import java.io.IOException;
import java.util.HashMap;
import java.util.List;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.apache.solr.client.solrj.SolrClient;
import org.apache.solr.client.solrj.SolrServerException;
import org.apache.solr.client.solrj.impl.Http2SolrClient;
import org.apache.solr.client.solrj.response.QueryResponse;
import org.apache.solr.common.params.MapSolrParams;

public class Searcher {
    private static final Logger LOGGER = LogManager.getLogger(Searcher.class);

    private SolrClient solrClient;

    public Searcher(String url, String user, String password) {
        solrClient = new Http2SolrClient.Builder(url)
                .connectionTimeout(10000)
                .withBasicAuthCredentials(user, password)
                .build();
    }

    public SearchResultSet search(String query, String collection, long offset, int limit) {
        final MapSolrParams queryParams = new MapSolrParams(new HashMap<String, String>() {
            {
                // https://solr.apache.org/guide/solr/latest/query-guide/standard-query-parser.html
                put("q", query);
                // put("q.op", "OR");
                put("df", "lemma4search");

                // pagination
                // https://solr.apache.org/guide/solr/latest/query-guide/pagination-of-results.html
                put("start", String.valueOf(offset)); // starts with 0
                put("rows", String.valueOf(limit));

                // highlighting
                // https://solr.apache.org/guide/solr/latest/query-guide/highlighting.html
                put("hl", "true");
                put("hl.fl", "dataview_hits"); // only highlight on "dataview_hits"
                put("hl.fragsize", "0"); // whole field
                put("hl.simple.pre", "<Hit>"); // no prefix so that we can parse more easily
                put("hl.simple.post", "</Hit>");
            }
        });

        try {
            final QueryResponse response = solrClient.query(collection, queryParams);
            final long total = response.getResults().getNumFound();
            final List<ResultEntry> entries = response.getBeans(ResultEntry.class);

            // process highlighting (update dataview_hits)
            for (ResultEntry entry : entries) {
                if (!response.getHighlighting().containsKey(entry.id)) {
                    continue;
                }
                final List<String> highlights = response.getHighlighting().get(entry.id).get("dataview_hits");
                if (highlights == null || highlights.size() == 0) {
                    continue;
                }
                final String highlight = highlights.get(0);
                entry.dataview_hits = highlight;
            }

            LOGGER.debug("results: {}", entries);
            return new SearchResultSet(collection, query, entries, total, offset);
        } catch (SolrServerException | IOException e) {
            LOGGER.error("Solr request error", e);
        }

        return null;
    }

}