CREATE OR REPLACE FUNCTION ams_index (my_user_id VARCHAR, my_locidispid BIGINT, my_audio_latency INTEGER) RETURNS VOID STRICT VOLATILE AS $$
  BEGIN
    -- output table to hold tagged music sessions with latency
    CREATE TEMPORARY TABLE ams_music_session_tmp (music_session_id VARCHAR(64) NOT NULL, tag INTEGER, latency INTEGER) ON COMMIT DROP;

    -- populate ams_music_session_tmp as all music sessions
    INSERT INTO ams_music_session_tmp SELECT DISTINCT id, NULL::INTEGER AS tag, NULL::INTEGER AS latency
      FROM active_music_sessions;

    -- TODO worry about active music session where my_user_id is the creator?
    -- eh, maybe, but if the music session is active and you're the creator wouldn't you already be in it?
    -- so maybe you're on another computer, so why care? plus seth is talking about auto rsvp'ing the session
    -- for you, so maybe not a problem.

    -- tag accepted rsvp as 1
    UPDATE ams_music_session_tmp q SET tag = 1 FROM rsvp_slots s, rsvp_requests_rsvp_slots rrs, rsvp_requests r WHERE
      q.music_session_id = s.music_session_id AND
      s.id = rrs.rsvp_slot_id AND
      rrs.rsvp_request_id = r.id AND
      r.user_id = my_user_id AND
      rrs.chosen = TRUE AND
      q.tag is NULL;

    -- tag invitation as 2
    UPDATE ams_music_session_tmp q SET tag = 2 FROM invitations i WHERE
      q.music_session_id = i.music_session_id AND
      i.receiver_id = my_user_id AND
      q.tag IS NULL;

    -- musician access as 3
    UPDATE ams_music_session_tmp q SET tag = 3 FROM music_sessions m WHERE
      q.music_session_id = m.id AND
      m.musician_access = TRUE AND
      q.tag IS NULL;

    -- delete anything not tagged
    DELETE FROM ams_music_session_tmp WHERE tag IS NULL;

    -- output table to hold users involved in the ams_music_session_tmp sessions and their latency
    CREATE TEMPORARY TABLE ams_users_tmp (music_session_id VARCHAR(64), user_id VARCHAR(64) NOT NULL, latency INTEGER) ON COMMIT DROP;

    -- populate ams_users_tmp with users that have a connection for sessions in the  ams_music_session_tmp table, accompanied with full latency and music session
    INSERT INTO ams_users_tmp SELECT c.music_session_id, c.user_id, (s.score+my_audio_latency+c.last_jam_audio_latency)/2 AS latency
      FROM ams_music_session_tmp q
      INNER JOIN connections c ON c.music_session_id = q.music_session_id
      LEFT OUTER JOIN current_scores s ON s.alocidispid = c.locidispid
      WHERE s.blocidispid = my_locidispid;

    -- populate ams_users_tmp with users that have an approved RSVP for sessions inthe ams_music_session_tmp table, accompanied with full latency and music session
    -- specify NULL for music_session_id, because we don't want RSVP users to affect the AVG computed for each session later
    INSERT INTO ams_users_tmp SELECT NULL, users.id, (s.score+my_audio_latency+users.last_jam_audio_latency)/2 AS latency
      FROM ams_music_session_tmp q
      INNER JOIN rsvp_slots               ON rsvp_slots.music_session_id = q.music_session_id
      INNER JOIN rsvp_requests_rsvp_slots ON rsvp_requests_rsvp_slots.rsvp_slot_id = rsvp_slots.id
      INNER JOIN rsvp_requests            ON rsvp_requests.id = rsvp_requests_rsvp_slots.rsvp_request_id
      INNER JOIN users                    ON rsvp_requests.user_id = users.id
      LEFT OUTER JOIN current_scores s    ON s.alocidispid = users.last_jam_locidispid
      WHERE
        s.blocidispid = my_locidispid AND
        rsvp_requests_rsvp_slots.chosen = TRUE AND
        users.id NOT IN (SELECT user_id FROM ams_users_tmp);

    -- calculate the average latency
    UPDATE ams_music_session_tmp q SET latency = (select AVG(u.latency) FROM ams_users_tmp u WHERE
      q.music_session_id = u.music_session_id);

    RETURN;
  END;
$$ LANGUAGE plpgsql;