By law, USCIS have 120 days to make a decision on your N-400 from the day you are interviewed or from the day they requested additional documents from you. Obviously, that time has long elapsed by now.
Since they have said it's "with an officer", if it were me I would give them until February to take action. If, by the beginning of February you've heard nothing, I would then take USCIS to court under 8 USC 1447(b), which specifically prescribes for a federal District court review of an N-400 which USCIS have failed to adjudicate within 120 days of the examination or requested documents.
See https://www.americanimmigrationcouncil.org/sites/default/files/practice_advisory/how_to_get_judicial_relief_under_8_u.s.c._ss_1447b_for_a_stalled_naturalization_application_fin_10-23-13.pdf for more information on this, which is an excellent overview of the process.
