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// Copyright (c) 2017 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 de
import (
"bytes"
"github.com/blevesearch/bleve/analysis"
"github.com/blevesearch/bleve/registry"
)
const NormalizeName = "normalize_de"
const (
N = 0 /* ordinary state */
V = 1 /* stops 'u' from entering umlaut state */
U = 2 /* umlaut state, allows e-deletion */
)
type GermanNormalizeFilter struct {
}
func NewGermanNormalizeFilter() *GermanNormalizeFilter {
return &GermanNormalizeFilter{}
}
func (s *GermanNormalizeFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
for _, token := range input {
term := normalize(token.Term)
token.Term = term
}
return input
}
func normalize(input []byte) []byte {
state := N
runes := bytes.Runes(input)
for i := 0; i < len(runes); i++ {
switch runes[i] {
case 'a', 'o':
state = U
case 'u':
if state == N {
state = U
} else {
state = V
}
case 'e':
if state == U {
runes = analysis.DeleteRune(runes, i)
i--
}
state = V
case 'i', 'q', 'y':
state = V
case 'ä':
runes[i] = 'a'
state = V
case 'ö':
runes[i] = 'o'
state = V
case 'ü':
runes[i] = 'u'
state = V
case 'ß':
runes[i] = 's'
i++
runes = analysis.InsertRune(runes, i, 's')
state = N
default:
state = N
}
}
return analysis.BuildTermFromRunes(runes)
}
func NormalizerFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
return NewGermanNormalizeFilter(), nil
}
func init() {
registry.RegisterTokenFilter(NormalizeName, NormalizerFilterConstructor)
}
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