SpatialComputedFields.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Sitecore.ContentSearch.ComputedFields;
using Sitecore.ContentSearch;
using Spatial4n.Core.Context;
using Lucene.Net.Spatial.Prefix.Tree;
using Lucene.Net.Spatial.Prefix;

namespace Sitecore.Contrib.ContentSearch.Spatial
{
    public class SpatialComputedFields : IComputedIndexField
    {
        public object ComputeFieldValue(Sitecore.ContentSearch.IIndexable indexable)
        {
            var indexableItem = indexable as SitecoreIndexableItem;
            if (indexableItem == null)
                return null;

            var item = (Sitecore.Data.Items.Item)indexableItem;
            if (item == null)
                return null;

            var latLon = item[FieldName];
            if (latLon == "")
                return null;
            
            var spatialContext = SpatialContext.GEO;
            var geohashTree = new GeohashPrefixTree(spatialContext, 10);
            var strategy = new RecursivePrefixTreeStrategy(geohashTree, FieldName);

            var shape = spatialContext.ReadShape(latLon);
            var grid = strategy.GetGrid();
            int levelForDistance = grid.GetLevelForDistance(strategy.DistErrPct);
            IList<Node> list = grid.GetNodes(shape, levelForDistance, true);

            return list.Select(node => node.GetTokenString());
        }

        public string FieldName
        {
            get;
            set;
        }

        public string ReturnType
        {
            get;
            set;
        }
    }
}