npc: respect wallmounted nodes should be placed before the attached node

less-prefer liquids

README.md

@@ -81,10 +81,12 @@ License: LGPLv2
     - content_id, node_def - game references, VoxelMap ID and registered_nodes definition
     - final_node_name      - if set, the node is not deleted from plan by place(). Contains the node name to be placed at the end. used for replacing by air before build the node
     - world_node_name      - contains the node name currently placed to the world
+    - param2_plan_rotation - param2 value before rotation
   - node_obj:place()         - place node to world using "add_node" and remove them from plan
   - node_obj:remove_from_plan() - remove this node from plan
   - node_obj:get_under()     - returns the node under this one if exists in plan
   - node_obj:get_above()     - returns the node above this one if exists in plan
+  - node_obj:get_attached_to() - returns the position the node is attached to
   - node_obj:rotate_facedir(facedir) - rotate the node - is internally used for plan rotation in get_mapped() - supported 0-3 (x+ axis) only
 
 ### object-attributes

node.lua

@@ -49,6 +49,7 @@ end
 function node_class:rotate_facedir(facedir)
 	-- rotate wallmounted
 	local mapped = self.mapped
+	mapped.param2_plan_rotation = mapped.param2
 	if mapped.node_def.paramtype2 == "wallmounted" then
 		local param2_dir = mapped.param2 % 8
 		local param2_color = mapped.param2 - param2_dir
@@ -121,6 +122,27 @@ function node_class:get_under()
 	return self.plan:get_node({x=self._plan_pos.x, y=self._plan_pos.y-1, z=self._plan_pos.z})
 end
 
+--------------------------------------
+-- get plan_pos of attached node, or nil if not attached
+--------------------------------------
+function node_class:get_attached_to()
+	local mapped = self:get_mapped()
+	local attached_wallmounted
+	if mapped.name == "doors:hidden" then
+		attached_wallmounted = 1 --bellow
+	elseif mapped.node_def.groups.attached_node then
+		if mapped.node_def.paramtype2 == "wallmounted" then
+			attached_wallmounted = mapped.param2_plan_rotation
+		else
+			attached_wallmounted = 1 --bellow
+		end
+	end
+	if attached_wallmounted then
+		local dir = node.wallmounted_to_dir[attached_wallmounted]
+		return vector.add(self._plan_pos, dir)
+	end
+end
+
 --------------------------------------
 -- get node above this one if exists
 --------------------------------------
@@ -173,6 +195,15 @@ node.rotation_facedir_map = {
 }
 node.rotation_facedir_mirrored_map = {3, 2, 1, 4, 7, 6, 5, 8, 11,10,9,16,19,18,17,12,15,14,13,20,23,22,21,[0] = 0}
 
+
+node.wallmounted_to_dir = {
+	[0] = {x=0,y=1,z=0},
+	[1] = {x=0,y=-1,z=0},
+	[2] = {x=1,y=0,z=0},
+	[3] = {x=-1,y=0,z=0},
+	[4] = {x=0,y=0,z=1},
+	[5] = {x=0,y=0,z=-1},
+}
 --[[
 --- Temporary code to calculate the wallmounted map
 node.rotation_wallmounted_map = {}

npc_ai.lua

@@ -53,8 +53,14 @@ function npc_ai_class:get_if_buildable(node)
 	end
 	node_index = self.plan.vm_area:indexp(world_pos)
 	world_content_id = self.plan.vm_data[node_index]
-
 	node.world_node_name = minetest.get_name_from_content_id(world_content_id)
+
+	-- place attached nodes after the node under
+	local attached_pos = node:get_attached_to()
+	if attached_pos and self.plan:get_node(attached_pos) then
+		return -- attaching not possible
+	end
+
 	if world_content_id == mapped.content_id then
 		-- right node is at the place. there are no costs to touch them. Check if a touch needed
 		if mapped.node_def.paramtype2 and (mapped.param2 ~= self.plan.vm_param2_data[node_index]) then
@@ -93,6 +99,11 @@ function npc_ai_class:get_node_rating(node, npcpos)
 	local distance_pos = table.copy(world_pos)
 	local prefer = 0
 
+	-- build water at the later time
+	if mapped.node_def.groups.liquid then
+		prefer = prefer - self.build_distance
+	end
+
 	--prefer same items in building order
 	if self.lasttarget_name then
 		if self.lasttarget_name == mapped.name then
@@ -111,7 +122,7 @@ function npc_ai_class:get_node_rating(node, npcpos)
 		prefer = prefer + self.build_distance + 1
 	else
 		if node:get_under() then
-			prefer = prefer - (2 * self.build_distance)
+			prefer = prefer - 2
 		end
 		distance_pos.y = distance_pos.y + self.build_distance
 	end