-- check that the music_sessions does not currently have an active_music_sessions
CREATE OR REPLACE FUNCTION sms_index (my_user_id VARCHAR, my_locidispid BIGINT, my_audio_latency INTEGER, session_id VARCHAR, include_pending BOOLEAN) 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;

    IF session_id = 'any' THEN
      -- 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
        AND id NOT IN (SELECT id FROM active_music_sessions);

      -- 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.open_rsvps = TRUE AND
        q.tag IS NULL;

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

    ELSE
      INSERT INTO sms_music_session_tmp SELECT DISTINCT id, NULL::INTEGER AS tag, NULL::INTEGER AS latency
        FROM music_sessions
        WHERE  music_sessions.id = session_id;
    END IF;

    -- 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, full_score INTEGER, audio_latency INTEGER, internet_score INTEGER) ON COMMIT DROP;

    IF my_audio_latency > -1 THEN

      IF include_pending 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 DISTINCT q.music_session_id, users.id, s.full_score AS full_score, s.a_audio_latency, s.score
        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.a_userid = users.id
        WHERE
          s.b_userid = my_user_id;

        -- 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.full_score AS full_score, s.a_audio_latency, s.score
        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.a_userid = users.id
        WHERE
          s.b_userid = my_user_id AND
          users.id NOT IN (SELECT user_id FROM sms_users_tmp);
      ELSE
        -- 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 DISTINCT q.music_session_id, users.id, s.full_score AS full_score, s.a_audio_latency, s.score
        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.a_userid = users.id
        WHERE
          s.b_userid = my_user_id AND
          rsvp_requests_rsvp_slots.chosen = TRUE AND
          rsvp_requests.canceled != TRUE;
      END IF;
    END IF;

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

    RETURN;
  END;
$$ LANGUAGE plpgsql;