| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You 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 org.apache.lucene.search.spans; |
| |
| |
| import java.io.IOException; |
| import java.util.Objects; |
| |
| import org.apache.lucene.search.TwoPhaseIterator; |
| |
| /** |
| * A {@link Spans} implementation wrapping another spans instance, |
| * allowing to filter spans matches easily by implementing {@link #accept} |
| */ |
| public abstract class FilterSpans extends Spans { |
| |
| /** The wrapped spans instance. */ |
| protected final Spans in; |
| |
| private boolean atFirstInCurrentDoc = false; |
| private int startPos = -1; |
| |
| /** Wrap the given {@link Spans}. */ |
| protected FilterSpans(Spans in) { |
| this.in = Objects.requireNonNull(in); |
| } |
| |
| /** |
| * Returns YES if the candidate should be an accepted match, |
| * NO if it should not, and NO_MORE_IN_CURRENT_DOC if iteration |
| * should move on to the next document. |
| */ |
| protected abstract AcceptStatus accept(Spans candidate) throws IOException; |
| |
| @Override |
| public final int nextDoc() throws IOException { |
| while (true) { |
| int doc = in.nextDoc(); |
| if (doc == NO_MORE_DOCS) { |
| return NO_MORE_DOCS; |
| } else if (twoPhaseCurrentDocMatches()) { |
| return doc; |
| } |
| } |
| } |
| |
| @Override |
| public final int advance(int target) throws IOException { |
| int doc = in.advance(target); |
| while (doc != NO_MORE_DOCS) { |
| if (twoPhaseCurrentDocMatches()) { |
| break; |
| } |
| doc = in.nextDoc(); |
| } |
| |
| return doc; |
| } |
| |
| @Override |
| public final int docID() { |
| return in.docID(); |
| } |
| |
| @Override |
| public final int nextStartPosition() throws IOException { |
| if (atFirstInCurrentDoc) { |
| atFirstInCurrentDoc = false; |
| return startPos; |
| } |
| |
| for (;;) { |
| startPos = in.nextStartPosition(); |
| if (startPos == NO_MORE_POSITIONS) { |
| return NO_MORE_POSITIONS; |
| } |
| switch(accept(in)) { |
| case YES: |
| return startPos; |
| case NO: |
| break; |
| case NO_MORE_IN_CURRENT_DOC: |
| return startPos = NO_MORE_POSITIONS; // startPos ahead for the current doc. |
| } |
| } |
| } |
| |
| @Override |
| public final int startPosition() { |
| return atFirstInCurrentDoc ? -1 : startPos; |
| } |
| |
| @Override |
| public final int endPosition() { |
| return atFirstInCurrentDoc ? -1 |
| : (startPos != NO_MORE_POSITIONS) ? in.endPosition() : NO_MORE_POSITIONS; |
| } |
| |
| @Override |
| public int width() { |
| return in.width(); |
| } |
| |
| @Override |
| public void collect(SpanCollector collector) throws IOException { |
| in.collect(collector); |
| } |
| |
| @Override |
| public final long cost() { |
| return in.cost(); |
| } |
| |
| @Override |
| public String toString() { |
| return "Filter(" + in.toString() + ")"; |
| } |
| |
| @Override |
| public final TwoPhaseIterator asTwoPhaseIterator() { |
| TwoPhaseIterator inner = in.asTwoPhaseIterator(); |
| if (inner != null) { |
| // wrapped instance has an approximation |
| return new TwoPhaseIterator(inner.approximation()) { |
| @Override |
| public boolean matches() throws IOException { |
| return inner.matches() && twoPhaseCurrentDocMatches(); |
| } |
| |
| @Override |
| public float matchCost() { |
| return inner.matchCost(); // underestimate |
| } |
| |
| @Override |
| public String toString() { |
| return "FilterSpans@asTwoPhaseIterator(inner=" + inner + ", in=" + in + ")"; |
| } |
| }; |
| } else { |
| // wrapped instance has no approximation, but |
| // we can still defer matching until absolutely needed. |
| return new TwoPhaseIterator(in) { |
| @Override |
| public boolean matches() throws IOException { |
| return twoPhaseCurrentDocMatches(); |
| } |
| |
| @Override |
| public float matchCost() { |
| return in.positionsCost(); // overestimate |
| } |
| |
| @Override |
| public String toString() { |
| return "FilterSpans@asTwoPhaseIterator(in=" + in + ")"; |
| } |
| }; |
| } |
| } |
| |
| @Override |
| public float positionsCost() { |
| throw new UnsupportedOperationException(); // asTwoPhaseIterator never returns null |
| } |
| |
| /** |
| * Returns true if the current document matches. |
| * <p> |
| * This is called during two-phase processing. |
| */ |
| // return true if the current document matches |
| @SuppressWarnings("fallthrough") |
| private final boolean twoPhaseCurrentDocMatches() throws IOException { |
| atFirstInCurrentDoc = false; |
| startPos = in.nextStartPosition(); |
| assert startPos != NO_MORE_POSITIONS; |
| for (;;) { |
| switch(accept(in)) { |
| case YES: |
| atFirstInCurrentDoc = true; |
| return true; |
| case NO: |
| startPos = in.nextStartPosition(); |
| if (startPos != NO_MORE_POSITIONS) { |
| break; |
| } |
| // else fallthrough |
| case NO_MORE_IN_CURRENT_DOC: |
| startPos = -1; |
| return false; |
| } |
| } |
| } |
| |
| /** |
| * Status returned from {@link FilterSpans#accept(Spans)} that indicates |
| * whether a candidate match should be accepted, rejected, or rejected |
| * and move on to the next document. |
| */ |
| public static enum AcceptStatus { |
| /** Indicates the match should be accepted */ |
| YES, |
| |
| /** Indicates the match should be rejected */ |
| NO, |
| |
| /** |
| * Indicates the match should be rejected, and the enumeration may continue |
| * with the next document. |
| */ |
| NO_MORE_IN_CURRENT_DOC |
| }; |
| } |