org.apache.lucene.spatial.prefix.tree.Cell.java Source code

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Here is the source code for org.apache.lucene.spatial.prefix.tree.Cell.java

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/*
 * 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);
}