extends Node3D

@export_group("Animation")
@export var life_time: float = 8.0
@export var fade_in_time: float = 4.0
@export var max_base_alpha: float = 1.0

var _visual_scale: Vector3 = Vector3.ONE
var _visual_rotation_degrees: Vector3 = Vector3.ZERO
var _mesh_base_position: Vector3 = Vector3.ZERO
var _mesh_base_rotation_degrees: Vector3 = Vector3.ZERO
var _mesh_base_scale: Vector3 = Vector3.ONE

@onready var godrays_mesh: MeshInstance3D = $GodRays

func _ready():
	_mesh_base_position = godrays_mesh.position
	_mesh_base_rotation_degrees = godrays_mesh.rotation_degrees
	_mesh_base_scale = godrays_mesh.scale
	_apply_visual_transform()

	var mat: ShaderMaterial = godrays_mesh.get_active_material(0).duplicate()
	godrays_mesh.set_surface_override_material(0, mat)
	
	#set alpha to 0 before first frame to avoid "pop"
	mat.set_shader_parameter("base_alpha", 0.0)
	orient_to_camera()
	
	animate_godray(mat)


func _process(_delta: float) -> void:
	orient_to_camera()


func set_visual_rotation_degrees(value: Vector3) -> void:
	_visual_rotation_degrees = value
	if is_node_ready():
		_apply_visual_transform()


func set_visual_scale(value: Vector3) -> void:
	_visual_scale = value
	if is_node_ready():
		_apply_visual_transform()


func orient_to_camera() -> void:
	var current_camera: Camera3D = get_viewport().get_camera_3d()
	if current_camera == null or not is_instance_valid(current_camera):
		return
	var look_direction: Vector3 = current_camera.global_basis.z
	if look_direction.is_zero_approx():
		return

	# Use the camera orientation instead of its position so every godray keeps
	# the same diagonal on screen, even when multiple rays are visible together.
	look_at(global_position + look_direction, current_camera.global_basis.y, true)


func _apply_visual_transform() -> void:
	godrays_mesh.position = _mesh_base_position
	godrays_mesh.rotation_degrees = _mesh_base_rotation_degrees + _visual_rotation_degrees
	godrays_mesh.scale = Vector3(
		_mesh_base_scale.x * _visual_scale.x,
		_mesh_base_scale.y * _visual_scale.y,
		_mesh_base_scale.z * _visual_scale.z
	)

func animate_godray(mat: ShaderMaterial):
	var tween_alpha = create_tween()
	tween_alpha.tween_property(mat, "shader_parameter/base_alpha", max_base_alpha, fade_in_time).from(0.0)

	var tween_intensity = create_tween()
	#tween from 1.0 to 2.0
	tween_intensity.tween_property(mat, "shader_parameter/intensity_multiplier", 0.2, life_time * 0.3).from(1.0)
	#tween to 0.5
	tween_intensity.tween_property(mat, "shader_parameter/intensity_multiplier", 0.5, life_time * 0.3)
	#tween to 0.0
	tween_intensity.tween_property(mat, "shader_parameter/intensity_multiplier", 0.0, life_time * 0.4)
	
	tween_intensity.tween_callback(queue_free)

	var tween_edge = create_tween()
	tween_edge.tween_property(mat, "shader_parameter/edge_fade_power", 0.5, life_time * 0.5).from(2.0)
	tween_edge.tween_property(mat, "shader_parameter/edge_fade_power", 2.0, life_time * 0.5)