package mx

//import "fmt"

// The type represents mathematical equation of line and line itself.
type LineExpr struct {
	K, C, X Float
	Vertical bool
}

// Returns the line itself. Made to implement the Liner interface.
func (l LineExpr) GetLineExpr() LineExpr {
	return l
}

func (e LineExpr) GetContainedPoints(pts Vectors) Vectors {
	ret := make(Vectors, 0, len(pts))
	for _, pt := range pts {
		if e.ContainsPoint(pt) {
			ret = append(ret, pt)
		}
	}
	return ret
}

func (l LineExpr) ContainsPoint(p Vector) bool {
	buf := LineExpr{0, p.Y, 0, false}
	pc, ok := DoLinersCross(l, buf)
	if !ok {
		return false
	}
	
	//Println("points:", l, p, pc)
	return Neq(pc.Point.X, p.X) && Neq(pc.Point.Y, p.Y)
}

func (l1 LineExpr) Crosses(l2 LineExpr) (Vector, bool) {
	var x, y Float
	if AreLinersParallel(l1, l2) {
		return ZV, false
	}

	switch {
	case l1.Vertical :
		x = l1.X
		y = l2.K*x + l2.C
		//Println("l1-vert:", x, y)
	case l2.Vertical :
		x = l2.X
		y = l1.K*x + l1.C
		//Println("l2-vert:", x, y)
	default:
		x = (l1.C - l2.C) / (l2.K - l1.K)
		y = l1.K*x + l1.C
	}

	//Println("in:", x, y)
	return Vector{x, y}, true
}