Add Station move handle has ghost

Stations/station_movement.gd

@@ -7,11 +7,15 @@ extends Node
 @export var station: StaticBody3D
 
 var move_handle_rigid: RigidBody3D
-var original_collision_layer
-var original_y_pos: float
+var original_collision_layer: int = 0
+var original_y_pos: float = 0.0
+var original_station_transform: Transform3D = Transform3D.IDENTITY
+var moving: bool = false
+var ghost_materials: Array[StandardMaterial3D] = []
+
+const GHOST_COLOR_VALID: Color = Color(0, 1, 0, 0.35)
+const GHOST_COLOR_INVALID: Color = Color(1, 0, 0, 0.35)
 
-# TODO: Reject placing station in occupied spot.
-# TODO: Make ghost version of station that is displayed instead of model.
 # TODO: public toggle to disable handle in build mode.
 # TODO: If game exits build mode, drop the handle before  disabling it.
 
@@ -19,28 +23,111 @@ var original_y_pos: float
 func _ready() -> void:
 	if not station:
 		push_error("StationMovement is missing referece to station")
-		
+	if not move_handle:
+		push_error("StationMovement is missing reference to move_handle")
+	if not move_ghost:
+		push_error("StationMovement is missing reference to move_ghost")
+
 	move_handle_rigid = move_handle as RigidBody3D
 	original_collision_layer = station.collision_layer
 	original_y_pos = move_handle.transform.origin.y
+	original_station_transform = station.global_transform
 	move_handle.picked_up.connect(_handle_pickup)
 	move_handle.dropped.connect(_handle_drop)
 
+	move_ghost.monitoring = true
+	move_ghost.visible = false
+	_cache_ghost_materials()
+	_set_ghost_color(GHOST_COLOR_VALID)
 
-func _handle_pickup(_by):
+
+func _cache_ghost_materials() -> void:
+	var combiner = move_ghost.get_node_or_null("CSGCombiner3D")
+	if not combiner:
+		return
+	_collect_ghost_materials(combiner)
+
+
+func _collect_ghost_materials(node: Node) -> void:
+	if node is CSGCombiner3D:
+		# Combiner nodes do not expose a material property to modify.
+		for child in node.get_children():
+			_collect_ghost_materials(child)
+		return
+
+	if node is CSGShape3D:
+		var material = node.material
+		if material and material is StandardMaterial3D:
+			var instance = material.duplicate() as StandardMaterial3D
+			instance.transparency = material.transparency
+			instance.albedo_color = material.albedo_color
+			node.material = instance
+			ghost_materials.append(instance)
+
+	for child in node.get_children():
+		_collect_ghost_materials(child)
+
+
+func _set_ghost_color(color: Color) -> void:
+	for material in ghost_materials:
+		material.albedo_color = color
+
+
+func _handle_pickup(_by: Node) -> void:
 	print("StationMovement handle pickup")
-	station.collision_layer = 0	
-		
-		
-func _handle_drop(_by):
+	moving = true
+	move_ghost.visible = true
+	station.visible = false
+	station.collision_layer = 0
+	original_station_transform = station.global_transform
+	move_ghost.global_transform = original_station_transform
+
+
+func _handle_drop(_by: Node) -> void:
 	print("StationMovement handle drop")
+	moving = false
+	move_ghost.visible = false
+	station.visible = true
 	station.collision_layer = original_collision_layer
+	if _is_move_position_valid():
+		station.global_transform = move_ghost.global_transform
+	else:
+		station.global_transform = original_station_transform
 	move_handle.global_position = station.global_position + Vector3(0, original_y_pos, 0)
 	move_handle.rotation = station.rotation
 
 
 func _process(_delta: float) -> void:
-	station.global_position.x = snappedf(move_handle.global_position.x, snap_grid_size)
-	station.global_position.z = snappedf(move_handle.global_position.z, snap_grid_size)
-	station.global_rotation_degrees.y = snappedf(move_handle.global_rotation_degrees.y, 90)
-	
+	if not moving:
+		return
+
+	var target_transform: Transform3D = move_handle.global_transform
+	target_transform.origin.x = snappedf(target_transform.origin.x, snap_grid_size)
+	target_transform.origin.z = snappedf(target_transform.origin.z, snap_grid_size)
+	target_transform.origin.y = original_station_transform.origin.y
+	var target_yaw: float = snappedf(move_handle.global_rotation_degrees.y, 90)
+	target_transform.basis = Basis(Vector3.UP, deg_to_rad(target_yaw))
+
+	move_ghost.global_transform = target_transform
+	if _is_move_position_valid():
+		_set_ghost_color(GHOST_COLOR_VALID)
+	else:
+		_set_ghost_color(GHOST_COLOR_INVALID)
+
+
+func _is_move_position_valid() -> bool:
+	for body in move_ghost.get_overlapping_bodies():
+		print("Overlapping body: ", body)
+		if body == move_handle:
+			continue
+		if body == station:
+			continue
+		return false
+
+	for area in move_ghost.get_overlapping_areas():
+		print("Overlapping area: ", area)
+		if area == move_ghost:
+			continue
+		return false
+
+	return true