package org.apache.lucene.search;

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 * reserved.
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 * modification, are permitted provided that the following conditions
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 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
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 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

import java.io.IOException;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermDocs;
import org.apache.lucene.index.IndexReader;

/** A Query that matches documents containing a term.
  This may be combined with other terms with a {@link BooleanQuery}.
  */
final public class TermQuery extends Query {
  private Term term;
  private int docFreq;
  private float boost = 1.0f;
  private float idf = 0.0f;
  private float weight = 0.0f;

  /** Constructs a query for the term <code>t</code>. */
  public TermQuery(Term t) {
    term = t;
  }

  /** Sets the boost for this term to <code>b</code>.  Documents containing
    this term will (in addition to the normal weightings) have their score
    multiplied by <code>b</code>. */
  public void setBoost(float b) { boost = b; }
  /** Gets the boost for this term.  Documents containing
    this term will (in addition to the normal weightings) have their score
    multiplied by <code>b</code>.   The boost is 1.0 by default.  */
  public float getBoost() { return boost; }
  
  final float sumOfSquaredWeights(Searcher searcher) throws IOException {
    docFreq = searcher.docFreq(term);
    idf = Similarity.idf(docFreq, searcher.maxDoc());
    weight = idf;
    return weight * weight;			  // square term weights
  }

  final void normalize(float norm) {
    weight *= norm;				  // normalize for query
    weight *= idf;				  // factor from document
    weight *= boost;                              // boost query
  }

  Scorer scorer(IndexReader reader)
       throws IOException {
    TermDocs termDocs = reader.termDocs(term);

    if (termDocs == null)
      return null;
    
    return new TermScorer(termDocs, docFreq,
                          reader.norms(term.field()), weight);
  }

  /** Prints a user-readable version of this query. */
  public String toString(String field) {
    StringBuffer buffer = new StringBuffer();
    if (!term.field().equals(field)) {
      buffer.append(term.field());
      buffer.append(":");
    }
    buffer.append(term.text());
    if (boost != 1.0f) {
      buffer.append("^");
      buffer.append(Float.toString(boost));
    }
    return buffer.toString();
  }
}