/*
* Copyright 2003-2014 JetBrains s.r.o.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package jetbrains.mps.core.aspects.behaviour;
import jetbrains.mps.smodel.SNodeUtil;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import org.jetbrains.mps.openapi.language.SAbstractConcept;
import org.jetbrains.mps.openapi.language.SConcept;
import org.jetbrains.mps.openapi.language.SInterfaceConcept;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
/**
* This class counts the linearization for a concept (method resolution order).
* It is almost C3, though it is fail-safe for the hierarchy like A impl B,C, C impl B.
* When the usual C3 algorithm fails our algorithm try to abandon the local order and preserve only super linearization.
* If that is not possible we pick up the first concept from the first super linearization.
*/
public final class C3StarMethodResolutionOrder implements CachingMethodResolutionOrder {
private ConcurrentMap<SAbstractConcept, List<SAbstractConcept>> myCache = new ConcurrentHashMap<SAbstractConcept, List<SAbstractConcept>>();
@Override
public List<SAbstractConcept> linearize(@NotNull SAbstractConcept concept) {
if (myCache.containsKey(concept)) {
return new ArrayList<SAbstractConcept>(myCache.get(concept));
}
List<List<SAbstractConcept>> superLinearizations = new ArrayList<List<SAbstractConcept>>();
List<SAbstractConcept> immediateParents = getImmediateParents(concept);
for (SAbstractConcept parent : immediateParents) {
superLinearizations.add(new C3StarMethodResolutionOrder().linearize(parent));
}
List<SAbstractConcept> linearization = new ArrayList<SAbstractConcept>();
linearization.add(concept);
linearization.addAll(merge(new MergingHelper<SAbstractConcept>(immediateParents, superLinearizations)));
myCache.putIfAbsent(concept, linearization);
return new ArrayList<SAbstractConcept>(linearization);
}
@Override
public void reset() {
myCache.clear();
}
private List<SAbstractConcept> merge(MergingHelper<SAbstractConcept> helper) {
List<SAbstractConcept> result = new ArrayList<SAbstractConcept>();
while (!helper.isEmpty()) {
boolean success = helper.findNextElement(result, KeepingLocalOrder.KEEPING_LOCAL_ORDER);
if (!success) { // trying not to preserve local order
success = helper.findNextElement(result, KeepingLocalOrder.NOT_KEEPING_LOCAL_ORDER);
if (!success) { // taking simply the first head
helper.addToResult(result, helper.head());
}
}
}
return result;
}
private static class MergingHelper<T> implements Iterable<List<T>> {
private final List<T> myLocalOrder;
private final List<List<T>> mySuperLinearizations;
private MergingHelper(List<T> immediateParents, List<List<T>> superLinearizations) {
myLocalOrder = immediateParents;
mySuperLinearizations = superLinearizations;
checkNoEmptyLins();
}
private void checkNoEmptyLins() {
for (Iterator<List<T>> iterator = mySuperLinearizations.iterator(); iterator.hasNext();) {
List<T> superLin = iterator.next();
if (superLin.isEmpty()) {
iterator.remove();
}
}
}
private boolean check(@NotNull T candidate, KeepingLocalOrder localOrder) {
for (List<T> superLinearization : mySuperLinearizations) {
if (superLinearization.lastIndexOf(candidate) > 0) return false; // only head is possible
}
if (localOrder.preserveOrder()) {
if (myLocalOrder.lastIndexOf(candidate) > 0) return false;
}
return true;
}
public void addToResult(List<T> result, T candidate) {
result.add(candidate);
myLocalOrder.remove(candidate);
List<List<T>> toRemove = new ArrayList<List<T>>();
for (List<T> list : mySuperLinearizations) {
list.remove(candidate);
if (list.isEmpty()) {
toRemove.add(list);
}
}
mySuperLinearizations.removeAll(toRemove);
}
public boolean isEmpty() {
return mySuperLinearizations.isEmpty();
}
@Override
public Iterator<List<T>> iterator() {
List<List<T>> allLists = new ArrayList<List<T>>();
allLists.addAll(mySuperLinearizations);
allLists.add(myLocalOrder);
return allLists.iterator();
}
@Nullable
public T head() {
for (List<T> superLin : mySuperLinearizations) {
if (!superLin.isEmpty()) {
return superLin.get(0);
}
}
return null;
}
private boolean checkCandidateAndAddToResult(List<T> result, T candidate, KeepingLocalOrder preserveLocalOrder) {
if (check(candidate, preserveLocalOrder)) {
addToResult(result, candidate);
return true;
}
return false;
}
/**
* trying to find the next element which is compatible with the super linearizations (and local order if localOrder is set accordingly)
* @param result if the element found it is added to the result list
* @param localOrder enum which tells not to preserve local order
* @return true if the element was found
*/
public boolean findNextElement(List<T> result, KeepingLocalOrder localOrder) {
for (List<T> candidateList : mySuperLinearizations) {
T candidate = candidateList.get(0);
boolean succeeded = checkCandidateAndAddToResult(result, candidate, localOrder);
if (succeeded) return true;
}
if (localOrder.preserveOrder()) {
if (myLocalOrder.isEmpty()) return false;
T candidate = myLocalOrder.get(0);
boolean succeeded = checkCandidateAndAddToResult(result, candidate, localOrder);
if (succeeded) return true;
}
return false;
}
}
@NotNull
private List<SAbstractConcept> getImmediateParents(SAbstractConcept concept) {
List<SAbstractConcept> immediateParents = new ArrayList<SAbstractConcept>();
if (concept instanceof SInterfaceConcept) {
for (SAbstractConcept superInt : ((SInterfaceConcept) concept).getSuperInterfaces()) {
immediateParents.add(superInt);
}
immediateParents.add(SNodeUtil.concept_BaseConcept); // hook for editor (interfaces are instances of base concept as well)
} else if (concept instanceof SConcept) {
SConcept superConcept = ((SConcept) concept).getSuperConcept();
if (superConcept != null) {
immediateParents.add(superConcept);
}
for (SAbstractConcept superInt : ((SConcept) concept).getSuperInterfaces()) {
immediateParents.add(superInt);
}
}
return immediateParents;
}
private enum KeepingLocalOrder {
KEEPING_LOCAL_ORDER,
NOT_KEEPING_LOCAL_ORDER;
public boolean preserveOrder() {
return this == KEEPING_LOCAL_ORDER;
}
}
}