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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 cjk
import (
"bytes"
"container/ring"
"unicode/utf8"
"github.com/blevesearch/bleve/analysis"
"github.com/blevesearch/bleve/registry"
)
const BigramName = "cjk_bigram"
type CJKBigramFilter struct {
outputUnigram bool
}
func NewCJKBigramFilter(outputUnigram bool) *CJKBigramFilter {
return &CJKBigramFilter{
outputUnigram: outputUnigram,
}
}
func (s *CJKBigramFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
r := ring.New(2)
itemsInRing := 0
pos := 1
outputPos := 1
rv := make(analysis.TokenStream, 0, len(input))
for _, tokout := range input {
if tokout.Type == analysis.Ideographic {
runes := bytes.Runes(tokout.Term)
sofar := 0
for _, run := range runes {
rlen := utf8.RuneLen(run)
token := &analysis.Token{
Term: tokout.Term[sofar : sofar+rlen],
Start: tokout.Start + sofar,
End: tokout.Start + sofar + rlen,
Position: pos,
Type: tokout.Type,
KeyWord: tokout.KeyWord,
}
pos++
sofar += rlen
if itemsInRing > 0 {
// if items already buffered
// check to see if this is aligned
curr := r.Value.(*analysis.Token)
if token.Start-curr.End != 0 {
// not aligned flush
flushToken := s.flush(r, &itemsInRing, outputPos)
if flushToken != nil {
outputPos++
rv = append(rv, flushToken)
}
}
}
// now we can add this token to the buffer
r = r.Next()
r.Value = token
if itemsInRing < 2 {
itemsInRing++
}
if itemsInRing > 1 && s.outputUnigram {
unigram := s.buildUnigram(r, &itemsInRing, outputPos)
if unigram != nil {
rv = append(rv, unigram)
}
}
bigramToken := s.outputBigram(r, &itemsInRing, outputPos)
if bigramToken != nil {
rv = append(rv, bigramToken)
outputPos++
}
}
} else {
// flush anything already buffered
flushToken := s.flush(r, &itemsInRing, outputPos)
if flushToken != nil {
rv = append(rv, flushToken)
outputPos++
}
// output this token as is
tokout.Position = outputPos
rv = append(rv, tokout)
outputPos++
}
}
// deal with possible trailing unigram
if itemsInRing == 1 || s.outputUnigram {
if itemsInRing == 2 {
r = r.Next()
}
unigram := s.buildUnigram(r, &itemsInRing, outputPos)
if unigram != nil {
rv = append(rv, unigram)
}
}
return rv
}
func (s *CJKBigramFilter) flush(r *ring.Ring, itemsInRing *int, pos int) *analysis.Token {
var rv *analysis.Token
if *itemsInRing == 1 {
rv = s.buildUnigram(r, itemsInRing, pos)
}
r.Value = nil
*itemsInRing = 0
return rv
}
func (s *CJKBigramFilter) outputBigram(r *ring.Ring, itemsInRing *int, pos int) *analysis.Token {
if *itemsInRing == 2 {
thisShingleRing := r.Move(-1)
shingledBytes := make([]byte, 0)
// do first token
prev := thisShingleRing.Value.(*analysis.Token)
shingledBytes = append(shingledBytes, prev.Term...)
// do second token
thisShingleRing = thisShingleRing.Next()
curr := thisShingleRing.Value.(*analysis.Token)
shingledBytes = append(shingledBytes, curr.Term...)
token := analysis.Token{
Type: analysis.Double,
Term: shingledBytes,
Position: pos,
Start: prev.Start,
End: curr.End,
}
return &token
}
return nil
}
func (s *CJKBigramFilter) buildUnigram(r *ring.Ring, itemsInRing *int, pos int) *analysis.Token {
if *itemsInRing == 2 {
thisShingleRing := r.Move(-1)
// do first token
prev := thisShingleRing.Value.(*analysis.Token)
token := analysis.Token{
Type: analysis.Single,
Term: prev.Term,
Position: pos,
Start: prev.Start,
End: prev.End,
}
return &token
} else if *itemsInRing == 1 {
// do first token
prev := r.Value.(*analysis.Token)
token := analysis.Token{
Type: analysis.Single,
Term: prev.Term,
Position: pos,
Start: prev.Start,
End: prev.End,
}
return &token
}
return nil
}
func CJKBigramFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
outputUnigram := false
outVal, ok := config["output_unigram"].(bool)
if ok {
outputUnigram = outVal
}
return NewCJKBigramFilter(outputUnigram), nil
}
func init() {
registry.RegisterTokenFilter(BigramName, CJKBigramFilterConstructor)
}
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