByte = digitPattern[value];
  
  digitalWrite(latchPin, HIGH);
  shiftOut(dataPin, clockPin, MSBFIRST, digitByte);  // Digits first
  shiftOut(dataPin, clockPin, LSBFIRST, segByte);    // Then segments
  digitalWrite(latchPin, LOW);
}