/**
 * Copyright (C) 2009-2013 FoundationDB, LLC
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package com.foundationdb.server.service.text;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.Tokenizer;
import org.apache.lucene.analysis.core.LowerCaseFilter;
import org.apache.lucene.analysis.core.StopAnalyzer;
import org.apache.lucene.analysis.core.StopFilter;
import org.apache.lucene.analysis.standard.StandardFilter;
import org.apache.lucene.analysis.standard.StandardTokenizer;
import org.apache.lucene.util.Version;

import java.io.Reader;
import java.util.Set;

public class SelectiveCaseAnalyzer extends Analyzer
{
    protected static final Version matchVersion = Version.LUCENE_40;
    
    private final Set<String> casePreservingFieldNames;

    static class CaseReuseStrategy extends ReuseStrategy {
        private final Set<String> casePreservingFieldNames;

        public CaseReuseStrategy(Set<String> casePreservingFieldNames) {
            this.casePreservingFieldNames = casePreservingFieldNames;
        }

        @Override
        public TokenStreamComponents getReusableComponents(String fieldName) {
            TokenStreamComponents[] stored = (TokenStreamComponents[])getStoredValue();
            if (stored == null) {
                return null;
            }
            else if (casePreservingFieldNames.contains(fieldName)) {
                return stored[0];
            }
            else {
                return stored[1];
            }
        }

        @Override
        public void setReusableComponents(String fieldName, TokenStreamComponents components) {
            TokenStreamComponents[] stored = (TokenStreamComponents[])getStoredValue();
            if (stored == null) {
                stored = new TokenStreamComponents[2];
                setStoredValue(stored);
            }
            if (casePreservingFieldNames.contains(fieldName)) {
                stored[0] = components;
            }
            else {
                stored[1] = components;
            }
        }
    }

    public SelectiveCaseAnalyzer(Set<String> casePreservingFieldNames) {
        super(new CaseReuseStrategy(casePreservingFieldNames));
        this.casePreservingFieldNames = casePreservingFieldNames;
    }

    @Override
    protected TokenStreamComponents createComponents(String fieldName, Reader reader) {
        final Tokenizer source = new StandardTokenizer(matchVersion, reader);
        TokenStream sink = new StandardFilter(matchVersion, source);
        if (!casePreservingFieldNames.contains(fieldName)) {
            sink = new LowerCaseFilter(matchVersion, sink);
        }
        sink = new StopFilter(matchVersion, sink, StopAnalyzer.ENGLISH_STOP_WORDS_SET);
        return new TokenStreamComponents(source, sink);
    }    

}