package mx

type Liner interface {
	PointContainer
	GetLineExpr() LineExpr
}
type Liners []Liner

// The type represents the cross of 2 Liners.
type LinersCrossing struct {
	Pair [2]LineExpr
	Point Vector
}

// Checks all possible combinations
// of Liners to cross and returns
// the crossings if are present.
func GetLinersCrossings(
	what, with Liners,
) []LinersCrossing {
	ret := make([]LinersCrossing, 0, len(with))
	for i := range what {
		for j := range with {
			cross, doCross := DoLinersCross(
				what[i],
				with[j],
			)
			if doCross {
				ret = append(ret, cross)
			}
		}
	}
	
	return ret
}

// Check if two LinerPointContainers do cross and return the
// crossing point.
func DoLinersCross(
	lp1, lp2 Liner,
) (LinersCrossing, bool) {
	l1 := lp1.GetLineExpr()
	l2 := lp2.GetLineExpr()
	
	crossPt, doCross := l1.Crosses(l2)
	if !lp1.ContainsPoint(crossPt) ||
			!lp2.ContainsPoint(crossPt) {
		return LinersCrossing{}, false
	}
	
	return LinersCrossing{
		Pair: [2]LineExpr{l1, l2},
		Point: crossPt,
	}, doCross
}

// Check whether the liner is parallel to the other liner.
func AreLinersParallel(
	first, second Liner,
) bool {
	l1 := first.GetLineExpr()
	l2 := second.GetLineExpr()
	
	return l1.Vertical && l2.Vertical ||
		l1.K == l2.K
}

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