module FFI
  module Library
    TYPE_MAP = {
      :string  => DL::TYPE_VOIDP,
      :pointer => DL::TYPE_VOIDP,
    }

    DL.constants.each do |const|
      next unless const.to_s =~ /^TYPE_/

      name = const.to_s.split('_', 2).last.downcase.to_sym
      TYPE_MAP[name] = DL.const_get(const)
    end

    def ffi_lib(lib)
      @lib = DL::Handle.new lib
    end

    def attach_function(name, args, ret)
      func = Fiddle::Function.new(
        @lib[name.to_s], args.map { |x| TYPE_MAP[x] }, TYPE_MAP[ret]
      )

      define_singleton_method(name) { |*args| func.call(*args) }
    end
  end
end