#include <Arduino.h>

// 74HC595 Pins (to STM32)
const int dataPin = 2;   // DS (Pin 14)
const int latchPin = 3;  // STCP (Pin 12)
const int clockPin = 4;  // SHCP (Pin 11)

// Digit Selectors for 10 digits (Common Cathodes)
// DD:MM:YYYY HH:MM
const int dig[] = {9, 10, 11, 12, 15, A0, A1, A2, A3, A4}; 

// Common Cathode segment patterns (0-9)
const byte numTable[] = {
  0x3F, 0x06, 0x5B, 0x4F, 0x66, 0x6D, 0x7D, 0x07, 0x7F, 0x6F
};

int d=23, mo=1, y=2026, h=12, mi=0;
unsigned long lastTick = 0;

void setup() {
  pinMode(dataPin, OUTPUT);
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  for(int i=0; i<10; i++) {
    pinMode(dig[i], OUTPUT);
    digitalWrite(dig[i], HIGH); // HIGH = OFF for Common Cathode
  }
}

void sendSegments(byte pattern) {
  digitalWrite(latchPin, LOW);
  shiftOut(dataPin, clockPin, MSBFIRST, pattern);
  digitalWrite(latchPin, HIGH);
}

void displayDigit(int digitIdx, int value) {
  // 1. Clear all digits
  for(int i=0; i<10; i++) digitalWrite(dig[i], HIGH);

  // 2. Load pattern into Shift Register
  sendSegments(numTable[value]);

  // 3. Activate current digit (Pull LOW to sink current)
  digitalWrite(dig[digitIdx], LOW);
  delayMicroseconds(800); // Short delay for persistence of vision
}

void loop() {
  // Timing Logic
  if (millis() - lastTick >= 1000) {
    lastTick = millis();
    // Simplified clock increment for demo
  }

  // Refresh DD:MM:YYYY
  displayDigit(0, d/10);     displayDigit(1, d%10);
  displayDigit(2, mo/10);    displayDigit(3, mo%10);
  displayDigit(4, y/1000);   displayDigit(5, (y/100)%10);
  displayDigit(6, (y/10)%10);displayDigit(7, y%10);

  // Refresh HH:MM
  displayDigit(8, h/10);     displayDigit(9, h%10);
  displayDigit(10, mi/10);   displayDigit(11, mi%10); 
}