package system

import "image"
import "git.tebibyte.media/tomo/tomo"
import "git.tebibyte.media/tomo/tomo/input"
import "git.tebibyte.media/tomo/tomo/canvas"

// eventCategory lists kinds of Tomo events.
type eventCategory int; const (
	eventCategoryDND eventCategory = iota
	eventCategoryMouse
	eventCategoryScroll
	eventCategoryKeyboard
)

// parent is any hierarchical type which contains other boxes. This can be a
// Hierarchy, containerBox, etc.
type parent interface {
	// hierarchy returns the hierarchy the parent is apart of.
	getHierarchy            () *Hierarchy
	// canvas returns the canvas held by the parent.
	getCanvas               () canvas.Canvas
	// notifyMinimumSizeChange informs the parent that the minimum size of
	// one of its children has changed.
	notifyMinimumSizeChange (anyBox)
	// drawBackgroundPart draws a part of the parent's background to the
	// given Canvas, filling the Canvas's entire bounds. The origin (0, 0)
	// of the given Canvas is assumed to be the same as the parent's canvas.
	drawBackgroundPart      (canvas.Canvas)
	// captures returns whether or not this parent captures the given event
	// category.
	captures                (eventCategory) bool
}

// anyBox is any tomo.Box type that is implemented by this package.
type anyBox interface {
	tomo.Box
	canvas.Drawer

	// setParent sets this anyBox's parent.
	// getParent returns this anyBox's parent as set by setParent.
	setParent (parent)
	getParent () parent
	
	// doDraw re-paints the anyBox onto its currently held Canvas non-recursively
	// doLayout re-calculates the layout of the anyBox non-recursively
	// doMinimumSize re-calculates the minimum size of the anyBox non-recursively
	doDraw        ()
	doLayout      ()
	doMinimumSize ()

	// flushActionQueue performs any queued actions, like invalidating the
	// minimum size or grabbing input focus.
	flushActionQueue    ()
	// recursiveRedo recursively recalculates the minimum size, layout, and
	// re-paints this anyBox and all of its children.
	recursiveRedo       ()
	// loseCanvas causes this anyBox and its children (if applicable) to
	// lose their canvases and re-cut them as needed.
	recursiveLoseCanvas ()
	// recursiveReAppply causes this anyBox and its children (if applicable)
	// to check whether they have an outdated style or icon set, and if so,
	// update it and trigger the appropriate event broadcasters.
	recursiveReApply    ()
	
	// contentMinimum returns the minimum dimensions of this box's content
	contentMinimum   () image.Point
	// canBeFocused returns whether or not this anyBox is capable of holding
	// input focus.
	canBeFocused     () bool
	// boxUnder returns the anyBox under the mouse pointer. It can be this
	// anyBox, one of its children (if applicable). It must return nil if
	// the mouse pointer is outside of this anyBox's bounds.
	boxUnder         (image.Point, eventCategory) anyBox
	// transparent returns whether or not this anyBox contains transparent
	// pixels or not, and thus needs its parent's backround to be painted
	// underneath it.
	transparent      () bool

	// propagate recursively calls a function on this anyBox, and all of its
	// children (if applicable) The normal propagate behavior calls the
	// callback on all children before calling it on this anyBox, and
	// propagateAlt calls the callback on this anyBox before calling it on
	// its children.
	propagate    (func (anyBox) bool) bool
	propagateAlt (func (anyBox) bool) bool

	handleFocusEnter  ()
	handleFocusLeave  ()
	// handleDndEnter    ()
	// handleDndLeave    ()
	// handleDndDrop     (data.Data)
	handleMouseEnter  ()
	handleMouseLeave  ()
	handleMouseMove   ()
	handleMouseDown   (input.Button)
	handleMouseUp     (input.Button)
	handleScroll      (float64, float64)
	handleKeyDown     (input.Key, bool)
	handleKeyUp       (input.Key, bool)
}

func assertAnyBox (unknown tomo.Box) anyBox {
	if box, ok := unknown.(anyBox); ok {
		return box
	} else {
		panic("system: foregin box implementation, i did not make this!")
	}
}