src/Lucene.Net.Spatial/Prefix/Tree/Node.cs

/*
 * 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.
 */

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics;
using System.Runtime.CompilerServices;
using Spatial4n.Core.Shapes;

namespace Lucene.Net.Spatial.Prefix.Tree
{
    public abstract class Node : IComparable<Node>
    {
        public static byte LEAF_BYTE = (byte)'+';//NOTE: must sort before letters & numbers

        // /*
        //Holds a byte[] and/or String representation of the cell. Both are lazy constructed from the other.
        //Neither contains the trailing leaf byte.
        // */
        //private byte[] bytes;
        //private int b_off;
        //private int b_len;

        private String token;//this is the only part of equality

        protected SpatialRelation shapeRel;//set in getSubCells(filter), and via setLeaf().
        protected readonly SpatialPrefixTree spatialPrefixTree;

        protected Node(SpatialPrefixTree spatialPrefixTree, String token)
        {
            this.spatialPrefixTree = spatialPrefixTree;
            this.token = token;
            if (token.Length > 0 && token[token.Length - 1] == (char)LEAF_BYTE)
            {
                this.token = token.Substring(0, token.Length - 1);
                SetLeaf();
            }

            if (GetLevel() == 0)
                GetShape();//ensure any lazy instantiation completes to make this threadsafe
        }

        public virtual void Reset(string newToken)
        {
            Debug.Assert(GetLevel() != 0);
            this.token = newToken;
            shapeRel = SpatialRelation.NULL_VALUE;
            b_fixLeaf();
        }

        private void b_fixLeaf()
        {
            if (GetLevel() == spatialPrefixTree.GetMaxLevels())
            {
                SetLeaf();
            }
        }

        public SpatialRelation GetShapeRel()
        {
            return shapeRel;
        }

        public bool IsLeaf()
        {
            return shapeRel == SpatialRelation.WITHIN;
        }

        public void SetLeaf()
        {
            Debug.Assert(GetLevel() != 0);
            shapeRel = SpatialRelation.WITHIN;
        }

        /*
         * Note: doesn't contain a trailing leaf byte.
         */
        public String GetTokenString()
        {
            if (token == null)
                throw new InvalidOperationException("Somehow we got a null token");
            return token;
        }

        ///// <summary>
        ///// Note: doesn't contain a trailing leaf byte.
        ///// </summary>
        ///// <returns></returns>
        //public byte[] GetTokenBytes()
        //{
        //    if (bytes != null)
        //    {
        //        if (b_off != 0 || b_len != bytes.Length)
        //        {
        //            throw new IllegalStateException("Not supported if byte[] needs to be recreated.");
        //        }
        //    }
        //    else
        //    {
        //        bytes = token.GetBytes(SpatialPrefixTree.UTF8);
        //        b_off = 0;
        //        b_len = bytes.Length;
        //    }
        //    return bytes;
        //}

        public int GetLevel()
        {
            return token.Length;
            //return token != null ? token.Length : b_len;
        }

        //TODO add getParent() and update some algorithms to use this?
        //public Cell getParent();

        /*
         * Like {@link #getSubCells()} but with the results filtered by a shape. If that shape is a {@link com.spatial4j.core.shape.Point} then it
         * must call {@link #getSubCell(com.spatial4j.core.shape.Point)};
         * 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.
         */
        public IList<Node> GetSubCells(Shape shapeFilter)
        {
            //Note: Higher-performing subclasses might override to consider the shape filter to generate fewer cells.
            var point = shapeFilter as Point;
            if (point != null)
            {
#if !NET35
                return new ReadOnlyCollectionBuilder<Node>(new[] { GetSubCell(point) }).ToReadOnlyCollection();
#else
                return new List<Node>(new[]{GetSubCell(point)}).AsReadOnly();
#endif

            }

            var cells = GetSubCells();
            if (shapeFilter == null)
            {
                return cells;
            }
            var copy = new List<Node>(cells.Count);//copy since cells contractually isn't modifiable
            foreach (var cell in cells)
            {
                SpatialRelation rel = cell.GetShape().Relate(shapeFilter);
                if (rel == SpatialRelation.DISJOINT)
                    continue;
                cell.shapeRel = rel;
                copy.Add(cell);
            }
            cells = copy;
            return cells;
        }

        /*
         * Performant implementations are expected to implement this efficiently by considering the current
         * cell's boundary.
         * Precondition: Never called when getLevel() == maxLevel.
         * Precondition: this.getShape().relate(p) != DISJOINT.
         */
        public abstract Node GetSubCell(Point p);

        //TODO Cell getSubCell(byte b)

        /*
         * Gets the cells at the next grid cell level that cover this cell.
         * Precondition: Never called when getLevel() == maxLevel.
         *
         * @return A set of cells (no dups), sorted. Not Modifiable.
         */
        public abstract IList<Node> GetSubCells();

        /*
         * {@link #getSubCells()}.size() -- usually a constant. Should be >=2
         */
        public abstract int GetSubCellsSize();

        public abstract Shape GetShape();

        public virtual Point GetCenter()
        {
            return GetShape().GetCenter();
        }


        public int CompareTo(Node o)
        {
            return System.String.CompareOrdinal(GetTokenString(), o.GetTokenString());
        }

        public override bool Equals(object obj)
        {
            return !(obj == null || !(obj is Node)) && GetTokenString().Equals(((Node)obj).GetTokenString());
        }

        public override int GetHashCode()
        {
            return GetTokenString().GetHashCode();
        }

        public override string ToString()
        {
            return GetTokenString() + (IsLeaf() ? new string(new[] { (char)LEAF_BYTE }) : string.Empty);
        }
    }
}