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possessive_filter_en.go
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possessive_filter_en.go
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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 en
import (
"unicode/utf8"
"github.com/blevesearch/bleve/analysis"
"github.com/blevesearch/bleve/registry"
)
// PossessiveName is the name PossessiveFilter is registered as
// in the bleve registry.
const PossessiveName = "possessive_en"
const rightSingleQuotationMark = '’'
const apostrophe = '\''
const fullWidthApostrophe = '''
const apostropheChars = rightSingleQuotationMark + apostrophe + fullWidthApostrophe
// PossessiveFilter implements a TokenFilter which
// strips the English possessive suffix ('s) from tokens.
// It handle a variety of apostrophe types, is case-insensitive
// and doesn't distinguish between possessive and contraction.
// (ie "She's So Rad" becomes "She So Rad")
type PossessiveFilter struct {
}
func NewPossessiveFilter() *PossessiveFilter {
return &PossessiveFilter{}
}
func (s *PossessiveFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
for _, token := range input {
lastRune, lastRuneSize := utf8.DecodeLastRune(token.Term)
if lastRune == 's' || lastRune == 'S' {
nextLastRune, nextLastRuneSize := utf8.DecodeLastRune(token.Term[:len(token.Term)-lastRuneSize])
if nextLastRune == rightSingleQuotationMark ||
nextLastRune == apostrophe ||
nextLastRune == fullWidthApostrophe {
token.Term = token.Term[:len(token.Term)-lastRuneSize-nextLastRuneSize]
}
}
}
return input
}
func PossessiveFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
return NewPossessiveFilter(), nil
}
func init() {
registry.RegisterTokenFilter(PossessiveName, PossessiveFilterConstructor)
}