/* Copyright (2007-2012) Schibsted ASA
* This file is part of Possom.
*
* Possom is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Possom is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with Possom. If not, see <http://www.gnu.org/licenses/>.
* AbstractAlternation.java
*
*
*/
package no.sesat.search.query.parser.alt;
import java.util.LinkedList;
import java.util.List;
import no.sesat.search.query.AndClause;
import no.sesat.search.query.AndNotClause;
import no.sesat.search.query.Clause;
import no.sesat.search.query.DefaultOperatorClause;
import no.sesat.search.query.BinaryClause;
import no.sesat.search.query.NotClause;
import no.sesat.search.query.UnaryClause;
import no.sesat.search.query.OrClause;
import no.sesat.search.query.XorClause;
import no.sesat.search.query.finder.ChildFinder;
import org.apache.log4j.Logger;
/** Base abstraction class for any Alternation implementation.
* Contains helper methods that are typically used within the alternation process.
* Some of these methods inturn delegate to visitor implementations found under the finder package.
*
*
* @version <tt>$Id$</tt>
*/
public abstract class AbstractAlternation implements Alternation{
// Constants -----------------------------------------------------
private static final Logger LOG = Logger.getLogger(AbstractAlternation.class);
private static final String ERR_MULTIPLE_POSSIBLE_PARENTS = "Multiple parents exist with same (or sub) class as ";
// Attributes ----------------------------------------------------
/**
* The context to work within.
*/
protected final Context context;
// Static --------------------------------------------------------
// Constructors --------------------------------------------------
/** Creates a new instance of AbstractAlternation
* @param cxt
*/
public AbstractAlternation(final Context cxt) {
context = cxt;
}
// Public --------------------------------------------------------
// Package protected ---------------------------------------------
// Protected -----------------------------------------------------
/** will return null instead of a leafClause
* @param clause
* @return
*/
protected <T extends BinaryClause> T leftOpChild(final T clause){
final Clause c = leftChild(clause);
return clause.getClass().isAssignableFrom(c.getClass()) ? (T) c : null;
}
/** return the left child, left or operation.
* @param clause
* @return
*/
protected Clause leftChild(final UnaryClause clause) {
final Clause c = clause.getFirstClause();
LOG.trace("leftChild -->" + c);
return c;
}
/** will return null instead of a leafClause
* @param clause
* @return
*/
protected <T extends BinaryClause> T rightOpChild(final T clause){
final Clause c = rightChild(clause);
return clause.getClass().isAssignableFrom(c.getClass()) ? (T) c : null;
}
/** will return right child, leaf or operation.
* @param clause
* @return
*/
protected Clause rightChild(final BinaryClause clause) {
final Clause c = clause.getSecondClause();
LOG.trace("rightChild -->" + c);
return c;
}
/** return the parent operation clause of the given child.
* And the child must be a descendant of the root.
* The result will also be assignable from the root argument's class.
* If there exists multiple parents all of the required class an IllegalStateException is thrown.
* @param child
* @param root
*/
protected <T extends UnaryClause> T parent(final T root, final Clause child) {
final List<UnaryClause> parents = context.getParentFinder().getParents(root, child);
T result = null;
for(UnaryClause c : parents){
if(root.getClass().isAssignableFrom(c.getClass())){
if(null != result){
throw new IllegalStateException(ERR_MULTIPLE_POSSIBLE_PARENTS + root.getClass());
}
result = (T)c;
}
}
return result;
}
/** return all parents operation clauses of the given child.
* @param root
* @param child
* @return
*/
protected <T extends UnaryClause> List<T> parents(final T root, final Clause child) {
return (List<T>) context.getParentFinder().getParents(root, child);
}
/** Build new DoubleOperatorClauses from newChild all the way back up to the root.
* XXX Only handles single splits, or one layer of variations, denoted by the originalParent argument.
* This could be solved by using an array, specifying ancestry line, for the argument instead. <br/><br/>
* If, under root, originalParent cannot be found then root is returned unaltered.
* @param root the root clause. an altered version of this will be returned.
* @param newChild the new child.
* @param originalChild the original child.
* @param originalParent the original parent of the original child. expected to be found under root.
* @return the root clause where the originalChild has been replaced with the newChild.
*/
protected UnaryClause replaceDescendant(
final BinaryClause root,
final BinaryClause newChild,
final BinaryClause originalChild,
final BinaryClause originalParent){
// pre-condition check: originalParent must be found under root somewhere
if(new ChildFinder().childExists(root, originalParent)){
UnaryClause nC = newChild;
UnaryClause rC = originalChild;
UnaryClause rCParent = originalParent;
do{
nC = replaceOperatorClause(nC, rC, rCParent);
for(UnaryClause parent : context.getParentFinder().getParents(root, rC)){
if(rCParent == parent){
rC = parent;
rCParent = root == rCParent
? rCParent
: context.getParentFinder().getParent(root, rCParent);
break;
}
}
}while(root != rC);
return nC;
}else{
LOG.error("originalParent does not live inside root\n" + originalParent + '\n' + root);
// return the unaltered root
return root;
}
}
/** Replace the originalChild that exists under the originalParent will the newChild.
*
* @param newChild
* @param originalChild
* @param originalParent
* @return
*/
protected <T extends UnaryClause> T replaceOperatorClause(
final Clause newChild,
final Clause originalChild,
final T originalParent) {
final Clause leftChild = leftChild(originalParent) == originalChild
? newChild
: leftChild(originalParent);
final Clause rightChild;
if(originalParent instanceof BinaryClause){
rightChild = rightChild((BinaryClause)originalParent) == originalChild
? newChild
: rightChild((BinaryClause)originalParent);
}else{
rightChild = null;
}
// XXX last argument needs to be from original branch
return createOperatorClause(leftChild, rightChild, originalParent);
}
/** Create a new operator clause, of type opCls, with the left and right children.
* We must also specify for whom it is to be a replacement for.
* The replacementFor must be from the original branch.
** @param left
* @param right
* @param replacementFor
* @return
*/
protected <T extends UnaryClause> T createOperatorClause(
final Clause left,
final Clause right,
final T replacementFor) {
LOG.debug("createOperatorClause(" + left + ", " + right + ", " + replacementFor + ")");
T clause = null;
if (AndClause.class.isAssignableFrom(replacementFor.getClass())) {
clause = (T) context.createAndClause(left, right);
} else if (XorClause.class.isAssignableFrom(replacementFor.getClass())) {
clause = (T) context.createXorClause(left, right, ((XorClause)replacementFor).getHint());
} else if (OrClause.class.isAssignableFrom(replacementFor.getClass())) {
clause = (T) context.createOrClause(left, right);
} else if (DefaultOperatorClause.class.isAssignableFrom(replacementFor.getClass())) {
clause = (T) context.createDefaultOperatorClause(left, right);
}else if (NotClause.class.isAssignableFrom(replacementFor.getClass())){
clause = (T) context.createNotClause(left);
}else if (AndNotClause.class.isAssignableFrom(replacementFor.getClass())){
clause = (T) context.createAndNotClause(left);
}
return clause;
}
/** Create XorClauses required to present all the alternatives in the query tree.
* There will be alternatives.size()-1 XorClauses aligned in a right-leaning branch.
*
* @param alternatives what will be leaves of the right-leaning XorClause branch returned
* @return the right-leaning XorClause branch
*/
protected XorClause createXorClause(final LinkedList<? extends Clause> alternatives){
return context.createXorClause(
alternatives.removeLast(),
alternatives.size() == 1 ? alternatives.removeLast() : createXorClause(alternatives),
getAlternationHint());
}
/** What XorClause.Hint is used for newly created XorClause alternations.
*
* @return the XorClause.Hint used during this alternation process.
*/
protected abstract XorClause.Hint getAlternationHint();
// Private -------------------------------------------------------
// Inner classes -------------------------------------------------
}