class_name StageGrid
extends Node2D
## StageGrid - Optional world-space grid overlay for the Sandbox Stage Builder.
##
## Draws grid lines that pan/zoom with the camera, with a heavier major line
## every few cells. Pure drawing; no hit-testing. Rendered behind the World by
## keeping this node as the first child of the stage root.

var camera: Camera2D = null
var grid_size: float = 15.0
var enabled: bool = true

const GRID_COLOR := Color(1.0, 1.0, 1.0, 0.08)
const MAJOR_COLOR := Color(1.0, 1.0, 1.0, 0.16)
const MAJOR_EVERY := 5

func _process(_delta: float) -> void:
	if enabled:
		queue_redraw()


func _draw() -> void:
	if not enabled or grid_size <= 0.0:
		return
	if camera == null or not is_instance_valid(camera):
		return
	var viewport_size := get_viewport_rect().size
	var zoom := maxf(camera.zoom.x, 0.0001)
	var half := viewport_size * 0.5 / zoom
	var center := camera.get_screen_center_position()
	var rect := Rect2(center - half, half * 2.0)
	var line_width := 1.0 / zoom

	var x := floorf(rect.position.x / grid_size) * grid_size
	while x <= rect.end.x:
		var grid_index := int(round(x / grid_size))
		var color := MAJOR_COLOR if grid_index % MAJOR_EVERY == 0 else GRID_COLOR
		draw_line(Vector2(x, rect.position.y), Vector2(x, rect.end.y), color, line_width)
		x += grid_size

	var y := floorf(rect.position.y / grid_size) * grid_size
	while y <= rect.end.y:
		var grid_index := int(round(y / grid_size))
		var color := MAJOR_COLOR if grid_index % MAJOR_EVERY == 0 else GRID_COLOR
		draw_line(Vector2(rect.position.x, y), Vector2(rect.end.x, y), color, line_width)
		y += grid_size