/*
 * 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.smrf.model.GlobalEvidence;
import ivory.smrf.model.GraphNode;

import java.util.List;

import org.w3c.dom.Node;

import com.google.common.base.Preconditions;

/**
 * Abstract base class for potential functions.
 *
 * @author Don Metzler
 */
public abstract class PotentialFunction {
  public abstract void configure(RetrievalEnvironment env, Node domNode)
      throws ConfigurationException;

  public abstract void initialize(List<GraphNode> nodes, GlobalEvidence evidence)
      throws ConfigurationException;

  public abstract float computePotential();

  public abstract int getNextCandidate();

  public abstract void reset();

  public abstract float getMinScore();

  public abstract float getMaxScore();

  public abstract void setNextCandidate(int docno);

  @SuppressWarnings("unchecked")
  public static PotentialFunction create(RetrievalEnvironment env, String type, Node functionNode)
      throws ConfigurationException {
    Preconditions.checkNotNull(env);
    Preconditions.checkNotNull(type);
    Preconditions.checkNotNull(functionNode);

    try {
      Class<? extends PotentialFunction> clz =
        (Class<? extends PotentialFunction>) Class.forName(type);
      PotentialFunction f = clz.newInstance();
      f.configure(env, functionNode);

      return f;
    } catch (Exception e) {
      throw new ConfigurationException(
          "Unable to instantiate scoring function \"" + type + "\"!", e);
    }
  }
}