class_name StatisticsView
extends Panel
## Shows every soundtrack on the server as a card with its play statistics. The cards
## can be searched, filtered on whether they have been played, and sorted.
##
## Shown instead of the quiz when the Statistics tab is chosen.

## Emitted when a card is clicked, to show all songs of [param soundtrack].
signal soundtrack_selected(soundtrack: SoundtrackWithSongs)

## The orders the cards can be sorted in, in the order of the sort menu.
enum SortOrder { A_TO_Z, Z_TO_A, MOST_PLAYED, LEAST_PLAYED }

## Which soundtracks are shown, in the order of the show menu.
enum ShowFilter { ALL, PLAYED, NEVER_PLAYED }

const CARD_SCENE: PackedScene = preload("res://statistics/SoundtrackCard.tscn")

## The cards in the order they are shown, hidden ones included.
var cards: Array[SoundtrackCard] = []

var _search: SoundtrackSearch = SoundtrackSearch.new()
var _loading: bool = false

@onready var search_field: LineEdit = %SearchField
@onready var clear_button: Button = %ClearButton
@onready var show_option: OptionButton = %ShowOption
@onready var sort_option: OptionButton = %SortOption
@onready var count_label: Label = %CountLabel
@onready var status_label: Label = %StatusLabel
@onready var retry_button: Button = %RetryButton
@onready var card_grid: GridContainer = %CardGrid


func _ready() -> void:
	search_field.text_changed.connect(func(_text: String) -> void: apply_filter())
	clear_button.pressed.connect(clear_search)
	show_option.item_selected.connect(func(_index: int) -> void: apply_filter())
	sort_option.item_selected.connect(func(_index: int) -> void: apply_sort())
	retry_button.pressed.connect(refresh)
	retry_button.visible = false


## Loads the statistics from the server. The cards already shown stay until the new
## ones arrive.
func refresh() -> void:
	if _loading:
		return
	_loading = true
	retry_button.visible = false
	if cards.is_empty():
		status_label.text = "Loading statistics…"
	MusicServerClient.fetch_soundtrack_statistics(_on_loaded, _on_load_failed)


## Shows every card again, keeping the show filter and the sort order.
func clear_search() -> void:
	search_field.text = ""
	apply_filter()


## Puts the cards in the order chosen in the sort menu.
func apply_sort() -> void:
	var order: SortOrder = sort_option.selected as SortOrder
	cards.sort_custom(func(a: SoundtrackCard, b: SoundtrackCard) -> bool:
		return _comes_before(a.soundtrack, b.soundtrack, order))
	for i: int in cards.size():
		card_grid.move_child(cards[i], i)


## Shows only the cards that match the search text and the show menu.
func apply_filter() -> void:
	var search_text: String = search_field.text.strip_edges()
	var matching: Dictionary = {}
	for soundtrack_name: String in _search.find_matches(search_text) \
			if !search_text.is_empty() else []:
		matching[soundtrack_name] = true
	var filter: ShowFilter = show_option.selected as ShowFilter
	var shown: int = 0
	for card: SoundtrackCard in cards:
		card.visible = (search_text.is_empty() || matching.has(card.soundtrack.soundtrack_name)) \
				&& _passes_filter(card.soundtrack, filter)
		if card.visible:
			shown += 1
	if shown == cards.size():
		count_label.text = "%d soundtracks" % cards.size()
	else:
		count_label.text = "%d of %d soundtracks" % [shown, cards.size()]


func _on_loaded(soundtracks: Array[SoundtrackWithSongs]) -> void:
	_loading = false
	status_label.text = ""
	# Cards are reused, so opening the tab again only updates their text
	while cards.size() < soundtracks.size():
		var card: SoundtrackCard = CARD_SCENE.instantiate()
		card_grid.add_child(card)
		card.pressed.connect(soundtrack_selected.emit)
		cards.append(card)
	while cards.size() > soundtracks.size():
		cards.pop_back().free()
	var names: Array[String] = []
	for i: int in soundtracks.size():
		cards[i].show_soundtrack(soundtracks[i])
		names.append(soundtracks[i].soundtrack_name)
	_search.set_names(names)
	apply_sort()
	apply_filter()


func _on_load_failed() -> void:
	_loading = false
	if cards.is_empty():
		status_label.text = "Could not load statistics"
		retry_button.visible = true


static func _passes_filter(soundtrack: SoundtrackWithSongs, filter: ShowFilter) -> bool:
	match filter:
		ShowFilter.PLAYED:
			return soundtrack.soundtrack_played > 0
		ShowFilter.NEVER_PLAYED:
			return soundtrack.soundtrack_played == 0
	return true


static func _comes_before(
		a: SoundtrackWithSongs, b: SoundtrackWithSongs, order: SortOrder) -> bool:
	var by_name: int = a.soundtrack_name.naturalnocasecmp_to(b.soundtrack_name)
	match order:
		SortOrder.Z_TO_A:
			return by_name > 0
		SortOrder.MOST_PLAYED:
			if a.soundtrack_played != b.soundtrack_played:
				return a.soundtrack_played > b.soundtrack_played
		SortOrder.LEAST_PLAYED:
			if a.soundtrack_played != b.soundtrack_played:
				return a.soundtrack_played < b.soundtrack_played
	return by_name < 0