char totalFrames[] = "\"totalFrames\":\"2\",";
char frame1[] = "\"frame1\":\"0,0,255,0,0;0,1,255,0,0;0,2,255,255,0;0,3,255,255,0;\",";
char frame2[] = "\"frame2\":\"0,0,255,255,0;0,2,255,255,0;\",";

void parseLine(char * line) {
  const size_t totalFrameLength = strlen("\"totalFrames\":\"");
  const size_t FrameIDLength = strlen("\"frame");

  if (strncmp(line, "\"totalFrames\":\"", totalFrameLength) == 0) {
    // totalFrames
    Serial.print("it's the total Frame count ==> ");
    char *endPtr;
    long n = strtol (line + totalFrameLength, &endPtr, 10); // https://cplusplus.com/reference/cstdlib/strtol/;
    if (*endPtr == '\"') {
      Serial.print("Expecting ");
      Serial.print(n);
      Serial.println(" frames.");
    } else {
      Serial.println("wrong format.");
    }
  }
  else if (strncmp(line, "\"frame", FrameIDLength) == 0) {
    Serial.print("it's a frame definition ==> ");
    char *endPtr;
    long n = strtol (line + FrameIDLength, &endPtr, 10);
    if (strncmp(endPtr, "\":\"", 3) == 0) {
      Serial.print("Frame ID ");
      Serial.println(n);
      char * startPtr = endPtr += 3; // go to the start of the [x,y,r,g,b;] repetition
      int x, y, r, g, b;
      while (*startPtr != '\"') {
        if (sscanf(startPtr, "%d,%d,%d,%d,%d;", &x, &y, &r, &g, &b) == 5) {
          Serial.print("point ("); Serial.print(x);
          Serial.print(", "); Serial.print(y);
          Serial.print(") - color ("); Serial.print(r);
          Serial.print(", "); Serial.print(g);
          Serial.print(", "); Serial.print(b);
          Serial.println(")");
        } else {
          Serial.println("wrong point format.");
          break;
        }
        startPtr = strchr(startPtr, ';') + 1;
      }
      Serial.println("------- END OF FRAME -------");
    } else {
      Serial.println("wrong frame format.");
    }
  }
  else {
    Serial.println("not recognized");
  }
}


void setup() {
  Serial.begin(115200);
  parseLine(totalFrames);
  parseLine(frame1);
  parseLine(frame2);
}

void loop() {}