class_name StatisticsView
extends Panel
## Shows every soundtrack on the server as a card with its play statistics, or every
## played song in a list with its soundtrack. Both can be searched and sorted, and the
## cards filtered on whether the soundtrack has been played.
##
## Shown instead of the quiz when the Statistics tab is chosen.
##
## Covers are loaded for the cards on screen as they scroll into view, a few at a time,
## not for every soundtrack when the tab opens. See [CoverCache].

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

## Whether soundtracks or songs are shown.
enum Mode { SOUNDTRACKS, SONGS }

const CARD_SCENE: PackedScene = preload("res://statistics/SoundtrackCard.tscn")
## How far outside the visible part cards still get their covers, so they are ready when
## scrolled to.
const COVER_MARGIN: float = 400.0

## The cards in the order they are shown, hidden ones included.
var cards: Array[SoundtrackCard] = []
## Whether soundtracks or songs are shown. Change it with [method set_mode].
var mode: Mode = Mode.SOUNDTRACKS

## The covers on disk, shared by the cards.
var covers: CoverCache = CoverCache.new()

var _search: SoundtrackSearch = SoundtrackSearch.new()
var _loading: bool = false
# The soundtracks last loaded, by name
var _soundtracks: Dictionary[String, SoundtrackWithSongs] = {}
# Every song sorted A to Z, made when songs are first shown after loading
var _songs_a_to_z: Array[SongInfoForStats] = []
var _song_search: SoundtrackSearch = SoundtrackSearch.new()
var _songs_ready: bool = false

@onready var search_field: LineEdit = %SearchField
@onready var clear_button: Button = %ClearButton
@onready var show_label: Label = $Toolbar/ShowLabel
@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
@onready var card_scroll: ScrollContainer = $ScrollContainer
@onready var song_list: SongStatsList = %SongList
@onready var soundtracks_mode_button: Button = %SoundtracksModeButton
@onready var songs_mode_button: Button = %SongsModeButton
@onready var search_delay: Timer = %SearchDelay


func _ready() -> void:
	search_field.text_changed.connect(_on_search_text_changed)
	search_delay.timeout.connect(apply_filter)
	soundtracks_mode_button.pressed.connect(set_mode.bind(Mode.SOUNDTRACKS))
	songs_mode_button.pressed.connect(set_mode.bind(Mode.SONGS))
	song_list.song_pressed.connect(_on_song_pressed)
	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
	# The cards have moved by the end of the frame
	card_scroll.get_v_scroll_bar().value_changed.connect(
			func(_value: float) -> void: load_covers_on_screen.call_deferred())
	card_scroll.resized.connect(load_covers_on_screen)
	visibility_changed.connect(load_covers_on_screen)


## 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 soundtracks or songs, keeping the search, the show filter and the sort order.
func set_mode(new_mode: Mode) -> void:
	mode = new_mode
	soundtracks_mode_button.set_pressed_no_signal(mode == Mode.SOUNDTRACKS)
	songs_mode_button.set_pressed_no_signal(mode == Mode.SONGS)
	card_scroll.visible = mode == Mode.SOUNDTRACKS
	song_list.visible = mode == Mode.SONGS
	# The song list only has played songs, so there is nothing to filter
	show_label.visible = mode == Mode.SOUNDTRACKS
	show_option.visible = mode == Mode.SOUNDTRACKS
	search_field.placeholder_text = "Search soundtracks" if mode == Mode.SOUNDTRACKS \
			else "Search songs and soundtracks"
	apply_sort()
	if mode == Mode.SOUNDTRACKS:
		apply_filter()


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


## Puts the cards or songs in the order chosen in the sort menu.
func apply_sort() -> void:
	if mode == Mode.SONGS:
		apply_filter()
		return
	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)
	load_covers_on_screen.call_deferred()


## Shows only the cards or songs that match the search text and the show menu.
func apply_filter() -> void:
	search_delay.stop()
	if mode == Mode.SONGS:
		_show_songs()
		return
	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:
		var was_visible: bool = card.visible
		card.visible = (search_text.is_empty() || matching.has(card.soundtrack.soundtrack_name)) \
				&& _passes_filter(card.soundtrack, filter)
		if card.visible:
			shown += 1
			# Cards that come back with the filter fade in
			if !was_visible:
				Anim.fade_in(card)
	if shown == cards.size():
		count_label.text = "%d soundtracks" % cards.size()
	else:
		count_label.text = "%d of %d soundtracks" % [shown, cards.size()]
	# The grid has moved the cards by the end of the frame
	load_covers_on_screen.call_deferred()


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()
	_soundtracks.clear()
	var cover_times: Dictionary = {}
	for i: int in soundtracks.size():
		cards[i].show_soundtrack(soundtracks[i])
		_soundtracks[soundtracks[i].soundtrack_name] = soundtracks[i]
		cover_times[soundtracks[i].soundtrack_uuid] = soundtracks[i].cover_modified
	covers.keep_only(cover_times)
	_update_search_names()
	_songs_ready = false
	apply_sort()
	if mode == Mode.SOUNDTRACKS:
		apply_filter()


## Asks for the covers of the cards that are on screen, or nearly.
func load_covers_on_screen() -> void:
	if !is_visible_in_tree() || mode != Mode.SOUNDTRACKS:
		return
	var view: Rect2 = card_scroll.get_global_rect().grow(COVER_MARGIN)
	for card: SoundtrackCard in cards:
		if card.visible && view.intersects(card.get_global_rect()):
			card.load_cover(covers)


## Shows the new alternative names of the soundtrack [param updated] and finds it by
## them, without loading the statistics again.
func update_alternative_names(updated: Soundtrack) -> void:
	for soundtrack: SoundtrackWithSongs in _soundtracks.values():
		if soundtrack.soundtrack_uuid == updated.uuid:
			soundtrack.alternative_names = updated.alternative_names
	_update_search_names()
	apply_filter()


func _update_search_names() -> void:
	var names: Array[String] = []
	var alternatives: Dictionary = {}
	for soundtrack: SoundtrackWithSongs in _soundtracks.values():
		names.append(soundtrack.soundtrack_name)
		alternatives[soundtrack.soundtrack_name] = soundtrack.alternative_names
	_search.set_names(names, alternatives)


# Typing in the song list waits for a pause, since searching every song takes a moment
func _on_search_text_changed(_text: String) -> void:
	if mode == Mode.SONGS:
		search_delay.start()
	else:
		apply_filter()


func _on_song_pressed(song: SongInfoForStats) -> void:
	if _soundtracks.has(song.soundtrack_name):
		soundtrack_selected.emit(_soundtracks[song.soundtrack_name])


# Shows the songs matching the search text, in the sort menu's order
func _show_songs() -> void:
	_prepare_songs()
	var search_text: String = search_field.text.strip_edges()
	var song_names: Dictionary = {}
	var soundtrack_names: Dictionary = {}
	if !search_text.is_empty():
		for song_name: String in _song_search.find_matches(search_text):
			song_names[song_name] = true
		for soundtrack_name: String in _search.find_matches(search_text):
			soundtrack_names[soundtrack_name] = true
	var shown: Array[SongInfoForStats] = []
	for song: SongInfoForStats in songs_in_order(_songs_a_to_z,
			sort_option.selected as SortOrder):
		if search_text.is_empty() || song_names.has(song.song_name) \
				|| soundtrack_names.has(song.soundtrack_name):
			shown.append(song)
	song_list.show_songs(shown, search_text)
	if shown.size() == _songs_a_to_z.size():
		count_label.text = "%d played songs" % shown.size()
	else:
		count_label.text = "%d of %d played songs" % [shown.size(), _songs_a_to_z.size()]


# Lists every played song once after loading, sorted A to Z, which the other orders
# start from. Songs never played are left out: there are many and they say nothing.
func _prepare_songs() -> void:
	if _songs_ready:
		return
	_songs_ready = true
	_songs_a_to_z.clear()
	var names: Dictionary = {}
	for soundtrack: SoundtrackWithSongs in _soundtracks.values():
		for song: SongInfoForStats in soundtrack.songs:
			if song.times_played == 0:
				continue
			# The song list finds a song's soundtrack by its name
			song.soundtrack_name = soundtrack.soundtrack_name
			_songs_a_to_z.append(song)
			names[song.song_name] = true
	_songs_a_to_z.sort_custom(func(a: SongInfoForStats, b: SongInfoForStats) -> bool:
		var by_name: int = a.song_name.naturalnocasecmp_to(b.song_name)
		if by_name != 0:
			return by_name < 0
		return a.soundtrack_name.naturalnocasecmp_to(b.soundtrack_name) < 0)
	_song_search.set_names(names.keys())


## [param a_to_z], songs sorted A to Z, in [param order]. Songs played as often stay in
## A to Z order.
static func songs_in_order(
		a_to_z: Array[SongInfoForStats], order: SortOrder) -> Array[SongInfoForStats]:
	match order:
		SortOrder.Z_TO_A:
			var z_to_a: Array[SongInfoForStats] = a_to_z.duplicate()
			z_to_a.reverse()
			return z_to_a
		SortOrder.MOST_PLAYED, SortOrder.LEAST_PLAYED:
			# Grouped by plays instead of sorted, which keeps the A to Z order within a
			# group and is quick for tens of thousands of songs
			var by_plays: Dictionary[int, Array] = {}
			for song: SongInfoForStats in a_to_z:
				if !by_plays.has(song.times_played):
					by_plays[song.times_played] = []
				by_plays[song.times_played].append(song)
			var plays: Array[int] = []
			plays.assign(by_plays.keys())
			plays.sort()
			if order == SortOrder.MOST_PLAYED:
				plays.reverse()
			var sorted: Array[SongInfoForStats] = []
			for times_played: int in plays:
				sorted.append_array(by_plays[times_played])
			return sorted
	return a_to_z


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