#include <Keypad.h>

const uint8_t ROWS = 4;
const uint8_t COLS = 4;
char keys[ROWS][COLS] = {
  { '1', '2', '3', 'A' },
  { '4', '5', '6', 'B' },
  { '7', '8', '9', 'C' },
  { '*', '0', '#', 'D' }
};

uint8_t colPins[COLS] = { 5, 4, 3, 2 }; // Pins connected to C1, C2, C3, C4
uint8_t rowPins[ROWS] = { 9, 8, 7, 6 }; // Pins connected to R1, R2, R3, R4

Keypad keypad = Keypad(makeKeymap(keys), rowPins, colPins, ROWS, COLS);

int indexes[9] = {0,0,0,0,0,0,0,0,0};

int16_t keypad_alpha[9][4] = {
  {230, 248, 229},      //  KP1 -> æ,ø,å
  {97,  98,  99},       //  KP2 -> a,b,c
  {100, 101, 102},      //  KP3 -> d,e,f
  {103, 104, 105},      //  KP4 -> g,h,i
  {106, 107, 108},      //  KP5 -> j,k,l
  {109, 110, 111},      //  KP6 -> m,n,o
  {112, 113, 114, 115}, //  KP7 -> p,q,r,s
  {116, 117, 118},      //  KP8 -> t,u,v
  {119, 120, 121, 122}, //  KP9 -> x,y,z
};


const char* hexChars = "B0,B1,B2,B3"; // 176, 177, 178, 179 in hex

int16_t parseHexChar(const char* hexStr) {
  return (int16_t)strtol(hexStr, NULL, 16);
}

struct myStruct {
  int16_t chars[3];
}
structo = {
  {230, 248, 229}
};

char* hex2char(unsigned char x, char hex[]) {
  hex[0] = (char)x;
  hex[1] = '\0';
  return hex;
}

void setup() {
  Serial.begin(9600);
  unsigned char extChar = 230;
  char str[2];  // Space for char + null terminator

  const char* n = hex2char(extChar, str);

  Serial.println(str);
  Serial.println(n);
  Serial.println("--------------");


  for(int i = 0; i < 3; i++) {
    int16_t ch = structo.chars[i];
    Serial.write(ch); Serial.print(" ("); Serial.print(ch); Serial.print(") ,");
    Serial.write(ch-32); Serial.print(" ("); Serial.print(ch); Serial.print(") ");
  } 


    /*
 for(int i = 0; i < 3; i++) {
  int16_t ch = structo.chars[i];
  Serial.write(ch); Serial.println();
  } 
  
  signed char x = (char)148U; Serial.print("X: "); Serial.write(x); Serial.println();
  */
  /*
  int16_t c = (int16_t)strtol("B2", NULL, 16);
  Serial.print(c); Serial.print(" > "); Serial.write(c); Serial.println();
 
  int16_t charCodes[] = {215, 216, 217, 218, 219};
  char charArray[5]; // +1 for null terminator

  for(int i = 0; i < 4; i++) {
      charArray[i] = (char)charCodes[i];  // Direct cast
  }
  charArray[2] = '\0'; // Null terminate
  Serial.println(charArray);
  //Serial.println(parseHexChar("B2"));
  for (;;);
  */
}

int mult = 0;
int16_t symbol;

void loop() {
  char key = keypad.getKey();

  int id = (int)(key - '0');

  --id %= 9;

  if (key != NO_KEY) {
    if (isdigit(key)) {
      symbol = keypad_alpha[id][ (indexes[id]) ];
      ++indexes[id] %= ((id == 6 || id == 8) ? 4 : 3);
      char b = (char)symbol-mult; 

      Serial.print("key:    "); Serial.println(key);
      Serial.print("id:     "); Serial.println(id);
      Serial.print("index:  "); Serial.println(indexes[id]);
      Serial.print("symbol: "); Serial.println(symbol); //Serial.print(" - "); Serial.write(symbol); Serial.println();
      Serial.print("result: "); Serial.println(symbol); //Serial.print(" - "); Serial.write(symbol-mult); Serial.println();
      Serial.print("char:   "); Serial.println(b);
      Serial.println("\n");
    }
    else {
      if (key == 'D') {
        mult = (mult > 0) ? 0 : 32;
        Serial.println(mult);
      }
    }
  }
}