-- my_audio_latency can have a special value of -1, which means 'unknown'.
CREATE OR REPLACE FUNCTION sms_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 sms_music_session_tmp (music_session_id VARCHAR(64) NOT NULL, tag INTEGER, latency INTEGER) ON COMMIT DROP;

    -- populate sms_music_session_tmp as all music sessions
    -- XXX: we should pass in enough info to match pagination/query to reduce the impact of this step
    INSERT INTO sms_music_session_tmp SELECT DISTINCT id, NULL::INTEGER AS tag, NULL::INTEGER AS latency
      FROM music_sessions where (scheduled_start IS NULL OR scheduled_start > (NOW() - (interval '15 minute'))) AND canceled = FALSE;

    -- tag accepted rsvp as 1
    UPDATE sms_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 sms_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 sms_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 sms_music_session_tmp WHERE tag IS NULL;

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

    IF my_audio_latency > -1 THEN
      -- populate sms_users_tmp with users that have an approved RSVP for sessions in the sms_music_session_tmp table, accompanied with full latency and music session
      INSERT INTO sms_users_tmp SELECT q.music_session_id, users.id, (s.score+my_audio_latency+users.last_jam_audio_latency)/2 AS latency
      FROM sms_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;

      -- populate sms_users_tmp with invited users for session in the sms_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 sms_users_tmp SELECT NULL, users.id, (s.score+my_audio_latency+users.last_jam_audio_latency)/2 AS latency
      FROM sms_music_session_tmp q
      INNER JOIN invitations              ON invitations.music_session_id = q.music_session_id
      INNER JOIN users                    ON invitations.receiver_id = users.id
      LEFT OUTER JOIN current_scores s    ON s.alocidispid = users.last_jam_locidispid
      WHERE
        s.blocidispid = my_locidispid AND
        users.id NOT IN (SELECT user_id FROM sms_users_tmp);
    END IF;

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

    RETURN;
  END;
$$ LANGUAGE plpgsql;