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package mountain_pass
import (
"database/sql"
"math"
"github.com/jftuga/geodist"
"github.com/martinlehoux/biking_home/ride"
)
// MountainPass is a pass extracted from OpenStreetMap: a node tagged
// mountain_pass=yes (or legacy natural=mountain_pass) with a name and an
// elevation, as filtered by the loaders.
type MountainPass struct {
Name string
Elevation int
Coord *geodist.Coord
}
type Crossing struct {
Pass MountainPass
DistanceToM float64
RideDistanceM float64
RideElevation float64
ElevationDiff float64
}
func LoadMountainPasses(db *sql.DB) ([]MountainPass, error) {
return loadMountainPasses(db, nil)
}
func LoadMountainPassesAroundRide(db *sql.DB, routeCoords []geodist.Coord, marginM float64) ([]MountainPass, error) {
return loadMountainPasses(db, rideBounds(routeCoords, marginM))
}
type coordinateBounds struct {
minLatitude float64
minLongitude float64
maxLatitude float64
maxLongitude float64
}
func rideBounds(coords []geodist.Coord, marginM float64) *coordinateBounds {
minLatitude, maxLatitude := coords[0].Lat, coords[0].Lat
minLongitude, maxLongitude := coords[0].Lon, coords[0].Lon
for index := 1; index < len(coords); index++ {
coordinate := coords[index]
minLatitude = math.Min(minLatitude, coordinate.Lat)
maxLatitude = math.Max(maxLatitude, coordinate.Lat)
minLongitude = math.Min(minLongitude, coordinate.Lon)
maxLongitude = math.Max(maxLongitude, coordinate.Lon)
}
latitudeMargin := marginM / 111_320
longitudeScale := math.Cos((minLatitude + maxLatitude) / 2 * math.Pi / 180)
longitudeMargin := marginM / (111_320 * math.Max(longitudeScale, 0.01))
return &coordinateBounds{
minLatitude: minLatitude - latitudeMargin,
minLongitude: minLongitude - longitudeMargin,
maxLatitude: maxLatitude + latitudeMargin,
maxLongitude: maxLongitude + longitudeMargin,
}
}
func loadMountainPasses(db *sql.DB, bounds *coordinateBounds) ([]MountainPass, error) {
query := `
SELECT name, elevation, latitude, longitude
FROM mountain_passes
WHERE elevation IS NOT NULL
AND name IS NOT NULL AND name != ''`
args := make([]any, 0, 4)
if bounds != nil {
query += `
AND latitude BETWEEN ? AND ?
AND longitude BETWEEN ? AND ?`
args = append(args, bounds.minLatitude, bounds.maxLatitude, bounds.minLongitude, bounds.maxLongitude)
}
query += `
ORDER BY elevation`
rows, err := db.Query(query, args...)
if err != nil {
return nil, err
}
defer rows.Close()
mountainPasses := make([]MountainPass, 0)
for rows.Next() {
var mountainPass MountainPass
var latitude, longitude float64
if err := rows.Scan(&mountainPass.Name, &mountainPass.Elevation, &latitude, &longitude); err != nil {
return nil, err
}
mountainPass.Coord = &geodist.Coord{Lat: latitude, Lon: longitude}
mountainPasses = append(mountainPasses, mountainPass)
}
return mountainPasses, rows.Err()
}
func DetectCrossings(coords []geodist.Coord, distances, elevations []float64, passes []MountainPass, radiusM, elevationToleranceM float64) []Crossing {
crossings := make([]Crossing, 0)
for _, mountainPass := range passes {
if mountainPass.Coord == nil {
continue
}
crossing, found := nearestCrossing(coords, distances, elevations, 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) {
topCoord := climb.TopCoord()
topElevation := climb.TopElevationM()
var best MountainPass
bestDistanceM := radiusM
found := false
for _, mountainPass := range passes {
if mountainPass.Coord == nil {
continue
}
distanceKm, _ := geodist.HaversineDistance(topCoord, *mountainPass.Coord)
distanceM := distanceKm * 1000
if distanceM > bestDistanceM {
continue
}
elevationDiff := absFloat64(topElevation - float64(mountainPass.Elevation))
if elevationDiff > elevationToleranceM {
continue
}
best = mountainPass
bestDistanceM = distanceM
found = true
}
return best, found
}
func nearestCrossing(coords []geodist.Coord, distances, elevations []float64, mountainPass MountainPass) (Crossing, bool) {
best := Crossing{Pass: mountainPass, DistanceToM: 1e18}
for i := 0; i < len(coords); i++ {
distanceKm, _ := geodist.HaversineDistance(coords[i], *mountainPass.Coord)
distanceM := distanceKm * 1000
if distanceM < best.DistanceToM {
best.DistanceToM = distanceM
best.RideDistanceM = distances[i]
best.RideElevation = elevations[i]
best.ElevationDiff = absFloat64(elevations[i] - 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
}
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