hopper.containers = {}
hopper.groups = {}
hopper.neighbors = {}

-- global function to add new containers
function hopper:add_container(list)
   for _, entry in pairs(list) do

      local target_node = entry[2]
      local neighbor_node

      if string.sub(target_node, 1, 6) == "group:" then
         local group_identifier, group_number
         local equals_index = string.find(target_node, "=")
         if equals_index ~= nil then
            group_identifier = string.sub(target_node, 7, equals_index-1)
            -- it's possible that the string was of the form "group:blah = 1", in which case we want to trim spaces off the end of the group identifier
            local space_index = string.find(group_identifier, " ")
            if space_index ~= nil then
               group_identifier = string.sub(group_identifier, 1, space_index-1)
            end
            group_number = tonumber(string.sub(target_node, equals_index+1, -1))
         else
            group_identifier = string.sub(target_node, 7, -1)
            group_number = "all" -- special value to indicate no number was provided
         end

         local group_info = hopper.groups[group_identifier]
         if group_info == nil then
            group_info = {}
         end
         if group_info[group_number] == nil then
            group_info[group_number] = {}
         end
         group_info[group_number][entry[1]] = entry[3]
         hopper.groups[group_identifier] = group_info
         neighbor_node = "group:"..group_identifier
         -- result is a table of the form groups[group_identifier][group_number][relative_position][inventory_name]
      else
         local node_info = hopper.containers[target_node]
         if node_info == nil then
            node_info = {}
         end
         node_info[entry[1]] = entry[3]
         hopper.containers[target_node] = node_info
         neighbor_node = target_node
         -- result is a table of the form containers[target_node_name][relative_position][inventory_name]
      end

      local already_in_neighbors = false
      for _, value in pairs(hopper.neighbors) do
         if value == neighbor_node then
            already_in_neighbors = true
            break
         end
      end
      if not already_in_neighbors then
         table.insert(hopper.neighbors, neighbor_node)
      end
   end
end

-- "top" indicates what inventory the hopper will take items from if this node is located at the hopper's wide end
-- "side" indicates what inventory the hopper will put items into if this node is located at the hopper's narrow end and at the same height as the hopper
-- "bottom" indicates what inventory the hopper will put items into if this node is located at the hopper's narrow end and either above or below the hopper.

hopper:add_container({
   {"top", "hopper:hopper", "main"},
   {"bottom", "hopper:hopper", "main"},
   {"side", "hopper:hopper", "main"},
   {"side", "hopper:hopper_side", "main"},

   {"bottom", "hopper:chute", "main"},
   {"side", "hopper:chute", "main"},

   {"bottom", "hopper:trash", "main"},
   {"side", "hopper:trash", "main"},

   {"bottom", "hopper:sorter", "main"},
   {"side", "hopper:sorter", "main"},
})

if minetest.get_modpath("default") then
   hopper:add_container({
      {"top", "default:chest", "main"},
      {"bottom", "default:chest", "main"},
      {"side", "default:chest", "main"},

      {"top", "default:chest_open", "main"},
      {"bottom", "default:chest_open", "main"},
      {"side", "default:chest_open", "main"},

      {"top", "default:furnace", "dst"},
      {"bottom", "default:furnace", "src"},
      {"side", "default:furnace", "fuel"},

      {"top", "default:furnace_active", "dst"},
      {"bottom", "default:furnace_active", "src"},
      {"side", "default:furnace_active", "fuel"},

      {"top", "default:chest_locked", "main"},
      {"bottom", "default:chest_locked", "main"},
      {"side", "default:chest_locked", "main"},

      {"top", "default:chest_locked_open", "main"},
      {"bottom", "default:chest_locked_open", "main"},
      {"side", "default:chest_locked_open", "main"},

      {"top", "biofuel:refinery", "dst"},
      {"bottom", "biofuel:refinery", "src"},
      {"side", "biofuel:refinery", "src"},

      {"top", "biofuel:refinery_active", "dst"},
      {"bottom", "biofuel:refinery_active", "src"},
      {"side", "biofuel:refinery_active", "src"},
   })
end

-- protector redo mod support
if minetest.get_modpath("protector") then
   hopper:add_container({
      {"top", "protector:chest", "main"},
      {"bottom", "protector:chest", "main"},
      {"side", "protector:chest", "main"},
   })
end

-- wine mod support
if minetest.get_modpath("wine") then
   hopper:add_container({
      {"top", "wine:wine_barrel", "dst"},
      {"bottom", "wine:wine_barrel", "src"},
      {"side", "wine:wine_barrel", "src"},
   })
end
