#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <Keypad.h>
#define R1    9
#define R2    8
#define R3    7
#define R4    6
#define C1    5
#define C2    4
#define C3    3
#define C4    2
#define message "enter password"
#define LED_GREEN   13 
#define LED_RED     12

//configure LCD
LiquidCrystal_I2C display(0x27,16,2);
//configure keypad
char key[4][4] = {
  {'1','2','3','A'},
  {'4','5','6','B'},
  {'7','8','9','C'},
  {'*','0','#','D'}
};

unsigned char row[4] = {9,8,7,6};
unsigned char col[4] = {5,4,3,2};
char buffer[16] = {0};
unsigned char posX = 0;
unsigned char posY = 0;

Keypad keypad = Keypad(makeKeymap(key),row,col,4,4);

void setup(){
  display.init();
  display.backlight();

  display.setCursor(0,0);
  display.print(message);

  pinMode(LED_GREEN, OUTPUT);
  pinMode(LED_RED, OUTPUT);
}

void loop(){

  char key = keypad.getKey();

  if(key)
  {
    if(posX == 0){
      display.clear();
      display.print(message);
    }
    buffer[posX] = key;
    display.setCursor(posX++,1);
    display.print(key);
    digitalWrite(LED_GREEN,LOW);
    digitalWrite(LED_RED, LOW);

    if(posX >= 5)
    {
      posX = 0;
      display.clear();
      if(!strcmp(buffer,"12345")){
        display.setCursor(0,0);
        display.print("valid password");
        digitalWrite(LED_GREEN, HIGH);
      }
      else if(!strcmp(buffer,"98765")){
        display.setCursor(0,0);
        display.print("valid password");
        digitalWrite(LED_GREEN,HIGH);
      }
      else{
        display.setCursor(0,0);
        display.print("invalid password");
        digitalWrite(LED_RED,HIGH);
      }
    }
  }
}