dp.go

package offset

import (
	"github.com/intdxdt/geom"
)

type EpsilonDecomposition struct {
	ScoreFn  func(geom.Coords) (int, float64)
	Relation func(float64) bool
}

//MaxOffset - computes maximum offset of intermediate vertices from
//segment formed by endpoints
func MaxOffset(coordinates geom.Coords) (int, float64) {
	return maxOffset(coordinates, geom.DistanceToPoint)
}

//SquareMaxOffset computes maximum offset of intermediate vertices from segment
//formed by endpoints
func SquareMaxOffset(coordinates geom.Coords) (int, float64) {
	return maxOffset(coordinates, geom.SquareDistanceToPoint)
}

//euclidean offset distance from dp - anchor line [i, j] to maximum
//vertex at i < k <= j - not maximum offset is may not  be perpendicular
//note : coordinates of node from begin 0 to n-1 find k
func maxOffset(coordinates geom.Coords,
	distFn func(*geom.Point, *geom.Point, *geom.Point) float64) (int, float64) {
	var n = coordinates.Len() - 1
	var index, offset = n, 0.0
	if n <= 1 {
		return index, offset
	}

	var dist float64
	var a, b = coordinates.Pt(0), coordinates.Pt(n)
	for k := 1; k < n; k++ { //exclusive range between 0 < k < n
		dist = distFn(a, b, coordinates.Pt(k))
		if dist >= offset {
			index, offset = k, dist
		}
	}

	return index, offset
}