#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#define INTERNAL_LED 13
#define TRUE 1
#define FALSE 0

#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 DELAY 1

LiquidCrystal_I2C lcd(0x27,20,4);  // set the LCD address to 0x27 for a 16 chars and 2 line display
int secs;
int minutes;
int hours;
int day;
int month;
int year;
int daysOfMonth[] = {31,28,31,30,31,30,31,31,30,31,30,31};
bool led13 = HIGH;
bool released = TRUE;

void setup() {
  //setup matrix pins
  pinMode(R1, INPUT_PULLUP);
  pinMode(R2, INPUT_PULLUP);
  pinMode(R3, INPUT_PULLUP);
  pinMode(R4, INPUT_PULLUP);

  lcd.init();                      // initialize the lcd 
  lcd.backlight();

  month = inputData  ("Month          ");
  day = inputData    ("Day            ");
  year = inputData   ("Year           ");
  hours = inputData  ("Hours (24)     "); 
  minutes = inputData("Minutes        "); 
  secs = inputData   ("Seconds        ");

  // Print a message to the LCD
  lcd.clear();
  lcd.setCursor(3,0);
  lcd.print("Hello, World!");
  lcd.setCursor(3,1);
  lcd.print("Date and Time");

  printTime();
}

int counter = 0;  
void loop() {
  bool keyPressed;
  int key;

  counter++;
  if (counter > 74){
    digitalWrite(INTERNAL_LED, led13);
    if (led13 == HIGH)
      led13 = LOW;
    else
      led13 = HIGH;
  
    delay(965);
    secs++;
    if (secs >= 60) {
      secs = 0;
      minutes++;
      if (minutes >= 60) {
        minutes = 0;
        hours++;
      }
      if (hours >=24) {
        day++;
        hours = 0;
        if (day > daysOfMonth[month-1]) {
          day = 1;
          month++;
          if (month > 12) {
            year++;
            month = 1;
          }
        }
      }
    }
    printTime();
    counter = 0;
  }

}

void printTime(){
  bool pm = false;
  int hoursP;

  lcd.setCursor(5,2);
  if (month < 10) {
    if (day < 10) 
      lcd.print(" ");
  }
  lcd.print(month);
  lcd.print("/");
  lcd.print(day);
  lcd.print("/");
  lcd.print(year);
  lcd.print(" ");

  lcd.setCursor(4,3);
  if (((hours > 0) && (hours < 10)) || ((hours > 12) && (hours <22)))
   lcd.print(" "); 
  if (hours > 11)
    pm = true;
  if (hours > 12)
    hoursP = hours-12;
  else if (hours == 0)
    hoursP = 12;
  else
    hoursP = hours;
  lcd.print(hoursP);
  lcd.print(":");
  if (minutes < 10) lcd.print("0");
  lcd.print(minutes);
  lcd.print(":"); 
  if (secs < 10) lcd.print("0");
  lcd.print(secs);
  if (pm) 
    lcd.print(" PM");
  else
    lcd.print(" AM");

}

bool readKey(int *keyPressed)
{
  int row;
  int col;
  int hexN;
  bool rv = false;

  if (getKey(&row, &col)) {
    hexN = hexConvert(row, col);
    *keyPressed = hexN;
    rv = true;
  } 
  return rv;
}

bool getKey(int *row, int *col) {
  bool pressed;
  
  pressed = Keypad(row, col);
  if (!pressed && !released) {
   	released = TRUE;
  } else if (pressed && released) {
    released = FALSE;
  } else {
    pressed = FALSE;
  }
  return pressed;
}
  
bool Keypad(int *row, int *col)
{  
  	int i,j,k;
  	int temp;
    bool pressed;

  
  pressed = FALSE;
  delay(DELAY);
  for (j=0;  j<4;  j++) {
    pinMode(C1-j, OUTPUT);
	digitalWrite(C1-j, LOW);
    delay(DELAY);
    for (k=0;  k<4;  k++) {
      temp = digitalRead(R1-k);
      if (temp == LOW) {
        *row = k;
        *col = j;
        pressed = TRUE;
        break;
      }
    }
    digitalWrite(C1-j, HIGH);
    pinMode(C1-j, INPUT);
    delay(DELAY);
    if (pressed){
      break;
    }
  }

  return pressed;
}

int hexConvert(int r, int c)
{
  int table[4][4] = {
    {1,2,3,0xA},
    {4,5,6,0xB},
    {7,8,9,0xC},
    {0xE, 0, 0xF, 0xD}
  };
  
  return table[r][c];
}

int inputData(char *strP){
  bool enter=false;
  bool keyPressed = false;
  int rv = 0;
  int key;
  int digit = 0;

  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("*:Backspace #:Enter");
  lcd.setCursor(0,1);
  lcd.print(strP);
  lcd.setCursor(0,2);

  while (!enter) {
    keyPressed = readKey(&key);
    if (keyPressed == true)
    {
      if (key < 10) {
        lcd.print(key);
        rv = rv * 10 + key;
        digit++;
      } else if (key == 15) {
        break;
      } else if (key == 14) {
        rv = rv / 10;
        digit--;
        lcd.setCursor(digit,2);
        lcd.print(" ");
        lcd.setCursor(digit,2);
      }

    }
  }
  return rv;
}