/*
* 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.spatial.prefix.tree;
import org.locationtech.spatial4j.shape.Shape;
import org.locationtech.spatial4j.shape.SpatialRelation;
import org.apache.lucene.util.BytesRef;
/**
* Represents a grid cell. Cell instances are generally very transient and may be re-used
* internally. To get an instance, you could start with {@link SpatialPrefixTree#getWorldCell()}.
* And from there you could either traverse down the tree with {@link #getNextLevelCells(org.locationtech.spatial4j.shape.Shape)},
* or you could read an indexed term via {@link SpatialPrefixTree#readCell(org.apache.lucene.util.BytesRef,Cell)}.
* When a cell is read from a term, it is comprised of just the base bytes plus optionally a leaf flag.
*
* @lucene.experimental
*/
public interface Cell {
// If we bring this back; perhaps do so as a method that un-shares its internal state: void unshare();
// /** Resets the state of this cell such that it is identical to {@code source}. This can be used for
// * cloning a cell to have a safe copy, and it also might be used to position this cell
// * before calling {@link #readCell(org.apache.lucene.util.BytesRef)} in a loop if you know the first term
// * is going to be close to some other cell, thereby saving some computations. */
// void copyFrom(Cell source);
/** Gets the relationship this cell has with the shape from which it was filtered from, assuming it came from a
* {@link CellIterator}. Arguably it belongs there but it's very convenient here. */
SpatialRelation getShapeRel();
/** See {@link #getShapeRel()}.
* @lucene.internal */
void setShapeRel(SpatialRelation rel);
/**
* Some cells are flagged as leaves, which are indexed as such. A leaf cell is either within some
* shape or it both intersects and the cell is at an accuracy threshold such that no smaller cells
* for the shape will be represented.
*/
boolean isLeaf();
/** Set this cell to be a leaf. Warning: never call on a cell
* initialized to reference the same bytes from termsEnum, which should be treated as immutable.
* Note: not supported at level 0.
* @lucene.internal */
void setLeaf();
/**
* Returns the bytes for this cell, with a leaf byte <em>if this is a leaf cell</em>.
* The result param is used to save object allocation, though its bytes aren't used.
* @param result where the result goes, or null to create new
*/
BytesRef getTokenBytesWithLeaf(BytesRef result);
/**
* Returns the bytes for this cell, without a leaf set. The bytes should sort before
* {@link #getTokenBytesWithLeaf(org.apache.lucene.util.BytesRef)}.
* The result param is used to save object allocation, though its bytes aren't used.
* @param result where the result goes, or null to create new
*/
BytesRef getTokenBytesNoLeaf(BytesRef result);
/** Level 0 is the world (and has no parent), from then on a higher level means a smaller
* cell than the level before it.
*/
int getLevel();
/**
* Gets the cells at the next grid cell level underneath this one, optionally filtered by
* {@code shapeFilter}. The returned cells should have {@link #getShapeRel()} set to
* their relation with {@code shapeFilter}. In addition, for non-points {@link #isLeaf()}
* must be true when that relation is WITHIN.
* <p>
* IMPORTANT: Cells returned from this iterator can be shared, as well as the bytes.
* <p>
* Precondition: Never called when getLevel() == maxLevel.
*
* @param shapeFilter an optional filter for the returned cells.
* @return A set of cells (no dups), sorted. Not Modifiable.
*/
CellIterator getNextLevelCells(Shape shapeFilter);
/** Gets the shape for this cell; typically a Rectangle. */
Shape getShape();
/**
* Returns if the target term is within/underneath this cell; not necessarily a direct
* descendant.
* @param c the term
*/
boolean isPrefixOf(Cell c);
/** Equivalent to {@code this.getTokenBytesNoLeaf(null).compareTo(fromCell.getTokenBytesNoLeaf(null))}. */
int compareToNoLeaf(Cell fromCell);
}