package gg

type Liner interface {
	Line() Line
}

type LinerPointContainer interface {
	Liner
	PointContainer
}

// The type represents the cross of 2 Liners.
type LineCross struct {
	Pair [2]Line
	Point Point
}

// Check if two LinerPointContainers do cross and return the
// crossing point.
func LinersCross(lp1, lp2 LinerPointContainer) (LineCross, bool) {
	l1 := lp1.Line()
	l2 := lp2.Line()
	
	crossPt, doCross := l1.crossesLine(l2)
	if !doCross ||
			len(lp1.ContainedPoints([]Point{crossPt}))==0 ||
			len(lp2.ContainedPoints([]Point{crossPt}))==0 {
		return LineCross{}, false
	}
	
	return LineCross{
		Pair: [2]Line{l1, l2},
		Point: crossPt,
	}, true
}

// Check whether the liner is parallel to the other liner.
func LinersParallel(first, second Liner) bool {
	l1 := first.Line()
	l2 := second.Line()
	
	return l1.K == l2.K
}

// Returns angle between liners in radians.
// The value fits the -Pi < Value < Pi condition.
func LinersAngle(first, second Liner) Float {
	l1 := first.Line()
	l2 := second.Line()
	
	if l1.K == l2.K {
		return 0
	}
	
	return Atan(l1.K/l2.K)
}