/**
   * set the active center for this molecule. The active center will be those which correspond with
   * [A*]-B=C .
   *
   * <pre>
   * A: Atom with single electron
   * -: Single bond
   * B: Atom
   * =: Double bond
   * C: Atom
   *  </pre>
   *
   * @param reactant The molecule to set the activity
   * @throws CDKException
   */
  private void setActiveCenters(IAtomContainer reactant) throws CDKException {
    if (AtomContainerManipulator.getTotalNegativeFormalCharge(reactant)
        != 0 /*|| AtomContainerManipulator.getTotalPositiveFormalCharge(reactant) != 0*/) return;
    Iterator<IAtom> atoms = reactant.atoms().iterator();
    while (atoms.hasNext()) {
      IAtom atomi = atoms.next();
      if (reactant.getConnectedSingleElectronsCount(atomi) == 1) {

        Iterator<IBond> bondis = reactant.getConnectedBondsList(atomi).iterator();

        while (bondis.hasNext()) {
          IBond bondi = bondis.next();

          if (bondi.getOrder() == IBond.Order.SINGLE) {

            IAtom atomj = bondi.getConnectedAtom(atomi);
            if ((atomj.getFormalCharge() == CDKConstants.UNSET ? 0 : atomj.getFormalCharge()) == 0
                && reactant.getConnectedSingleElectronsCount(atomj) == 0) {

              Iterator<IBond> bondjs = reactant.getConnectedBondsList(atomj).iterator();
              while (bondjs.hasNext()) {
                IBond bondj = bondjs.next();

                if (bondj.equals(bondi)) continue;

                if (bondj.getOrder() == IBond.Order.DOUBLE) {

                  IAtom atomk = bondj.getConnectedAtom(atomj);
                  if ((atomk.getFormalCharge() == CDKConstants.UNSET ? 0 : atomk.getFormalCharge())
                          == 0
                      && reactant.getConnectedSingleElectronsCount(atomk) == 0) {

                    atomi.setFlag(CDKConstants.REACTIVE_CENTER, true);
                    atomj.setFlag(CDKConstants.REACTIVE_CENTER, true);
                    atomk.setFlag(CDKConstants.REACTIVE_CENTER, true);
                    bondi.setFlag(CDKConstants.REACTIVE_CENTER, true);
                    bondj.setFlag(CDKConstants.REACTIVE_CENTER, true);
                  }
                }
              }
            }
          }
        }
      }
    }
  }
  /**
   * Initiate process. It is needed to call the addExplicitHydrogensToSatisfyValency from the class
   * tools.HydrogenAdder.
   *
   * @exception CDKException Description of the Exception
   * @param reactants reactants of the reaction.
   * @param agents agents of the reaction (Must be in this case null).
   */
  @TestMethod("testInitiate_IAtomContainerSet_IAtomContainerSet")
  public IReactionSet initiate(IAtomContainerSet reactants, IAtomContainerSet agents)
      throws CDKException {

    logger.debug("initiate reaction: RearrangementRadicalReaction");

    if (reactants.getAtomContainerCount() != 1) {
      throw new CDKException("RearrangementRadicalReaction only expects one reactant");
    }
    if (agents != null) {
      throw new CDKException("RearrangementRadicalReaction don't expects agents");
    }

    IReactionSet setOfReactions =
        DefaultChemObjectBuilder.getInstance().newInstance(IReactionSet.class);
    IAtomContainer reactant = reactants.getAtomContainer(0);

    /* if the parameter hasActiveCenter is not fixed yet, set the active centers*/
    IParameterReact ipr = super.getParameterClass(SetReactionCenter.class);
    if (ipr != null && !ipr.isSetParameter()) setActiveCenters(reactant);

    Iterator<IAtom> atoms = reactants.getAtomContainer(0).atoms().iterator();
    while (atoms.hasNext()) {
      IAtom atomi = atoms.next();
      if (atomi.getFlag(CDKConstants.REACTIVE_CENTER)
          && reactant.getConnectedSingleElectronsCount(atomi) == 1) {

        Iterator<IBond> bondis = reactant.getConnectedBondsList(atomi).iterator();

        while (bondis.hasNext()) {
          IBond bondi = bondis.next();

          if (bondi.getFlag(CDKConstants.REACTIVE_CENTER)
              && bondi.getOrder() == IBond.Order.SINGLE) {

            IAtom atomj = bondi.getConnectedAtom(atomi);
            if (atomi.getFlag(CDKConstants.REACTIVE_CENTER)
                && (atomj.getFormalCharge() == CDKConstants.UNSET ? 0 : atomj.getFormalCharge())
                    == 0
                && reactant.getConnectedSingleElectronsCount(atomj) == 0) {

              Iterator<IBond> bondjs = reactant.getConnectedBondsList(atomj).iterator();
              while (bondjs.hasNext()) {
                IBond bondj = bondjs.next();

                if (bondj.equals(bondi)) continue;

                if (bondj.getFlag(CDKConstants.REACTIVE_CENTER)
                    && bondj.getOrder() == IBond.Order.DOUBLE) {

                  IAtom atomk = bondj.getConnectedAtom(atomj);
                  if (atomk.getFlag(CDKConstants.REACTIVE_CENTER)
                      && (atomk.getFormalCharge() == CDKConstants.UNSET
                              ? 0
                              : atomk.getFormalCharge())
                          == 0
                      && reactant.getConnectedSingleElectronsCount(atomk) == 0) {

                    ArrayList<IAtom> atomList = new ArrayList<IAtom>();
                    atomList.add(atomi);
                    atomList.add(atomj);
                    atomList.add(atomk);
                    ArrayList<IBond> bondList = new ArrayList<IBond>();
                    bondList.add(bondi);
                    bondList.add(bondj);

                    IAtomContainerSet moleculeSet =
                        reactant.getBuilder().newInstance(IAtomContainerSet.class);
                    moleculeSet.addAtomContainer(reactant);
                    IReaction reaction = mechanism.initiate(moleculeSet, atomList, bondList);
                    if (reaction == null) continue;
                    else setOfReactions.addReaction(reaction);
                  }
                }
              }
            }
          }
        }
      }
    }
    return setOfReactions;
  }