extends Node2D

@export var number_of_particles : int

var particle_child : GPUParticles2D
var up_material : ParticleProcessMaterial = load("res://Materials/Particles/up_particles_bg.tres")
var down_material : ParticleProcessMaterial = load("res://Materials/Particles/down_particles_bg.tres")

# Called when the node enters the scene tree for the first time.
func _ready() -> void:
	
	up_material = up_material.duplicate()
	down_material = down_material.duplicate()
	reloadParticles()
	
func _physics_process(delta: float) -> void:
	if Input.is_action_just_pressed("flip"):
		print("input detected")
		reloadParticles()		
		
func reloadParticles() -> void:
	
	#If the particle node does not already exist, do the initial setup, and add it as a child node.
	if !has_node("BGParticles"):
		var bgparticle := GPUParticles2D.new()
		bgparticle.amount = number_of_particles
		bgparticle.emitting = true
		bgparticle.top_level = true
		bgparticle.name = "BGParticles"
		add_child(bgparticle)
		particle_child = get_node_or_null("BGParticles")
	
	#Set up the material we want to set the particle node to, and set up a screen size variable.
	var material : ParticleProcessMaterial
	var size : Vector2 = get_viewport_rect().size
	
	#Simple gravity direction detection.
	if al_globals.y_gravity > 0:
		material = up_material
	elif al_globals.y_gravity < 0:
		material = down_material
	
	#Set the emission shape and the size, relative to size of screen.
	material.emission_shape = ParticleProcessMaterial.EMISSION_SHAPE_BOX
	material.emission_box_extents = Vector3(size.x, size.y, 0)
	
	#Set the material of the particle child object to the created material.
	particle_child.process_material = material