Allow stacking tools with compatible data (#17)

* Allow stacking tools with compatible data

* declare `separated` as local

Best to test in production, tried to test most situations but there is possibility for item duplication or loss of items. Not that bad with these tools even if it happens.

Co-authored-by: SX <sx@minetest>

metatool/api.lua

@@ -30,7 +30,7 @@ local register_metatool_item = function(name, definition)
 	local texture = definition.texture or 'metatool_wand.png'
 	local liquids_pointable = definition.liquids_pointable == nil and false or definition.liquids_pointable
 	local craft_count = definition.craft_count or 1
-	local stack_max = definition.stack_max or 1
+	local stack_max = definition.stack_max or 99
 	craft_count = craft_count > stack_max and stack_max or craft_count
 
 	minetest.register_craftitem(itemname, {
@@ -41,7 +41,6 @@ local register_metatool_item = function(name, definition)
 		wield_image = texture,
 		wield_scale = { x = 0.8, y = 1, z = 0.8 },
 		liquids_pointable = liquids_pointable,
-		node_placement_prediction = nil,
 		on_use = function(...)
 			return metatool:on_use(itemname_clean, unpack({...}))
 		end,
@@ -61,6 +60,39 @@ local register_metatool_item = function(name, definition)
 	return itemname_clean
 end
 
+local separate_stack = function(itemstack)
+	if itemstack:get_count() > 1 then
+		local toolname = itemstack:get_name()
+		local separated = ItemStack(toolname)
+		separated:set_count(1)
+		itemstack:take_item(1)
+		return itemstack, separated
+	end
+	return itemstack, false
+end
+
+local return_itemstack = function(player, itemstack, separated)
+	if separated then
+		-- stack was separated, try to recombine
+		local meta1 = itemstack:get_meta()
+		local meta2 = separated:get_meta()
+		if meta1:equals(meta2) then
+			-- stacks can be recombinined, do it
+			itemstack:set_count(itemstack:get_count() + 1)
+		else
+			-- stacks cannot be recombined, give or drop new stack
+			local inv = player:get_inventory()
+			if inv:room_for_item("main", separated) then
+				-- item fits to inventory
+				inv:add_item("main", separated)
+			else
+				-- item will not fit to inventory
+				minetest.item_drop(separated, player, player:get_pos())
+			end
+		end
+	end
+end
+
 local validate_tool_definition = function(definition)
 	local function F(key)
 		local res = type(definition[key]) == 'function'
@@ -97,7 +129,11 @@ metatool = {
 		if controls.aux1 or controls.sneak then
 			-- Execute on_read_node when tool is used on node and special or sneak is held
 			local data, group, description = tooldef.itemdef.on_read_node(tooldef, player, pointed_thing, node, pos)
-			metatool.write_data(itemstack, {data=data,group=group}, description)
+			local separated
+			itemstack, separated = separate_stack(itemstack)
+			metatool.write_data(separated or itemstack, {data=data,group=group}, description)
+			-- if stack was separated give missing items to player
+			return_itemstack(player, itemstack, separated)
 		else
 			local data = metatool.read_data(itemstack)
 			if type(data) == 'table' then