class_name SongStatsList
extends Control
## A scrollable list of songs with their soundtrack and how often they were played, under
## a header naming the columns. Shown in the statistics view instead of the soundtrack
## cards when Songs is chosen.
##
## The server has tens of thousands of songs, so only the rows on screen exist. They are
## reused for other songs as the list scrolls.

## Emitted when a song is clicked.
signal song_pressed(song: SongInfoForStats)

const ROW_SCENE: PackedScene = preload("res://statistics/SongStatsRow.tscn")
## How many rows one turn of the mouse wheel scrolls.
const ROWS_PER_WHEEL_STEP: int = 3

## The songs in the list, in the order shown.
var songs: Array[SongInfoForStats] = []

# The rows that fit on screen, top to bottom
var _rows: Array[SongStatsRow] = []
var _row_height: float = 0.0
var _search_text: String = ""

@onready var rows_area: Control = %RowsArea
@onready var scroll_bar: VScrollBar = %ScrollBar


func _ready() -> void:
	var measured: SongStatsRow = ROW_SCENE.instantiate()
	add_child(measured)
	_row_height = measured.get_combined_minimum_size().y
	measured.free()
	rows_area.resized.connect(_fit_rows)
	scroll_bar.value_changed.connect(func(_value: float) -> void: _show_rows())
	rows_area.gui_input.connect(_on_gui_input)
	_fit_rows()


## Shows [param new_songs] from the top, with the letters [param search_text] matched
## highlighted.
func show_songs(new_songs: Array[SongInfoForStats], search_text: String = "") -> void:
	songs = new_songs
	_search_text = search_text
	_update_scroll_bar()
	scroll_bar.value = 0
	_show_rows()


## The rows showing a song now, top to bottom.
func shown_rows() -> Array[SongStatsRow]:
	var shown: Array[SongStatsRow] = []
	for row: SongStatsRow in _rows:
		if row.visible:
			shown.append(row)
	return shown


## Scrolls so song number [param index] is at the top, as far as the list goes.
func scroll_to(index: int) -> void:
	scroll_bar.value = index * _row_height


# Makes as many rows as fit on screen, plus one for the row partly scrolled out
func _fit_rows() -> void:
	var needed: int = ceili(rows_area.size.y / _row_height) + 1
	while _rows.size() < needed:
		var row: SongStatsRow = ROW_SCENE.instantiate()
		rows_area.add_child(row)
		row.pressed.connect(song_pressed.emit)
		_rows.append(row)
	while _rows.size() > needed:
		_rows.pop_back().free()
	for row: SongStatsRow in _rows:
		row.size = Vector2(rows_area.size.x, _row_height)
	_update_scroll_bar()
	_show_rows()


func _update_scroll_bar() -> void:
	scroll_bar.max_value = songs.size() * _row_height
	scroll_bar.page = rows_area.size.y
	scroll_bar.step = 0
	scroll_bar.visible = scroll_bar.max_value > scroll_bar.page


func _show_rows() -> void:
	var first: int = floori(scroll_bar.value / _row_height)
	var offset: float = scroll_bar.value - first * _row_height
	for i: int in _rows.size():
		var row: SongStatsRow = _rows[i]
		var index: int = first + i
		row.visible = index < songs.size()
		if row.visible:
			row.position = Vector2(0, i * _row_height - offset)
			row.show_song(songs[index], index, _search_text)


func _on_gui_input(event: InputEvent) -> void:
	if !(event is InputEventMouseButton) || !event.pressed:
		return
	var step: float = _row_height * ROWS_PER_WHEEL_STEP
	match event.button_index:
		MOUSE_BUTTON_WHEEL_UP:
			scroll_bar.value -= step * event.factor if event.factor > 0 else step
		MOUSE_BUTTON_WHEEL_DOWN:
			scroll_bar.value += step * event.factor if event.factor > 0 else step
		_:
			return
	rows_area.accept_event()