2014-07-30 18:30:38 +02:00
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// Copyright (c) 2014 Couchbase, Inc.
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
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// except in compliance with the License. You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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// Unless required by applicable law or agreed to in writing, software distributed under the
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// License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
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// either express or implied. See the License for the specific language governing permissions
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// and limitations under the License.
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2014-06-26 17:43:13 +02:00
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2014-09-01 17:15:38 +02:00
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package simple
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2014-06-26 17:43:13 +02:00
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2014-09-01 17:15:38 +02:00
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import (
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"unicode/utf8"
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2014-09-01 17:15:38 +02:00
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"github.com/blevesearch/bleve/registry"
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"github.com/blevesearch/bleve/search/highlight"
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)
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const Name = "simple"
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const defaultFragmentSize = 200
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2014-09-04 01:16:46 +02:00
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type Fragmenter struct {
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fragmentSize int
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}
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2014-09-04 01:16:46 +02:00
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func NewFragmenter(fragmentSize int) *Fragmenter {
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return &Fragmenter{
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fragmentSize: fragmentSize,
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}
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}
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2014-09-04 01:16:46 +02:00
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func (s *Fragmenter) Fragment(orig []byte, ot highlight.TermLocations) []*highlight.Fragment {
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rv := make([]*highlight.Fragment, 0)
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maxbegin := 0
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OUTER:
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for currTermIndex, termLocation := range ot {
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// start with this
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// it should be the highest scoring fragment with this term first
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start := termLocation.Start
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end := start
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used := 0
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for end < len(orig) && used < s.fragmentSize {
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r, size := utf8.DecodeRune(orig[end:])
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if r == utf8.RuneError {
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continue OUTER // bail
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}
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end += size
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used += 1
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}
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// if we still have more characters available to us
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// push back towards begining
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// without cross maxbegin
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for start > 0 && used < s.fragmentSize {
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r, size := utf8.DecodeLastRune(orig[0:start])
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if r == utf8.RuneError {
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continue OUTER // bail
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}
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if start-size >= maxbegin {
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start -= size
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used += 1
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} else {
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break
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}
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}
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2014-06-26 17:43:13 +02:00
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// however, we'd rather have the tokens centered more in the frag
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// lets try to do that as best we can, without affecting the score
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// find the end of the last term in this fragment
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minend := end
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for _, innerTermLocation := range ot[currTermIndex:] {
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if innerTermLocation.End > end {
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break
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}
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minend = innerTermLocation.End
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}
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// find the smaller of the two rooms to move
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roomToMove := utf8.RuneCount(orig[minend:end])
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roomToMoveStart := 0
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if start >= maxbegin {
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roomToMoveStart = utf8.RuneCount(orig[maxbegin:start])
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}
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if roomToMoveStart < roomToMove {
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roomToMove = roomToMoveStart
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}
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offset := roomToMove / 2
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for offset > 0 {
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r, size := utf8.DecodeLastRune(orig[0:start])
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if r == utf8.RuneError {
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continue OUTER // bail
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}
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start -= size
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r, size = utf8.DecodeLastRune(orig[0:end])
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if r == utf8.RuneError {
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continue OUTER // bail
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}
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end -= size
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offset--
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}
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2014-09-01 17:15:38 +02:00
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rv = append(rv, &highlight.Fragment{Orig: orig, Start: start - offset, End: end - offset})
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// set maxbegin to the end of the current term location
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// so that next one won't back up to include it
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maxbegin = termLocation.End
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}
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2014-08-28 20:46:30 +02:00
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if len(ot) == 0 {
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// if there were no terms to highlight
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// produce a single fragment from the beginning
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start := 0
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end := start + s.fragmentSize
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if end > len(orig) {
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end = len(orig)
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}
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rv = append(rv, &highlight.Fragment{Orig: orig, Start: start, End: end})
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}
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return rv
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}
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func Constructor(config map[string]interface{}, cache *registry.Cache) (highlight.Fragmenter, error) {
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size := defaultFragmentSize
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sizeVal, ok := config["size"].(float64)
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if ok {
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size = int(sizeVal)
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}
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2014-09-04 01:16:46 +02:00
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return NewFragmenter(size), nil
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}
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func init() {
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registry.RegisterFragmenter(Name, Constructor)
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}
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