/*we used Serial.readStringUntil() insted of Serial.readBytesUntil() because we are dealing with a
string and we are going to count the characters in the string.*/
//libraries
#include <MD_Parola.h>
#include <MD_MAX72xx.h>
#include <SPI.h>

//definitions
#define HARDWARE_TYPE MD_MAX72XX::PAROLA_HW
#define devices 4
#define clk    13
#define data   11
#define CS     10

MD_Parola play = MD_Parola(HARDWARE_TYPE, data, clk, CS, devices);

//methods
//a method used to count the number of characters
int numbers_of_characters(String s){
  int count = 0;
  while(s[count] != NULL){
    count++;
  }
  return count;
}
//taking the string and breaking it to its characters
char* returning_characters(String x){
  int count = numbers_of_characters(x);
  char* y = malloc(count);
  strcpy(y, x.c_str());
  return y;
}
//to keep displayig the message
void displaying(){
  while(1){
    if(Serial.available() > 0){
      break;
    }
    else {
      if(play.displayAnimate()){
        play.displayReset();
      }
    }
  }
}

void setup(void)
{
  Serial.begin(9600);//the serial communication
  //initiating the message
  Serial.println(F("Enter a message: "));
  Serial.println(F("- REMEMBER: max. of 20 characters only -"));
  //initiate the displaying process
  play.begin();
}

void loop(void)
{
  if(Serial.available() > 0){//if there is any message in the serial port, then true = more than a zero
    String msg = Serial.readStringUntil('\n');/*read what's written until there is a new line.*/
    int x = numbers_of_characters(msg);

    if(x >= 20){
      Serial.println(F("Your message size exceeds the limit."));
    }
    else {
      Serial.print(F("Your message: "));
      Serial.println(msg);

      char* message = returning_characters(msg);
      play.displayText(message, PA_CENTER, 100, 0, PA_SCROLL_LEFT, PA_SCROLL_LEFT);
    }
  }
  displaying();
}