// Rectangle draws a rectangle using a path between (x1,y1) and (x2,y2)
func Rectangle(path draw2d.PathBuilder, x1, y1, x2, y2 float64) {
	path.MoveTo(x1, y1)
	path.LineTo(x2, y1)
	path.LineTo(x2, y2)
	path.LineTo(x1, y2)
	path.Close()
}

// Circle draws a circle using a path with center (cx,cy) and radius
func Circle(path draw2d.PathBuilder, cx, cy, radius float64) {
	path.ArcTo(cx, cy, radius, radius, 0, -math.Pi*2)
	path.Close()
}

// Ellipse draws an ellipse using a path with center (cx,cy) and radius (rx,ry)
func Ellipse(path draw2d.PathBuilder, cx, cy, rx, ry float64) {
	path.ArcTo(cx, cy, rx, ry, 0, -math.Pi*2)
	path.Close()
}

// RoundedRectangle draws a rectangle using a path between (x1,y1) and (x2,y2)
func RoundedRectangle(path draw2d.PathBuilder, x1, y1, x2, y2, arcWidth, arcHeight float64) {
	arcWidth = arcWidth / 2
	arcHeight = arcHeight / 2
	path.MoveTo(x1, y1+arcHeight)
	path.QuadCurveTo(x1, y1, x1+arcWidth, y1)
	path.LineTo(x2-arcWidth, y1)
	path.QuadCurveTo(x2, y1, x2, y1+arcHeight)
	path.LineTo(x2, y2-arcHeight)
	path.QuadCurveTo(x2, y2, x2-arcWidth, y2)
	path.LineTo(x1+arcWidth, y2)
	path.QuadCurveTo(x1, y2, x1, y2-arcHeight)
	path.Close()
}

// DrawContour draws the given closed contour at the given sub-pixel offset.
func DrawContour(path draw2d.PathBuilder, ps []truetype.Point, dx, dy float64) {
	if len(ps) == 0 {
		return
	}
	startX, startY := pointToF64Point(ps[0])
	path.MoveTo(startX+dx, startY+dy)
	q0X, q0Y, on0 := startX, startY, true
	for _, p := range ps[1:] {
		qX, qY := pointToF64Point(p)
		on := p.Flags&0x01 != 0
		if on {
			if on0 {
				path.LineTo(qX+dx, qY+dy)
			} else {
				path.QuadCurveTo(q0X+dx, q0Y+dy, qX+dx, qY+dy)
			}
		} else {
			if on0 {
				// No-op.
			} else {
				midX := (q0X + qX) / 2
				midY := (q0Y + qY) / 2
				path.QuadCurveTo(q0X+dx, q0Y+dy, midX+dx, midY+dy)
			}
		}
		q0X, q0Y, on0 = qX, qY, on
	}
	// Close the curve.
	if on0 {
		path.LineTo(startX+dx, startY+dy)
	} else {
		path.QuadCurveTo(q0X+dx, q0Y+dy, startX+dx, startY+dy)
	}
}

func rCubicCurveTo(path draw2d.PathBuilder, dcx1, dcy1, dcx2, dcy2, dx, dy float64) {
	x, y := path.LastPoint()
	path.CubicCurveTo(x+dcx1, y+dcy1, x+dcx2, y+dcy2, x+dx, y+dy)
}

func rQuadCurveTo(path draw2d.PathBuilder, dcx, dcy, dx, dy float64) {
	x, y := path.LastPoint()
	path.QuadCurveTo(x+dcx, y+dcy, x+dx, y+dy)
}

func rLineTo(path draw2d.PathBuilder, x, y float64) {
	x0, y0 := path.LastPoint()
	path.LineTo(x0+x, y0+y)
}