class_name PrecipitationOcclusion
extends RefCounted

## A secondary visual layer used only when building the local rain height field.
## Canopy meshes remain on layer 1 for ordinary cameras.
const RENDER_LAYER_NUMBER: int = 20
const RENDER_LAYER_MASK: int = 1 << (RENDER_LAYER_NUMBER - 1)
const CANOPY_MATERIAL_NAMES: Array[String] = [
	"leaf",
	"leaf_light",
	"leaf_mid",
	"leaf_dark",
	"pine",
	"tree",
]


static func mark_canopy_meshes(root_node: Node) -> int:
	if root_node == null:
		return 0
	var marked_count: int = 0
	var mesh_instance := root_node as MeshInstance3D
	if mesh_instance != null and _has_canopy_material(mesh_instance):
		mesh_instance.layers |= RENDER_LAYER_MASK
		marked_count += 1
	for child: Node in root_node.get_children():
		marked_count += mark_canopy_meshes(child)
	return marked_count


## Generated tree definitions are already explicit terrain metadata, so every
## mesh in their visual scene can safely participate. This also supports older
## combined tree meshes whose imported material name does not identify leaves.
static func mark_tree_meshes(root_node: Node) -> int:
	if root_node == null:
		return 0
	var marked_count: int = 0
	var mesh_instance := root_node as MeshInstance3D
	if mesh_instance != null:
		mesh_instance.layers |= RENDER_LAYER_MASK
		marked_count += 1
	for child: Node in root_node.get_children():
		marked_count += mark_tree_meshes(child)
	return marked_count


static func _has_canopy_material(mesh_instance: MeshInstance3D) -> bool:
	if mesh_instance == null or mesh_instance.mesh == null:
		return false
	for surface_index: int in mesh_instance.mesh.get_surface_count():
		var material := mesh_instance.mesh.surface_get_material(surface_index)
		if material == null:
			continue
		if material.resource_name.to_lower() in CANOPY_MATERIAL_NAMES:
			return true
	return false