// Define the pins
const int dataPin = 2;    // DS pin of 74HC595
const int clockPin = 3;   // SHCP pin of 74HC595
const int latchPin = 4;   // STCP pin of 74HC595
const int incrementPin = 5; // Button for incrementing
const int decrementPin = 6; // Button for decrementing
const int ledPin = 7;     // LED for even/odd indication

// Variables for the 7-segment display
int currentNumber = 0;
bool lastIncrementState = HIGH;  // For button debouncing
bool lastDecrementState = HIGH;  // For button debouncing
unsigned long lastDebounceTime = 0;  // the last time the button state was toggled
unsigned long debounceDelay = 150;   // the debounce time; increase if the output flickers

// Define the bit patterns for 0-9 on the 7-segment display (for common anode)
// For common anode, 0 means the segment is ON, and 1 means it's OFF
const byte patterns[10] = {
  0xC0, // 0: 0b11000000 - segments A,B,C,D,E,F ON
  0xF9, // 1: 0b11111001 - segments B,C ON
  0xA4, // 2: 0b10100100 - segments A,B,D,E,G ON
  0xB0, // 3: 0b10110000 - segments A,B,C,D,G ON
  0x99, // 4: 0b10011001 - segments B,C,F,G ON
  0x92, // 5: 0b10010010 - segments A,C,D,F,G ON
  0x82, // 6: 0b10000010 - segments A,C,D,E,F,G ON
  0xF8, // 7: 0b11111000 - segments A,B,C ON
  0x80, // 8: 0b10000000 - segments A,B,C,D,E,F,G ON
  0x90  // 9: 0b10010000 - segments A,B,C,D,F,G ON
};

void setup() {
  pinMode(dataPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(latchPin, OUTPUT);
  pinMode(incrementPin, INPUT_PULLUP);
  pinMode(decrementPin, INPUT_PULLUP);
  pinMode(ledPin, OUTPUT);
  
  // Initialize display to 0
  updateDisplay(currentNumber);
  
  // Initialize LED based on number parity
  updateLED(currentNumber);
}

void loop() {
  // Read the state of the increment button
  bool incrementState = digitalRead(incrementPin);
  
  // Check if the increment button state has changed
  if (incrementState != lastIncrementState) {
    lastDebounceTime = millis();
  }
  
  // Read the state of the decrement button
  bool decrementState = digitalRead(decrementPin);
  
  // Check if the decrement button state has changed
  if (decrementState != lastDecrementState) {
    lastDebounceTime = millis();
  }
  
  // If enough time has passed since the last state change, check for a valid button press
  if ((millis() - lastDebounceTime) > debounceDelay) {
    // Check if the increment button is pressed
    if (incrementState == LOW && lastIncrementState == HIGH) {
      // Button is pressed, increment the number
      currentNumber = (currentNumber + 1) % 10;
      updateDisplay(currentNumber);
      updateLED(currentNumber);
    }
    
    // Check if the decrement button is pressed
    if (decrementState == LOW && lastDecrementState == HIGH) {
      // Button is pressed, decrement the number
      currentNumber = (currentNumber - 1 + 10) % 10;  // Add 10 before modulo to avoid negative numbers
      updateDisplay(currentNumber);
      updateLED(currentNumber);
    }
  }
  
  // Save the current state for next loop iteration
  lastIncrementState = incrementState;
  lastDecrementState = decrementState;
}

void updateDisplay(int number) {
  // Update the 7-segment display with the current number
  digitalWrite(latchPin, LOW);
  shiftOut(dataPin, clockPin, MSBFIRST, patterns[number]);
  digitalWrite(latchPin, HIGH);
}

void updateLED(int number) {
  // Update the LED based on the number parity
  if (number % 2 == 0) {
    // Even number, turn LED on
    digitalWrite(ledPin, HIGH);
  } else {
    // Odd number, turn LED off
    digitalWrite(ledPin, LOW);
  }
}