Annotate refreshment stops, improved logging and error handling.

pkg/cafes/ctccam.go

@@ -0,0 +1,93 @@
+package cafes
+
+import (
+	"encoding/xml"
+	"fmt"
+	"io"
+	"net/http"
+
+	"github.com/dhconnelly/rtreego"
+	"github.com/fofanov/go-osgb"
+)
+
+const ctcCamWaypointsUrl = "https://ctccambridge.org.uk/ctccambridge-waypoints.gpx"
+
+type Waypoint struct {
+	Lat  float64 `xml:"lat,attr"`
+	Lon  float64 `xml:"lon,attr"`
+	Name string  `xml:"name"`
+	Url  string  `xml:"url"`
+}
+
+type Waypoints struct {
+	Waypoints []Waypoint `xml:"wpt"`
+}
+
+type RefreshmentStop struct {
+	Name     string
+	Url      string
+	Easting  float64
+	Northing float64
+}
+
+func (s *RefreshmentStop) Bounds() *rtreego.Rect {
+	p := rtreego.Point{s.Easting, s.Northing}
+	return p.ToRect(100)
+}
+
+func (s *RefreshmentStop) Contains(p rtreego.Point) bool {
+	if len(p) != 2 {
+		panic("Expected a 2-dimensional point")
+	}
+	bounds := s.Bounds()
+	for i := 0; i < 2; i++ {
+		if p[i] < bounds.PointCoord(i) || p[i] > bounds.PointCoord(i)+bounds.LengthsCoord(i) {
+			return false
+		}
+	}
+	return true
+}
+
+func BuildCtcCamIndex(r io.Reader) (*rtreego.Rtree, error) {
+	dec := xml.NewDecoder(r)
+	var wpt Waypoints
+	err := dec.Decode(&wpt)
+	if err != nil {
+		return nil, err
+	}
+	trans, err := osgb.NewOSTN15Transformer()
+	if err != nil {
+		return nil, err
+	}
+	stops := make([]rtreego.Spatial, len(wpt.Waypoints))
+	for i, w := range wpt.Waypoints {
+		gpsCoord := osgb.NewETRS89Coord(w.Lon, w.Lat, 0)
+		ngCoord, err := trans.ToNationalGrid(gpsCoord)
+		if err != nil {
+			return nil, fmt.Errorf("Error translating coordinates %v: %v", gpsCoord, err)
+		}
+		stops[i] = &RefreshmentStop{
+			Name:     w.Name,
+			Url:      w.Url,
+			Easting:  ngCoord.Easting,
+			Northing: ngCoord.Northing,
+		}
+	}
+	return rtreego.NewTree(2, 25, 50, stops...), nil
+}
+
+func FetchCtcCamIndex() (*rtreego.Rtree, error) {
+	res, err := http.Get(ctcCamWaypointsUrl)
+	if err != nil {
+		return nil, fmt.Errorf("error getting %s: %v", ctcCamWaypointsUrl, err)
+	}
+	defer res.Body.Close()
+	if res.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("unexpected status fetching %s: %s", ctcCamWaypointsUrl, res.Status)
+	}
+	index, err := BuildCtcCamIndex(res.Body)
+	if err != nil {
+		return nil, fmt.Errorf("error building CTC Cambridge stops index: %v", err)
+	}
+	return index, nil
+}