gitea/vendor/github.com/blevesearch/bleve/search/searcher/search_geopolygon.go
2019-11-27 11:23:33 +02:00

111 lines
3.3 KiB
Go

// Copyright (c) 2019 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 searcher
import (
"github.com/blevesearch/bleve/geo"
"github.com/blevesearch/bleve/index"
"github.com/blevesearch/bleve/numeric"
"github.com/blevesearch/bleve/search"
"math"
)
func NewGeoBoundedPolygonSearcher(indexReader index.IndexReader,
polygon []geo.Point, field string, boost float64,
options search.SearcherOptions) (search.Searcher, error) {
// compute the bounding box enclosing the polygon
topLeftLon, topLeftLat, bottomRightLon, bottomRightLat, err :=
geo.BoundingRectangleForPolygon(polygon)
if err != nil {
return nil, err
}
// build a searcher for the bounding box on the polygon
boxSearcher, err := boxSearcher(indexReader,
topLeftLon, topLeftLat, bottomRightLon, bottomRightLat,
field, boost, options, true)
if err != nil {
return nil, err
}
dvReader, err := indexReader.DocValueReader([]string{field})
if err != nil {
return nil, err
}
// wrap it in a filtering searcher that checks for the polygon inclusivity
return NewFilteringSearcher(boxSearcher,
buildPolygonFilter(dvReader, field, polygon)), nil
}
const float64EqualityThreshold = 1e-6
func almostEqual(a, b float64) bool {
return math.Abs(a-b) <= float64EqualityThreshold
}
// buildPolygonFilter returns true if the point lies inside the
// polygon. It is based on the ray-casting technique as referred
// here: https://wrf.ecse.rpi.edu/nikola/pubdetails/pnpoly.html
func buildPolygonFilter(dvReader index.DocValueReader, field string,
polygon []geo.Point) FilterFunc {
return func(d *search.DocumentMatch) bool {
var lon, lat float64
var found bool
err := dvReader.VisitDocValues(d.IndexInternalID, func(field string, term []byte) {
// only consider the values which are shifted 0
prefixCoded := numeric.PrefixCoded(term)
shift, err := prefixCoded.Shift()
if err == nil && shift == 0 {
i64, err := prefixCoded.Int64()
if err == nil {
lon = geo.MortonUnhashLon(uint64(i64))
lat = geo.MortonUnhashLat(uint64(i64))
found = true
}
}
})
// Note: this approach works for points which are strictly inside
// the polygon. ie it might fail for certain points on the polygon boundaries.
if err == nil && found {
nVertices := len(polygon)
var inside bool
// check for a direct vertex match
if almostEqual(polygon[0].Lat, lat) &&
almostEqual(polygon[0].Lon, lon) {
return true
}
for i := 1; i < nVertices; i++ {
if almostEqual(polygon[i].Lat, lat) &&
almostEqual(polygon[i].Lon, lon) {
return true
}
if (polygon[i].Lat > lat) != (polygon[i-1].Lat > lat) &&
lon < (polygon[i-1].Lon-polygon[i].Lon)*(lat-polygon[i].Lat)/
(polygon[i-1].Lat-polygon[i].Lat)+polygon[i].Lon {
inside = !inside
}
}
return inside
}
return false
}
}