## Abstract class representing a range of notes in some kind of array,
## expressed by a beginning index and an ending index: [begin, end).
@abstract class_name View extends Node

## Get the array this View refers to.
@abstract func get_data() -> Variant

## Update the view to be relative to beat.
## Can be connected to a beat update signal.
@abstract func update(beat: float) -> void

## Reset the view.
func reset_view() -> void:
	_begin = -1
	_end = -1

## Beginning of the range relative to te current beat where notes will be visible.
## Any notes where (hit_beat < current_beat + offset_begin) will NOT be visible.
@export var offset_begin: float = -4.0

## End of the range relative to the current beat where notes will be visible.
## Any notes where (hit_beat > current_beat + offset_end) will NOT be visible.
@export var offset_end: float = 4.0

## Return the index to the first element.
func begin() -> int:
	return _begin

## Return the index after the last element (equal to last index + 1).
func end() -> int:
	return _end

## Size of the range encompassed by begin() and end().
func size() -> int:
	return int(_begin >= 0) * _end - _begin

# ======= IMPLEMENETATION ======= #
var _begin: int = -1
var _end: int = -1