extends Control

var vscrollbar:			VScrollBar
var labels:				Control
var labels_positions:	Array
var labels_sizes:		Array
var font:				Font

var items: Array = [
	"item 1",
	"item 22",
	"item 333",
	"item 4444",
	"item 55555",
	"item 666666",
	"item 7777777",
	"item 88888888",
	"item 999999999",
	"This is the longest item of all, but eventually stops.",
	"item 1",
	"item 22",
	"item 333",
	"item 4444",
	"item 55555",
	"item 666666",
	"item 7777777",
	"item 88888888",
	"item 999999999",
	"This is the longest item of all, but eventually stops.",
	"item 1",
	"item 22",
	"item 333",
	"item 4444",
	"item 55555",
	"item 666666",
	"item 7777777",
	"item 88888888",
	"item 999999999",
	"This is the longest item of all, but eventually stops.",
]


func _init():
	font =  get_font("font")
	connect("resized", self, "build_labels")
	
	labels = Control.new()
	labels.anchor_right = 1.0
	labels.anchor_bottom = 1.0
	add_child(labels)
	
	vscrollbar = VScrollBar.new()
	vscrollbar.anchor_left		= 1.0
	vscrollbar.anchor_bottom	= 1.0
	vscrollbar.grow_horizontal = Control.GROW_DIRECTION_BEGIN
	vscrollbar.name = "vscrollbar"
	add_child(vscrollbar)

# @DAM This is only used once so, why not inline it?
func max_required_labels() -> int:
	var max_labels := ceil(rect_size.y / font.get_height()) + 1
	return int(min(items.size(), max_labels))


func build_labels():
	var new_max_required_labels := max_required_labels()
	var delta := new_max_required_labels - labels.get_child_count()

	while delta > 0:
		var label := Label.new()
		label.autowrap = true
		label.anchor_left = 0.0
		label.anchor_right = 1.0
		label.valign = Label.VALIGN_TOP
		labels.add_child(label)
		delta -= 1
	
	while delta < 0:
		var label := labels.get_child(0) as Label
		labels.remove_child(label)
		label.free()
		delta += 1


func process_labels():
	labels_positions.clear()
	labels_sizes.clear()
	var position := 0.0
	var limit := rect_size.x
	limit = labels.rect_size.x
#	labels_positions.append(0)
	for it in items:
		var size := font.get_wordwrap_string_size(it, limit).y
		var lines = size / font.get_height()
		var height = size + font.get_descent() * lines
		position += height
		labels_positions.append(position)
		labels_sizes.append(height)
	vscrollbar.raise()


func _process(delta):
	
	# @DAM We are recalculating the labels size and position on every update.
	# This only has to be done on resize or when items change.
	process_labels()
	
	vscrollbar.min_value = 0
	vscrollbar.max_value = rect_size.y
	var ratio := rect_size.y / float(labels_positions[labels_positions.size()-1])
	vscrollbar.visible = ratio < 1.0
	vscrollbar.page = ratio * (vscrollbar.max_value - vscrollbar.min_value)
	
	var offset := vscrollbar.value
	var bs_value := offset / ratio
	var offset_idx := labels_positions.bsearch(bs_value)

#	offset_idx = 0
	var idx := 0
	for label in labels.get_children():
		if idx + offset_idx >= items.size():
			label.text = ""
			break # @DAM Or should we use continue?
		label.text = items[idx + offset_idx]
		label.rect_position.y = labels_positions[idx + offset_idx] - labels_sizes[idx + offset_idx] - bs_value
		idx += 1
	
#	if Engine.get_idle_frames() % 30 == 1:
#		print_debug("> %s | %5.3f > %s > %d | lastPos: %s" % [labels.size(), offset, bs_value, offset_idx, labels_positions[-1]])
	
	labels.margin_right = -vscrollbar.rect_size.x if vscrollbar.visible else 0.0