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}
}