/**
     *
     * Returns the encounter with the obs that aren't used when populating form are removed.
     * This *doesn't* save the encounter.
     * TODO: handle Orders?
     *
     * @param e
     * @param htmlform
     * @return
     * @throws Exception
     */
    public static Encounter trimEncounterToMatchForm(Encounter e, HtmlForm htmlform) throws Exception {

       //this should move existing obs from session to tag handlers.
        FormEntrySession session = new FormEntrySession(e.getPatient(), e, FormEntryContext.Mode.VIEW, htmlform, null); // session gets a null HttpSession
        session.getHtmlToDisplay();

        if (log.isDebugEnabled()){
            Map<Concept, List<Obs>>  map = session.getContext().getExistingObs();
            if (map != null){
                for (Map.Entry<Concept, List<Obs>> existingObs : map.entrySet()){
                    List<Obs> oList = existingObs.getValue();
                    for (Obs oInner : oList)
                        log.debug("Obs in existingObs " + existingObs.getKey() + " " + oInner.getConcept());
                }
            }
            Map<Obs, Set<Obs>> map2 = session.getContext().getExistingObsInGroups();
            if (map2 != null){
                for (Map.Entry<Obs, Set<Obs>> existingObsInGroups : map2.entrySet()){
                    Set<Obs> oList = existingObsInGroups.getValue();
                    for (Obs oInner : oList)
                        log.debug("Obs in existingObsInGroups " + existingObsInGroups.getKey().getConcept() + " " + oInner.getConcept());
                }
            }
        }
        Encounter ret = new Encounter();
        ret.setCreator(e.getCreator());
        ret.setEncounterDatetime(e.getEncounterDatetime());
        EncounterCompatibility.setProvider(ret, EncounterCompatibility.getProvider(e));
        ret.setLocation(e.getLocation());
        ret.setDateCreated(e.getDateCreated());
        ret.setPatient(e.getPatient());
        //renders new encounter unsave-able:
        ret.setEncounterId(e.getEncounterId());

        for (Obs oTest : e.getAllObs()){
            boolean found = false;
            if (session.getContext().getExistingObs() != null && !oTest.isObsGrouping()){
                List<Obs> obsList = session.getContext().getExistingObs().get(oTest.getConcept());
                if (obsList != null && obsList.size() > 0){
                    for (Obs o : obsList){
                        if (o.getObsId().equals(oTest.getObsId())){
                            found = true;
                            continue;
                        }
                    }
                }
            }
            if (!found && session.getContext().getExistingObsInGroups() != null){
                for (Map.Entry<Obs, Set<Obs>> mapEntry : session.getContext().getExistingObsInGroups().entrySet()){
                    if (mapEntry.getKey().equals(oTest)){
                        found = true;
                        continue;
                    } else {
                        Set<Obs> oSet = mapEntry.getValue();
                        //note: oSet.contains fails for some reason
                        for (Obs o:oSet){
                              if (o.getObsId().equals(oTest.getObsId())){
                                  found = true;
                                  continue;
                              }
                        }
                    }
                }
            }
            if (!found)
                ret.addObs(oTest);
        }
        session = null;
        return ret;
    }