@tool
extends Node2D

@export var grid_size: float = 50.0

func _ready():
	set_process(true)
	
func _process(delta):
	queue_redraw()

func _draw():
	var camera_transform = get_viewport().get_canvas_transform()
	var camera_scale = camera_transform.get_scale().x
	var line_width = 1.0 / camera_scale
	
	# Get the visible rectangle in world coordinates.
	var viewport_rect_in_world = camera_transform.affine_inverse() * get_viewport().get_visible_rect()
	var visible_rect_min = viewport_rect_in_world.position
	var visible_rect_max = viewport_rect_in_world.end

	# --- Draw the Axes (always 2px thick in screen space) ---
	draw_line(Vector2(visible_rect_min.x, 0), Vector2(visible_rect_max.x, 0), Color.RED, 2 / camera_scale)
	draw_line(Vector2(0, visible_rect_min.y), Vector2(0, visible_rect_max.y), Color.GREEN, 2 / camera_scale)

	# --- Draw the Major Grid Lines with Culling ---
	var major_step = grid_size
	const MIN_SCREEN_SPACING = 30.0 # Minimum pixel spacing between grid lines.
	# Skip lines if they would be too close on screen.
	while major_step * camera_scale < MIN_SCREEN_SPACING:
		major_step *= 2
	
	var first_x_major = floor(visible_rect_min.x / major_step) * major_step
	var last_x_major = ceil(visible_rect_max.x / major_step) * major_step
	var first_y_major = floor(visible_rect_min.y / major_step) * major_step
	var last_y_major = ceil(visible_rect_max.y / major_step) * major_step
	
	# Draw major vertical lines
	for x in range(int(first_x_major / major_step), int(last_x_major / major_step) + 1):
		var draw_x = x * major_step
		draw_line(Vector2(draw_x, visible_rect_min.y), Vector2(draw_x, visible_rect_max.y), Color(Color.GRAY, 0.5), line_width)

	# Draw major horizontal lines
	for y in range(int(first_y_major / major_step), int(last_y_major / major_step) + 1):
		var draw_y = y * major_step
		draw_line(Vector2(visible_rect_min.x, draw_y), Vector2(visible_rect_max.x, draw_y), Color(Color.GRAY, 0.5), line_width)

	# --- Draw Minor Grid Lines (only when zoomed in) ---
	if major_step == grid_size:
		var minor_step = grid_size / 5.0
		var first_x_minor = floor(visible_rect_min.x / minor_step) * minor_step
		var last_x_minor = ceil(visible_rect_max.x / minor_step) * minor_step
		var first_y_minor = floor(visible_rect_min.y / minor_step) * minor_step
		var last_y_minor = ceil(visible_rect_max.y / minor_step) * minor_step

		# Draw minor vertical lines
		for x in range(int(first_x_minor / minor_step), int(last_x_minor / minor_step) + 1):
			var draw_x = x * minor_step
			# Skip major lines to avoid drawing over them.
			if fmod(draw_x, major_step) != 0:
				draw_line(Vector2(draw_x, visible_rect_min.y), Vector2(draw_x, visible_rect_max.y), Color(Color.GRAY, 0.2), line_width)

		# Draw minor horizontal lines
		for y in range(int(first_y_minor / minor_step), int(last_y_minor / minor_step) + 1):
			var draw_y = y * minor_step
			# Skip major lines to avoid drawing over them.
			if fmod(draw_y, major_step) != 0:
				draw_line(Vector2(visible_rect_min.x, draw_y), Vector2(visible_rect_max.x, draw_y), Color(Color.GRAY, 0.2), line_width)