package org.apache.lucene.analysis;

import java.io.Reader;

import org.apache.lucene.analysis.standard.StandardAnalyzer;

/**
 * An NGramAnalyzerWrapper wraps an NGramFilter around another analyzer.
 * 
 * @author Sebastian Kirsch <skirsch@sebastian-kirsch.org>
 *
 */
public class NGramAnalyzerWrapper extends Analyzer {

	protected Analyzer defaultAnalyzer;
	protected int nGramSize = 2;
	protected boolean outputUnigrams = true;
	/**
	 * 
	 */
	public NGramAnalyzerWrapper(Analyzer defaultAnalyzer) {
		super();
		this.defaultAnalyzer = defaultAnalyzer;
	}

	public NGramAnalyzerWrapper(Analyzer defaultAnalyzer, int nGramSize) {
		this(defaultAnalyzer);
		this.nGramSize = nGramSize;
	}
	
	public NGramAnalyzerWrapper() {
		super();
		this.defaultAnalyzer = new StandardAnalyzer();
	}
	
	public NGramAnalyzerWrapper(int nGramSize) {
		this();
		this.nGramSize = nGramSize;
	}

  /**
   * Set the maximum size of output n-grams (default: 2)
   * 
   * @param n n-gram size
   * @return receiver
   */
	public NGramAnalyzerWrapper setNGramSize(int n) {
		this.nGramSize = n;
		return this;
	}
	
  /**
   * Shall the filter pass the original tokens (the "unigrams") to the output 
   * stream? (default: true)
   * 
   * @param flag
   * @return receiver
   */
	public NGramAnalyzerWrapper setOutputUnigrams(boolean flag) {
		this.outputUnigrams = flag;
		return this;
	}
	
	public TokenStream tokenStream(String fieldName, Reader reader) {
		return new NGramFilter(defaultAnalyzer.tokenStream(fieldName, reader))
				.setNGramSize(nGramSize)
				.setOutputUnigrams(outputUnigrams);
		
	}
}