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map.go
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map.go
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package atlas
import (
"bytes"
"compress/gzip"
"context"
"fmt"
"log"
"strings"
"sync"
"github.com/go-spatial/geom"
"github.com/go-spatial/geom/slippy"
"github.com/go-spatial/tegola"
"github.com/go-spatial/tegola/basic"
"github.com/go-spatial/tegola/dict"
"github.com/go-spatial/tegola/internal/convert"
"github.com/go-spatial/tegola/mvt"
"github.com/go-spatial/tegola/provider"
"github.com/go-spatial/tegola/provider/debug"
"github.com/golang/protobuf/proto"
)
// NewMap creates a new map with the necessary default values
func NewWebMercatorMap(name string) Map {
return Map{
Name: name,
// default bounds
Bounds: tegola.WGS84Bounds,
Layers: []Layer{},
SRID: tegola.WebMercator,
TileExtent: 4096,
TileBuffer: uint64(tegola.DefaultTileBuffer),
}
}
type Map struct {
Name string
// Contains an attribution to be displayed when the map is shown to a user.
// This string is sanatized so it can't be abused as a vector for XSS or beacon tracking.
Attribution string
// The maximum extent of available map tiles in WGS:84
// latitude and longitude values, in the order left, bottom, right, top.
// Default: [-180, -85, 180, 85]
Bounds *geom.Extent
// The first value is the longitude, the second is latitude (both in
// WGS:84 values), the third value is the zoom level.
Center [3]float64
Layers []Layer
SRID uint64
// MVT output values
TileExtent uint64
TileBuffer uint64
}
// AddDebugLayers returns a copy of a Map with the debug layers appended to the layer list
func (m Map) AddDebugLayers() Map {
// make an explicit copy of the layers
layers := make([]Layer, len(m.Layers))
copy(layers, m.Layers)
m.Layers = layers
// setup a debug provider
debugProvider, _ := debug.NewTileProvider(dict.Dict{})
m.Layers = append(layers, []Layer{
{
Name: debug.LayerDebugTileOutline,
ProviderLayerName: debug.LayerDebugTileOutline,
Provider: debugProvider,
GeomType: geom.LineString{},
MinZoom: 0,
MaxZoom: MaxZoom,
},
{
Name: debug.LayerDebugTileCenter,
ProviderLayerName: debug.LayerDebugTileCenter,
Provider: debugProvider,
GeomType: geom.Point{},
MinZoom: 0,
MaxZoom: MaxZoom,
},
}...)
return m
}
// FilterLayersByZoom returns a copy of a Map with a subset of layers that match the given zoom
func (m Map) FilterLayersByZoom(zoom uint) Map {
var layers []Layer
for i := range m.Layers {
if (m.Layers[i].MinZoom <= zoom || m.Layers[i].MinZoom == 0) && (m.Layers[i].MaxZoom >= zoom || m.Layers[i].MaxZoom == 0) {
layers = append(layers, m.Layers[i])
continue
}
}
// overwrite the Map's layers with our subset
m.Layers = layers
return m
}
// FilterLayersByName returns a copy of a Map with a subset of layers that match the supplied list of layer names
func (m Map) FilterLayersByName(names ...string) Map {
var layers []Layer
nameStr := strings.Join(names, ",")
for i := range m.Layers {
// if we have a name set, use it for the lookup
if m.Layers[i].Name != "" && strings.Contains(nameStr, m.Layers[i].Name) {
layers = append(layers, m.Layers[i])
continue
} else if m.Layers[i].ProviderLayerName != "" && strings.Contains(nameStr, m.Layers[i].ProviderLayerName) { // default to using the ProviderLayerName for the lookup
layers = append(layers, m.Layers[i])
continue
}
}
// overwrite the Map's layers with our subset
m.Layers = layers
return m
}
// TODO (arolek): support for max zoom
func (m Map) Encode(ctx context.Context, tile *slippy.Tile) ([]byte, error) {
// tile container
var mvtTile mvt.Tile
// wait group for concurrent layer fetching
var wg sync.WaitGroup
// layer stack
mvtLayers := make([]*mvt.Layer, len(m.Layers))
// set our waitgroup count
wg.Add(len(m.Layers))
// iterate our layers
for i, layer := range m.Layers {
// go routine for fetching the layer concurrently
go func(i int, l Layer) {
mvtLayer := mvt.Layer{
Name: l.MVTName(),
DontSimplify: l.DontSimplify,
DontClip: l.DontClip,
}
// on completion let the wait group know
defer wg.Done()
// fetch layer from data provider
err := l.Provider.TileFeatures(ctx, l.ProviderLayerName, tile, func(f *provider.Feature) error {
// skip row if geometry collection empty.
g, ok := f.Geometry.(geom.Collection)
if ok && len(g.Geometries()) == 0 {
return nil
}
// TODO: remove this geom conversion step once the mvt package has adopted the new geom package
geo, err := convert.ToTegola(f.Geometry)
if err != nil {
return err
}
// check if the feature SRID and map SRID are different. If they are then reporject
if f.SRID != m.SRID {
// TODO(arolek): support for additional projections
g, err := basic.ToWebMercator(f.SRID, geo)
if err != nil {
return fmt.Errorf("unable to transform geometry to webmercator from SRID (%v) for feature %v due to error: %v", f.SRID, f.ID, err)
}
geo = g.Geometry
}
// add default tags, but don't overwrite a tag that already exists
for k, v := range l.DefaultTags {
if _, ok := f.Tags[k]; !ok {
f.Tags[k] = v
}
}
mvtLayer.AddFeatures(mvt.Feature{
ID: &f.ID,
Tags: f.Tags,
Geometry: geo,
})
return nil
})
if err != nil {
switch err {
case context.Canceled:
// TODO (arolek): add debug logs
default:
z, x, y := tile.ZXY()
// TODO (arolek): should we return an error to the response or just log the error?
// we can't just write to the response as the waitgroup is going to write to the response as well
log.Printf("err fetching tile (z: %v, x: %v, y: %v) features: %v", z, x, y, err)
}
return
}
// add the layer to the slice position
mvtLayers[i] = &mvtLayer
}(i, layer)
}
// wait for the waitgroup to finish
wg.Wait()
// stop processing if the context has an error. this check is necessary
// otherwise the server continues processing even if the request was canceled
// as the waitgroup was not notified of the cancel
if ctx.Err() != nil {
return nil, ctx.Err()
}
// add layers to our tile
mvtTile.AddLayers(mvtLayers...)
z, x, y := tile.ZXY()
// TODO (arolek): change out the tile type for VTile. tegola.Tile will be deprecated
tegolaTile := tegola.NewTile(uint(z), uint(x), uint(y))
// generate our tile
vtile, err := mvtTile.VTile(ctx, tegolaTile)
if err != nil {
return nil, err
}
// encode our mvt tile
tileBytes, err := proto.Marshal(vtile)
if err != nil {
return nil, err
}
// buffer to store our compressed bytes
var gzipBuf bytes.Buffer
// compress the encoded bytes
w := gzip.NewWriter(&gzipBuf)
_, err = w.Write(tileBytes)
if err != nil {
return nil, err
}
// flush and close the writer
if err = w.Close(); err != nil {
return nil, err
}
// return encoded, gzipped tile
return gzipBuf.Bytes(), nil
}