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Core of the Object/Lucene mapper, query engine and index management

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/*
 * Hibernate Search, full-text search for your domain model
 *
 * License: GNU Lesser General Public License (LGPL), version 2.1 or later
 * See the lgpl.txt file in the root directory or .
 */

package org.hibernate.search.query.dsl.impl;

import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;
import java.util.ArrayList;
import java.util.List;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.hibernate.search.exception.AssertionFailure;
import org.hibernate.search.exception.SearchException;

/**
 * @author Emmanuel Bernard
 */
final class Helper {

	private Helper() {
		//not allowed
	}

	/**
	 * return the analyzed value for a given field. If several terms are created, an exception is raised.
	 */
	static String getAnalyzedTerm(String fieldName, String value, String name, Analyzer queryAnalyzer, FieldContext fieldContext) {
		if ( !fieldContext.applyAnalyzer() ) {
			return value;
		}

		try {
			final List termsFromText = getAllTermsFromText(
					fieldName, value, queryAnalyzer
			);
			if ( termsFromText.size() > 1 ) {
				StringBuilder error = new StringBuilder( "The " )
						.append( name )
						.append( " parameter leads to several terms when analyzed: " );
				for ( String term : termsFromText ) {
					error.append( term ).append( ", " );
				}
				final int length = error.length();
				throw new SearchException( error.delete( length - 1, length ).toString() );
			}
			return termsFromText.size() == 0 ? null : termsFromText.get( 0 );
		}
		catch (IOException e) {
			throw new AssertionFailure( "IO exception while reading String stream??", e );
		}
	}

	static List getAllTermsFromText(String fieldName, String localText, Analyzer analyzer) throws IOException {
		List terms = new ArrayList();

		// Can't deal with null at this point. Likely returned by some FieldBridge not recognizing the type.
		if ( localText == null ) {
			throw new SearchException( "Search parameter on field '" + fieldName + "' could not be converted. " +
					"Are the parameter and the field of the same type?" +
					"Alternatively, apply the ignoreFieldBridge() option to " +
					"pass String parameters" );
		}
		final Reader reader = new StringReader( localText );
		final TokenStream stream = analyzer.tokenStream( fieldName, reader );
		try {
			CharTermAttribute attribute = stream.addAttribute( CharTermAttribute.class );
			stream.reset();
			while ( stream.incrementToken() ) {
				if ( attribute.length() > 0 ) {
					String term = new String( attribute.buffer(), 0, attribute.length() );
					terms.add( term );
				}
			}
			stream.end();
		}
		finally {
			stream.close();
		}
		return terms;
	}

}