Improve group matching for 'copy to craft'

group.lua

@@ -1,4 +1,5 @@
 local S = minetest.get_translator("unified_inventory")
+local ui = unified_inventory
 
 function unified_inventory.extract_groupnames(groupname)
 	local specname = ItemStack(groupname):get_name()
@@ -26,6 +27,7 @@ end
 -- It may be a comma-separated list of group names.  This is really a
 -- "group:..." ingredient specification, minus the "group:" prefix.
 
+-- TODO Replace this with the more efficient spec matcher (below)
 local function compute_group_item(group_name_list)
 	local group_names = group_name_list:split(",")
 	local candidate_items = {}
@@ -84,3 +86,61 @@ function unified_inventory.get_group_item(group_name)
 	return group_item_cache[group_name]
 end
 
+
+--[[
+This is for filtering known items by groups
+e.g. find all items that match "group:flower,yellow" (flower AND yellow groups)
+]]
+local spec_matcher = {}
+function unified_inventory.init_matching_cache()
+	for _, name in ipairs(ui.items_list) do
+		-- we only need to care about groups, exact items are handled separately
+		for group, value in pairs(minetest.registered_items[name].groups) do
+			if value and value ~= 0 then
+				if not spec_matcher[group] then
+					spec_matcher[group] = {}
+				end
+				spec_matcher[group][name] = true
+			end
+		end
+	end
+end
+
+--[[
+Retrieves all matching items
+
+Arguments:
+	specname (string): Item name or group(s) to filter
+
+Output:
+	{
+		matchingitem1 = true,
+		...
+	}
+]]
+function unified_inventory.get_matching_items(specname)
+	if specname:sub(1,6) ~= "group:" then
+		return { [specname] = true }
+	end
+
+	local accepted = {}
+	for i, group in ipairs(specname:sub(7):split(",")) do
+		if i == 1 then
+			-- First step: Copy all possible item names in this group
+			for name, _ in pairs(spec_matcher[group] or {}) do
+				accepted[name] = true
+			end
+		else
+			-- Perform filtering
+			if spec_matcher[group] then
+				for name, _ in pairs(accepted) do
+					accepted[name] = spec_matcher[group][name]
+				end
+			else
+				-- No matching items
+				return {}
+			end
+		end
+	end
+	return accepted
+end