ShuffleBag implementation in gdscript

some_singleton.gd

#You can add this to any singleton where you have helper classes and functions

class ShuffleBag:
	var _shuffled_list
	var _current_pos = -1
	func _init(array_from):
		var _unshuffled = array_from.duplicate()
		var _shuffled = []
		var _current_pos
		# Pick a random element from the unshuffled list
		# Add it to the shuffled list
		# Repeat until the unshuffled list is empty
		while _unshuffled.size() > 0:
			_current_pos = randi() % _unshuffled.size()
			_shuffled.append(_unshuffled[_current_pos])
			_unshuffled.remove(_current_pos)
		_shuffled_list = _shuffled

	func next():
		# If we haven't finished traversing the list
		if _current_pos >= 0:
			# Pick a random item we haven't picked before
			var random_pos = randi() % (_current_pos + 1)
			var value = _shuffled_list[random_pos]
			# Swap it with the value in our current position
			_shuffled_list[random_pos] = _shuffled_list[_current_pos]
			_shuffled_list[_current_pos] = value
			# Decrement the counter
			_current_pos -= 1
			# Return the random item we picked
			return value
		else:
			# we've finished traversing the list
			# so we reset _currentPos, but we
			# still need to return a value so
			# we call ourselves.
			_current_pos = _shuffled_list.size() - 1
			return next()
	
	func size():
		return _shuffled_list.size()