package system

import "image"
import "image/color"
import "git.tebibyte.media/tomo/tomo"
import "git.tebibyte.media/tomo/tomo/data"
import "git.tebibyte.media/tomo/tomo/input"
import "git.tebibyte.media/tomo/tomo/event"
import "git.tebibyte.media/tomo/tomo/canvas"
import "git.tebibyte.media/tomo/backend/internal/util"

type box struct {
	system *System
	parent parent
	outer  anyBox

	tags             util.Set[string]
	role             tomo.Role
	lastStyleNonce   int
	lastIconSetNonce int
	styleApplicator  *styleApplicator

	minSize             util.Memo[image.Point]
	bounds              image.Rectangle
	innerClippingBounds image.Rectangle
	
	focusQueued *bool

	attrColor       attrHierarchy[tomo.AttrColor]
	attrTexture     attrHierarchy[tomo.AttrTexture]
	attrTextureMode attrHierarchy[tomo.AttrTextureMode]
	attrBorder      attrHierarchy[tomo.AttrBorder]
	attrMinimumSize attrHierarchy[tomo.AttrMinimumSize]
	attrPadding     attrHierarchy[tomo.AttrPadding]

	dndData   data.Data
	dndAccept []data.Mime
	focusable bool

	hovered bool
	focused bool
	pressed bool
	
	canvas util.Memo[canvas.Canvas]
	drawer canvas.Drawer

	on struct {
		focusEnter    event.FuncBroadcaster
		focusLeave    event.FuncBroadcaster
		dndEnter      event.FuncBroadcaster
		dndLeave      event.FuncBroadcaster
		dndDrop       event.Broadcaster[func (data.Data)]
		mouseEnter    event.FuncBroadcaster
		mouseLeave    event.FuncBroadcaster
		mouseMove     event.Broadcaster[func ()                 bool]
		buttonDown    event.Broadcaster[func (input.Button)     bool]
		buttonUp      event.Broadcaster[func (input.Button)     bool]
		scroll        event.Broadcaster[func (float64, float64) bool]
		keyDown       event.Broadcaster[func (input.Key, bool)  bool]
		keyUp         event.Broadcaster[func (input.Key, bool)  bool]
		styleChange   event.FuncBroadcaster
		iconSetChange event.FuncBroadcaster
	}
}

func (this *System) newBox (outer anyBox) *box {
	box := &box {
		system:  this,
		outer:   outer,
		drawer:  outer,
		tags:    make(util.Set[string]),
	}
	box.attrColor.SetFallback(tomo.AColor(color.Transparent))
	box.canvas = util.NewMemo (func () canvas.Canvas {
		if box.parent == nil { return nil }
		parentCanvas := box.parent.getCanvas()
		if parentCanvas == nil { return nil }
		return parentCanvas.SubCanvas(box.bounds)
	})
	if outer == nil {
		box.drawer = box
		box.outer  = box
	}
	box.minSize = util.NewMemo(box.calculateMinimumSize)
	return box
}

func (this *System) NewBox () tomo.Box {
	return this.newBox(nil)
}

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

func (this *box) GetBox () tomo.Box {
	return this.outer
}

func (this *box) Window () tomo.Window {
	hierarchy := this.getHierarchy()
	if hierarchy == nil { return nil }
	return hierarchy.getWindow()
}

func (this *box) Bounds () image.Rectangle {
	return this.bounds
}

func (this *box) InnerBounds () image.Rectangle {
	return tomo.Inset(this.attrPadding.Value()).Apply(this.innerClippingBounds)
}

func (this *box) Role () tomo.Role {
	return this.role
}

func (this *box) SetRole (role tomo.Role) {
	if this.role == role { return }
	this.role = role
	this.lastStyleNonce = -1
	this.outer.recursiveReApply()
}

func (this *box) Tag (tag string) bool {
	switch tag {
	case "hovered": return this.hovered
	case "focused": return this.focused
	case "pressed": return this.pressed
	default:        return this.tags.Has(tag)
	}
}

func (this *box) SetTag (tag string, on bool) {
	if on {
		this.tags.Add(tag)
	} else {
		delete(this.tags, tag)
	}
}

func (this *box) SetAttr (attr tomo.Attr) {
	this.outer.setAttr(attr, true)
}

func (this *box) UnsetAttr (kind tomo.AttrKind) {
	this.outer.unsetAttr(kind, true)
}

func (this *box) SetDNDData (dat data.Data) {
	this.dndData = dat
}

func (this *box) SetDNDAccept (types ...data.Mime) {
	this.dndAccept = types
}

func (this *box) SetFocused (focused bool) {
	hierarchy := this.getHierarchy()
	if hierarchy == nil {
		focusedCopy := focused
		this.focusQueued = &focusedCopy
		return
	}
	if !this.focusable { return }
	
	if this.Focused () && !focused {
		hierarchy.focus(nil)
	} else if !this.Focused() && focused {
		hierarchy.focus(this.outer)
	}
}

func (this *box) Focused () bool {
	hierarchy := this.getHierarchy()
	if hierarchy == nil { return false }
	return hierarchy.isFocused(this.outer)
}

func (this *box) SetFocusable (focusable bool) {
	if this.focusable == focusable { return }
	this.focusable = focusable
	if !focusable {
		this.SetFocused(false)
	}
}

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

func (this *box) setAttr (attr tomo.Attr, user bool) {
	switch attr := attr.(type) {
	case tomo.AttrColor:
		if this.attrColor.Set(attr, user) {
			this.invalidateDraw()
		}
		
	case tomo.AttrTexture:
		if this.attrTexture.Set(attr, user) {
			this.invalidateDraw()
		}
		
	case tomo.AttrTextureMode:
		if this.attrTextureMode.Set(attr, user) {
			this.invalidateDraw()
		}
		
	case tomo.AttrBorder:
		previousBorderSum := this.borderSum()
		different         := this.attrBorder.Set(attr, user)
		this.handleBorderChange(previousBorderSum, different)
		
	case tomo.AttrMinimumSize:
		if this.attrMinimumSize.Set(attr, user) {
			this.invalidateMinimum()
		}
		
	case tomo.AttrPadding:
		if this.attrPadding.Set(attr, user) {
			this.invalidateLayout()
			this.invalidateMinimum()
		}
	}
}

func (this *box) unsetAttr (kind tomo.AttrKind, user bool) {
	switch kind {
	case tomo.AttrKindColor:
		if this.attrColor.Unset(user) {
			this.invalidateDraw()
		}
		
	case tomo.AttrKindTexture:
		if this.attrTexture.Unset(user) {
			this.invalidateDraw()
		}
		
	case tomo.AttrKindTextureMode:
		if this.attrTextureMode.Unset(user) {
			this.invalidateDraw()
		}
		
	case tomo.AttrKindBorder:
		previousBorderSum := this.borderSum()
		different         := this.attrBorder.Unset(user)
		this.handleBorderChange(previousBorderSum, different)
	
	case tomo.AttrKindMinimumSize:
		if this.attrMinimumSize.Unset(user) {
			this.invalidateMinimum()
		}
		
	case tomo.AttrKindPadding:
		if this.attrPadding.Unset(user) {
			this.invalidateLayout()
			this.invalidateMinimum()
		}
	}
}

func (this *box) setBounds (bounds image.Rectangle) {
	if this.bounds == bounds { return }
	this.bounds = bounds
	this.invalidateLayout()
}

func (this *box) minimumSize () image.Point {
	return this.minSize.Value()
}

func (this *box) borderSum () tomo.Inset {
	sum := tomo.Inset { }
	for _, border := range this.attrBorder.Value() {
		sum[0] += border.Width[0]
		sum[1] += border.Width[1]
		sum[2] += border.Width[2]
		sum[3] += border.Width[3]
	}
	return sum
}

func (this *box) borderAndPaddingSum () tomo.Inset {
	sum := this.borderSum()
	padding := this.attrPadding.Value()
	sum[0] += padding[0]
	sum[1] += padding[1]
	sum[2] += padding[2]
	sum[3] += padding[3]
	return sum
}

// ----- event handler setters ---------------------------------------------- //
func (this *box) OnFocusEnter (callback func()) event.Cookie {
	return this.on.focusEnter.Connect(callback)
}
func (this *box) OnFocusLeave (callback func()) event.Cookie {
	return this.on.focusLeave.Connect(callback)
}
func (this *box) OnDNDEnter (callback func()) event.Cookie {
	return this.on.dndEnter.Connect(callback)
}
func (this *box) OnDNDLeave (callback func()) event.Cookie {
	return this.on.dndLeave.Connect(callback)
}
func (this *box) OnDNDDrop (callback func(data.Data)) event.Cookie {
	return this.on.dndDrop.Connect(callback)
}
func (this *box) OnMouseEnter (callback func()) event.Cookie {
	return this.on.mouseEnter.Connect(callback)
}
func (this *box) OnMouseLeave (callback func()) event.Cookie {
	return this.on.mouseLeave.Connect(callback)
}
func (this *box) OnMouseMove (callback func() bool) event.Cookie {
	return this.on.mouseMove.Connect(callback)
}
func (this *box) OnButtonDown (callback func(input.Button) bool) event.Cookie {
	return this.on.buttonDown.Connect(callback)
}
func (this *box) OnButtonUp (callback func(input.Button) bool) event.Cookie {
	return this.on.buttonUp.Connect(callback)
}
func (this *box) OnScroll (callback func(float64, float64) bool) event.Cookie {
	return this.on.scroll.Connect(callback)
}
func (this *box) OnKeyDown (callback func(input.Key, bool) bool) event.Cookie {
	return this.on.keyDown.Connect(callback)
}
func (this *box) OnKeyUp (callback func(input.Key, bool) bool) event.Cookie {
	return this.on.keyUp.Connect(callback)
}
func (this *box) OnStyleChange (callback func()) event.Cookie {
	return this.on.styleChange.Connect(callback)
}
func (this *box) OnIconSetChange (callback func()) event.Cookie {
	return this.on.iconSetChange.Connect(callback)
}
func (this *box) handleFocusEnter () {
	this.focused = true
	this.invalidateStyle()
	this.on.focusEnter.Broadcast()
}
func (this *box) handleFocusLeave () {
	this.focused = false
	this.invalidateStyle()
	this.on.focusLeave.Broadcast()
}
func (this *box) handleMouseEnter () {
	this.hovered = true
	this.invalidateStyle()
	this.on.mouseEnter.Broadcast()
}
func (this *box) handleMouseLeave () {
	this.hovered = false
	this.invalidateStyle()
	this.on.mouseLeave.Broadcast()
}
func (this *box) handleMouseMove () (caught bool) {
	for _, listener := range this.on.mouseMove.Listeners() {
		if listener() { caught = true }
	}
	return
}
func (this *box) handleMouseDown (button input.Button) (caught bool) {
	if button == input.ButtonLeft {
		this.pressed = true
		this.invalidateStyle()
	}
	
	for _, listener := range this.on.buttonDown.Listeners() {
		if listener(button) { caught = true }
	}
	return
}
func (this *box) handleMouseUp (button input.Button) (caught bool) {
	if button == input.ButtonLeft {
		this.pressed = false
		this.invalidateStyle()
	}
	
	for _, listener := range this.on.buttonUp.Listeners() {
		if listener(button) { caught = true }
	}
	return
}
func (this *box) handleScroll (x, y float64) (caught bool) {
	for _, listener := range this.on.scroll.Listeners() {
		if listener(x, y) { caught = true }
	}
	return
}
func (this *box) handleKeyDown (key input.Key, numberPad bool) (caught bool) {
	for _, listener := range this.on.keyDown.Listeners() {
		if listener(key, numberPad) { caught = true }
	}
	return
}
func (this *box) handleKeyUp (key input.Key, numberPad bool) (caught bool) {
	for _, listener := range this.on.keyUp.Listeners() {
		if listener(key, numberPad) { caught = true }
	}
	return
}
// -------------------------------------------------------------------------- //

func (this *box) Draw (can canvas.Canvas) {
	if can == nil { return }
	pen := can.Pen()
	bounds := this.Bounds()

	// get values
	textureMode := tomo.TextureMode(this.attrTextureMode.Value())
	texture     := this.attrTexture.Value().Texture
	col         := this.attrColor.Value().Color
	if col == nil { col = color.Transparent }

	// background
	if this.transparent() && this.parent != nil {
		this.parent.drawBackgroundPart(can)
	}
	pen.Fill(col)
	if textureMode == tomo.TextureModeTile && texture != nil {
		pen.Texture(texture)
	}
	pen.Rectangle(bounds)

	// centered texture
	if textureMode == tomo.TextureModeCenter && texture != nil {
		textureBounds := texture.Bounds()
		textureOrigin :=
			bounds.Min.
			Add(image.Pt (
				bounds.Dx() / 2,
				bounds.Dy() / 2)).
			Sub(image.Pt (
				textureBounds.Dx() / 2,
				textureBounds.Dy() / 2))
	
		pen.Fill(color.Transparent)
		pen.Texture(texture)
		pen.Rectangle(textureBounds.Sub(textureBounds.Min).Add(textureOrigin))
	}
}

func (this *box) drawBorders (can canvas.Canvas) {
	if can == nil { return }
	pen := can.Pen()
	bounds := this.bounds

	rectangle := func (x0, y0, x1, y1 int, c color.Color) {
		area := image.Rect(x0, y0, x1, y1)
		if area.Empty() { return }
		if util.Transparent(c) && this.parent != nil {
			this.parent.drawBackgroundPart(can.SubCanvas(area))
		}
		pen.Fill(c)
		pen.Rectangle(area)
	}
	
	for _, border := range this.attrBorder.Value() {
		rectangle (
			bounds.Min.X,
			bounds.Min.Y,
			bounds.Max.X,
			bounds.Min.Y + border.Width[tomo.SideTop],
			border.Color[tomo.SideTop])
		rectangle (
			bounds.Min.X,
			bounds.Max.Y - border.Width[tomo.SideBottom],
			bounds.Max.X,
			bounds.Max.Y,
			border.Color[tomo.SideBottom])
		rectangle (
			bounds.Min.X,
			bounds.Min.Y + border.Width[tomo.SideTop],
			bounds.Min.X + border.Width[tomo.SideLeft],
			bounds.Max.Y - border.Width[tomo.SideBottom],
			border.Color[tomo.SideLeft])
		rectangle (
			bounds.Max.X - border.Width[tomo.SideRight],
			bounds.Min.Y + border.Width[tomo.SideTop],
			bounds.Max.X,
			bounds.Max.Y - border.Width[tomo.SideBottom],
			border.Color[tomo.SideRight])

		bounds = border.Width.Apply(bounds)
	}
}

func (this *box) contentMinimum () image.Point {
	var minimum image.Point
	padding := tomo.Inset(this.attrPadding.Value())
	minimum.X += padding.Horizontal()
	minimum.Y += padding.Vertical()
	borderSum := this.borderSum()
	minimum.X += borderSum.Horizontal()
	minimum.Y += borderSum.Vertical()
	return minimum
}

func (this *box) calculateMinimumSize () image.Point {
	userMinSize := this.attrMinimumSize.Value()
	minSize := this.outer.contentMinimum()
	if minSize.X < userMinSize.X {
		minSize.X = userMinSize.X
	}
	if minSize.Y < userMinSize.Y {
		minSize.Y = userMinSize.Y
	}
	
	return minSize
}

// var drawcnt int
func (this *box) doDraw () {
	// println("DRAW", drawcnt)
	// drawcnt ++

	canvas := this.canvas.Value()
	if canvas == nil { return }
	if this.drawer != nil {
		this.drawBorders(canvas)
		this.drawer.Draw(canvas.SubCanvas(this.innerClippingBounds))
	}
}

// var laycnt int
func (this *box) doLayout () {
	// println("LAYOUT", laycnt)
	// laycnt ++
	
	this.innerClippingBounds = this.borderSum().Apply(this.bounds)
	this.outer.recursiveLoseCanvas()
}

func (this *box) doStyle () {
	this.styleApplicator.apply(this.outer)
}

func (this *box) setParent (parent parent) {
	if this.parent != parent && this.Focused() {
		this.SetFocused(false)
	}
	this.parent = parent
	this.outer.recursiveReApply()
}

func (this *box) getParent () parent {
	return this.parent
}

func (this *box) flushActionQueue () {
	if this.getHierarchy() == nil { return }
	if this.focusQueued != nil {
		this.SetFocused(*this.focusQueued)
	}
}

func (this *box) recursiveRedo () {
	this.doLayout()
	this.doDraw()
}

func (this *box) recursiveLoseCanvas () {
	this.canvas.Invalidate()
}

func (this *box) handleBorderChange (previousBorderSum tomo.Inset, different bool) {
	// only invalidate the layout if the border is sized differently
	if this.borderSum() != previousBorderSum {
		this.invalidateLayout()
		this.invalidateMinimum()
	}

	// if the border takes up the same amount of space, only invalidate the
	// drawing if it looks different
	if different {
		this.invalidateDraw()
	}
}

func (this *box) invalidateStyle () {
	hierarchy := this.getHierarchy()
	if hierarchy == nil { return }
	hierarchy.invalidateStyle(this.outer)
}

func (this *box) invalidateLayout () {
	hierarchy := this.getHierarchy()
	if hierarchy == nil { return }
	hierarchy.invalidateLayout(this.outer)
}

func (this *box) invalidateDraw () {
	hierarchy := this.getHierarchy()
	if hierarchy == nil { return }
	hierarchy.invalidateDraw(this.outer)
}

func (this *box) invalidateMinimum () {
	this.minSize.Invalidate()
	if this.parent != nil {
		this.parent.notifyMinimumSizeChange(this)
	}
}

func (this *box) recursiveReApply () {
	if this.getHierarchy() == nil { return }
	
	// re-apply styling, icons *if needed*

	// style
	hierarchyStyleNonce := this.getStyleNonce()
	if this.lastStyleNonce != hierarchyStyleNonce {
		// i should probably explain why we have a specific style
		// applicator for every box, it's so style applicators can cache
		// information about the boxes they're linked to (like all rules
		// with a matching role).
		this.lastStyleNonce = hierarchyStyleNonce
		this.styleApplicator = this.getHierarchy().newStyleApplicator()
		this.invalidateStyle()
		this.on.styleChange.Broadcast()
	}

	// icons
	hierarchyIconSetNonce := this.getIconSetNonce()
	if this.lastIconSetNonce != hierarchyIconSetNonce {
		this.lastIconSetNonce = hierarchyIconSetNonce
		this.on.iconSetChange.Broadcast()
	}
}

func (this *box) canBeFocused () bool {
	return this.focusable
}

func (this *box) boxUnder (point image.Point) anyBox {
	if point.In(this.bounds) {
		return this.outer
	} else {
		return nil
	}
}

func (this *box) propagate (callback func (anyBox) bool) bool {
	return callback(this.outer)
}

func (this *box) propagateAlt (callback func (anyBox) bool) bool {
	return callback(this.outer)
}

func (this *box) transparent () bool {
	// TODO uncomment once we have
	// a way to detect texture transparency
	col := this.attrColor.Value().Color
	return col == nil || util.Transparent(col) /*&&
		(this.texture == nil || !this.texture.Opaque())*/
}

func (this *box) getWindow () tomo.Window {
	hierarchy := this.getHierarchy()
	if hierarchy == nil { return nil }
	return hierarchy.getWindow()
}

func (this *box) getHierarchy () *Hierarchy {
	if this.parent == nil { return nil }
	return this.parent.getHierarchy()
}

func (this *box) getStyleNonce () int {
	// should panic if not in the tree
	return this.getHierarchy().getStyleNonce()
}

func (this *box) getIconSetNonce () int {
	// should panic if not in the tree
	return this.getHierarchy().getIconSetNonce()
}