rect/rectangle.go

package rect

import (
	"math"
	"sort"
)

type Rectangle struct {
	P1, P2, P3, P4 Point
}

func (r Rectangle) IsRect() bool {
	// make sure they aren't all just the same point
	if (r.P1.X == r.P2.X && r.P1.X == r.P3.X && r.P1.X == r.P4.X) &&
		(r.P1.Y == r.P2.Y && r.P1.Y == r.P3.Y && r.P1.Y == r.P4.Y) {
		return false
	}

	cx := (r.P1.X + r.P2.X + r.P3.X + r.P4.X) / 4.0
	cy := (r.P1.Y + r.P2.Y + r.P3.Y + r.P4.Y) / 4.0

	dd1 := math.Sqrt(math.Abs(cx-r.P1.X)) + math.Sqrt(math.Abs(cy-r.P1.Y))
	dd2 := math.Sqrt(math.Abs(cx-r.P2.X)) + math.Sqrt(math.Abs(cy-r.P2.Y))
	dd3 := math.Sqrt(math.Abs(cx-r.P3.X)) + math.Sqrt(math.Abs(cy-r.P3.Y))
	dd4 := math.Sqrt(math.Abs(cx-r.P4.X)) + math.Sqrt(math.Abs(cy-r.P4.Y))
	return dd1 == dd2 && dd1 == dd3 && dd1 == dd4
}

func (r Rectangle) Neighbors(p Point) (Point, Point) {
	keys := []float64{distance(r.P1, p), distance(r.P2, p), distance(r.P3, p), distance(r.P4, p)}
	sort.Float64s(keys)
	n := []Point{}
	d := distance(r.P1, p)
	if keys[1] == d || keys[2] == d {
		n = append(n, r.P1)
	}
	d = distance(r.P2, p)
	if keys[1] == d || keys[2] == d {
		n = append(n, r.P2)
	}
	d = distance(r.P3, p)
	if keys[1] == d || keys[2] == d {
		n = append(n, r.P3)
	}
	d = distance(r.P4, p)
	if keys[1] == d || keys[2] == d {
		n = append(n, r.P4)
	}
	return n[0], n[1]
}

func (r Rectangle) Size() float64 {
	n1, n2 := r.Neighbors(r.P1)
	return distance(r.P1, n1) * distance(r.P1, n2)
}

//
//func Containment(r1, r2, Rectangle) bool {
//}