package x

import "image"
import "image/color"
import "golang.org/x/image/font"
import "golang.org/x/image/math/fixed"
import "git.tebibyte.media/tomo/tomo"
import "git.tebibyte.media/tomo/typeset"
import "git.tebibyte.media/tomo/tomo/text"
import "git.tebibyte.media/tomo/tomo/event"
import "git.tebibyte.media/tomo/tomo/canvas"

type textBox struct {
	*box
	
	hOverflow, vOverflow bool
	contentBounds image.Rectangle
	scroll        image.Point

	text      string
	textColor color.Color
	face      font.Face
	wrap      bool
	hAlign    tomo.Align

	selectable bool
	dot        text.Dot
	dotColor   color.Color
	
	drawer typeset.Drawer
	
	on struct {
		contentBoundsChange event.FuncBroadcaster
		dotChange           event.FuncBroadcaster
	}
}

func (backend *Backend) NewTextBox() tomo.TextBox {
	box := &textBox {
		box:       backend.NewBox().(*box),
		textColor: color.Black,
	}
	box.box.drawer = box
	box.outer  = box
	return box
}

func (this *textBox) SetOverflow (horizontal, vertical bool) {
	if this.hOverflow == horizontal && this.vOverflow == vertical { return }
	this.hOverflow = horizontal
	this.vOverflow = vertical
	this.invalidateLayout()
}

func (this *textBox) ContentBounds () image.Rectangle {
	return this.contentBounds
}

func (this *textBox) ScrollTo (point image.Point) {
	// TODO: constrain scroll
	this.scroll = point
	this.invalidateLayout()
}

func (this *textBox) OnContentBoundsChange (callback func()) event.Cookie {
	return this.on.contentBoundsChange.Connect(callback)
}

func (this *textBox) SetText (text string) {
	if this.text == text { return }
	this.text = text
	this.drawer.SetText([]rune(text))
	this.recalculateMinimumSize()
	this.invalidateLayout()
}

func (this *textBox) SetTextColor (c color.Color) {
	if this.textColor == c { return }
	this.textColor = c
	this.invalidateDraw()
}

func (this *textBox) SetFace (face font.Face) {
	if this.face == face { return }
	this.face = face
	this.drawer.SetFace(face)
	this.recalculateMinimumSize()
	this.invalidateLayout()
}

func (this *textBox) SetWrap (wrap bool) {
	if this.wrap == wrap { return }
	this.drawer.SetWrap(wrap)
	this.recalculateMinimumSize()
	this.invalidateLayout()
}

func (this *textBox) SetSelectable (selectable bool) {
	if this.selectable == selectable { return }
	this.selectable = selectable
}

func (this *textBox) SetDotColor (c color.Color) {
	if this.dotColor == c { return }
	this.dotColor = c
	if !this.dot.Empty() {
		this.invalidateDraw()
	}
}

func (this *textBox) Select (dot text.Dot) {
	if !this.selectable { return }
	if this.dot == dot  { return }
	this.SetFocused(true)
	this.dot = dot
	this.on.dotChange.Broadcast()
	this.invalidateDraw()
}

func (this *textBox) Dot () text.Dot {
	return this.dot
}

func (this *textBox) OnDotChange (callback func ()) event.Cookie {
	return this.on.dotChange.Connect(callback)
}

func (this *textBox) SetAlign (x, y tomo.Align) {
	if this.hAlign == x { return }
	this.hAlign = x

	switch x {
	case tomo.AlignStart:  this.drawer.SetAlign(typeset.AlignLeft)
	case tomo.AlignMiddle: this.drawer.SetAlign(typeset.AlignCenter)
	case tomo.AlignEnd:    this.drawer.SetAlign(typeset.AlignRight)
	case tomo.AlignEven:   this.drawer.SetAlign(typeset.AlignJustify)
	}
	
	this.invalidateDraw()
}

func (this *textBox) Draw (can canvas.Canvas) {
	if can == nil { return }
	this.drawBorders(can)
	pen := can.Pen()
	pen.Fill(this.color)
	pen.Rectangle(can.Bounds())

	if this.selectable && this.Focused() {
		this.drawDot(can)
	}

	if this.face == nil { return }
	this.drawer.Draw(can, this.textColor, this.textOffset())
}

func roundPt (point fixed.Point26_6) image.Point {
	return image.Pt(point.X.Round(), point.Y.Round())
}

func fixPt (point image.Point) fixed.Point26_6 {
	return fixed.P(point.X, point.Y)
}

func (this *textBox) drawDot (can canvas.Canvas) {
	pen := can.Pen()
	pen.Fill(color.Transparent)
	pen.Stroke(this.textColor)
	pen.StrokeWeight(1)

	bounds  := this.InnerBounds()
	metrics := this.face.Metrics()
	dot     := this.dot.Canon()
	start   := this.drawer.PositionAt(dot.Start).Add(fixPt(this.textOffset()))
	end     := this.drawer.PositionAt(dot.End  ).Add(fixPt(this.textOffset()))
	height  := this.drawer.LineHeight().Round()
	ascent  := fixed.Point26_6 { Y: metrics.Descent }
	descent := fixed.Point26_6 { Y: metrics.Ascent  }
	
	switch {
	case dot.Empty():
		pen.Path(roundPt(start.Add(ascent)), roundPt(start.Sub(descent)))
		
	case start.Y == end.Y:
		pen.Fill(this.dotColor)
		pen.StrokeWeight(0)
		pen.Rectangle(image.Rectangle {
			Min: roundPt(start.Add(ascent)),
			Max: roundPt(end.Sub(descent)),
		})
		
	default:
		pen.Fill(this.dotColor)
		pen.StrokeWeight(0)
		
		rect := image.Rectangle {
			Min: roundPt(start.Add(ascent)),
			Max: roundPt(start.Sub(descent)),
		}
		rect.Max.X = bounds.Max.X
		pen.Rectangle(rect)
		if end.Y - start.Y > fixed.I(height) {
			rect.Min.X = bounds.Min.X
			rect.Min.Y = roundPt(start.Sub(descent)).Y + height
			rect.Max.X = bounds.Max.X
			rect.Max.Y = roundPt(end.Add(ascent)).Y - height
			pen.Rectangle(rect)
		}
		rect = image.Rectangle {
			Min: roundPt(end.Add(ascent)),
			Max: roundPt(end.Sub(descent)),
		}
		rect.Min.X = bounds.Min.X
		pen.Rectangle(rect)
	}
}

func (this *textBox) textOffset () image.Point {
	return this.InnerBounds().Min.
		Sub(this.scroll).
		Sub(this.drawer.LayoutBoundsSpace().Min)
}

func (this *textBox) handleFocusLeave () {
	this.dot = text.EmptyDot(0)
	this.on.dotChange.Broadcast()
	this.invalidateDraw()
	this.box.handleFocusLeave()
}

func (this *textBox) normalizedLayoutBoundsSpace () image.Rectangle {
	bounds := this.drawer.LayoutBoundsSpace()
	return bounds.Sub(bounds.Min)
}

func (this *textBox) recalculateMinimumSize () {
	minimum := image.Pt (
		this.drawer.Em().Round(),
		this.drawer.LineHeight().Round())

	textSize := this.drawer.MinimumSize()
	if !this.hOverflow && !this.wrap {
		minimum.X = textSize.X
	}
	if !this.vOverflow {
		 minimum.Y = textSize.Y
	}
	
	minimum.X += this.padding.Horizontal()
	minimum.Y += this.padding.Vertical()
	borderSum := this.borderSum()
	minimum.X += borderSum.Horizontal()
	minimum.Y += borderSum.Vertical()
	this.SetMinimumSize(minimum)
}

func (this *textBox) doLayout () {
	this.box.doLayout()
	previousContentBounds := this.contentBounds

	innerBounds := this.InnerBounds()
	this.drawer.SetMaxWidth(innerBounds.Dx())
	this.drawer.SetMaxHeight(innerBounds.Dy())
	
	this.contentBounds = this.normalizedLayoutBoundsSpace().Sub(this.scroll)
	
	if previousContentBounds != this.contentBounds {
		this.on.contentBoundsChange.Broadcast()
	}
}