;; Simple wallet smart contract

cell create_state(int seqno, int public_key) {
  return begin_cell().store_uint(seqno, 32).store_uint(public_key, 256).end_cell();
}

(int, int) load_state() {
  var cs2 = begin_parse(get_data());
  return (cs2~load_uint(32), cs2~load_uint(256));
}

() save_state(int seqno, int public_key) impure {
  set_data(create_state(seqno, public_key));
}

() recv_internal(slice in_msg) impure {
  ;; do nothing for internal messages
}

slice do_verify_message(slice in_msg, int seqno, int public_key) {
  var signature = in_msg~load_bits(512);
  var cs = in_msg;
  int msg_seqno = cs~load_uint(32);
  throw_unless(33, msg_seqno == seqno);
  throw_unless(34, check_signature(slice_hash(in_msg), signature, public_key));
  return cs;
}

() recv_external(slice in_msg) impure {
  (int stored_seqno, int public_key) = load_state();
  var cs = do_verify_message(in_msg, stored_seqno, public_key);
  accept_message();
  cs~touch();
  if (cs.slice_refs()) {
    var mode = cs~load_uint(8);
    send_raw_message(cs~load_ref(), mode);
  }
  cs.end_parse();
  save_state(stored_seqno + 1, public_key);
}

;; Get methods

int seqno() method_id {
  return get_data().begin_parse().preload_uint(32);
}

int get_public_key() method_id {
  var (seqno, public_key) = load_state();
  return public_key;
}

cell create_init_state(int public_key) method_id {
  return create_state(0, public_key);
}

cell prepare_send_message_with_seqno(int mode, cell msg, int seqno) method_id {
  return begin_cell().store_uint(seqno, 32).store_uint(mode, 8).store_ref(msg).end_cell();
}

cell prepare_send_message(int mode, cell msg) method_id {
  return prepare_send_message_with_seqno(mode, msg, seqno());
}

slice verify_message(slice msg) method_id {
  var (stored_seqno, public_key) = load_state();
  return do_verify_message(msg, stored_seqno, public_key);
}