Arduino AT command function

int8_t sendATcommand(char* ATcommand, char* expected_answer, unsigned int timeout){

    uint8_t x=0,  answer=0;
    char response[100];
    unsigned long previous;

    memset(response, '\0', 100); // Clean response buffer
    
    delay(100); // Delay to be sure no passed commands interfere
    
    while( Serial.available() > 0) Serial.read();    // Wait for clean input buffer
    
    Serial.println(ATcommand);    // Send the AT command 

    previous = millis();

    // this loop waits for the answer
    do{
        // if there are data in the UART input buffer, reads it and checks for the asnwer
        if(Serial.available() != 0){    
            response[x] = Serial.read();
            x++;
            // check if the desired answer is in the response of the module
            if (strstr(response, expected_answer) != NULL){
                answer = 1;
            }
        }
    // Waits for the answer with time out
    } while((answer == 0) && ((millis() - previous) < timeout));    

    return answer;
}