package eu.openaire.pdf_aggregation_statistics.services;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.dao.EmptyResultDataAccessException;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Service;

import java.sql.SQLException;
import java.util.concurrent.ConcurrentHashMap;


@Service
public class StatsServiceImpl implements StatsService {

    private static final Logger logger = LoggerFactory.getLogger(StatsServiceImpl.class);

    @Autowired
    private JdbcTemplate jdbcTemplate;

    @Value("${database-name}")
    private String databaseName;

    // No DB-lock is required for these READ-operations.

    public static final ConcurrentHashMap<String, Integer> datasourcesWithNumOfPayloads = new ConcurrentHashMap<>(105_000);  // The number of datasources is around 10_000.


    public void gatherNumberOfPayloadsPerDatasource()
    {
        final String getNumberOfPayloadsPerDatasourceQuery =
                "select d.id, count(p.id) as payload_count from " + databaseName + ".datasource d\n" +
                        "            join " + databaseName + ".publication pu on pu.datasourceid=d.id\n" +
                        "            left join " + databaseName + ".payload p on p.id=pu.id\n" + // We want the datasources with 0 payloads too, so we use "left join"
                        "        group by d.id";    // The group-by is needed.

        if ( logger.isTraceEnabled() )
            logger.trace("getNumberOfPayloadsPerDatasourceQuery:\n" + getNumberOfPayloadsPerDatasourceQuery);

        logger.info("Going to populate/update the \"datasourcesWithNumOfPayloads\" map.");
        try {
            jdbcTemplate.query(getNumberOfPayloadsPerDatasourceQuery, rs -> {
                try {   // For each of the 4 columns returned. The indexing starts from  1
                    datasourcesWithNumOfPayloads.put(rs.getString(1), rs.getInt(2));    // Updates then number for an existing datasourceId or adds a new mapping for a new datasourceId.
                } catch (SQLException sqle) {
                    logger.error("No value was able to be retrieved from one of the columns of row_" + rs.getRow(), sqle);
                }
            });
            logger.info("The \"datasourcesWithNumOfPayloads\" map was populated/updated.");
        } catch (EmptyResultDataAccessException erdae) {
            logger.warn("The number of payloads per datasource could not be retrieved from the database \"" + databaseName + "\" using the getNumberOfPayloadsPerDatasourceQuery: " + getNumberOfPayloadsPerDatasourceQuery);
        } catch (Exception e) {
            logger.error("Problem when executing \"getNumberOfPayloadsPerDatasourceQuery\": " + getNumberOfPayloadsPerDatasourceQuery, e);
        }
    }

    // To get the human-friendly timestamp format from the BigInt in the database:
    // select from_timestamp(CAST(CAST(`date` as decimal(30,0))/1000 AS timestamp), "yyyy-MM-dd HH:mm:ss.SSS") from payload

}