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