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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 shingle
import (
"container/ring"
"fmt"
"github.com/blevesearch/bleve/analysis"
"github.com/blevesearch/bleve/registry"
)
const Name = "shingle"
type ShingleFilter struct {
min int
max int
outputOriginal bool
tokenSeparator string
fill string
}
func NewShingleFilter(min, max int, outputOriginal bool, sep, fill string) *ShingleFilter {
return &ShingleFilter{
min: min,
max: max,
outputOriginal: outputOriginal,
tokenSeparator: sep,
fill: fill,
}
}
func (s *ShingleFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
rv := make(analysis.TokenStream, 0, len(input))
ring := ring.New(s.max)
itemsInRing := 0
currentPosition := 0
for _, token := range input {
if s.outputOriginal {
rv = append(rv, token)
}
// if there are gaps, insert filler tokens
offset := token.Position - currentPosition
for offset > 1 {
fillerToken := analysis.Token{
Position: 0,
Start: -1,
End: -1,
Type: analysis.AlphaNumeric,
Term: []byte(s.fill),
}
ring.Value = &fillerToken
if itemsInRing < s.max {
itemsInRing++
}
rv = append(rv, s.shingleCurrentRingState(ring, itemsInRing)...)
ring = ring.Next()
offset--
}
currentPosition = token.Position
ring.Value = token
if itemsInRing < s.max {
itemsInRing++
}
rv = append(rv, s.shingleCurrentRingState(ring, itemsInRing)...)
ring = ring.Next()
}
return rv
}
func (s *ShingleFilter) shingleCurrentRingState(ring *ring.Ring, itemsInRing int) analysis.TokenStream {
rv := make(analysis.TokenStream, 0)
for shingleN := s.min; shingleN <= s.max; shingleN++ {
// if there are enough items in the ring
// to produce a shingle of this size
if itemsInRing >= shingleN {
thisShingleRing := ring.Move(-(shingleN - 1))
shingledBytes := make([]byte, 0)
pos := 0
start := -1
end := 0
for i := 0; i < shingleN; i++ {
if i != 0 {
shingledBytes = append(shingledBytes, []byte(s.tokenSeparator)...)
}
curr := thisShingleRing.Value.(*analysis.Token)
if pos == 0 && curr.Position != 0 {
pos = curr.Position
}
if start == -1 && curr.Start != -1 {
start = curr.Start
}
if curr.End != -1 {
end = curr.End
}
shingledBytes = append(shingledBytes, curr.Term...)
thisShingleRing = thisShingleRing.Next()
}
token := analysis.Token{
Type: analysis.Shingle,
Term: shingledBytes,
}
if pos != 0 {
token.Position = pos
}
if start != -1 {
token.Start = start
}
if end != -1 {
token.End = end
}
rv = append(rv, &token)
}
}
return rv
}
func ShingleFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
minVal, ok := config["min"].(float64)
if !ok {
return nil, fmt.Errorf("must specify min")
}
min := int(minVal)
maxVal, ok := config["max"].(float64)
if !ok {
return nil, fmt.Errorf("must specify max")
}
max := int(maxVal)
outputOriginal := false
outVal, ok := config["output_original"].(bool)
if ok {
outputOriginal = outVal
}
sep := " "
sepVal, ok := config["separator"].(string)
if ok {
sep = sepVal
}
fill := "_"
fillVal, ok := config["filler"].(string)
if ok {
fill = fillVal
}
return NewShingleFilter(min, max, outputOriginal, sep, fill), nil
}
func init() {
registry.RegisterTokenFilter(Name, ShingleFilterConstructor)
}
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