class_name BuildSystem
extends Node

const CAMERA_SPEED = 4.0
const COLLISION_MASK_WORLD = 1
const COLLISION_MASK_STRUCTURES = 32

@onready var build_preview = %BuildPreview
@onready var player = %Player
@onready var built_structures = %BuiltStructures

@onready var camera:Camera3D = %Camera

@export var build_item:Item = null

var camera_velocity:Vector3 = Vector3.ZERO
var is_active:bool = false
var hovered_existing_structure:StaticBody3D = null

func update_build_preview_item() -> void:
	hovered_existing_structure = null
	
	for child in build_preview.get_children():
		if build_item == null or child.scene_file_path != build_item.scene.resource_path:
			child.get_parent().remove_child(child)
			child.queue_free()
			
	if build_preview.get_child_count() == 0 and build_item != null:
		var build_preview_scene = build_item.scene.instantiate() as StaticBody3D
		if build_preview_scene == null:
			push_error("Cannot create build preview: item scene not derived from StaticBody3D for item: ", build_item)
			return
		
		# ensure we do not detect the preview object when querying for destroyable structures
		build_preview_scene.collision_layer = 0
		build_preview.add_child(build_preview_scene)


func move_build_camera(delta):
	var input_dir = Input.get_vector("walk_left", "walk_right", "walk_forward", "walk_back")
	var direction = (camera.basis * Vector3(input_dir.x, 0, input_dir.y)).normalized()
	if direction:
		camera_velocity.x = direction.x * CAMERA_SPEED
		camera_velocity.z = direction.z * CAMERA_SPEED
	else:
		camera_velocity.x = move_toward(camera_velocity.x, 0, CAMERA_SPEED)
		camera_velocity.z = move_toward(camera_velocity.z, 0, CAMERA_SPEED)

	camera_velocity.y = 0

	camera.global_position = camera.global_position + camera_velocity * delta	


func update_build_preview():
	var mouse_view_coords = get_viewport().get_mouse_position() # / get_viewport().get_visible_rect().size
	var mouse_ray_origin = camera.project_ray_origin(mouse_view_coords)
	var mouse_ray_normal = camera.project_ray_normal(mouse_view_coords)
	
	var world_space_state = camera.get_world_3d().direct_space_state
	var ray_query:PhysicsRayQueryParameters3D = PhysicsRayQueryParameters3D.create(mouse_ray_origin, mouse_ray_origin + mouse_ray_normal * 100)
	ray_query.collision_mask = COLLISION_MASK_WORLD | COLLISION_MASK_STRUCTURES
	var ray_result:Dictionary = world_space_state.intersect_ray(ray_query)
	
	if not ray_result.is_empty():
		var grid_map_object = ray_result.collider as GridMap
		var collision_body_3d = ray_result.collider as CollisionObject3D
		
		if not collision_body_3d and not grid_map_object:
			print ("Invalid collision object found. Object has no collision object: ", ray_result.collider)
			return

		if collision_body_3d:
			if collision_body_3d.collision_layer & COLLISION_MASK_STRUCTURES != 0:
				hovered_existing_structure = collision_body_3d as StaticBody3D
				if hovered_existing_structure == null:
					print ("Invalid structure found. Object is not derived from StaticBody3D: ", ray_result.collider)
					return
			else:
				hovered_existing_structure = null
			
		if grid_map_object != null and Vector3.UP.dot(ray_result["normal"]) > 0.9:
			var build_location:Vector3 = ray_result["position"]
			build_location = Vector3(roundf(build_location.x * 4), build_location.y, roundf(build_location.z * 4)) * 0.25
			build_preview.global_position = build_location

func _physics_process(_delta):
	if not is_active:
		return
	
	update_build_preview_item()		
	
	#move_build_camera(delta)
	
	update_build_preview()

func _unhandled_input(event: InputEvent) -> void:
	if not is_active:
		build_preview.hide()
		return
	
	build_preview.show()
	
	if event.is_action_pressed("rotate_clockwise"):
		build_preview.global_basis = build_preview.basis.rotated(Vector3.UP, deg_to_rad(45))
		get_viewport().set_input_as_handled()
		return
	
	if event.is_action_pressed("rotate_counter_clockwise"):
		build_preview.global_basis = build_preview.basis.rotated(Vector3.UP, -deg_to_rad(45))
		get_viewport().set_input_as_handled()
		return
	
	if build_item != null and event.is_action_pressed("interaction"):
		var new_structure:Node3D = build_item.scene.instantiate()
		new_structure.transform = build_preview.transform
		built_structures.add_child(new_structure)
		get_viewport().set_input_as_handled()
		return
	
	var mouse_button_event = event as InputEventMouseButton
	if hovered_existing_structure and mouse_button_event and mouse_button_event.pressed and mouse_button_event.button_index == MOUSE_BUTTON_MIDDLE:
		hovered_existing_structure.get_parent().remove_child(hovered_existing_structure)
		hovered_existing_structure.queue_free()
		get_viewport().set_input_as_handled()
		return