package de.dlr.shepard.influxDB;
   
   import de.dlr.shepard.util.Constants;
   import de.dlr.shepard.util.IConnector;
   import io.quarkus.logging.Log;
   import jakarta.enterprise.context.ApplicationScoped;
   import jakarta.inject.Inject;
   import java.util.ArrayList;
   import java.util.Collections;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import org.eclipse.microprofile.config.ConfigProvider;
  import org.influxdb.BatchOptions;
  import org.influxdb.InfluxDB;
  import org.influxdb.InfluxDBException;
  import org.influxdb.InfluxDBFactory;
  import org.influxdb.dto.Pong;
  import org.influxdb.dto.Query;
  import org.influxdb.dto.QueryResult;
  
  /**
   * Connector for read and write access to the Influx timeseries database. The
   * class represents the lowest level of data access to the Influx database. The
   * Influx database is accessed directly by using query strings.
   */
  @ApplicationScoped
  public class InfluxDBConnector implements IConnector {
  
    private InfluxDB influxDB;
  
    /* Use this constructor for testing purpose only.
     *  As soon as influxDB is provided via dependency injection, this constructor can be used for that purpose. */
    InfluxDBConnector(InfluxDB influxDb) {
      this.influxDB = influxDb;
    }
  
    @Inject
    InfluxDBConnector() {}
  
    /**
     * Establishes a connection to the Influx server by using the URL saved in the
     * config.properties file returned by the DatabaseHelper. In addition the
     * logging is being configured.
     *
     */
    @Override
    public boolean connect() {
      if (this.influxDB == null) {
        String host = ConfigProvider.getConfig().getValue("influx.host", String.class);
        String username = ConfigProvider.getConfig().getValue("influx.username", String.class);
        String password = ConfigProvider.getConfig().getValue("influx.password", String.class);
  
        influxDB = InfluxDBFactory.connect(String.format("http://%s", host), username, password);
      }
  
      influxDB.enableBatch(
        BatchOptions.DEFAULTS.exceptionHandler((failedPoints, throwable) ->
          Log.errorf("Exception while writing the following points: %s, Exception: %s", failedPoints, throwable)
        )
      );
      return true;
    }
  
    @Override
    public boolean disconnect() {
      if (influxDB != null) influxDB.close();
      return true;
    }
  
    /**
     * Tests whether a connection exists.
     *
     * @return True if connection exists, otherwise false.
     */
    @Override
    public boolean alive() {
      Pong response;
      try {
        response = influxDB.ping();
      } catch (InfluxDBException ex) {
        return false;
      }
      return response != null && !response.getVersion().equalsIgnoreCase("unknown");
    }
  
    /**
     * Creates a new database.
     *
     * @param databaseName Name of the new database to be created.
     */
    public void createDatabase(String databaseName) {
      String query = String.format("CREATE DATABASE \"%s\"", databaseName);
      influxDB.query(new Query(query));
    }
  
    /**
     * Deletes a database.
     *
    * @param databaseName Name of the database to be deleted.
    */
   public void deleteDatabase(String databaseName) {
     String query = String.format("DROP DATABASE \"%s\"", databaseName);
     influxDB.query(new Query(query));
   }
 
   /**
    * Writes all InfluxPoint objects, saved in the TimeseriesPayload object, into
    * the influx database. Therefore the method uses the name of the database, the
    * name of the measurement, the location, the device, the symbolic name and the
    * name of the field provided by the given TimeseriesPayload object. The actual
    * write operation is done by using the unix timestamp in nanoseconds and the
    * value of every InfluxPoint object in the TimeseriesPayload object. All these
    * variables have to be defined in the given Timeseries object for a successful
    * write operation.
    *
    * @param database The database to store the payload in
    * @param payload  Combines the required attributes in a structured way.
    * @return An error if there was a problem, empty string if all went well
    */
   public String saveTimeseriesPayload(String database, TimeseriesPayload payload) {
     var timeseries = payload.getTimeseries();
     var expectedType = getExpectedDatatype(database, timeseries.getMeasurement(), timeseries.getField());
     var batchPoints = InfluxUtil.createBatch(database, payload, expectedType);
     try {
       influxDB.write(batchPoints);
     } catch (InfluxDBException e) {
       Log.errorf("InfluxdbException while writing payload %s: %s", payload.getTimeseries(), e.getMessage());
       return e.getMessage();
     }
     return "";
   }
 
   /**
    * Returns a Timeseries object containing all the influx data points which match
    * the given conditions consigned to the method. The returned InfluxPoint
    * objects are in the given measurement of the specific database between the
    * start and the end timestamp.
    *
    * @param startTimeStamp Start timestamp from which values should be returned
    * @param endTimeStamp   End timestamp to which values should be returned
    * @param database       Name of the database
    * @param timeseries     Specifies the data to load from database
    * @param function       The aggregate function
    * @param groupBy        The time interval measurements get grouped by
    * @param fillOption     The fill option for missing values
    * @return A Timeseries object containing a list of all InfluxPoints in the
    *         given measurement of the specific database between the two given
    *         timestamps matching the "device"-tag, the "location"-tag and the
    *         "symbolic_name"-tag.
    */
   public TimeseriesPayload getTimeseriesPayload(
     long startTimeStamp,
     long endTimeStamp,
     String database,
     Timeseries timeseries,
     SingleValuedUnaryFunction function,
     Long groupBy,
     FillOption fillOption
   ) {
     Query query = InfluxUtil.buildQuery(
       startTimeStamp,
       endTimeStamp,
       database,
       timeseries,
       function,
       groupBy,
       fillOption
     );
     Log.debugf("Influx Query: %s", query.getCommand());
     QueryResult queryResult;
 
     try {
       queryResult = influxDB.query(query);
     } catch (InfluxDBException e) {
       queryResult = null;
       Log.errorf("Could not parse query: %s", query.getCommand());
     }
     if (InfluxUtil.isQueryResultValid(queryResult)) {
       return InfluxUtil.extractPayload(queryResult, timeseries);
     }
     return new TimeseriesPayload(timeseries, Collections.emptyList());
   }
 
   /**
    * Returns a list of timeseries objects that are in the given database.
    *
    * @param database the given database
    * @return a list of timeseries objects
    */
   public List<Timeseries> getTimeseriesAvailable(String database) {
     Query query = new Query(String.format("SHOW SERIES ON \"%s\"", database));
     QueryResult queryResult = influxDB.query(query);
     if (!InfluxUtil.isQueryResultValid(queryResult)) {
       Log.warn("There was an error while querying the Influxdb for available timeseries");
       return Collections.emptyList();
     }
     var values = queryResult.getResults().get(0).getSeries().get(0).getValues();
     var fields = getFields(database);
     var result = new ArrayList<Timeseries>(values.size());
     for (var value : values) {
       var series = ((String) value.get(0)).split(",");
       // The first entry is the measurement
       var meas = series[0];
       var tags = extractTags(series);
       var dev = tags.getOrDefault(Constants.DEVICE, "");
       var loc = tags.getOrDefault(Constants.LOCATION, "");
       var symName = tags.getOrDefault(Constants.SYMBOLICNAME, "");
       for (var field : fields.getOrDefault(meas, Collections.emptyList())) {
         result.add(new Timeseries(meas, dev, loc, symName, field));
       }
     }
     return result;
   }
 
   private Map<String, String> extractTags(String[] series) {
     var result = new HashMap<String, String>();
     for (var tagString : series) {
       var tags = tagString.split("=", 2);
 
       // Skip entries with less than 2 tuples (most likely the measurement)
       if (tags.length < 2) continue;
 
       result.put(tags[0], tags[1]);
     }
     return result;
   }
 
   private Map<String, List<String>> getFields(String database) {
     Query query = new Query(String.format("SHOW FIELD KEYS ON \"%s\"", database));
     QueryResult queryResult = influxDB.query(query);
     if (!InfluxUtil.isQueryResultValid(queryResult)) {
       Log.warn("There was an error while querying the Influxdb for available fields");
       return Collections.emptyMap();
     }
     var series = queryResult.getResults().get(0).getSeries();
     var result = new HashMap<String, List<String>>();
     for (var s : series) {
       var fields = new ArrayList<String>();
       for (var value : s.getValues()) {
         fields.add((String) value.get(0));
       }
       result.put(s.getName(), fields);
     }
     return result;
   }
 
   public boolean databaseExist(String database) {
     QueryResult queryResult = influxDB.query(new Query("SHOW DATABASES"));
     if (!InfluxUtil.isQueryResultValid(queryResult)) {
       Log.warn("There was an error while querying the Influxdb for databases");
       return false;
     }
 
     var values = queryResult.getResults().get(0).getSeries().get(0).getValues();
     for (var databaseName : values) {
       if (databaseName.get(0).toString().trim().equals(database)) {
         return true;
       }
     }
 
     return false;
   }
 
   /**
    * Returns the expected data type of a field or an empty string according to
    * https://docs.influxdata.com/influxdb/v1.8/write_protocols/line_protocol_reference/#data-types
    */
   private String getExpectedDatatype(String database, String measurement, String field) {
     String queryString = String.format("SHOW FIELD KEYS ON \"%s\" FROM %s", database, measurement);
     QueryResult result = influxDB.query(new Query(queryString));
     if (!InfluxUtil.isQueryResultValid(result)) {
       Log.infof("Could not get expected datatype query string \"%s\"", queryString);
       return "";
     }
 
     var values = result.getResults().get(0).getSeries().get(0).getValues();
     for (var value : values) {
       if (value.get(0).equals(field)) return (String) value.get(1);
     }
 
     return "";
   }
 }