package geom

import (
	"math"
)

// PointF32 is an X, Y coordinate pair (floating point, 32 bits).
type PointF32 struct {
	X, Y float32
}

// ZeroPtF32 is initialized on (0, 0).
var ZeroPtF32 = PointF32{X: 0, Y: 0}

// PtF32 is a shorthand function to create a point.
func PtF32(x, y float32) PointF32 {
	return PointF32{x, y}
}

// Add adds q as a vector to p.
func (p PointF32) Add(q PointF32) PointF32 {
	return PointF32{p.X + q.X, p.Y + q.Y}
}

// Add2D adds x and y to X and Y of point p and returns the sum.
func (p PointF32) Add2D(x, y float32) PointF32 {
	return PtF32(p.X+x, p.Y+y)
}

// AngleTo calculates the angle [0..2*Pi) from point p to point q.
func (p PointF32) AngleTo(q PointF32) float32 {
	a := float32(math.Atan(float64((p.Y - q.Y) / (p.X - q.X))))
	if q.X < p.X {
		return a + math.Pi
	}
	if a < 0 {
		a += 2 * math.Pi
	}
	return a
}

// Distance calculates the distance between points p and q.
func (p PointF32) Distance(q PointF32) float32 {
	return float32(math.Sqrt(float64(p.Distance2(q))))
}

// Distance2 calculates the squared distance between points p and q.
func (p PointF32) Distance2(q PointF32) float32 {
	dx := q.X - p.X
	dy := q.Y - p.Y
	return dx*dx + dy*dy
}

// DistanceToLine calculates the distance to the line segment a, b.
func (p PointF32) DistanceToLine(a, b PointF32) float32 {
	dx1, dy1 := (a.X - p.X), (a.Y - p.Y)
	dx2, dy2 := (b.X - a.X), (b.Y - a.Y)
	t := -((dx1*dx2 + dy1*dy2) / (dx2*dx2 + dy2*dy2))
	if 0 <= t && t <= 1 {
		return Abs32(dx2*dy1-dy2*dx1) / Sqrt32(dx2*dx2+dy2*dy2)
	}
	d1, d2 := Sqrt32(Sq32(b.X-p.X)+Sq32(b.Y-p.Y)), Sqrt32(dx1*dx1+dy1*dy1)
	if d1 < d2 {
		return d1
	}
	return d2
}

// DistanceToLines calculates the smallest distance to the line segments of q.
func (p PointF32) DistanceToLines(q PointsF32) float32 {
	n := len(q)
	if n == 0 {
		return NaN32()
	}
	if n == 1 {
		return p.Distance(q[0])
	}
	min := p.DistanceToLine(q[0], q[1])
	for i := range q {
		if i < 2 {
			continue
		}
		d := p.DistanceToLine(q[i-1], q[i])
		if d < min {
			min = d
		}
	}
	return min
}

// DistanceToPolygon calculates the smallest distance to the polygon q.
func (p PointF32) DistanceToPolygon(q PolygonF32) float32 {
	if len(q.Points) == 0 {
		return NaN32()
	}
	return p.DistanceToLines(append(q.Points, q.Points[0]))
}

// Div divides the X and Y values of point p with t and returns the result.
func (p PointF32) Div(t float32) PointF32 {
	return PtF32(p.X/t, p.Y/t)
}

// In tests if the point p is inside the rectangle r.
func (p PointF32) In(r RectangleF32) bool {
	if p.X < r.Min.X || p.X >= r.Max.X || p.Y < r.Min.Y || p.Y >= r.Max.Y {
		return false
	}
	return true
}

// InPolygon tests is the point p is inside the polygon q.
func (p PointF32) InPolygon(q PolygonF32) bool {
	var n = len(q.Points)
	var c = false

	var i = 0
	var j = n - 1
	for i < n {
		if ((q.Points[i].Y >= p.Y) != (q.Points[j].Y >= p.Y)) &&
			(p.X <= (q.Points[j].X-q.Points[i].X)*(p.Y-q.Points[i].Y)/(q.Points[j].Y-q.Points[i].Y)+q.Points[i].X) {
			c = !c
		}
		j = i
		i++
	}
	return c
}

// Invert changes the sign of the components.
func (p PointF32) Invert() PointF32 {
	return PointF32{-p.X, -p.Y}
}

// Mul multiplier the X and Y values of point p with t and returns the result.
func (p PointF32) Mul(t float32) PointF32 {
	return PtF32(p.X*t, p.Y*t)
}

// Sub subtracts q as a vector from p.
func (p PointF32) Sub(q PointF32) PointF32 {
	return PointF32{p.X - q.X, p.Y - q.Y}
}

// To64 transforms the point p into a PointF.
func (p PointF32) To64() PointF {
	return PointF{float64(p.X), float64(p.Y)}
}

// ToInt transforms the point p into a Point.
func (p PointF32) ToInt() Point {
	return Point{int(p.X), int(p.Y)}
}

// MaxPtF32 returns the point that is at the largest X & Y position of a and b.
func MaxPtF32(a, b PointF32) PointF32 {
	return PtF32(Max32(a.X, b.X), Max32(a.Y, b.Y))
}

// MinPtF32 returns the point that is at the smallest X & Y position of a and b.
func MinPtF32(a, b PointF32) PointF32 {
	return PtF32(Min32(a.X, b.X), Min32(a.Y, b.Y))
}