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// Copyright (c) 2014 Couchbase, Inc.
//
// Licensed 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 elision
import (
"fmt"
"unicode/utf8"
"github.com/blevesearch/bleve/analysis"
"github.com/blevesearch/bleve/registry"
)
const Name = "elision"
const RightSingleQuotationMark = '’'
const Apostrophe = '\''
type ElisionFilter struct {
articles analysis.TokenMap
}
func NewElisionFilter(articles analysis.TokenMap) *ElisionFilter {
return &ElisionFilter{
articles: articles,
}
}
func (s *ElisionFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
for _, token := range input {
term := token.Term
for i := 0; i < len(term); {
r, size := utf8.DecodeRune(term[i:])
if r == Apostrophe || r == RightSingleQuotationMark {
// see if the prefix matches one of the articles
prefix := term[0:i]
_, articleMatch := s.articles[string(prefix)]
if articleMatch {
token.Term = term[i+size:]
break
}
}
i += size
}
}
return input
}
func ElisionFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
articlesTokenMapName, ok := config["articles_token_map"].(string)
if !ok {
return nil, fmt.Errorf("must specify articles_token_map")
}
articlesTokenMap, err := cache.TokenMapNamed(articlesTokenMapName)
if err != nil {
return nil, fmt.Errorf("error building elision filter: %v", err)
}
return NewElisionFilter(articlesTokenMap), nil
}
func init() {
registry.RegisterTokenFilter(Name, ElisionFilterConstructor)
}
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