// Plot implements the Plotter interface, drawing a line
// that connects each point in the Line.
func (f *Function) Plot(c draw.Canvas, p *plot.Plot) {
	trX, trY := p.Transforms(&c)

	d := (p.X.Max - p.X.Min) / float64(f.Samples-1)
	line := make([]draw.Point, f.Samples)
	for i := range line {
		x := p.X.Min + float64(i)*d
		line[i].X = trX(x)
		line[i].Y = trY(f.F(x))
	}
	c.StrokeLines(f.LineStyle, c.ClipLinesXY(line)...)
}

// Plot implements the Plotter interface, drawing labels.
func (l *Labels) Plot(c draw.Canvas, p *plot.Plot) {
	trX, trY := p.Transforms(&c)
	for i, label := range l.Labels {
		x := trX(l.XYs[i].X)
		y := trY(l.XYs[i].Y)
		if !c.Contains(draw.Point{X: x, Y: y}) {
			continue
		}
		x += l.XOffset
		y += l.YOffset
		c.FillText(l.TextStyle, x, y, l.XAlign, l.YAlign, label)
	}
}

// Plot implements the Plotter interface, drawing labels.
func (e *XErrorBars) Plot(c draw.Canvas, p *plot.Plot) {
	trX, trY := p.Transforms(&c)
	for i, err := range e.XErrors {
		y := trY(e.XYs[i].Y)
		xlow := trX(e.XYs[i].X - math.Abs(err.Low))
		xhigh := trX(e.XYs[i].X + math.Abs(err.High))

		bar := c.ClipLinesX([]draw.Point{{xlow, y}, {xhigh, y}})
		c.StrokeLines(e.LineStyle, bar...)
		e.drawCap(&c, xlow, y)
		e.drawCap(&c, xhigh, y)
	}
}

// Draw draws a plot to a draw.Canvas.
//
// Plotters are drawn in the order in which they were
// added to the plot.  Plotters that  implement the
// GlyphBoxer interface will have their GlyphBoxes
// taken into account when padding the plot so that
// none of their glyphs are clipped.
func (p *Plot) Draw(c draw.Canvas) {
	if p.BackgroundColor != nil {
		c.SetColor(p.BackgroundColor)
		c.Fill(c.Rectangle.Path())
	}
	if p.Title.Text != "" {
		c.FillText(p.Title.TextStyle, c.Center().X, c.Max.Y, -0.5, -1, p.Title.Text)
		c.Max.Y -= p.Title.Height(p.Title.Text) - p.Title.Font.Extents().Descent
		c.Max.Y -= p.Title.Padding
	}

	p.X.sanitizeRange()
	x := horizontalAxis{p.X}
	p.Y.sanitizeRange()
	y := verticalAxis{p.Y}

	ywidth := y.size()
	x.draw(padX(p, draw.Crop(c, ywidth, 0, 0, 0)))
	xheight := x.size()
	y.draw(padY(p, draw.Crop(c, 0, 0, xheight, 0)))

	dataC := padY(p, padX(p, draw.Crop(c, ywidth, 0, xheight, 0)))
	for _, data := range p.plotters {
		data.Plot(dataC, p)
	}

	p.Legend.draw(draw.Crop(draw.Crop(c, ywidth, 0, 0, 0), 0, 0, xheight, 0))
}

// Plot implements the plot.Plotter interface.
func (g *Grid) Plot(c draw.Canvas, plt *plot.Plot) {
	trX, trY := plt.Transforms(&c)

	if g.Vertical.Color == nil {
		goto horiz
	}
	for _, tk := range plt.X.Tick.Marker.Ticks(plt.X.Min, plt.X.Max) {
		if tk.IsMinor() {
			continue
		}
		x := trX(tk.Value)
		c.StrokeLine2(g.Vertical, x, c.Min.Y, x, c.Min.Y+c.Size().Y)
	}

horiz:
	if g.Horizontal.Color == nil {
		return
	}
	for _, tk := range plt.Y.Tick.Marker.Ticks(plt.Y.Min, plt.Y.Max) {
		if tk.IsMinor() {
			continue
		}
		y := trY(tk.Value)
		c.StrokeLine2(g.Horizontal, c.Min.X, y, c.Min.X+c.Size().X, y)
	}
}

// bottomMost returns the bottom-most GlyphBox.
func bottomMost(c *draw.Canvas, boxes []GlyphBox) GlyphBox {
	miny := c.Min.Y
	l := GlyphBox{}
	for _, b := range boxes {
		if b.Size().Y <= 0 {
			continue
		}
		if y := c.Y(b.Y) + b.Min.Y; y < miny && b.Y >= 0 {
			miny = y
			l = b
		}
	}
	return l
}

// topMost returns the top-most GlyphBox.
func topMost(c *draw.Canvas, boxes []GlyphBox) GlyphBox {
	maxy := c.Max.Y
	t := GlyphBox{Y: 1}
	for _, b := range boxes {
		if b.Size().Y <= 0 {
			continue
		}
		if y := c.Y(b.Y) + b.Min.Y + b.Size().Y; y > maxy && b.Y <= 1 {
			maxy = y
			t = b
		}
	}
	return t
}

// leftMost returns the left-most GlyphBox.
func leftMost(c *draw.Canvas, boxes []GlyphBox) GlyphBox {
	minx := c.Min.X
	l := GlyphBox{}
	for _, b := range boxes {
		if b.Size().X <= 0 {
			continue
		}
		if x := c.X(b.X) + b.Min.X; x < minx && b.X >= 0 {
			minx = x
			l = b
		}
	}
	return l
}

// rightMost returns the right-most GlyphBox.
func rightMost(c *draw.Canvas, boxes []GlyphBox) GlyphBox {
	maxx := c.Max.X
	r := GlyphBox{X: 1}
	for _, b := range boxes {
		if b.Size().X <= 0 {
			continue
		}
		if x := c.X(b.X) + b.Min.X + b.Size().X; x > maxx && b.X <= 1 {
			maxx = x
			r = b
		}
	}
	return r
}

// DrawGlyphBoxes draws red outlines around the plot's
// GlyphBoxes.  This is intended for debugging.
func (p *Plot) DrawGlyphBoxes(c *draw.Canvas) {
	c.SetColor(color.RGBA{R: 255, A: 255})
	for _, b := range p.GlyphBoxes(p) {
		b.Rectangle.Min.X += c.X(b.X)
		b.Rectangle.Min.Y += c.Y(b.Y)
		c.Stroke(b.Rectangle.Path())
	}
}

// Thumbnail fulfills the plot.Thumbnailer interface.
func (b *BarChart) Thumbnail(c *draw.Canvas) {
	pts := []draw.Point{
		{c.Min.X, c.Min.Y},
		{c.Min.X, c.Max.Y},
		{c.Max.X, c.Max.Y},
		{c.Max.X, c.Min.Y},
	}
	poly := c.ClipPolygonY(pts)
	c.FillPolygon(b.Color, poly)

	pts = append(pts, draw.Point{X: c.Min.X, Y: c.Min.Y})
	outline := c.ClipLinesY(pts)
	c.StrokeLines(b.LineStyle, outline...)
}

func (b *BoxPlotWithConfidenceIntervals) Plot(c draw.Canvas, plt *plot.Plot) {
	if b.Horizontal {
		panic("not handling horizontal BoxPlotWithConfidenceIntervals")
	}

	b.BoxPlot.Plot(c, plt)

	trX, trY := plt.Transforms(&c)
	x := trX(b.Location)
	if !c.ContainsX(x) {
		return
	}
	x += b.Offset

	mean, err, _ := meanAndConf95(b.Values)

	meanLength := trY(mean)
	lowLength := trY(mean - err)
	highLength := trY(mean + err)

	confidenceVertices := []draw.Point{
		{x - b.Width/4, lowLength},
		{x + b.Width/4, lowLength},
		{x + b.Width/4, highLength},
		{x - b.Width/4, highLength},
	}
	confidencePoly := c.ClipPolygonY(confidenceVertices)
	gray := color.RGBA{200, 200, 200, 255}
	c.FillPolygon(gray, confidencePoly)

	meanLine := c.ClipLinesY([]draw.Point{
		{x - b.Width/4, meanLength},
		{x + b.Width/4, meanLength},
	})

	meanStyle := b.BoxStyle
	meanStyle.Color = color.RGBA{150, 150, 150, 255}
	c.StrokeLines(meanStyle, meanLine...)
}

// Plot implements the Plot method of the plot.Plotter interface.
func (h *Contour) Plot(c draw.Canvas, plt *plot.Plot) {
	if naive {
		h.naivePlot(c, plt)
		return
	}

	var pal []color.Color
	if h.Palette != nil {
		pal = h.Palette.Colors()
	}

	trX, trY := plt.Transforms(&c)

	// Collate contour paths and draw them.
	//
	// The alternative naive approach is to draw each line segment as
	// conrec returns it. The integrated path approach allows graphical
	// optimisations and is necessary for contour fill shading.
	cp := contourPaths(h.GridXYZ, h.Levels, trX, trY)

	// ps is a palette scaling factor to scale the palette uniformly
	// across the given levels. This enables a discordance between the
	// number of colours and the number of levels. Sorting is not
	// necessary since contourPaths sorts the levels as a side effect.
	ps := float64(len(pal)-1) / (h.Levels[len(h.Levels)-1] - h.Levels[0])
	if len(h.Levels) == 1 {
		ps = 0
	}

	for i, z := range h.Levels {
		if math.IsNaN(z) {
			continue
		}
		for _, pa := range cp[z] {
			if isLoop(pa) {
				pa.Close()
			}

			style := h.LineStyles[i%len(h.LineStyles)]
			var col color.Color
			switch {
			case z < h.Min:
				col = h.Underflow
			case z > h.Max:
				col = h.Overflow
			case len(pal) == 0:
				col = style.Color
			default:
				col = pal[int((z-h.Levels[0])*ps+0.5)] // Apply palette scaling.
			}
			if col != nil && style.Width != 0 {
				c.SetLineStyle(style)
				c.SetColor(col)
				c.Stroke(pa)
			}
		}
	}
}

// Plot implements the Plotter interface, drawing a line
// that connects each point in the Line.
func (h *Histogram) Plot(c draw.Canvas, p *plot.Plot) {
	trX, trY := p.Transforms(&c)

	for _, bin := range h.Bins {
		pts := []draw.Point{
			{trX(bin.Min), trY(0)},
			{trX(bin.Max), trY(0)},
			{trX(bin.Max), trY(bin.Weight)},
			{trX(bin.Min), trY(bin.Weight)},
		}
		if h.FillColor != nil {
			c.FillPolygon(h.FillColor, c.ClipPolygonXY(pts))
		}
		pts = append(pts, draw.Point{trX(bin.Min), trY(0)})
		c.StrokeLines(h.LineStyle, c.ClipLinesXY(pts)...)
	}
}

// draw draws the legend to the given draw.Canvas.
func (l *Legend) draw(c draw.Canvas) {
	iconx := c.Min.X
	textx := iconx + l.ThumbnailWidth + l.TextStyle.Width(" ")
	xalign := 0.0
	if !l.Left {
		iconx = c.Max.X - l.ThumbnailWidth
		textx = iconx - l.TextStyle.Width(" ")
		xalign = -1
	}
	textx += l.XOffs
	iconx += l.XOffs

	enth := l.entryHeight()
	y := c.Max.Y - enth
	if !l.Top {
		y = c.Min.Y + (enth+l.Padding)*(vg.Length(len(l.entries))-1)
	}
	y += l.YOffs

	icon := &draw.Canvas{
		Canvas: c.Canvas,
		Rectangle: draw.Rectangle{
			Min: draw.Point{iconx, y},
			Max: draw.Point{iconx + l.ThumbnailWidth, y + enth},
		},
	}
	for _, e := range l.entries {
		for _, t := range e.thumbs {
			t.Thumbnail(icon)
		}
		yoffs := (enth - l.TextStyle.Height(e.text)) / 2
		c.FillText(l.TextStyle, textx, icon.Min.Y+yoffs, xalign, 0, e.text)
		icon.Min.Y -= enth + l.Padding
		icon.Max.Y -= enth + l.Padding
	}
}

// Thumbnail the thumbnail for the Line,
// implementing the plot.Thumbnailer interface.
func (pts *Line) Thumbnail(c *draw.Canvas) {
	if pts.ShadeColor != nil {
		points := []draw.Point{
			{c.Min.X, c.Min.Y},
			{c.Min.X, c.Max.Y},
			{c.Max.X, c.Max.Y},
			{c.Max.X, c.Min.Y},
		}
		poly := c.ClipPolygonY(points)
		c.FillPolygon(*pts.ShadeColor, poly)

		points = append(points, draw.Point{c.Min.X, c.Min.Y})
	} else {
		y := c.Center().Y
		c.StrokeLine2(pts.LineStyle, c.Min.X, y, c.Max.X, y)
	}
}

// Thumbnail draws a rectangle in the given style of the histogram.
func (h *Histogram) Thumbnail(c *draw.Canvas) {
	ymin := c.Min.Y
	ymax := c.Max.Y
	xmin := c.Min.X
	xmax := c.Max.X

	pts := []draw.Point{
		{xmin, ymin},
		{xmax, ymin},
		{xmax, ymax},
		{xmin, ymax},
	}
	if h.FillColor != nil {
		c.FillPolygon(h.FillColor, c.ClipPolygonXY(pts))
	}
	pts = append(pts, draw.Point{xmin, ymin})
	c.StrokeLines(h.LineStyle, c.ClipLinesXY(pts)...)
}

func (g GlyphBoxes) Plot(c draw.Canvas, plt *plot.Plot) {
	for _, b := range plt.GlyphBoxes(plt) {
		x := c.X(b.X) + b.Rectangle.Min.X
		y := c.Y(b.Y) + b.Rectangle.Min.Y
		c.StrokeLines(g.LineStyle, []draw.Point{
			{x, y},
			{x + b.Rectangle.Size().X, y},
			{x + b.Rectangle.Size().X, y + b.Rectangle.Size().Y},
			{x, y + b.Rectangle.Size().Y},
			{x, y},
		})
	}
}

// Plot draws the Line, implementing the plot.Plotter
// interface.
func (pts *Line) Plot(c draw.Canvas, plt *plot.Plot) {
	trX, trY := plt.Transforms(&c)
	ps := make([]draw.Point, len(pts.XYs))

	for i, p := range pts.XYs {
		ps[i].X = trX(p.X)
		ps[i].Y = trY(p.Y)
	}

	if pts.ShadeColor != nil && len(ps) > 0 {
		c.SetColor(*pts.ShadeColor)
		minY := trY(plt.Y.Min)
		var pa vg.Path
		pa.Move(ps[0].X, minY)
		for i := range pts.XYs {
			pa.Line(ps[i].X, ps[i].Y)
		}
		pa.Line(ps[len(pts.XYs)-1].X, minY)
		pa.Close()
		c.Fill(pa)
	}

	c.StrokeLines(pts.LineStyle, c.ClipLinesXY(ps)...)
}

// Plot implements the Plot method of the plot.Plotter interface.
func (bs *Bubbles) Plot(c draw.Canvas, plt *plot.Plot) {
	trX, trY := plt.Transforms(&c)

	c.SetColor(bs.Color)

	for _, d := range bs.XYZs {
		x := trX(d.X)
		y := trY(d.Y)
		if !c.Contains(draw.Point{x, y}) {
			continue
		}

		rad := bs.radius(d.Z)

		// draw a circle centered at x, y
		var p vg.Path
		p.Move(x+rad, y)
		p.Arc(x, y, rad, 0, 2*math.Pi)
		p.Close()
		c.Fill(p)
	}
}