/*
bool waitWrite(const char *str, String &output, unsigned long timeout) {
  int n = strlen(str);
  const char *pC = str;
  unsigned long done = ( millis() + timeout );
  
  while (n && (millis() < done)) {
    if (Serial.available()) {
      char c = (char)Serial.read();
      output += c;
      if (c == *pC)
        pC++, n--;
    }
  }
  return (n == 0);
}
//--------------------------------------------
*/

#define BUF_SIZE 256
char buf[BUF_SIZE] = {'\0'};

void checkLine(String &line) {
  Serial1.print("line: "); Serial1.println(line);
  line = "";
}

bool waitFor(String match, unsigned long period = 5000, bool flush = false, char lineSep = '\n') {
  unsigned long timeout = ( millis() + period );
  String line = "";
  bool found = false;
  int n = 0;

  Serial1.println(match.length());

  memset(buf, '\0', BUF_SIZE);

  while (!found && (millis() < timeout)) {
    if (Serial1.available()) {
      char c = Serial1.read();

      if (c == lineSep) {
        checkLine(line);
      }
      else { line += c;
        if (c == match[n]) n++;
        if (n == match.length()) 
          found = true;
      } 
    }
    delay(1);
  }
  if (flush) 
    Serial1.readStringUntil(lineSep);
  return true;
}

void setup() {
  Serial1.begin(115200);
  Serial1.println("");
}

void loop() {
  while (!Serial1.available()) delay(1);
  waitFor("OK",10000UL,true); 
  Serial1.println("DONE");
  Serial1.flush();
}