#include <GSM.h>

// PIN Number
#define PINNUMBER ""

// initialize the library instance
GSM gsmAccess; // include a 'true' parameter for debug enabled
GSMVoiceCall vcs;

char numtel[20];           // buffer for the incoming call

void setup()
{
  // initialize serial communications
  Serial.begin(9600);
  Serial.println("Receive Voice Call");

  // connection state
  boolean notConnected = true;

  // Start GSM shield
  // If your SIM has PIN, pass it as a parameter of begin() in quotes
  while(notConnected)
  {
    if(gsmAccess.begin(PINNUMBER)==GSM_READY)
      notConnected = false;
    else
    {
      Serial.println("Not connected");
      delay(1000);
    }
  }

  //Enable dtmf
  theGSM3ShieldV1ModemCore.genericCommand_rqc("AT+QTONEDET=1", true); // Send command
  delay(1000); // Wait for response
  bool resp;
  theGSM3ShieldV1ModemCore.genericParse_rsp(resp);
  if(resp){
     Serial.println("DTMF Enabled");
  }else{
    Serial.println("DTMF NOT Enabled");
  }


  // This makes sure the modem notifies correctly incoming events
  vcs.hangCall();

  Serial.println("Waiting Call");
}

void loop()
{
  // Check the status of the voice call
  switch (vcs.getvoiceCallStatus())
  {
    case IDLE_CALL: // Nothing is happening

      break;

    case CALLING: // This should never happen, as we are not placing a call

      Serial.println("CALLING");
      break;

    case RECEIVINGCALL: // Yes! Someone is calling us

      Serial.println("RECEIVING CALL");

      // Retrieve the calling number
      vcs.retrieveCallingNumber(numtel, 20);

      // Print the calling number
      Serial.print("Number:");
      Serial.println(numtel);

      // Answer the call, establish the call
      vcs.answerCall();
      break;

    case TALKING:  // In this case the call would be established

      Serial.println("TALKING. Enter line to interrupt.");
      uint8_t charToneSum = 0;
      const char* strToneSearch = "QTONEDET: ";
      uint8_t len = strlen(strToneSearch);

      while(Serial.read()!='\n'){
        int toneNum = detectTone(&charToneSum , len, strToneSearch);
        if(toneNum != -1){
          charToneSum = 0;
          Serial.print("Tone detected:");Serial.println(toneNum);
        }
        delay(100);
      }

      vcs.hangCall();
      Serial.println("HANG. Waiting Call.");
      break;
  }
  delay(1000);
}

int detectTone(uint8_t* sum , uint8_t len, const char* strSearch){
  char c = theGSM3ShieldV1ModemCore.theBuffer().read();
  *sum = (c==strSearch[*sum]) ? *sum+1 : 0;
  if(*sum == len){
    char cc[2];
    cc[0] = (char)theGSM3ShieldV1ModemCore.theBuffer().read();
    cc[1] = (char)theGSM3ShieldV1ModemCore.theBuffer().read();
    int n;
    n = atoi(cc);
    return n -48;
  }
  return -1;
}