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/**
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* Copyright (C) 2018 EDIT
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* European Distributed Institute of Taxonomy
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* http://www.e-taxonomy.eu
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*
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* The contents of this file are subject to the Mozilla Public License Version 1.1
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* See LICENSE.TXT at the top of this package for the full license terms.
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*/
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package eu.etaxonomy.cdm.model.metadata;
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import java.util.ArrayList;
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import java.util.List;
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import eu.etaxonomy.cdm.common.CdmUtils;
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import eu.etaxonomy.cdm.model.metadata.CdmPreference.PrefKey;
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/**
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* @author a.mueller
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* @since 28.11.2018
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*/
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public class PreferenceResolver {
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protected static final String MULTI_BEST_MATCHING = "There are 2 best matching preferences with equal key but differing values";
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/**
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* Returns the best matching {@link CdmPreference preference} for the
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* given preference list and for the given {@link PrefKey preference key}
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* or <code>null</code> if none is matching.<BR>
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* A preference is matching if the preference key is matching the given key.
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* Keys are matching if they {@link PreferencePredicate predicates} are
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* equal and if the given {@link PreferenceSubject subject} matches
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* the preferences subject.<BR>
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* A subject A matches another subject B if all parts of A can also be found
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* in B in the same order. However, A may have parts that can not be found in B
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* but still it matches. But B must not have parts that can not be found in A
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* and all parts of B must be in the same order as in A otherwise it does not match.<BR>
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* The <b>best</b> key match is computed from the back recursively.
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* If the last part matches it matches better then matching only the second but last.
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* If !=1 keys match the last part the best matching is computed on
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* the first n-1 parts of the key.<BR>
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*
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* If key or one of its parts is <code>null</code>, <code>null</code> is returned.
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*
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* @return the best matching preference
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* @throws IllegalArgumentException if the given preferences list contains 2 preference
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* with completely equal best matching keys but with different values.
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*/
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public static CdmPreference resolve(List<CdmPreference> preferences, PrefKey key) throws IllegalArgumentException{
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if (key == null ||key.getPredicate() == null || key.getSubject() == null){
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return null;
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}
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List<CdmPreference> matchingPreferences = new ArrayList<>();
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for (CdmPreference preference : preferences){
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if (preference == null|| preference.getKey()== null){
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continue;
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}
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if (key.getPredicate().equals(preference.getKey().getPredicate())){
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if (subjectMatches(PreferenceSubject.NewInstance(key.getSubject()), PreferenceSubject.NewInstance(preference.getKey().getSubject()))){
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matchingPreferences.add(preference);
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}
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}
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}
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CdmPreference bestMatching = null;
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boolean multipleBestMatching = false;
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for (CdmPreference preference : matchingPreferences){
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if (bestMatching == null){
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bestMatching = preference;
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continue;
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}else{
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int c = compare(PreferenceSubject.fromPreference(preference), PreferenceSubject.fromPreference(bestMatching), PreferenceSubject.fromKey(key) );
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if (c < 0){
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bestMatching = preference;
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multipleBestMatching = false;
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}else if (c == 0){
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if(!CdmUtils.nullSafeEqual(preference.getValue(), bestMatching.getValue())||
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preference.isAllowOverride()!= bestMatching.isAllowOverride()){
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multipleBestMatching = true;
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}
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}else{
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multipleBestMatching = false;
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}
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}
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}
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if (multipleBestMatching){
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throw new IllegalArgumentException(MULTI_BEST_MATCHING);
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}
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return bestMatching;
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}
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/**
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* Compares 2 subjects. Returns a value < 0, if subject1 is better matching,
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* returns a value >0 if subject2 is better matching.
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* Returns 0 if both subjects are equal.
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* @param subject1
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* @param subject2
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* @return
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*/
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private static int compare(PreferenceSubject subject1, PreferenceSubject subject2,
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PreferenceSubject compareAgainst) {
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String last = compareAgainst.getLastPart();
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String last1 = subject1.getLastPart();
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String last2 = subject2.getLastPart();
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if (compareAgainst.isRoot()){
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return 0;
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}
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if (last.equals(last1)){
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if (!last.equals(last2)){
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return -1;
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}else{
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return compare(subject1.getNextHigher(), subject2.getNextHigher(), compareAgainst.getNextHigher());
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}
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}else if(last.equals(last2)){
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return 1;
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}else{
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return compare(subject1, subject2, compareAgainst.getNextHigher());
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}
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}
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/**
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* @param subject
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* @param subject2
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* @return
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*/
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private static boolean subjectMatches(PreferenceSubject subjectA, PreferenceSubject subjectB) {
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List<String> partsA = subjectA.getParts();
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List<String> partsB = subjectB.getParts();
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for (int a = partsA.size()-1 ; a>=0 ; a--){
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String lastA = partsA.get(a);
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String lastB = partsB.get(partsB.size()-1);
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if (lastA.equals(lastB) && !partsB.isEmpty()){
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partsB = partsB.subList(0, partsB.size()-1);
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}
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}
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return partsB.isEmpty();
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}
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}
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