// Monitor serial (debug) and modem At commands
#define SerialMon SerialUSB
#define SerialAt Serial1 // Serial1 = UART-A

// At commands responses will be allocated here
u_int8_t signal_quality;
char buffer[1000];

void configureIos () {
  pinMode(GSM_PWRKEY, OUTPUT);
  pinMode(GSM_PWREN, OUTPUT);
  pinMode(GPS_EN, OUTPUT);
  pinMode(GSM_STATUS, INPUT);
}

void configureSerial () {
  SerialMon.begin(38400);
  while (!SerialMon) {}

  SerialAt.begin(38400);
  while (!SerialAt) {}
}

/**
 * @brief Turn on the modem
 *
 * To be able to use the SIM868 module we have to activate the PWREN line and
 * make a pulse of 1.5 seconds in the PWRKEY line. The modem will have been
 * turned on when the STATUS line goes to high level.
 *
 * This allows the MCU to control the power of the device, necessary for low
 * power applications. By default the modem will be turned off and will only
 * turn on if we perform the turn on routine as seen in this method.
 *
 * @return true if the modem has been turned on
 * @return false
 */
bool powerOn () {
  uint8_t gsm_status;

  digitalWrite(GSM_PWREN, HIGH);

  for (char i=0; i<5; i++) {
    gsm_status = digitalRead(GSM_STATUS);
    if (gsm_status == HIGH){
      SerialMon.println(F("GSM HIGH!!"));
      break;
    } else {
      SerialMon.println(F("GSM LOW!"));
      digitalWrite(GSM_PWRKEY, HIGH);
      delay(1500);
      digitalWrite(GSM_PWRKEY, LOW);
      delay(1500);
    }
  }

  if (!gsm_status) {
    return false;
  }

  // Turn on the GPS. It is not necessary for modem operation but this demo
  // will make use of GPS.
  digitalWrite(GPS_EN, HIGH);
  SerialAt.println("AT+CGNSPWR=1");
  delay(3000);

  // We obviate the result of enabling GPS
  return true;
}

void sendAt(const char * command){
  memset(buffer, 0, sizeof buffer);
  SerialMon.println(command);
  SerialAt.println(command);
  uint32_t init=millis();

  int count=0;
  while ((millis() - init) < 5000) {
    delay(1);
    if (!SerialAt.available()) continue;

    while (SerialAt.available()) {
      buffer[count] = (char) SerialAt.read();
      count++;
      delay(10);
    }

    buffer[count]='\n';
    break; // hemos acabado, salimos del while
  }

  SerialMon.print("La respuesta es: ");
  SerialMon.println(buffer);
}

void setup () {
  configureIos();
  configureSerial();

  if (!powerOn()) {
    SerialMon.println("Fail to power on the modem. Is the SIM868 connected to the Socket 1?");
    for (;;) {}
  }

  sendAt("AT"); // test modem, should return "OK"
  if(strcmp(buffer,"OK")){
    sendAt("AT+SHUT");   //sets down any previous gprs conexions, should return "SHUT OK"
    sendAt("AT+CIPMUX=0");   //sets single conexion mode, should return "OK"
    sendAt("AT+CGATT=1");    //attaches GPRS Service, should return "OK"
    sendAt("AT+CSTT=RH_apn,RH_apnUser,RH_apnPass");
    sendAt("AT+CIICR"); //brings up the GPRS connexions, sometimes it takes a bit to respond, but should return "OK"
    sendAt("AT+CIFSR");   //gives us our IP Address
    sendAt("AT+CIPSTART=TCP,RH_remoteServer,RH_remotePort");
  }

}

bool checkCreg () {
  for (auto i = 0; i < 20; i++) {
    sendAt("AT+CSQ");
    sendAt("AT+CREG?");
    if (strstr(buffer, ",1") || strstr(buffer, ",5")) {
      // tenemos CREG!!!
      return true;
    }
    delay(1000);
  }

  return false;
}

void loop () {
  // Get GPS. It will be necessary a few minutes before obtaining data.
  // The important thing for this demo is not to get GPS data, but to check
  // that we can send a command to the modem and get a response.
  // SerialAt.println("AT+CGNSINF");   (Read GPS location data)
  // delay(1000);

  sendAt("AT");
  if (strcmp(buffer, "OK")) {
    SerialMon.println("El modem funciona!!");
  } else {
    SerialMon.println("Huston tenemos un problema");
  }

  if (checkCreg()) {
    SerialMon.println("Tenemos conexión a red!!");
  }

  //sendAt("AT+CSQ");



  // wait for loop
  delay(5000);
}

//AT+CSQ (Comando AT que indica la calidad de la señal o la cobertura)