#include <LiquidCrystal_I2C.h>
#include "Keypad.h"

#define ROWS 4
#define COLS 4

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

const String alpha = "!@_$%?1 ABC2 DEF3 GHI4 JKL5 MNO6 PQRS7 TUV8 WXYZ9  0 ";
const byte rowPins[ROWS] = {9, 8, 7, 6};
const byte colPins[COLS] = {5, 4, 3, 2};

int x = 0, y = 0, minValue = 0, maxValue = 0, keyPressTime = 100;
String msg = "";
Keypad customKeypad = Keypad(makeKeymap(hexaKeys), rowPins, colPins, ROWS, COLS);
LiquidCrystal_I2C lcd(0x27, 16, 2);

void setup() {
  lcd.begin(16, 2);
  lcd.clear();
  lcd.setBacklight(HIGH);
}

void loop() {
  enterMSG();
}

void parseKey(int minValue, int maxValue, char keyPress, String& msg, int& x, int& y, int keyPressTime, String removeDirection = "", int numLines = 1) {
  int ch = minValue;
  char key = keyPress;
  if (removeDirection == "up") {
    for (int i = 0; i < numLines; i++) {
      int lastLineIndex = msg.lastIndexOf('\n', msg.length() - 2);
      if (lastLineIndex < 0) {
        msg = "";
        x = 0;
        y = 0;
        lcd.clear();
        lcd.setCursor(x,y);
      } else {
        msg = msg.substring(0, lastLineIndex + 1);
        y--;
        if (y < 0) {
          y = 1;
        }
        x = msg.lastIndexOf('\n', lastLineIndex - 1);
        if (x < 0) {
          x = 0;
        } else {
          x = lastLineIndex - x;
        }
        lcd.setCursor(x, y);
        if (i == numLines - 1 && msg.indexOf('\n', lastLineIndex + 1) < 0) {
          msg = msg.substring(0, lastLineIndex + 1);
          lcd.setCursor(0, y);
          lcd.print("");
          lcd.setCursor(0, y);
          x = 0;
          y--;
          if (y < 0) {
            y = 1;
          }
        }
      }
    }
  } else if (removeDirection == "down") {
    for (int i = 0; i < numLines; i++) {
      int nextLineIndex = msg.indexOf('\n', msg.length() - 1);
      if (nextLineIndex < 0) {
        msg = "";
        x = 0;
        y = 0;
        lcd.clear();
        lcd.setCursor(x,y);
      } else {
        msg = msg.substring(0, nextLineIndex + 1);
        x = 0;
        y++;
        if (y > 1) {
          y = 0;
        }
        lcd.setCursor(x, y);
      }
    }
  } else if (keyPress == 'A') {
    if ((x > 0) || (y > 0)) {
      x--;
      lcd.setCursor(x,y);
      lcd.print(" ");
      msg.remove(msg.length() - 1);
    }
  } else {
    for (int i = 0; i < keyPressTime; i++) {
      if (key == keyPress) {
        lcd.setCursor(x, y);
        lcd.print(alpha[ch]);
        ch++;
        if (ch > maxValue) {
          ch = minValue;
          i = 0;
        }
      }
      key = customKeypad.getKey();
      delay(15);
    }
    x++;
    msg += alpha[ch - 1];
    if (x > 15) {
      y = 1;
      x = 0;
    }
  }
}

void enterMSG() {
  char key;       
  lcd.clear();  
  x = 0;        
  y = 0;        
  msg = "";     

  while (true) {
    key = customKeypad.waitForKey();
    if (key == '#') break; 
    int rangeStart, rangeEnd;
    switch(key) {
      case '1': rangeStart = 0; rangeEnd = 7; break;
      case '2': rangeStart = 8; rangeEnd = 12; break;
      case '3': rangeStart = 13; rangeEnd = 17; break;
      case '4': rangeStart = 18; rangeEnd = 22; break;
      case '5': rangeStart = 23; rangeEnd = 27; break;
      case '6': rangeStart = 28; rangeEnd = 32; break;
      case '7': rangeStart = 33; rangeEnd = 38; break;
      case '8': rangeStart = 39; rangeEnd = 43; break;
      case '9': rangeStart = 44; rangeEnd = 49; break;
      case '0': rangeStart = 50; rangeEnd = 53; break;
      case 'A': rangeStart = 54; rangeEnd = 55; break;
      default: continue; 
    }
    parseKey(rangeStart, rangeEnd, key, msg, x, y, keyPressTime);        
  }
}