package system

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

type textBox struct {
	*box

	contentBounds image.Rectangle
	scroll        image.Point

	attrTextColor attrHierarchy[tomo.AttrTextColor]
	attrDotColor  attrHierarchy[tomo.AttrDotColor]
	attrFace      attrHierarchy[tomo.AttrFace]
	attrWrap      attrHierarchy[tomo.AttrWrap]
	attrAlign     attrHierarchy[tomo.AttrAlign]
	attrOverflow  attrHierarchy[tomo.AttrOverflow]

	text        string
	selectable  bool
	selecting   bool
	selectStart int
	dot         text.Dot

	drawer typeset.Drawer

	on struct {
		contentBoundsChange event.FuncBroadcaster
		dotChange           event.FuncBroadcaster
	}
}

func (this *System) NewTextBox () tomo.TextBox {
	box := &textBox { }
	box.box = this.newBox(box)
	return box
}

// ----- public methods ----------------------------------------------------- //

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

func (this *textBox) ScrollTo (point image.Point) {
	if this.scroll == point { return }
	this.scroll = point
	this.invalidateLayout()
}

func (this *textBox) RecommendedHeight (width int) int {
	return this.drawer.ReccomendedHeightFor(width) + this.borderAndPaddingSum().Vertical()
}

func (this *textBox) RecommendedWidth (height int) int {
	// TODO maybe not the best idea?
	return this.minimumSize().X
}

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.invalidateMinimum()
	this.invalidateLayout()
}

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

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

// ----- private methods ---------------------------------------------------- //

func (this *textBox) Draw (can canvas.Canvas) {
	if can == nil { return }

	texture     := this.attrTexture.Value().Texture
	col         := this.attrColor.Value().Color
	if col == nil { col = color.Transparent }
	
	this.drawBorders(can)
	pen := can.Pen()
	pen.Fill(col)
	pen.Texture(texture)
	
	if this.transparent() && this.parent != nil {
		this.parent.drawBackgroundPart(can)
	}
	pen.Rectangle(can.Bounds())

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

	if this.attrFace.Value().Face != nil {
		textColor := this.attrTextColor.Value().Color
		if textColor == nil { textColor = color.Black }
		this.drawer.Draw(can, textColor, this.textOffset())
	}
}

func (this *textBox) setAttr (attr tomo.Attr, user bool) {
	switch attr := attr.(type) {
	case tomo.AttrTextColor:
		if this.attrTextColor.Set(attr, user) && !this.dot.Empty() {
			this.invalidateDraw()
		}
		
	case tomo.AttrDotColor:
		if this.attrDotColor.Set(attr, user) && !this.dot.Empty() {
			this.invalidateDraw()
		}
		
	case tomo.AttrFace:
		if this.attrFace.Set(attr, user) {
			this.drawer.SetFace(attr.Face)
			this.invalidateMinimum()
			this.invalidateLayout()
		}
		
	case tomo.AttrWrap:
		if this.attrWrap.Set(attr, user) {
			this.invalidateMinimum()
			this.invalidateLayout()
		}
		
	case tomo.AttrAlign:
		if this.attrAlign.Set(attr, user) {
			this.invalidateDraw()
		}
		
	case tomo.AttrOverflow:
		if this.attrOverflow.Set(attr, user) {
			this.invalidateLayout()
		}
		
	default: this.box.setAttr(attr, user)
	}
}

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) {
	if this.attrFace.Value().Face == nil { return }

	face      := this.attrFace.Value().Face
	textColor := this.attrTextColor.Value().Color
	dotColor  := this.attrDotColor.Value().Color
	if textColor == nil { textColor = color.Transparent }
	if dotColor  == nil { dotColor  = color.RGBA { G: 255, B: 255, A: 255 } }
	
	pen := can.Pen()
	pen.Fill(color.Transparent)
	pen.Stroke(textColor)

	bounds  := this.InnerBounds()
	metrics := 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.StrokeWeight(1)
		pen.Path(roundPt(start.Add(ascent)), roundPt(start.Sub(descent)))

	case start.Y == end.Y:
		pen.Fill(dotColor)
		pen.StrokeWeight(0)
		pen.Rectangle(image.Rectangle {
			Min: roundPt(start.Add(ascent)),
			Max: roundPt(end.Sub(descent)),
		})

	default:
		pen.Fill(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.
		Add(this.scroll).
		Sub(this.drawer.LayoutBoundsSpace().Min)
}

func (this *textBox) handleFocusLeave () {
	this.on.dotChange.Broadcast()
	this.invalidateDraw()
	this.box.handleFocusLeave()
}

func (this *textBox) handleMouseDown (button input.Button) bool {
	if button == input.ButtonLeft {
		index           := this.runeUnderMouse()
		this.selectStart = index
		this.selecting   = true
		this.Select(text.Dot { Start: this.selectStart, End: index })
	}
	return this.box.handleMouseDown(button)
}

func (this *textBox) handleMouseUp (button input.Button) bool {
	if button == input.ButtonLeft && this.selecting {
		index         := this.runeUnderMouse()
		this.selecting = false
		this.Select(text.Dot { Start: this.selectStart, End: index })
	}
	return this.box.handleMouseUp(button)
}

func (this *textBox) handleMouseMove () bool {
	if this.selecting {
		index := this.runeUnderMouse()
		this.Select(text.Dot { Start: this.selectStart, End: index })
	}
	return this.box.handleMouseMove()
}

func (this *textBox) runeUnderMouse () int {
	window := this.Window()
	if window == nil { return 0 }
	position := window.MousePosition().Sub(this.textOffset())
	return this.drawer.AtPosition(fixPt(position))
}

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

func (this *textBox) contentMinimum () image.Point {
	minimum := this.drawer.MinimumSize()

	if this.attrOverflow.Value().X || bool(this.attrWrap.Value()) {
		minimum.X = this.drawer.Em().Round()
	}
	if this.attrOverflow.Value().Y {
		minimum.Y = this.drawer.LineHeight().Round()
	}

	return minimum.Add(this.box.contentMinimum())
}

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

	innerBounds := this.InnerBounds()
	this.drawer.SetWidth(innerBounds.Dx())
	this.drawer.SetHeight(innerBounds.Dy())

	this.contentBounds = this.normalizedLayoutBoundsSpace()
	this.constrainScroll()
	this.contentBounds = this.contentBounds.Add(this.scroll)
	// println(this.InnerBounds().String(), this.contentBounds.String())

	if previousContentBounds != this.contentBounds {
		this.on.contentBoundsChange.Broadcast()
	}
}

func (this *textBox) constrainScroll () {
	innerBounds := this.InnerBounds()
	width  := this.contentBounds.Dx()
	height := this.contentBounds.Dy()

	// X
	if width <= innerBounds.Dx() {
		this.scroll.X = 0
	} else if this.scroll.X > 0 {
		this.scroll.X = 0
	} else if this.scroll.X < innerBounds.Dx() - width  {
		this.scroll.X =  innerBounds.Dx() - width
	}

	// Y
	if height <= innerBounds.Dy() {
		this.scroll.Y = 0
	} else if this.scroll.Y > 0 {
		this.scroll.Y = 0
	} else if this.scroll.Y < innerBounds.Dy() - height {
		this.scroll.Y = innerBounds.Dy() - height
	}
}

func (this *textBox) scrollToDot () {
	dot := roundPt(this.drawer.PositionAt(this.dot.End)).Add(this.textOffset())
	innerBounds := this.InnerBounds()
	scroll      := this.scroll
	em          := this.drawer.Em().Round()
	lineHeight  := this.drawer.LineHeight().Round()

	// X
	if dot.X < innerBounds.Min.X + em {
		scroll.X += innerBounds.Min.X - dot.X + em
	} else if dot.X > innerBounds.Max.X - em {
		scroll.X -= dot.X - innerBounds.Max.X + em
	}

	// Y
	if dot.Y < innerBounds.Min.Y + lineHeight {
		scroll.Y += innerBounds.Min.Y - dot.Y + lineHeight
	} else if dot.Y > innerBounds.Max.Y - lineHeight {
		scroll.Y -= dot.Y - innerBounds.Max.Y + lineHeight
	}
	
	this.ScrollTo(scroll)
}