From 9707f9ad09db935af7d06b5de08bc52de13ba6a7 Mon Sep 17 00:00:00 2001
From: Martin Kagamino Lehoux <martin@lehoux.net>
Date: Mon, 3 Aug 2026 08:25:07 +0200
Subject: feat: Detect mountain pass crossings, name climbs after passes,
 render ride charts

- osmpass: extract mountain_pass=yes nodes from an OSM PBF, enrich centcols passes with OSM coordinates, resumable -fetch-osm download
- mountain_pass: DetectCrossings for a ride, MatchClimb to name a climb after the pass it tops
- ride: expose Points(), add Climb.Top() and Climb.Name
- chart: -chart renders elevation profile with climb bands and pass markers
- commands: -fetch-osm, -extract-osm, -import-cached, -enrich
---
 mountain_pass/detection.go | 115 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100644 mountain_pass/detection.go

(limited to 'mountain_pass/detection.go')

diff --git a/mountain_pass/detection.go b/mountain_pass/detection.go
new file mode 100644
index 0000000..e30fddc
--- /dev/null
+++ b/mountain_pass/detection.go
@@ -0,0 +1,115 @@
+package mountain_pass
+
+import (
+	"database/sql"
+	"fmt"
+
+	"github.com/jftuga/geodist"
+	"github.com/martinlehoux/biking_home/ride"
+)
+
+type Crossing struct {
+	Pass          MountainPass
+	DistanceToM   float64
+	RideDistanceM float64
+	RideElevation float64
+	ElevationDiff float64
+}
+
+func LoadMountainPasses(db *sql.DB) ([]MountainPass, error) {
+	rows, err := db.Query(`
+		SELECT external_id, name, country_code, department_code, elevation, latitude, longitude
+		FROM mountain_passes
+		ORDER BY elevation
+	`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	mountainPasses := make([]MountainPass, 0)
+	for rows.Next() {
+		var mountainPass MountainPass
+		var latitude, longitude sql.NullFloat64
+		if err := rows.Scan(&mountainPass.ExternalID, &mountainPass.Name, &mountainPass.CountryCode, &mountainPass.DepartmentCode, &mountainPass.Elevation, &latitude, &longitude); err != nil {
+			return nil, err
+		}
+		if latitude.Valid && longitude.Valid {
+			mountainPass.Coord = &geodist.Coord{Lat: latitude.Float64, Lon: longitude.Float64}
+		}
+		mountainPasses = append(mountainPasses, mountainPass)
+	}
+	return mountainPasses, rows.Err()
+}
+
+func DetectCrossings(ride ride.Ride, passes []MountainPass, radiusM, elevationToleranceM float64) []Crossing {
+	crossings := make([]Crossing, 0)
+	for _, mountainPass := range passes {
+		if mountainPass.Coord == nil {
+			continue
+		}
+		crossing, found := nearestCrossing(ride, mountainPass)
+		if found && crossing.DistanceToM <= radiusM && crossing.ElevationDiff <= elevationToleranceM {
+			crossings = append(crossings, crossing)
+		}
+	}
+	return crossings
+}
+
+// MatchClimb returns the pass whose coordinates lie within radiusM of the
+// climb's highest point and whose elevation is within elevationToleranceM of
+// that point's elevation, nearest first. Found is false when no pass matches.
+func MatchClimb(climb ride.Climb, passes []MountainPass, radiusM, elevationToleranceM float64) (MountainPass, bool) {
+	top := climb.Top()
+	var best MountainPass
+	bestDistanceM := radiusM
+	found := false
+	for _, mountainPass := range passes {
+		if mountainPass.Coord == nil {
+			continue
+		}
+		distanceKm, _ := geodist.HaversineDistance(top.Coord, *mountainPass.Coord)
+		distanceM := distanceKm * 1000
+		if distanceM > bestDistanceM {
+			continue
+		}
+		elevationDiff := absFloat64(top.ElevationM - float64(mountainPass.Elevation))
+		if elevationDiff > elevationToleranceM {
+			continue
+		}
+		best = mountainPass
+		bestDistanceM = distanceM
+		found = true
+	}
+	return best, found
+}
+
+func nearestCrossing(ride ride.Ride, mountainPass MountainPass) (Crossing, bool) {
+	best := Crossing{Pass: mountainPass, DistanceToM: 1e18}
+	for _, point := range ride.Points() {
+		distanceKm, _ := geodist.HaversineDistance(point.Coord, *mountainPass.Coord)
+		distanceM := distanceKm * 1000
+		if distanceM < best.DistanceToM {
+			best.DistanceToM = distanceM
+			best.RideDistanceM = point.DistanceM
+			best.RideElevation = point.ElevationM
+			best.ElevationDiff = absFloat64(point.ElevationM - float64(mountainPass.Elevation))
+		}
+	}
+	if best.DistanceToM > 1e17 {
+		return best, false
+	}
+	return best, true
+}
+
+func absFloat64(value float64) float64 {
+	if value < 0 {
+		return -value
+	}
+	return value
+}
+
+func (crossing Crossing) String() string {
+	return fmt.Sprintf("%s (%dm) at %.1fkm, %.0fm away, Δelev %.0fm",
+		crossing.Pass.Name, crossing.Pass.Elevation, crossing.RideDistanceM/1000, crossing.DistanceToM, crossing.ElevationDiff)
+}
-- 
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