Multiple updates:

1)  Refactor autoplace,

There was a lot of redundant code and like a dozen unneccessary string
scans for every node next to every tube placed! I put it all into
indexed tables and loops instead of bizarre and unexplainable variable
names and copy and pasted code. There was also no support for notifying
a chest when an item has been taken from it by a filter, so I added
something for that.

I also thought it prudent to fall back on the
allow_metadata_inventory_take function should a special can_remove not
exist. In fact if can_insert doesn't exist, it calls
allow_metadata_inventory_put instead.

I also added a thing for allowing pipes to attach to nodes of other
modules, without having to hard code type all those node names into
autoplace.lua.  Basically node.tube.collects(i,param2) and i is the
direction from the pipe and param2 is the param2 of what it's pointing
at.

I also abstracted the inscrutable correlation between i and
param2 by trial and error (and the paramwand mod) into understandable
functions. There was no pipeworks namespace so I created it, and put
these functions into pipeworks.collects (as distinguished from a
        node.tube.collects function, which uses those functions)

And now it's too late to cart my old clothes to the thrift store,
dangit.

2)  My "node.tube.collects" idea might be redundant with the
node.tube.connect_sides thing, though possibly more versatile so I'll
leave it in.

3) I was using node.tube.connects and fancy functions for checking if it's
the sides or top or whatnot, and this connect_side thing came in. This
should make both my way and the way using connect_side work.

Also removed some debugging cruft

1 files changed, 69 insertions, 57 deletions

diff --git a/item_transport.lua b/item_transport.lua
index f350ba0..ff2d865 100644
--- a/item_transport.lua
+++ b/item_transport.lua
@@ -100,6 +100,56 @@ minetest.register_craftitem("pipeworks:filter", {
 	stack_max = 99,
 })
 
+local fakePlayer = {
+    get_player_name = function() return ":pipeworks" end,
+    -- any other player functions called by allow_metadata_inventory_take anywhere...
+    -- perhaps a custom metaclass that errors specially when fakePlayer.<property> is not found?
+}
+
+-- adding two tube functions
+-- can_remove(pos,node,stack,dir) returns true if an item can be removed from that stack on that node
+-- remove_items(pos,node,stack,dir,count) removes count items and returns them
+-- both optional w/ sensible defaults and fallback to normal allow_* function
+-- XXX: possibly change insert_object to insert_item
+
+-- sname = the current name to allow for, or nil if it allows anything
+
+function grabAndFire(frominv,frominvname,frompos,fromnode,sname,tube,idef,dir,all)
+    for spos,stack in ipairs(frominv:get_list(frominvname)) do
+        if ( sname == nil and stack:get_name() ~= "") or stack:get_name()==sname then
+            local doRemove = true
+            if tube.can_remove then
+                doRemove = tube.can_remove(frompos, fromnode, stack, dir)
+            elseif idef.allow_metadata_inventory_take then
+                doRemove = idef.allow_metadata_inventory_take(frompos,"main",spos, stack, fakePlayer)
+            end
+            -- stupid lack of continue statements grumble
+            if doRemove then
+                local item
+                local count
+                if all then
+                    count = stack:get_count()
+                else
+                    count = 1
+                end
+                if tube.remove_items then
+                    -- it could be the entire stack...
+                    item=tube.remove_items(frompos,fromnode,stack,dir,count)
+                else
+                    item=stack:take_item(count)
+                    frominv:set_stack(frominvname,spos,stack)
+                    idef.on_metadata_inventory_take(frompos, "main", spos, item, fakePlayer)
+                end
+                item1=tube_item(frompos,item)
+                item1:get_luaentity().start_pos = frompos
+                item1:setvelocity(dir)
+                item1:setacceleration({x=0, y=0, z=0})
+                return -- only fire one item, please
+            end
+        end
+    end
+end
+
 minetest.register_node("pipeworks:filter", {
 	description = "Filter",
 	tiles = {"pipeworks_filter_top.png", "pipeworks_filter_top.png", "pipeworks_filter_output.png",
@@ -139,44 +189,26 @@ minetest.register_node("pipeworks:filter", {
 	local dir = facedir_to_right_dir(node.param2)
 	local frompos = {x=pos.x - dir.x, y=pos.y - dir.y, z=pos.z - dir.z}
 	local fromnode=minetest.get_node(frompos)
+    if not fromnode then return end
 	local frominv
-	if (not fromnode) or (not minetest.registered_nodes[fromnode.name]) or (not (minetest.registered_nodes[fromnode.name].tube and 
-		minetest.registered_nodes[fromnode.name].tube.input_inventory)) then
-			return
-	end
+    local idef = minetest.registered_nodes[fromnode.name]
+    -- assert(idef)
+    local tube = idef.tube
+    if not (tube and tube.input_inventory) then
+        return
+    end
 	local frommeta=minetest.get_meta(frompos)
-	local frominvname=minetest.registered_nodes[fromnode.name].tube.input_inventory
+	local frominvname=tube.input_inventory
 	local frominv=frommeta:get_inventory()
 	for _,filter in ipairs(inv:get_list("main")) do
 		local sname=filter:get_name()
 		if sname ~="" then
-			for spos,stack in ipairs(frominv:get_list(frominvname)) do
-				if stack:get_name()==sname then
-					item=stack:take_item()
-					frominv:set_stack(frominvname,spos,stack)
-					pos1=pos
-					item1=tube_item({x=pos1.x,y=pos1.y,z=pos1.z},item)
-					item1:get_luaentity().start_pos = {x=pos1.x,y=pos1.y,z=pos1.z}
-					item1:setvelocity(dir)
-					item1:setacceleration({x=0, y=0, z=0})
-					return
-				end
-			end
+            -- XXX: that's a lot of parameters
+            grabAndFire(frominv,frominvname,frompos,fromnode,sname,tube,idef,dir)
 		end
 	end
 	if inv:is_empty("main") then
-		for spos,stack in ipairs(frominv:get_list(frominvname)) do
-			if stack:get_name()~="" then
-				item=stack:take_item()
-				frominv:set_stack(frominvname,spos,stack)
-				pos1=pos
-				item1=tube_item({x=pos1.x,y=pos1.y,z=pos1.z},item)
-				item1:get_luaentity().start_pos = {x=pos1.x,y=pos1.y,z=pos1.z}
-				item1:setvelocity(dir)
-				item1:setacceleration({x=0, y=0, z=0})
-				return
-			end
-		end
+        grabAndFire(frominv,frominvname,frompos,fromnode,nil,tube,idef,dir)
 	end
 end,
 })
@@ -226,43 +258,23 @@ minetest.register_node("pipeworks:mese_filter", {
 	local frompos = {x=pos.x - dir.x, y=pos.y - dir.y, z=pos.z - dir.z}
 	local fromnode=minetest.get_node(frompos)
 	local frominv
-	if not (minetest.registered_nodes[fromnode.name].tube and 
-		minetest.registered_nodes[fromnode.name].tube.input_inventory) then
-			return
-	end
+    local idef = minetest.registered_nodes[fromnode.name]
+    -- assert(idef)
+    local tube = idef.tube
+    if not (tube and tube.input_inventory) then
+        return
+    end
 	local frommeta=minetest.get_meta(frompos)
 	local frominvname=minetest.registered_nodes[fromnode.name].tube.input_inventory
 	local frominv=frommeta:get_inventory()
 	for _,filter in ipairs(inv:get_list("main")) do
 		local sname=filter:get_name()
 		if sname ~="" then
-			for spos,stack in ipairs(frominv:get_list(frominvname)) do
-				if stack:get_name()==sname then
-					item=stack:take_item(stack:get_count())
-					frominv:set_stack(frominvname,spos,stack)
-					pos1=pos
-					item1=tube_item({x=pos1.x,y=pos1.y,z=pos1.z},item)
-					item1:get_luaentity().start_pos = {x=pos1.x,y=pos1.y,z=pos1.z}
-					item1:setvelocity(dir)
-					item1:setacceleration({x=0, y=0, z=0})
-					return
-				end
-			end
+            grabAndFire(frominv,frominvname,frompos,fromnode,sname,tube,idef,dir,true)
 		end
 	end
 	if inv:is_empty("main") then
-		for spos,stack in ipairs(frominv:get_list(frominvname)) do
-			if stack:get_name()~="" then
-				item=stack:take_item(stack:get_count())
-				frominv:set_stack(frominvname,spos,stack)
-				pos1=pos
-				item1=tube_item({x=pos1.x,y=pos1.y,z=pos1.z},item)
-				item1:get_luaentity().start_pos = {x=pos1.x,y=pos1.y,z=pos1.z}
-				item1:setvelocity(dir)
-				item1:setacceleration({x=0, y=0, z=0})
-				return
-			end
-		end
+        grabAndFire(frominv,frominvname,frompos,fromnode,sname,tube,idef,dir,true)
 	end
 end,
 })