/*
    * Tentackle - https://tentackle.org
    *
    * This library is free software; you can redistribute it and/or
    * modify it under the terms of the GNU Lesser General Public
    * License as published by the Free Software Foundation; either
    * version 2.1 of the License, or (at your option) any later version.
    *
    * This library is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with this library; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  package org.tentackle.dbms;
  
  import org.tentackle.common.Service;
  import org.tentackle.session.PersistenceException;
  import org.tentackle.sql.Backend;
  
  import java.util.StringTokenizer;
  
  /**
   * Default {@link IdSourceConfigurator}.
   * <p>
   * There are 2 configuration options:
   * <ol>
   * <li>table:&lt;name&gt;: an {@link ObjectId} counting in the given table</li>
   * <li>sequence:&lt;name&gt;[:&lt;sequence-multiplier&gt;:&lt;global-multiplier&gt;]: an {@link ObjectSequenceId}
   * on the given sequence</li>
   * </ol>
   * Without a configuration, the default is {@code sequence:object_sequence_id} if the backend supports
   * sequences, otherwise {@code table:object_id}.
   *
   * @author harald
   */
  @Service(IdSourceConfigurator.class)
  public class DefaultIdSourceConfigurator implements IdSourceConfigurator {
  
    /** table-based id source. */
    public static final String TABLE_BASED = "table";
  
    /** sequence-based id source. */
    public static final String SEQUENCE_BASED = "sequence";
  
  
    /**
     * Creates an IdSource configurator.
     */
    public DefaultIdSourceConfigurator() {
      // see -Xlint:missing-explicit-ctor since Java 16
    }
  
    @Override
    public IdSource configure(String idConfig) {
      // parse
      String type = null;
      String name = null;
      Integer sequenceMultiplier = null;
      Integer globalMultiplier = null;
  
      StringTokenizer stok = new StringTokenizer(idConfig, ":");
      while (stok.hasMoreTokens()) {
        String token = stok.nextToken();
        if (type == null) {
          type = token;
        }
        else if (name == null) {
          name = token;
        }
        else if (sequenceMultiplier == null) {
          sequenceMultiplier = Integer.parseInt(token);
        }
        else if (globalMultiplier == null) {
          globalMultiplier = Integer.parseInt(token);
        }
        else {
          throw new PersistenceException("malformed idSource configuration: " + idConfig);
        }
      }
  
      if (type == null) {
        throw new PersistenceException("empty id configuration");
      }
  
      return switch (type) {
        case SEQUENCE_BASED -> {
          if (sequenceMultiplier == null) {   // implies globalMultiplier == null
            yield ObjectSequenceId.get(name);
          }
          else if (globalMultiplier != null) {
            yield ObjectSequenceId.get(name, sequenceMultiplier, globalMultiplier);
          }
          throw new PersistenceException("sequenceMultiplier and globalMultiplier must be defined both or not at all");
        }
       case TABLE_BASED -> ObjectId.get(name);
       default -> throw new PersistenceException("unsupported idSource type: " + type);
     };
   }
 
   @Override
   public IdSource configure(Backend backend) {
     if (backend.isSequenceSupported()) {
       return configure(SEQUENCE_BASED + ":object_sequence_id");
     }
     else  {
       return configure(TABLE_BASED + ":object_id");
     }
   }
 
 }