Method getPrecursorSpectrum

src/openms/source/KERNEL/MSExperiment.cpp:514–561

@brief Returns the precursor spectrum of the scan pointed to by @p iterator If there is no precursor scan the past-the-end iterator is returned. This assumes that precursors occur somewhere before the current spectrum but not necessarily the first one from the last MS level (we double-check with the annotated precursorList. */

  the annotated precursorList.
  */
  MSExperiment::ConstIterator MSExperiment::getPrecursorSpectrum(ConstIterator iterator) const
  {
    // if we are after the end or at the beginning where we can't go "up"
    if (iterator == spectra_.end() || iterator == spectra_.begin())
    {
      return spectra_.end();
    }
    UInt ms_level = iterator->getMSLevel();

    if (ms_level == 1) // assumes there is not level 0
    {
      return spectra_.end();
    }

    if (!iterator->getPrecursors().empty())
    {
      //TODO warn about taking first with the blocking LOG_WARN in such a central class?
      //if (iterator->getPrecursors().size() > 1) ...

      const auto precursor = iterator->getPrecursors()[0];
      if (precursor.metaValueExists("spectrum_ref"))
      {
        String ref = precursor.getMetaValue("spectrum_ref");
        auto tmp_spec_iter = iterator; // such that we can reiterate later
        do
        {
          --tmp_spec_iter;
          if ((ms_level - tmp_spec_iter->getMSLevel() == 1) && (tmp_spec_iter->getNativeID() == ref))
          {
            return tmp_spec_iter;
          }
        } while (tmp_spec_iter != spectra_.begin());
      }
    }

    // if no precursor annotation was found or it did not have a spectrum reference,
    // just
    do
    {
      --iterator;
      if (ms_level - iterator->getMSLevel() == 1)
      {
        return iterator;
      }
    } while (iterator != spectra_.begin());

    return spectra_.end();
  }

  // same as above but easier to wrap in python
  int MSExperiment::getPrecursorSpectrum(int zero_based_index) const