haproxy.cfg

frontend http-in-ext
  bind 0.0.0.0:80
  bind 0.0.0.0:443 ssl crt /SSL/yourcert.pem
  option forwardfor

  reqrep (.*)/seamedia/(.*)   \1/seahub/seamedia/\2
  acl path_seahub path_beg /seahub
  acl path_seafile path_beg /seafhttp
  
  #Force https
  redirect scheme https if path_seahub !{ ssl_fc }
  redirect scheme https if path_seafile !{ ssl_fc }

  use_backend seahub if path_seahub
  use_backend seafile if path_seafile
  
backend seahub
  server pi1 pi1:8000 check
  
backend seafile
  reqrep (.*)/seafhttp/(.*)   \1/\2
  server pi1 pi1:8082 check

seafile is hosted on pi1, with port 8000 for seahub and 8082 for seafile.