Add Clear cache to the settings

A new row, "Downloaded pictures and songs", shows how much space the cached
character pictures, covers and downloaded songs take, with a Clear cache
button. Clearing deletes them, but keeps the songs the current quiz uses,
the settings, config.ini and the saved quiz. The characters are loaded
again at once; covers come back when they are shown.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/integration/test_clear_cache.gd

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+extends MainWindowTestSuite
+## Clear cache in the settings: deletes the downloaded character pictures, covers and
+## songs, but not the songs the quiz uses, the settings or the saved quiz.
+
+var _popup: SettingsPopup
+
+
+func before_test() -> void:
+	# The cache is kept next to the settings, which the tests keep in a folder of their own
+	OS.set_environment(Settings.CONFIG_DIR_ENV, create_temp_dir("clear_cache_%d" % randi()))
+	await super()
+	_popup = _window.get_node("SettingsPopup")
+
+
+func _write(path: String, size: int) -> void:
+	DirAccess.make_dir_recursive_absolute(path.get_base_dir())
+	var file: FileAccess = FileAccess.open(path, FileAccess.WRITE)
+	var bytes: PackedByteArray = PackedByteArray()
+	bytes.resize(size)
+	file.store_buffer(bytes)
+	file.close()
+
+
+func _files_in(dir: String) -> PackedStringArray:
+	return DirAccess.get_files_at(dir) if DirAccess.dir_exists_absolute(dir) \
+			else PackedStringArray()
+
+
+func _fill_cache() -> String:
+	_write(CharacterCache.folder().path_join("Crono.png"), 3000)
+	_write(CoverCache.folder().path_join("st-1"), 2000)
+	var old_song: String = Playlist.songs_folder().path_join("old.mp3")
+	_write(old_song, 5000)
+	return old_song
+
+
+func test_shows_how_much_the_cache_takes() -> void:
+	_fill_cache()
+
+	_popup.open()
+
+	assert_str(_popup.cache_size_label.text).is_equal(
+			SettingsPopup.size_text(SettingsPopup.cache_size()))
+	assert_int(SettingsPopup.cache_size()).is_greater_equal(10000)
+	assert_bool(_popup.clear_cache_button.disabled).is_false()
+
+
+func test_clear_cache_deletes_pictures_covers_and_old_songs() -> void:
+	var old_song: String = _fill_cache()
+	var playing: PackedStringArray = Playlist.song_files_in_use()
+	assert_array(playing).is_not_empty()
+	var lists_before: int = _server.count("/character/list")
+	_popup.open()
+
+	_popup.clear_cache()
+
+	assert_array(_files_in(CharacterCache.folder())).is_empty()
+	assert_array(_files_in(CoverCache.folder())).is_empty()
+	assert_bool(FileAccess.file_exists(old_song)).is_false()
+	# The quiz's songs stay, so they can still be played
+	for path: String in playing:
+		assert_bool(FileAccess.file_exists(path)).is_true()
+	assert_str(_popup.cache_size_label.text).starts_with("Cleared ")
+	assert_bool(_popup.clear_cache_button.disabled).is_true()
+	# The characters are loaded again at once
+	assert_int(_server.count("/character/list")).is_greater(lists_before)
+
+
+func test_clear_cache_keeps_the_settings_and_the_saved_quiz() -> void:
+	Settings.save_settings()
+	_quiz.save_soon()
+	await _runner.simulate_frames(1)
+	_popup.open()
+
+	_popup.clear_cache()
+
+	assert_bool(FileAccess.file_exists(Settings.saved_settings_path())).is_true()
+	assert_bool(FileAccess.file_exists(QuizSave.path())).is_true()
+
+
+func test_nothing_to_clear() -> void:
+	for dir: String in [CharacterCache.folder(), CoverCache.folder()]:
+		for file_name: String in _files_in(dir):
+			DirAccess.remove_absolute(dir.path_join(file_name))
+	Playlist.clear_song_files(Playlist.song_files_in_use())
+
+	_popup.open()
+
+	assert_str(_popup.cache_size_label.text).is_equal("Nothing")
+	assert_bool(_popup.clear_cache_button.disabled).is_true()
+
+
+@warning_ignore("unused_parameter")
+func test_size_text(bytes: int, text: String, test_parameters: Array = [
+	[0, "Nothing"],
+	[1, "1 KB"],
+	[350 * 1024, "350 KB"],
+	[int(14.2 * 1024 * 1024), "14.2 MB"],
+]) -> void:
+	assert_str(SettingsPopup.size_text(bytes)).is_equal(text)

tests/integration/test_clear_cache.gd.uid

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+uid://da5wh1me3wncq