pollForResponse function

Future<BinaryBlob> pollForResponse(Agent agent, Principal canisterId, RequestId requestId, PollStrategy strategy, String method,)

Implementation

Future<BinaryBlob> pollForResponse(
  Agent agent,
  Principal canisterId,
  RequestId requestId,
  PollStrategy strategy,
  String method,
) async {
  final Principal? caller;
  if (agent is HttpAgent) {
    caller = agent.identity?.getPrincipal();
  } else {
    caller = null;
  }
  final path = [blobFromText('request_status'), requestId];
  final state = await agent.readState(
    canisterId,
    ReadStateOptions(paths: [path]),
    null,
  );
  final cert = Certificate(state, agent);
  final verified = await cert.verify();
  if (!verified) {
    throw StateError('Fail to verify certificate.');
  }
  final maybeBuf = cert.lookup([...path, blobFromText('status').buffer]);
  final RequestStatusResponseStatus status;
  if (maybeBuf == null) {
    // Missing requestId means we need to wait.
    status = RequestStatusResponseStatus.unknown;
  } else {
    status = RequestStatusResponseStatus.fromName(maybeBuf.u8aToString());
  }

  switch (status) {
    case RequestStatusResponseStatus.replied:
      return cert.lookup([...path, blobFromText('reply')]) as BinaryBlob;
    case RequestStatusResponseStatus.received:
    case RequestStatusResponseStatus.unknown:
    case RequestStatusResponseStatus.processing:
      // Execute the polling strategy, then retry.
      await strategy(canisterId, requestId, status);
      return pollForResponse(agent, canisterId, requestId, strategy, method);
    case RequestStatusResponseStatus.rejected:
      final rejectCode = cert.lookup(
        [...path, blobFromText('reject_code')],
      )!.toBn();
      final rejectMessage = cert.lookup(
        [...path, blobFromText('reject_message')],
      )!.u8aToString();
      throw PollingResponseRejectedException(
        canisterId: canisterId,
        requestId: requestIdToHex(requestId),
        status: status,
        method: method,
        rejectCode: rejectCode,
        rejectMessage: rejectMessage,
        caller: caller,
      );
    case RequestStatusResponseStatus.done:
      // This is _technically_ not an error, but we still didn't see the
      // `Replied` status so we don't know the result and cannot decode it.
      throw PollingResponseNoReplyException(
        canisterId: canisterId,
        requestId: requestIdToHex(requestId),
        status: status,
        method: method,
        caller: caller,
      );
  }
}