make distance stuff greate again

geoutils/distance.go

@@ -0,0 +1,54 @@
+package geoutils
+
+import (
+	"math"
+
+	"github.com/paulmach/orb"
+	"github.com/paulmach/orb/geo"
+	"github.com/rs/zerolog/log"
+)
+
+func DistanceFromLineString(point orb.Point, lineString orb.LineString) (distance float64, closestIndex int) {
+	minDistance := math.Inf(1)
+	closest := -1
+
+	for i := 0; i < len(lineString)-1; i++ {
+		a := lineString[i]
+		b := lineString[i+1]
+		pointOnSegment := projectToSegment(point, a, b)
+		dist := geo.Distance(point, pointOnSegment)
+		if dist < minDistance {
+			minDistance = dist
+			closest = i
+		}
+	}
+
+	log.Debug().
+		Float64("min distance", minDistance).
+		Int("index", closest).
+		Any("point", point).
+		Any("linestring", lineString).
+		Msg("minimum distance to polyline")
+	return minDistance, closest
+}
+
+func projectToSegment(point, a, b orb.Point) orb.Point {
+	x := a[0]
+	y := a[1]
+	dx := b[0] - x
+	dy := b[1] - y
+
+	if dx != 0 || dy != 0 {
+		t := ((point[0]-x)*dx + (point[1]-y)*dy) / (dx*dx + dy*dy)
+
+		if t > 1 {
+			x = b[0]
+			y = b[1]
+		} else if t > 0 {
+			x += dx * t
+			y += dy * t
+		}
+	}
+
+	return orb.Point{x, y}
+}