96 lines
2.1 KiB
Go
96 lines
2.1 KiB
Go
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// Copyright (c) 2017 Couchbase, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package de
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import (
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"bytes"
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"github.com/blevesearch/bleve/analysis"
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"github.com/blevesearch/bleve/registry"
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)
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const NormalizeName = "normalize_de"
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const (
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N = 0 /* ordinary state */
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V = 1 /* stops 'u' from entering umlaut state */
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U = 2 /* umlaut state, allows e-deletion */
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)
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type GermanNormalizeFilter struct {
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}
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func NewGermanNormalizeFilter() *GermanNormalizeFilter {
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return &GermanNormalizeFilter{}
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}
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func (s *GermanNormalizeFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
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for _, token := range input {
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term := normalize(token.Term)
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token.Term = term
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}
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return input
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}
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func normalize(input []byte) []byte {
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state := N
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runes := bytes.Runes(input)
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for i := 0; i < len(runes); i++ {
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switch runes[i] {
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case 'a', 'o':
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state = U
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case 'u':
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if state == N {
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state = U
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} else {
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state = V
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}
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case 'e':
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if state == U {
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runes = analysis.DeleteRune(runes, i)
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i--
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}
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state = V
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case 'i', 'q', 'y':
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state = V
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case 'ä':
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runes[i] = 'a'
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state = V
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case 'ö':
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runes[i] = 'o'
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state = V
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case 'ü':
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runes[i] = 'u'
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state = V
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case 'ß':
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runes[i] = 's'
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i++
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runes = analysis.InsertRune(runes, i, 's')
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state = N
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default:
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state = N
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}
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}
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return analysis.BuildTermFromRunes(runes)
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}
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func NormalizerFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
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return NewGermanNormalizeFilter(), nil
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}
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func init() {
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registry.RegisterTokenFilter(NormalizeName, NormalizerFilterConstructor)
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}
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