#include <Sim800l.h>
#include <SoftwareSerial.h>
#include <EDB.h>

#include <SPI.h>
#include <SD.h>

#define SD_PIN 4
#define TABLE_SIZE 3686793216
Sim800l Sim800l;
String text;     // to storage the text of the sms
int index = 1;   // to indicate the message to read.

String phone_no;

//database initialization
char* sys_var = "/db/sys_var.db";
File dbFile;

struct logEventgetsysvar{
  int id;
  char username[11];
  char password[5];
  float liquid_price;
  bool delivered;
}
logEventgetsysvar;

void writer(unsigned long address, byte data){
  digitalWrite(13, HIGH);
  dbFile.seek(address);
  dbFile.write(data);
  dbFile.flush();
  digitalWrite(13, LOW);
}
byte reader(unsigned long address){
  digitalWrite(13, HIGH);
  dbFile.seek(address);
  byte b = dbFile.read();
  digitalWrite(13, LOW);
  return b;
}
EDB db(&writer, &reader);

void setup(){
  Serial.begin(9600); // only for debug the results .
  //SPI.begin();
  randomSeed(analogRead(0));

  get_sys_var();  //  Initialization of System Variable Database and read of liquid price from the SD Card

  Sim800l.begin(); // initialize the library.
  Serial.println("Initialization Complete");
}

void loop(){
  Serial.println("Starting to Read");

  text=Sim800l.readSms(index);   //Code hangs here and does not read the SMS.
  phone_no=Sim800l.getNumberSms(index);

  Serial.println("Read Message");
} //end of loop

void get_sys_var()
{
  if (!SD.begin(SD_PIN)){
    Serial.println("No SD-card.");
    return;
  }

  if (!SD.exists("/db")){
    Serial.println("Error: System Variable Database Does not Exist...");
    exit;
  }

  if (SD.exists(sys_var)){
    dbFile = SD.open(sys_var, FILE_WRITE);

    if (!dbFile){
      Serial.println("Error: System Variable Database Does not Exist...");
      exit;
    }
    if (dbFile){
      Serial.print("Opening current table... ");
      EDB_Status result = db.open(0);
      if (result == EDB_OK){
        Serial.println("DONE");
    }else {
        Serial.println("ERROR");
        Serial.println("Did not find database in the file " + String(sys_var));
        exit;
        return;
      }
    }else {
            Serial.println("Could not open file " + String(sys_var));
            return;
        }
    }else {
      Serial.println("Error: System Variable Database Does not Exist...");
      exit;
    }
//-------------------------------------------------------------------------------
//   Read function of liquid price
//---------------------------------------------------------------------------------

Serial.println("Reading Liquid Price: ");

EDB_Status result = db.readRec(1, EDB_REC logEventgetsysvar);
if (result == EDB_OK)
{
    memcpy(session_username, logEventgetsysvar.username, 11);
    memcpy(session_password, logEventgetsysvar.password, 5);
    session_liquid_price = logEventgetsysvar.liquid_price;
}
Serial.print("Username: ");
Serial.println(session_username);

Serial.print("Password: ");
Serial.println(session_password);

Serial.print("Liquid Price: ");
Serial.println(session_liquid_price);
}

get_sys_var()