package gel

import (
	"image"
	"image/color"

	"github.com/p9c/p9/pkg/gel/gio/font"
	l "github.com/p9c/p9/pkg/gel/gio/layout"
	"github.com/p9c/p9/pkg/gel/gio/op"
	"github.com/p9c/p9/pkg/gel/gio/op/clip"
	"github.com/p9c/p9/pkg/gel/gio/op/paint"
	"github.com/p9c/p9/pkg/gel/gio/text"
	"github.com/p9c/p9/pkg/gel/gio/unit"

	"golang.org/x/image/math/fixed"
)

// Label is text drawn inside an empty box
type Label struct {
	*Window
	// Face defines the text style.
	font font.Font
	// Color is the text color.
	color color.NRGBA
	// Alignment specify the text alignment.
	alignment text.Alignment
	// MaxLines limits the number of lines. Zero means no limit.
	maxLines int
	text     string
	textSize unit.Sp
	shaper   *text.Shaper
}

// Fn renders the label as specified
func (lbl *Label) Fn(gtx l.Context) l.Dimensions {
	cs := gtx.Constraints
	textSize := fixed.I(gtx.Sp(lbl.textSize))

	lbl.shaper.LayoutString(text.Parameters{
		Font:      lbl.font,
		PxPerEm:   textSize,
		MaxLines:  lbl.maxLines,
		Alignment: lbl.alignment,
		MaxWidth:  cs.Max.X,
		MinWidth:  cs.Min.X,
		Locale:    gtx.Locale,
	}, lbl.text)

	// Record the material (color) for text
	m := op.Record(gtx.Ops)
	paint.ColorOp{Color: lbl.color}.Add(gtx.Ops)
	textMaterial := m.Stop()

	m2 := op.Record(gtx.Ops)
	viewport := image.Rectangle{Max: cs.Max}
	it := GlyphIterator{
		Viewport: viewport,
		MaxLines: lbl.maxLines,
		Material: textMaterial,
	}
	var glyphs [32]text.Glyph
	line := glyphs[:0]
	for g, ok := lbl.shaper.NextGlyph(); ok; g, ok = lbl.shaper.NextGlyph() {
		var ok bool
		if line, ok = it.PaintGlyph(gtx, lbl.shaper, g, line); !ok {
			break
		}
	}
	call := m2.Stop()
	viewport.Min = viewport.Min.Add(it.Padding.Min)
	viewport.Max = viewport.Max.Add(it.Padding.Max)
	clipStack := clip.Rect(viewport).Push(gtx.Ops)
	call.Add(gtx.Ops)
	dims := l.Dimensions{Size: it.Bounds.Size()}
	dims.Size = cs.Constrain(dims.Size)
	dims.Baseline = dims.Size.Y - it.Baseline
	clipStack.Pop()
	return dims
}

// Label creates a new label widget
func (w *Window) Label() *Label {
	return &Label{
		Window:   w,
		font:     font.Font{},
		color:    w.Colors.GetNRGBAFromName("DocText"),
		textSize: w.TextSize,
		shaper:   w.shaper,
	}
}

// Text sets the label text
func (lbl *Label) Text(txt string) *Label {
	lbl.text = txt
	return lbl
}

// Color sets the text color
func (lbl *Label) Color(col string) *Label {
	lbl.color = lbl.Theme.Colors.GetNRGBAFromName(col)
	return lbl
}

// Font sets the font
func (lbl *Label) Font(fontName string) *Label {
	if fnt, e := lbl.Theme.collection.Font(fontName); e == nil {
		lbl.font = fnt
	}
	return lbl
}

// TextScale sets the text size as a scale factor
func (lbl *Label) TextScale(scale float32) *Label {
	lbl.textSize = unit.Sp(float32(lbl.Theme.TextSize) * scale)
	return lbl
}

// Alignment sets the text alignment
func (lbl *Label) Alignment(alignment text.Alignment) *Label {
	lbl.alignment = alignment
	return lbl
}

// MaxLines sets the maximum number of lines
func (lbl *Label) MaxLines(maxLines int) *Label {
	lbl.maxLines = maxLines
	return lbl
}

// H1 creates a large headline label
func (w *Window) H1(txt string) *Label {
	return w.Label().Text(txt).TextScale(Scales["H1"])
}

// H2 creates a headline label
func (w *Window) H2(txt string) *Label {
	return w.Label().Text(txt).TextScale(Scales["H2"])
}

// H3 creates a headline label
func (w *Window) H3(txt string) *Label {
	return w.Label().Text(txt).TextScale(Scales["H3"])
}

// H4 creates a headline label
func (w *Window) H4(txt string) *Label {
	return w.Label().Text(txt).TextScale(Scales["H4"])
}

// H5 creates a headline label
func (w *Window) H5(txt string) *Label {
	return w.Label().Text(txt).TextScale(Scales["H5"])
}

// H6 creates a headline label
func (w *Window) H6(txt string) *Label {
	return w.Label().Text(txt).TextScale(Scales["H6"])
}

// Subtitle1 creates a subtitle label
func (w *Window) Subtitle1(txt string) *Label {
	return w.Label().Text(txt).TextScale(Scales["Subtitle1"])
}

// Subtitle2 creates a subtitle label
func (w *Window) Subtitle2(txt string) *Label {
	return w.Label().Text(txt).TextScale(Scales["Subtitle2"])
}

// Body1 creates a body text label
func (w *Window) Body1(txt string) *Label {
	return w.Label().Text(txt).TextScale(Scales["Body1"])
}

// Body2 creates a body text label
func (w *Window) Body2(txt string) *Label {
	return w.Label().Text(txt).TextScale(Scales["Body2"])
}

// Caption creates a caption label
func (w *Window) Caption(txt string) *Label {
	return w.Label().Text(txt).TextScale(Scales["Caption"])
}

// Overline creates an overline label
func (w *Window) Overline(txt string) *Label {
	return w.Label().Text(txt).TextScale(Scales["Overline"])
}