first release

internal/gpx/gpx.go

@@ -0,0 +1,157 @@
+// Package gpx 解析 GPX 轨迹文件（标准 WGS-84 坐标），
+// 用来给 rond 的「地点到地点」直线位移补上真实路径。
+package gpx
+
+import (
+	"encoding/xml"
+	"errors"
+	"fmt"
+	"math"
+	"strings"
+	"time"
+)
+
+// Track 是一条轨迹（GPX 的 trk / rte），坐标是 WGS-84。
+type Track struct {
+	Name   string
+	Points []Point
+	Time   time.Time
+}
+
+type Point struct {
+	Lat float64
+	Lon float64
+	Ele float64
+	T   time.Time
+}
+
+type gpxDoc struct {
+	XMLName xml.Name `xml:"gpx"`
+	Name    string   `xml:"metadata>name"`
+	Trks    []trk    `xml:"trk"`
+	Rtes    []rte    `xml:"rte"`
+}
+
+type trk struct {
+	Name   string   `xml:"name"`
+	Trkseg []trkseg `xml:"trkseg"`
+}
+
+type trkseg struct {
+	Pts []wpt `xml:"trkpt"`
+}
+
+type rte struct {
+	Name string `xml:"name"`
+	Pts  []wpt  `xml:"rtept"`
+}
+
+type wpt struct {
+	Lat float64 `xml:"lat,attr"`
+	Lon float64 `xml:"lon,attr"`
+	Ele float64 `xml:"ele"`
+	T   string  `xml:"time"`
+}
+
+// Parse 解析 GPX 文本，返回其中的全部轨迹。trk 优先，没有则退回 rte。
+func Parse(data []byte) ([]Track, error) {
+	var doc gpxDoc
+	if err := xml.Unmarshal(data, &doc); err != nil {
+		return nil, fmt.Errorf("GPX 解析失败: %w", err)
+	}
+	var out []Track
+	base := strings.TrimSpace(doc.Name)
+	for _, t := range doc.Trks {
+		tr := Track{Name: firstNonEmpty(strings.TrimSpace(t.Name), base)}
+		for _, seg := range t.Trkseg {
+			for _, p := range seg.Pts {
+				if p.Lat == 0 && p.Lon == 0 {
+					continue
+				}
+				pt := Point{Lat: p.Lat, Lon: p.Lon, Ele: p.Ele}
+				if p.T != "" {
+					pt.T, _ = time.Parse(time.RFC3339, strings.TrimSpace(p.T))
+				}
+				tr.Points = append(tr.Points, pt)
+			}
+		}
+		if len(tr.Points) > 1 {
+			if tr.Time.IsZero() {
+				tr.Time = tr.Points[0].T
+			}
+			out = append(out, tr)
+		}
+	}
+	for _, r := range doc.Rtes {
+		tr := Track{Name: firstNonEmpty(strings.TrimSpace(r.Name), base)}
+		for _, p := range r.Pts {
+			if p.Lat == 0 && p.Lon == 0 {
+				continue
+			}
+			pt := Point{Lat: p.Lat, Lon: p.Lon}
+			if p.T != "" {
+				pt.T, _ = time.Parse(time.RFC3339, strings.TrimSpace(p.T))
+			}
+			tr.Points = append(tr.Points, pt)
+		}
+		if len(tr.Points) > 1 {
+			if tr.Time.IsZero() {
+				tr.Time = tr.Points[0].T
+			}
+			out = append(out, tr)
+		}
+	}
+	if len(out) == 0 {
+		return nil, errors.New("文件里没有找到轨迹点（需要 trk/trkpt 或 rte/rtept）")
+	}
+	return out, nil
+}
+
+func firstNonEmpty(vals ...string) string {
+	for _, v := range vals {
+		if v != "" {
+			return v
+		}
+	}
+	return ""
+}
+
+// LengthKm 计算轨迹里程（Haversine）。
+func (t Track) LengthKm() float64 {
+	sum := 0.0
+	for i := 1; i < len(t.Points); i++ {
+		sum += haversine(t.Points[i-1], t.Points[i])
+	}
+	return sum
+}
+
+// BBox 返回 [minLon, minLat, maxLon, maxLat]。
+func (t Track) BBox() [4]float64 {
+	b := [4]float64{180, 90, -180, -90}
+	for _, p := range t.Points {
+		if p.Lon < b[0] {
+			b[0] = p.Lon
+		}
+		if p.Lat < b[1] {
+			b[1] = p.Lat
+		}
+		if p.Lon > b[2] {
+			b[2] = p.Lon
+		}
+		if p.Lat > b[3] {
+			b[3] = p.Lat
+		}
+	}
+	return b
+}
+
+func haversine(a, b Point) float64 {
+	const r = 6371.0
+	dLat := (b.Lat - a.Lat) * math.Pi / 180
+	dLon := (b.Lon - a.Lon) * math.Pi / 180
+	la1 := a.Lat * math.Pi / 180
+	la2 := b.Lat * math.Pi / 180
+	h := math.Sin(dLat/2)*math.Sin(dLat/2) +
+		math.Cos(la1)*math.Cos(la2)*math.Sin(dLon/2)*math.Sin(dLon/2)
+	return 2 * r * math.Asin(math.Sqrt(h))
+}