package org.apache.lucene.queryparser.flexible.aqp.processors;

import org.apache.lucene.queryparser.flexible.messages.MessageImpl;
import org.apache.lucene.queryparser.flexible.core.QueryNodeException;
import org.apache.lucene.queryparser.flexible.core.messages.QueryParserMessages;
import org.apache.lucene.queryparser.flexible.core.nodes.ModifierQueryNode;
import org.apache.lucene.queryparser.flexible.core.nodes.QueryNode;
import org.apache.lucene.queryparser.flexible.aqp.nodes.AqpANTLRNode;
import org.apache.lucene.queryparser.flexible.aqp.nodes.AqpBooleanQueryNode;

/**
 * Creates a {@link ModifierQueryNode} from the MODIFIER node last child
 * 
 * If MODIFIER node contains only one child, we return that child and do
 * nothing.
 * 
 * <p>
 * 
 * If BOOST node contains two children, we take the first and check its input,
 * eg.
 * 
 * <pre>
 *               MODIFIER
 *                  /  \
 *                 +  rest
 * </pre>
 * 
 * We create a new node ModifierQueryNode(rest, Modifier) and return that node.
 * 
 * <p>
 * 
 * This processor should run before {@link AqpOPERATORProcessor} to ensure that
 * local modifiers have precedence over the boolean operations. For example:
 * 
 * <pre>
 * title:(+a -b c)
 * </pre>
 * 
 * Should produce (when OR is a default operator):
 * 
 * <pre>
 *  +title:a -title:b title:c
 * </pre>
 * 
 * and when AND is the default operator:
 * 
 * <pre>
 *  +title:a -title:b +title:c
 * </pre>
 * 
 * @see AqpBooleanQueryNode
 */
public class AqpMODIFIERProcessor extends AqpQProcessor {

  public boolean nodeIsWanted(AqpANTLRNode node) {
    if (node.getTokenLabel().equals("MODIFIER")) {
      return true;
    }
    return false;
  }

  public AqpANTLRNode getModifierNode(QueryNode node) {
    return ((AqpANTLRNode) node.getChildren().get(0));
  }

  public QueryNode getValueNode(QueryNode node) {
    return node.getChildren().get(node.getChildren().size() - 1);
  }

  public QueryNode createQNode(AqpANTLRNode node) throws QueryNodeException {

    if (node.getChildren().size() == 1) {
      return node.getChildren().get(0);
    }

    AqpANTLRNode modifierNode = getModifierNode(node);
    String modifier = modifierNode.getTokenName();

    QueryNode childNode = getValueNode(node);

    if (modifier.equals("PLUS")) {
      return new ModifierQueryNode(childNode,
          ModifierQueryNode.Modifier.MOD_REQ);
    } else if (modifier.equals("MINUS")) {
      return new ModifierQueryNode(childNode,
          ModifierQueryNode.Modifier.MOD_NOT);
    } else {
      throw new QueryNodeException(new MessageImpl(
          QueryParserMessages.LUCENE_QUERY_CONVERSION_ERROR,
          "Unknown modifier: " + modifier + "\n" + node.toString()));
    }

  }

}