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geojson.go
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geojson.go
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package mbt
import (
"encoding/json"
"io/ioutil"
"github.com/buckhx/diglet/geo"
"github.com/buckhx/diglet/util"
"github.com/deckarep/golang-set"
"github.com/kpawlik/geojson"
//"github.com/buckhx/diglet/mbt/mvt"
//"github.com/buckhx/diglet/mbt/mvt/vector_tile"
)
type GeojsonSource struct {
path string
filter mapset.Set
}
func NewGeojsonSource(path string, filter []string) *GeojsonSource {
var set mapset.Set
if filter == nil {
set = nil
} else {
set = mapset.NewSet()
for _, k := range filter {
set.Add(k)
}
}
return &GeojsonSource{path, set}
}
func (gj *GeojsonSource) Publish(workers int) (features chan *geo.Feature, err error) {
collection := readGeoJson(gj.path)
f := make(chan *geo.Feature, 10)
wg := util.NWork(func() {
for _, feature := range collection.Features {
f <- geojsonFeatureAdapter(feature)
}
}, workers)
go func() {
wg.Wait()
close(features)
}()
features = f
/*
for i := 0; i < workers; i++ {
go func() {
defer wg.Done()
for _, feature := range collection.Features {
features <- geojsonFeatureAdapter(feature)
}
}()
}
go func() {
wg.Wait()
close(features)
}()
*/
return
}
// Flatten all the points of a feature into single list. This can hel in identifying which tiles are going to be
// created
func geojsonFeatureAdapter(gj *geojson.Feature) (feature *geo.Feature) {
// TODO: This sucks... I just want to switch on Coordinates.(type)
igeom, err := gj.GetGeometry()
util.Check(err)
feature = geo.NewFeature(igeom.GetType())
//TODO filter properties
feature.Properties = gj.Properties
feature.ID = gj.Id
//TODO if id == nil assign a fake one
feature.Type = igeom.GetType()
switch geom := igeom.(type) {
case *geojson.Point:
shape := coordinatesAdapter(geojson.Coordinates{geom.Coordinates})
feature.AddShape(shape)
case *geojson.LineString:
shape := coordinatesAdapter(geom.Coordinates)
feature.AddShape(shape)
case *geojson.MultiPoint:
shape := coordinatesAdapter(geom.Coordinates)
feature.AddShape(shape)
case *geojson.MultiLineString:
for _, line := range geom.Coordinates {
shape := coordinatesAdapter(line)
feature.AddShape(shape)
}
case *geojson.Polygon:
// mvt need exterior ring to be clockwise
// and interior rings to counter-clockwise
exterior := true
for _, line := range geom.Coordinates {
shape := coordinatesAdapter(line)
if exterior {
if !shape.IsClockwise() {
shape.Reverse()
}
exterior = false
} else {
if shape.IsClockwise() {
shape.Reverse()
}
}
feature.AddShape(shape)
}
case *geojson.MultiPolygon:
for _, multiline := range geom.Coordinates {
exterior := true
for _, line := range multiline {
shape := coordinatesAdapter(line)
if exterior {
if !shape.IsClockwise() {
shape.Reverse()
}
exterior = false
} else {
if shape.IsClockwise() {
shape.Reverse()
}
}
feature.AddShape(shape)
}
}
default:
panic("Invalid Coordinate Type in GeoJson Feature") // + feature.String())
}
return
}
func coordinatesAdapter(line geojson.Coordinates) (shape *geo.Shape) {
shape = geo.MakeShape(len(line))
for i, point := range line {
lat := float64(point[1])
lon := float64(point[0])
coord := geo.Coordinate{Lat: lat, Lon: lon}
shape.Coordinates[i] = coord
}
return
}
func readGeoJson(path string) (features *geojson.FeatureCollection) {
file, err := ioutil.ReadFile(path)
if err != nil {
util.Check(err)
}
if err := json.Unmarshal(file, &features); err != nil {
util.Check(err)
}
return features
}
func publishFeatureCollection(collection *geojson.FeatureCollection) (features chan *geo.Feature) {
features = make(chan *geo.Feature, 10)
go func() {
defer close(features)
for _, feature := range collection.Features {
features <- geojsonFeatureAdapter(feature)
}
}()
return
}