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- // 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 (
- "fmt"
- "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) {
-
- if len(polygon) < 3 {
- return nil, fmt.Errorf("Too few points specified for the polygon boundary")
- }
-
- // 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 {
- // check geo matches against all numeric type terms indexed
- var lons, lats []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 {
- lons = append(lons, geo.MortonUnhashLon(uint64(i64)))
- lats = append(lats, 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)
- if len(polygon) < 3 {
- return false
- }
- rayIntersectsSegment := func(point, a, b geo.Point) bool {
- return (a.Lat > point.Lat) != (b.Lat > point.Lat) &&
- point.Lon < (b.Lon-a.Lon)*(point.Lat-a.Lat)/(b.Lat-a.Lat)+a.Lon
- }
-
- for i := range lons {
- pt := geo.Point{Lon: lons[i], Lat: lats[i]}
- inside := rayIntersectsSegment(pt, polygon[len(polygon)-1], polygon[0])
- // check for a direct vertex match
- if almostEqual(polygon[0].Lat, lats[i]) &&
- almostEqual(polygon[0].Lon, lons[i]) {
- return true
- }
-
- for j := 1; j < nVertices; j++ {
- if almostEqual(polygon[j].Lat, lats[i]) &&
- almostEqual(polygon[j].Lon, lons[i]) {
- return true
- }
- if rayIntersectsSegment(pt, polygon[j-1], polygon[j]) {
- inside = !inside
- }
- }
- if inside {
- return true
- }
- }
- }
- return false
- }
- }
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