A draft of user agent determination

ua.erl

-spec user_agent_platform(binary()) -> undefined | atom().

user_agent_platform(Header) ->
  user_agent(cowboy_bstr:to_lower(Header), [
      {<<"windows">>,   windows},
      {<<"linux">>,     linux},
      {<<"os x ">>,     osx},
      {<<"android">>,   android},
      {<<"ipod">>,      ipod},
      {<<"iphone">>,    iphone},
      {<<"ipad">>,      ipad}
    ]).

-spec user_agent(binary()) -> undefined | atom().

user_agent(Header) ->
  user_agent(cowboy_bstr:to_lower(Header), [
      {<<"msie">>,      ie},
      {<<"chrome">>,    chrome},
      {<<"firefox">>,   firefox},
      {<<"opera">>,     opera},
      {<<"safari">>,    safari},
      {<<"konqueror">>, konqueror},
      {<<"curl">>,      curl}
    ]).

user_agent(_Header, []) ->
  undefined;
user_agent(Header, [{Pattern, UA} | Rest]) ->
  case binary:match(Header, Pattern) of
    nomatch -> user_agent(Header, Rest);
    _ -> UA
  end.