extends SpaceEntity

class_name SpaceRegion


@export var elevation: float = 0.0
@export var height: float = 100.0
@export var wall_texture: Texture2D
@export var floor_texture: Texture2D


func generate_geometry(space: Space) -> Node3D:
	return _generate_geometry(space, true)


func _generate_geometry(space: Space, looked_from_inside: bool) -> Node3D:
	var geometry := MeshInstance3D.new()
	geometry.name = name

	var mesh := ArrayMesh.new()
	mesh.add_surface_from_arrays(Mesh.PRIMITIVE_TRIANGLES, _generate_wall_arrays(space, looked_from_inside))

	var wall_material := StandardMaterial3D.new()
	wall_material.albedo_texture = wall_texture
	mesh.surface_set_material(0, wall_material)

	if (looked_from_inside):
		mesh.add_surface_from_arrays(Mesh.PRIMITIVE_TRIANGLES, _generate_floor_arrays(space))
		var floor_material := StandardMaterial3D.new()
		floor_material.albedo_texture = floor_texture
		mesh.surface_set_material(1, floor_material)

	geometry.mesh = mesh

	for child in get_children():
		if child is SpaceRegion:
			geometry.add_child(child._generate_geometry(space, not looked_from_inside))

	return geometry


func _generate_wall_arrays(space: Space, looked_from_inside: bool) -> Array:
	var polygon = self.polygon
	var polygon_pairs = Array()
	for i in range(-1, polygon.size() - 1):
		polygon_pairs.append([polygon[i], polygon[i+1]])

	var vertices = PackedVector3Array()
	var uvs = PackedVector2Array()
	for line in polygon_pairs:
		_push_line(space, line, vertices, uvs, looked_from_inside)

	var arrays := Array()
	arrays.resize(Mesh.ARRAY_MAX)
	arrays[Mesh.ARRAY_VERTEX] = vertices
	arrays[Mesh.ARRAY_TEX_UV] = uvs

	return arrays


func _push_line(space: Space,
				line: Array,
				vertices: PackedVector3Array,
				uvs: PackedVector2Array,
				looked_from_inside: bool
):
	var v0 := Vector3(
		line[0][0] * space.unit_scale, elevation * space.unit_scale,
		line[0][1] * space.unit_scale)
	var v1 := Vector3(
		line[1][0] * space.unit_scale, (elevation + height) * space.unit_scale,
		line[1][1] * space.unit_scale)
	var v2 := Vector3(
		line[1][0] * space.unit_scale, elevation * space.unit_scale,
		line[1][1] * space.unit_scale)
	var v3 := Vector3(
		line[0][0] * space.unit_scale, (elevation + height) * space.unit_scale,
		line[0][1] * space.unit_scale)

	if looked_from_inside:
		vertices.append_array([v0, v1, v2, v1, v0, v3])
	else:
		vertices.append_array([v0, v2, v1, v1, v3, v0])

	uvs.append(Vector2(0, 1))
	uvs.append(Vector2(1, 0))
	uvs.append(Vector2(1, 1))
	uvs.append(Vector2(1, 0))
	uvs.append(Vector2(0, 1))
	uvs.append(Vector2(0, 0))


func _generate_floor_arrays(space: Space) -> Array:
	var triangulation := Geometry2D.triangulate_polygon(self.polygon)
	var vertices := PackedVector3Array()
	var uvs := PackedVector2Array()
	vertices.resize(triangulation.size())
	uvs.resize(triangulation.size())

	for i in range(triangulation.size()):
		vertices[i] = Vector3(
			self.polygon[triangulation[i]].x * space.unit_scale,
			elevation * space.unit_scale,
			self.polygon[triangulation[i]].y * space.unit_scale,
		)
		uvs[i] = self.polygon[triangulation[i]] * space.unit_scale

	var arrays := Array()
	arrays.resize(Mesh.ARRAY_MAX)
	arrays[Mesh.ARRAY_VERTEX] = vertices
	arrays[Mesh.ARRAY_TEX_UV] = uvs

	return arrays