#include <Keypad.h>

const byte ROWS = 4; //four rows
const byte COLS = 4; //four columns
char keys[ROWS][COLS] = {
  { 1,  2,  3,  4},
  { 5,  6,  7,  8},
  { 9, 10, 11, 12},
  {13, 14, 15, 16},
};
byte rowPins[ROWS] = {2, 3, 4, 5}; //connect to the row pinouts of the keypad
byte colPins[COLS] = {6, 7, 8, 9}; //connect to the column pinouts of the keypad

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


// abc1        def2    ghi3    <vol up>
// jkl4        mno5    pqr6    <vol down>
// stu7        vwx8    yz9.    <caps lock>
// <backspace> <space> <enter> <esc>

// 97,98,99,49     100,101,102,50  103,104,105,51  v.up
// 106,107,108,52  109,110,111,53  112,113,114,54  v.dn
// 115,116,117,55  118,119,120,56  121,122,57,46   cps
// bckspc          spc             enter           esc

const char keyCharArray[16][5] PROGMEM = {
  "abc1", "def2", "ghi3", "1",
  "jkl4", "mno5", "pqr6", "2",
  "stu7", "vwx8", "yz9.", "3",
  "7",       "6",    "5", "4",
};

char finalText[80] = "";
size_t finalTextIndex = 0;

void setup() {
  Serial.begin(9600);
}

void loop() {
  char key = mygetKey();
}

char mygetKey() {
  const unsigned long keyDelay = 500ul; //maximum delay between multiple presses of same key
  static unsigned long keyTimer; 
  static size_t keyCharIndex = 0; //index of current character for multi-character key
  static char keyPrevious = '\0'; //previous key pressed
  static char keyPending = '\0';  //temporary storeage for key pressed within multi-charactere delay for another key
  char key;
  char keyChar = '\0'; //character to be returned from this function
  
  if (keyPending == '\0') { //check for key pressed during multi-character delay for another key
    key = keypad.getKey();
  } else {
    key = keyPending;
    keyPending = '\0';
  }
  
  if (key) {
    if (keyPrevious == '\0') {
      if (strlen_P(keyCharArray[key - 1]) == 1) { 
        //key represents a single character
        keyChar = (char)pgm_read_byte(&keyCharArray[key - 1][0]);
      } else {
        //key represents multiple characters
        keyTimer = millis();
        keyPrevious = key;
        keyCharIndex = 0;
      }
    } else {
      if (keyPrevious == key) { //same key has been pressed multiple times
        if ((millis() - keyTimer) < keyDelay) {
          keyCharIndex++; //advance to next character for key
          if (keyCharIndex >= strlen_P(keyCharArray[key - 1])) {
            keyCharIndex = 0;
          }
          keyTimer = millis();
        }
      } else { //key pressed during the timer delay for another key
        keyChar = (char)pgm_read_byte(&keyCharArray[keyPrevious - 1][keyCharIndex]); //return character from previous key
        keyPrevious = '\0';
        keyPending = key;  //save current key to be processed next time function is called
      }
    }
  }
  if ((keyPrevious != '\0') && ((millis() - keyTimer) > keyDelay)) { //return multi-character key press when timer runs out
    keyChar = (byte)pgm_read_byte(&keyCharArray[keyPrevious - 1][keyCharIndex]);
    keyPrevious = '\0';
  }
  if (keyChar == '1' || keyChar == '2' || keyChar == '3' || keyChar == '4' || keyChar == '5' || keyChar == '6' || keyChar == '7')  {
  Serial.print(F("fuck key"));
  }
  else
  {
  Serial.print(keyChar);
  return keyChar;
}
}