nc_extended_rotating/registry.lua

local minetest
    = minetest

-- Table of nodes that can be rotated by the mod.
local registered_rotatables = {}


local registry = {}

function registry.register_rotatable(name, facedir_lookup)
    local def = minetest.registered_nodes[name]
    if not def then error("Unknown node '" .. name .. "'") end
    if def.paramtype2 ~= "facedir" then error("Node '" .. name .. "' must be 'facedir'") end
    registered_rotatables[name] = { lookup = facedir_lookup }
end

-- Returns whether the specified `node` is rotatable by this mod.
function registry.is_rotatable(node)
    return not not registered_rotatables[node.name]
end

-- Fixes facedir for the specified `node` when rotated to `facedir`.
-- * Returns `nil` if the node can't rotate this way.
-- * Returns `facedir` when the node can rotate this way.
-- * Returns another facedir when the node should rotate another equivalent way.
function registry.fix_rotatable_facedir(node, facedir)
    local name  = node and node.name or ""
    local entry = registered_rotatables[name]
    if not entry then return nil end
    if not entry.lookup then return facedir end
    return entry.lookup[facedir]
end

return registry