[#316] locode: Implement polygons DB based on GeoJSON polygons

Define database of Earth's polygons in GeoJSON format. Implement resolving
of geo point to continent in which it is located through point-in-polygon
calculation.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

go.mod

@@ -20,6 +20,7 @@ require (
 	github.com/nspcc-dev/neofs-crypto v0.3.0
 	github.com/nspcc-dev/tzhash v1.4.0
 	github.com/panjf2000/ants/v2 v2.3.0
+	github.com/paulmach/orb v0.2.1
 	github.com/pkg/errors v0.9.1
 	github.com/prometheus/client_golang v1.6.0
 	github.com/spf13/cobra v1.0.0
@@ -36,7 +37,7 @@ require (
 	golang.org/x/sys v0.0.0-20201024232916-9f70ab9862d5 // indirect
 	golang.org/x/tools v0.0.0-20200123022218-593de606220b // indirect
 	google.golang.org/grpc v1.29.1
-	google.golang.org/protobuf v1.23.0
+	google.golang.org/protobuf v1.25.0
 )
 
 // Used for debug reasons

pkg/util/locode/db/continents/geojson/calls.go

@@ -0,0 +1,90 @@
+package continentsdb
+
+import (
+	"io/ioutil"
+
+	locodedb "github.com/nspcc-dev/neofs-node/pkg/util/locode/db"
+	"github.com/paulmach/orb"
+	"github.com/paulmach/orb/geojson"
+	"github.com/paulmach/orb/planar"
+	"github.com/pkg/errors"
+)
+
+const continentProperty = "Continent"
+
+// PointContinent goes through all polygons, and returns continent
+// in which point is located.
+//
+// Returns locodedb.ContinentUnknown if no entry matches.
+//
+// All GeoJSON feature are parsed from file once and stored in memory.
+func (db *DB) PointContinent(point *locodedb.Point) (*locodedb.Continent, error) {
+	var err error
+
+	db.once.Do(func() {
+		err = db.init()
+	})
+
+	if err != nil {
+		return nil, err
+	}
+
+	planarPoint := orb.Point{point.Longitude(), point.Latitude()}
+
+	var continent string
+
+	for _, feature := range db.features {
+		if multiPolygon, ok := feature.Geometry.(orb.MultiPolygon); ok {
+			if planar.MultiPolygonContains(multiPolygon, planarPoint) {
+				continent = feature.Properties.MustString(continentProperty)
+				break
+			}
+		} else if polygon, ok := feature.Geometry.(orb.Polygon); ok {
+			if planar.PolygonContains(polygon, planarPoint) {
+				continent = feature.Properties.MustString(continentProperty)
+				break
+			}
+		}
+	}
+
+	c := continentFromString(continent)
+
+	return &c, nil
+}
+
+func (db *DB) init() error {
+	data, err := ioutil.ReadFile(db.path)
+	if err != nil {
+		return errors.Wrap(err, "could not read data file")
+	}
+
+	features, err := geojson.UnmarshalFeatureCollection(data)
+	if err != nil {
+		return errors.Wrap(err, "could not unmarshal GeoJSON feature collection")
+	}
+
+	db.features = features.Features
+
+	return nil
+}
+
+func continentFromString(c string) locodedb.Continent {
+	switch c {
+	default:
+		return locodedb.ContinentUnknown
+	case "Africa":
+		return locodedb.ContinentAfrica
+	case "Asia":
+		return locodedb.ContinentAsia
+	case "Europe":
+		return locodedb.ContinentEurope
+	case "North America":
+		return locodedb.ContinentNorthAmerica
+	case "South America":
+		return locodedb.ContinentSouthAmerica
+	case "Antarctica":
+		return locodedb.ContinentAntarctica
+	case "Australia", "Oceania":
+		return locodedb.ContinentOceania
+	}
+}

pkg/util/locode/db/continents/geojson/db.go

@@ -0,0 +1,63 @@
+package continentsdb
+
+import (
+	"fmt"
+	"sync"
+
+	"github.com/paulmach/orb/geojson"
+)
+
+// Prm groups the required parameters of the DB's constructor.
+//
+// All values must comply with the requirements imposed on them.
+// Passing incorrect parameter values will result in constructor
+// failure (error or panic depending on the implementation).
+type Prm struct {
+	// Path to polygons of Earth's continents in GeoJSON format.
+	//
+	// Must not be empty.
+	Path string
+}
+
+// DB is a descriptor of the Earth's polygons in GeoJSON format.
+//
+// For correct operation, DB must be created
+// using the constructor (New) based on the required parameters
+// and optional components. After successful creation,
+// The DB is immediately ready to work through API.
+type DB struct {
+	path string
+
+	once sync.Once
+
+	features []*geojson.Feature
+}
+
+const invalidPrmValFmt = "invalid parameter %s (%T):%v"
+
+func panicOnPrmValue(n string, v interface{}) {
+	panic(fmt.Sprintf(invalidPrmValFmt, n, v, v))
+}
+
+// New creates a new instance of the DB.
+//
+// Panics if at least one value of the parameters is invalid.
+//
+// The created DB does not require additional
+// initialization and is completely ready for work.
+func New(prm Prm, opts ...Option) *DB {
+	switch {
+	case prm.Path == "":
+		panicOnPrmValue("Path", prm.Path)
+	}
+
+	o := defaultOpts()
+
+	for i := range opts {
+		opts[i](o)
+	}
+
+	return &DB{
+		path: prm.Path,
+	}
+}

pkg/util/locode/db/continents/geojson/opts.go

@@ -0,0 +1,10 @@
+package continentsdb
+
+// Option sets an optional parameter of DB.
+type Option func(*options)
+
+type options struct{}
+
+func defaultOpts() *options {
+	return &options{}
+}