/*
 * Ivory: A Hadoop toolkit for web-scale information retrieval
 *
 * Licensed under the Apache 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://www.apache.org/licenses/LICENSE-2.0
 *
 * 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 ivory.smrf.model.potential;

import ivory.core.ConfigurationException;
import ivory.core.RetrievalEnvironment;
import ivory.core.util.XMLTools;
import ivory.smrf.model.DocumentNode;
import ivory.smrf.model.GlobalEvidence;
import ivory.smrf.model.GraphNode;

import java.util.List;

import org.w3c.dom.Node;

import com.google.common.base.Preconditions;

/**
 * Document potential.
 *
 * @author Don Metzler
 */
public class DocumentPotential extends PotentialFunction {
  private RetrievalEnvironment env;
  private DocumentNode docNode;
  private String type;

  @Override
  public void configure(RetrievalEnvironment env, Node domNode) throws ConfigurationException {
    this.env = Preconditions.checkNotNull(env);
    Preconditions.checkNotNull(domNode);

    String type = XMLTools.getAttributeValueOrThrowException(domNode, "type",
        "A DocumentPotential requires a type attribute!");

    this.type = type;
  }

  @Override
  public void initialize(List<GraphNode> nodes, GlobalEvidence globalEvidence)
      throws ConfigurationException {
    Preconditions.checkNotNull(nodes);
    Preconditions.checkNotNull(globalEvidence);

    docNode = null;

    for (GraphNode node : nodes) {
      if (node.getType().equals(GraphNode.Type.DOCUMENT) && docNode != null) {
        throw new ConfigurationException("Only one document node allowed in DocumentPotential!");
      } else if (node.getType().equals(GraphNode.Type.DOCUMENT)) {
        docNode = (DocumentNode) node;
      } else if (node.getType().equals(GraphNode.Type.TERM)) {
        throw new ConfigurationException("TermNodes are not allowed in DocumentPotential!");
      }
    }
  }

  @Override
  public float computePotential() {
    return env.getDocScore(type, docNode.getDocno());
  }

  @Override
  public int getNextCandidate() {
    return Integer.MAX_VALUE;
  }

  @Override
  public String toString() {
    return "<potential type=\"DocumentPotential\" />\n";
  }

  @Override
  public float getMinScore() {
    return Float.NEGATIVE_INFINITY;
  }

  @Override
  public float getMaxScore() {
    return Float.POSITIVE_INFINITY;
  }

  /**
   * Does nothing in the context of this potential.
   */
  @Override
  public void reset() {
  }

  /**
   * Does nothing in the context of this potential.
   */
  @Override
  public void setNextCandidate(int docid) {}
}