package org.ggp.base.util.gdl.transforms;
import java.util.List;
import java.util.Set;
import org.ggp.base.util.gdl.GdlUtils;
import org.ggp.base.util.gdl.grammar.Gdl;
import org.ggp.base.util.gdl.grammar.GdlDistinct;
import org.ggp.base.util.gdl.grammar.GdlLiteral;
import org.ggp.base.util.gdl.grammar.GdlNot;
import org.ggp.base.util.gdl.grammar.GdlPool;
import org.ggp.base.util.gdl.grammar.GdlRule;
import org.ggp.base.util.gdl.grammar.GdlSentence;
import org.ggp.base.util.gdl.grammar.GdlVariable;
import com.google.common.collect.Lists;
import com.google.common.collect.Sets;
/**
* As a GDL transformer, this class takes in a GDL description of a game,
* transforms it in some way, and outputs a new GDL descriptions of a game
* which is functionally equivalent to the original game.
*
* The AimaProver does not correctly apply "distinct" literals in rules if
* they have not yet been bound. (See test_distinct_beginning_rule.kif for
* an example where this comes up.) The same is true for "not" literals.
* This transformation moves "distinct" and "not" literals later in the
* rule, so they always appear after sentence literals have defined those
* variables.
*
* This should be applied to the input to the ProverStateMachine until this
* bug is fixed some other way.
*/
public class DistinctAndNotMover {
public static List<Gdl> run(List<Gdl> oldRules) {
oldRules = DeORer.run(oldRules);
List<Gdl> newRules = Lists.newArrayListWithCapacity(oldRules.size());
for (Gdl gdl : oldRules) {
if (gdl instanceof GdlRule) {
GdlRule rule = (GdlRule) gdl;
newRules.add(reorderRule(rule));
} else {
newRules.add(gdl);
}
}
return newRules;
}
private static GdlRule reorderRule(GdlRule oldRule) {
List<GdlLiteral> newBody = Lists.newArrayList(oldRule.getBody());
rearrangeDistinctsAndNots(newBody);
return GdlPool.getRule(oldRule.getHead(), newBody);
}
private static void rearrangeDistinctsAndNots(List<GdlLiteral> ruleBody) {
Integer oldIndex = findDistinctOrNotToMoveIndex(ruleBody);
while (oldIndex != null) {
GdlLiteral literalToMove = ruleBody.get(oldIndex);
ruleBody.remove((int) oldIndex);
reinsertLiteralInRightPlace(ruleBody, literalToMove);
oldIndex = findDistinctOrNotToMoveIndex(ruleBody);
}
}
//Returns null if no distincts have to be moved.
private static Integer findDistinctOrNotToMoveIndex(List<GdlLiteral> ruleBody) {
Set<GdlVariable> setVars = Sets.newHashSet();
for (int i = 0; i < ruleBody.size(); i++) {
GdlLiteral literal = ruleBody.get(i);
if (literal instanceof GdlSentence) {
setVars.addAll(GdlUtils.getVariables(literal));
} else if (literal instanceof GdlDistinct
|| literal instanceof GdlNot) {
if (!allVarsInLiteralAlreadySet(literal, setVars)) {
return i;
}
}
}
return null;
}
private static void reinsertLiteralInRightPlace(List<GdlLiteral> ruleBody,
GdlLiteral literalToReinsert) {
Set<GdlVariable> setVars = Sets.newHashSet();
for (int i = 0; i < ruleBody.size(); i++) {
GdlLiteral literal = ruleBody.get(i);
if (literal instanceof GdlSentence) {
setVars.addAll(GdlUtils.getVariables(literal));
if (allVarsInLiteralAlreadySet(literalToReinsert, setVars)) {
ruleBody.add(i + 1, literalToReinsert);
return;
}
}
}
}
private static boolean allVarsInLiteralAlreadySet(GdlLiteral literal,
Set<GdlVariable> setVars) {
List<GdlVariable> varsInLiteral = GdlUtils.getVariables(literal);
for (GdlVariable varInLiteral : varsInLiteral) {
if (!setVars.contains(varInLiteral)) {
return false;
}
}
return true;
}
}