ListRecordsResponse.java

/**
 * Licensed to The Apereo Foundation under one or more contributor license
 * agreements. See the NOTICE file distributed with this work for additional
 * information regarding copyright ownership.
 *
 *
 * The Apereo Foundation licenses this file to you under the Educational
 * Community 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://opensource.org/licenses/ecl2.txt
 *
 * 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.opencastproject.oaipmh.harvester;

import static org.apache.commons.lang3.StringUtils.trimToNull;
import static org.opencastproject.util.data.Option.option;

import org.opencastproject.oaipmh.OaiPmhConstants;
import org.opencastproject.util.data.Option;

import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * The "ListRecords" response.
 * See <a href="http://www.openarchives.org/OAI/openarchivesprotocol.html#ListRecords">4.5 ListRecords</a> for further
 * information.
 * <p>
 * todo implement missing element accessors
 */
public class ListRecordsResponse extends OaiPmhResponse {

  public ListRecordsResponse(Document doc) {
    super(doc);
  }

  public boolean isErrorBadArgument() {
    return isError(OaiPmhConstants.ERROR_BAD_ARGUMENT);
  }

  public boolean isErrorBadResumptionToken() {
    return isError(OaiPmhConstants.ERROR_BAD_RESUMPTION_TOKEN);
  }

  public boolean isErrorCannotDisseminateFormat() {
    return isError(OaiPmhConstants.ERROR_CANNOT_DISSEMINATE_FORMAT);
  }

  public boolean isErrorNoRecordsMatch() {
    return isError(OaiPmhConstants.ERROR_NO_RECORDS_MATCH);
  }

  public boolean isErrorNoSetHierarchy() {
    return isError(OaiPmhConstants.ERROR_NO_SET_HIERARCHY);
  }

  /**
   * Get the content of all metadata elements in the current response.
   */
  public NodeList getMetadataElems() {
    return xpathNodeList("/oai20:OAI-PMH/oai20:ListRecords/oai20:record/oai20:metadata/*[1]");
  }

  /**
   * Get all records in the current response.
   * <pre>
   *  <record>
   *    <header>...
   *    </header>
   *    <metadata>...
   *    </metadata>
   *  </record>
   * </pre>
   */
  public NodeList getRecords() {
    return xpathNodeList("/oai20:OAI-PMH/oai20:ListRecords/oai20:record");
  }

  /**
   * Extract the content, i.e. the first child node, of the metadata node of a record.
   * <pre>
   *  <record>
   *    <header>...
   *    </header>
   *    <metadata>
   *      <myMd>
   *      </myMd>
   *    </metadata>
   *  </record>
   *
   *  =>
   *
   *  <myMd>
   *  </myMd>
   * </pre>
   */
  public static Node metadataOfRecord(Node recordNode) {
    return xpathNode(createXPath(), recordNode, "oai20:metadata/*[1]");
  }

  /**
   * Get all records performing a complete request resuming any partial responses.
   */
  public static Iterable<Node> getAllRecords(final ListRecordsResponse first, final OaiPmhRepositoryClient client) {
    return new Iterable<Node>() {
      @Override
      public Iterator<Node> iterator() {
        return new ResponseIterator(first) {
          @Override
          protected OaiPmhRepositoryClient getClient() {
            return client;
          }

          @Override
          protected NodeList extractNodes(ListRecordsResponse response) {
            return response.getRecords();
          }
        };
      }
    };
  }

  /**
   * Get all metadata performing a complete request resuming any partial responses.
   */
  public static Iterable<Node> getAllMetadataElems(final ListRecordsResponse first, final OaiPmhRepositoryClient client) {
    return new Iterable<Node>() {
      @Override
      public Iterator<Node> iterator() {
        return new ResponseIterator(first) {
          @Override
          protected OaiPmhRepositoryClient getClient() {
            return client;
          }

          @Override
          protected NodeList extractNodes(ListRecordsResponse response) {
            return response.getMetadataElems();
          }
        };
      }
    };
  }

  public String getMetadataPrefix() {
    return xpathString("/oai20:OAI-PMH/oai20:request/@metadataPrefix");
  }

  public Option<String> getResumptionToken() {
    return option(trimToNull(xpathString("/oai20:OAI-PMH/oai20:ListRecords/oai20:resumptionToken/text()")));
  }

  //

  private abstract static class ResponseIterator implements Iterator<Node> {

    private NodeList elems;
    private Option<String> token;
    private int i;

    ResponseIterator(ListRecordsResponse response) {
      initIteration(response);
    }

    private void initIteration(ListRecordsResponse response) {
      elems = extractNodes(response);
      token = response.getResumptionToken();
      i = 0;
    }

    protected abstract OaiPmhRepositoryClient getClient();

    /**
     * Extract the relevant part of the response.
     */
    protected abstract NodeList extractNodes(ListRecordsResponse response);

    @Override
    public boolean hasNext() {
      if (hasNextInCurrent()) {
        return true;
      } else {
        if (token.isSome()) {
          initIteration(getClient().resumeListRecords(token.get()));
          return hasNextInCurrent();
        } else {
          return false;
        }
      }
    }

    @Override
    public Node next() {
      if (!hasNext())
        throw new NoSuchElementException();
      return elems.item(i++);
    }

    @Override
    public void remove() {
      throw new UnsupportedOperationException();
    }

    private boolean hasNextInCurrent() {
      return i < elems.getLength();
    }
  }
}