Analysis: expose Lucene StemmerOverrideFilter. Closes #1053

modules/elasticsearch/src/main/java/org/elasticsearch/index/analysis/AnalysisModule.java

@@ -386,6 +386,7 @@ public class AnalysisModule extends AbstractModule {
             tokenFiltersBindings.processTokenFilter("russian_stem", RussianStemTokenFilterFactory.class);
 
             tokenFiltersBindings.processTokenFilter("keyword_marker", KeywordMarkerTokenFilterFactory.class);
+            tokenFiltersBindings.processTokenFilter("stemmer_override", StemmerOverrideTokenFilterFactory.class);
         }
 
         @Override public void processTokenizers(TokenizersBindings tokenizersBindings) {

modules/elasticsearch/src/main/java/org/elasticsearch/index/analysis/StemmerOverrideTokenFilterFactory.java

@@ -0,0 +1,77 @@
+/*
+ * Licensed to Elastic Search and Shay Banon under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Elastic Search licenses this
+ * file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.index.analysis;
+
+import org.apache.lucene.analysis.TokenStream;
+import org.apache.lucene.analysis.miscellaneous.StemmerOverrideFilter;
+import org.elasticsearch.ElasticSearchIllegalArgumentException;
+import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.inject.Inject;
+import org.elasticsearch.common.inject.assistedinject.Assisted;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.env.Environment;
+import org.elasticsearch.index.Index;
+import org.elasticsearch.index.settings.IndexSettings;
+import org.apache.lucene.util.Version;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+@AnalysisSettingsRequired
+public class StemmerOverrideTokenFilterFactory extends AbstractTokenFilterFactory {
+
+    private final Map<String,String> dictionary;
+
+    @Inject public StemmerOverrideTokenFilterFactory(Index index, @IndexSettings Settings indexSettings, Environment env, @Assisted String name, @Assisted Settings settings) {
+        super(index, indexSettings, name, settings);
+
+        List<String> rules = Analysis.getWordList(env, settings, "rules");
+        if (rules == null) {
+            throw new ElasticSearchIllegalArgumentException("stemmer override filter requires either `rules` or `rules_path` to be configured");
+        }
+        dictionary = new HashMap<String, String>();
+        parseRules(rules, dictionary, "=>");
+    }
+
+    @Override public TokenStream create(TokenStream tokenStream) {
+        return new StemmerOverrideFilter(Version.LUCENE_32, tokenStream, dictionary);
+    }
+
+    static void parseRules(List<String> rules, Map<String, String> rulesMap, String mappingSep) {
+        for (String rule : rules) {
+            String key, override;
+            List<String> mapping = Strings.splitSmart(rule, mappingSep, false);
+            if (mapping.size() == 2) {
+                key = mapping.get(0).trim();
+                override = mapping.get(1).trim();
+            } else {
+                throw new RuntimeException("Invalid Keyword override Rule:" + rule);
+            }
+
+            if (key.isEmpty() || override.isEmpty()) {
+                throw new RuntimeException("Invalid Keyword override Rule:" + rule);
+            } else {
+                rulesMap.put(key, override);
+            }
+        }
+    }
+
+}