snapshot of https://github.com/blevesearch/bleve.git (master, 2026-09-15; blobs > 131072B omitted)

analysis/lang/de/light_stemmer_de.go

@@ -0,0 +1,119 @@
+//  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/v2/analysis"
+	"github.com/blevesearch/bleve/v2/registry"
+)
+
+const LightStemmerName = "stemmer_de_light"
+
+type GermanLightStemmerFilter struct {
+}
+
+func NewGermanLightStemmerFilter() *GermanLightStemmerFilter {
+	return &GermanLightStemmerFilter{}
+}
+
+func (s *GermanLightStemmerFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
+	for _, token := range input {
+		runes := bytes.Runes(token.Term)
+		runes = stem(runes)
+		token.Term = analysis.BuildTermFromRunes(runes)
+	}
+	return input
+}
+
+func stem(input []rune) []rune {
+
+	for i, r := range input {
+		switch r {
+		case 'ä', 'à', 'á', 'â':
+			input[i] = 'a'
+		case 'ö', 'ò', 'ó', 'ô':
+			input[i] = 'o'
+		case 'ï', 'ì', 'í', 'î':
+			input[i] = 'i'
+		case 'ü', 'ù', 'ú', 'û':
+			input[i] = 'u'
+		}
+	}
+
+	input = step1(input)
+	return step2(input)
+}
+
+func stEnding(ch rune) bool {
+	switch ch {
+	case 'b', 'd', 'f', 'g', 'h', 'k', 'l', 'm', 'n', 't':
+		return true
+	}
+	return false
+}
+
+func step1(s []rune) []rune {
+	l := len(s)
+	if l > 5 && s[l-3] == 'e' && s[l-2] == 'r' && s[l-1] == 'n' {
+		return s[:l-3]
+	}
+
+	if l > 4 && s[l-2] == 'e' {
+		switch s[l-1] {
+		case 'm', 'n', 'r', 's':
+			return s[:l-2]
+		}
+	}
+
+	if l > 3 && s[l-1] == 'e' {
+		return s[:l-1]
+	}
+
+	if l > 3 && s[l-1] == 's' && stEnding(s[l-2]) {
+		return s[:l-1]
+	}
+
+	return s
+}
+
+func step2(s []rune) []rune {
+	l := len(s)
+	if l > 5 && s[l-3] == 'e' && s[l-2] == 's' && s[l-1] == 't' {
+		return s[:l-3]
+	}
+
+	if l > 4 && s[l-2] == 'e' && (s[l-1] == 'r' || s[l-1] == 'n') {
+		return s[:l-2]
+	}
+
+	if l > 4 && s[l-2] == 's' && s[l-1] == 't' && stEnding(s[l-3]) {
+		return s[:l-2]
+	}
+
+	return s
+}
+
+func GermanLightStemmerFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
+	return NewGermanLightStemmerFilter(), nil
+}
+
+func init() {
+	err := registry.RegisterTokenFilter(LightStemmerName, GermanLightStemmerFilterConstructor)
+	if err != nil {
+		panic(err)
+	}
+}