#include <Keypad.h>

// Configuración del teclado
const byte ROWS = 4;
const byte COLS = 4;
char hexKeys[ROWS][COLS] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};
byte rowPins[ROWS] = {18, 19, 21, 22};
byte colPins[COLS] = {23, 16, 17, 5};
Keypad customKeypad = Keypad(makeKeymap(hexKeys), rowPins, colPins, ROWS, COLS);

// Pines del display
int digitPins[] = {15, 2, 4, 5}; // D1, D2, D3, D4
int segmentPins[] = {13, 12, 14, 27, 26, 25, 33}; // A, B, C, D, E, F, G

// Patrones de segmentos (0-9, A-F, E, r, o)
const String digits[] = {
  "1111110", "0110000", "1101101", "1111001",  // 0-3
  "0110011", "1011011", "1011111", "1110000",   // 4-7
  "1111111", "1111011", "1110111", "0011111",   // 8-9, A-B
  "1001110", "0111101", "1001111", "1000111",   // C-E, F
  "0000101", "0011101", "0000000"               // r, o, espacio
};

// Variables de estado
char inputBuffer[2] = {' ', ' '};
char displayDigits[4] = {' ', ' ', ' ', ' '};
bool errorState = false;
int currentDigit = 0;

void setup() {
  for (int i = 0; i < 4; i++) {
    pinMode(digitPins[i], OUTPUT);
    digitalWrite(digitPins[i], HIGH);
  }
  for (int i = 0; i < 7; i++) {
    pinMode(segmentPins[i], OUTPUT);
    digitalWrite(segmentPins[i], LOW);
  }
}

void loop() {
  handleInput();
  updateDisplay();
}

void handleInput() {
  char key = customKeypad.getKey();
  
  if (key) {
    inputBuffer[1] = inputBuffer[0];
    inputBuffer[0] = key;
    
    if (isValidHex(inputBuffer[0]) && isValidHex(inputBuffer[1])) {
      processInput();
    }
  }
}

bool isValidHex(char c) {
  return (c >= '0' && c <= '9') || (c >= 'A' && c <= 'F');
}

int hexToDec(char c) {
  if (c >= '0' && c <= '9') return c - '0';
  return 10 + (c - 'A');
}

void processInput() {
  int val1 = hexToDec(inputBuffer[0]);
  int val2 = hexToDec(inputBuffer[1]);
  
  if (val1 == val2) {
    errorState = true;
    strcpy(displayDigits, "Erro");
  } else {
    errorState = false;
    int smaller = min(val1, val2);
    int complement = 15 - smaller;
    
    displayDigits[0] = inputBuffer[0];
    displayDigits[1] = inputBuffer[1];
    displayDigits[2] = (complement / 10) + '0';
    displayDigits[3] = (complement % 10) + '0';
  }
}

void updateDisplay() {
  digitalWrite(digitPins[currentDigit], HIGH); // Apagar dígito actual
  
  currentDigit = (currentDigit + 1) % 4;
  
  if (errorState) {
    showError();
    return;
  }
  
  int charIndex = charToIndex(displayDigits[currentDigit]);
  activateSegments(charIndex);
  digitalWrite(digitPins[currentDigit], LOW); // Encender nuevo dígito
}

int charToIndex(char c) {
  if (c >= '0' && c <= '9') return c - '0';
  if (c >= 'A' && c <= 'F') return 10 + (c - 'A');
  if (c == 'E') return 14;
  if (c == 'r') return 16;
  if (c == 'o') return 17;
  return 18; // Espacio
}

void activateSegments(int index) {
  String pattern = digits[index];
  for (int i = 0; i < 7; i++) {
    digitalWrite(segmentPins[i], pattern.charAt(i) == '1' ? HIGH : LOW);
  }
}

void showError() {
  for (int i = 0; i < 4; i++) {
    digitalWrite(digitPins[i], LOW);
    int index = charToIndex(displayDigits[i]);
    activateSegments(index);
    delay(2);
    digitalWrite(digitPins[i], HIGH);
  }
}