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Apache Solr (module: core)
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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.solr.response;

import java.io.IOException;
import java.io.Writer;
import java.util.Iterator;
import java.util.List;

import org.apache.lucene.index.IndexableField;
import org.apache.solr.common.SolrDocument;
import org.apache.solr.common.SolrDocumentList;
import org.apache.solr.common.SolrException;
import org.apache.solr.common.SolrException.ErrorCode;
import org.apache.solr.common.params.CommonParams;
import org.apache.solr.common.util.NamedList;
import org.apache.solr.request.SolrQueryRequest;
import org.apache.solr.response.transform.WriteableGeoJSON;
import org.apache.solr.schema.AbstractSpatialFieldType;
import org.apache.solr.schema.SchemaField;
import org.apache.solr.search.ReturnFields;
import org.locationtech.spatial4j.context.SpatialContext;
import org.locationtech.spatial4j.io.ShapeWriter;
import org.locationtech.spatial4j.io.SupportedFormats;
import org.locationtech.spatial4j.shape.Shape;

/**
 * Extend the standard JSONResponseWriter to support GeoJSON.  This writes
 * a {@link SolrDocumentList} with a 'FeatureCollection', following the
 * specification in geojson.org
 */
public class GeoJSONResponseWriter extends JSONResponseWriter {
  
  public static final String FIELD = "geojson.field";
  
  @Override
  public void write(Writer writer, SolrQueryRequest req, SolrQueryResponse rsp) throws IOException {
    
    String geofield = req.getParams().get(FIELD, null);
    if(geofield==null || geofield.length()==0) {
      throw new SolrException(ErrorCode.BAD_REQUEST, "GeoJSON.  Missing parameter: '"+FIELD+"'");
    }
    
    SchemaField sf = req.getSchema().getFieldOrNull(geofield);
    if(sf==null) {
      throw new SolrException(ErrorCode.BAD_REQUEST, "GeoJSON.  Unknown field: '"+FIELD+"'="+geofield);
    }
    
    SupportedFormats formats = null;
    if(sf.getType() instanceof AbstractSpatialFieldType) {
      SpatialContext ctx = ((AbstractSpatialFieldType)sf.getType()).getSpatialContext();
      formats = ctx.getFormats();
    }

    JSONWriter w = new GeoJSONWriter(writer, req, rsp, 
        geofield,
        formats); 
    
    try {
      w.writeResponse();
    } finally {
      w.close();
    }
  }
}

class GeoJSONWriter extends JSONWriter {
  
  final SupportedFormats formats;
  final ShapeWriter geowriter;
  final String geofield;
  
  public GeoJSONWriter(Writer writer, SolrQueryRequest req, SolrQueryResponse rsp, 
      String geofield, SupportedFormats formats) {
    super(writer, req, rsp);
    this.geofield = geofield;
    this.formats = formats;
    if(formats==null) {
      this.geowriter = null;
    }
    else {
      this.geowriter = formats.getGeoJsonWriter();
    }
  }

  @Override
  public void writeResponse() throws IOException {
    if(req.getParams().getBool(CommonParams.OMIT_HEADER, false)) {
      if(wrapperFunction!=null) {
          writer.write(wrapperFunction + "(");
      }
      rsp.removeResponseHeader();

      NamedList