/**
   * Gets values referenced by sequential keys, e.g. {@code key1...keyN}.
   *
   * @param keyPrefix Key prefix, e.g. {@code key} for {@code key1...keyN}.
   * @param params Parameters map.
   * @return Values.
   */
  @Nullable
  protected List<Object> values(String keyPrefix, Map<String, Object> params) {
    assert keyPrefix != null;

    List<Object> vals = new LinkedList<>();

    for (int i = 1; ; i++) {
      String key = keyPrefix + i;

      if (params.containsKey(key)) vals.add(params.get(key));
      else break;
    }

    return vals;
  }
  /**
   * Creates REST request.
   *
   * @param cmd Command.
   * @param params Parameters.
   * @return REST request.
   * @throws GridException If creation failed.
   */
  @Nullable
  private GridRestRequest createRequest(
      GridRestCommand cmd, Map<String, Object> params, ServletRequest req) throws GridException {
    GridRestRequest restReq;

    switch (cmd) {
      case CACHE_GET:
      case CACHE_GET_ALL:
      case CACHE_PUT:
      case CACHE_PUT_ALL:
      case CACHE_REMOVE:
      case CACHE_REMOVE_ALL:
      case CACHE_ADD:
      case CACHE_CAS:
      case CACHE_METRICS:
      case CACHE_REPLACE:
      case CACHE_DECREMENT:
      case CACHE_INCREMENT:
      case CACHE_APPEND:
      case CACHE_PREPEND:
        {
          GridRestCacheRequest restReq0 = new GridRestCacheRequest();

          restReq0.cacheName((String) params.get("cacheName"));
          restReq0.key(params.get("key"));
          restReq0.value(params.get("val"));
          restReq0.value2(params.get("val2"));

          Object val1 = params.get("val1");

          if (val1 != null) restReq0.value(val1);

          restReq0.cacheFlags(intValue("cacheFlags", params, 0));
          restReq0.ttl(longValue("exp", params, null));
          restReq0.initial(longValue("init", params, null));
          restReq0.delta(longValue("delta", params, null));

          if (cmd == CACHE_GET_ALL || cmd == CACHE_PUT_ALL || cmd == CACHE_REMOVE_ALL) {
            List<Object> keys = values("k", params);
            List<Object> vals = values("v", params);

            if (keys.size() < vals.size())
              throw new GridException(
                  "Number of keys must be greater or equals to number of values.");

            Map<Object, Object> map = U.newHashMap(keys.size());

            Iterator<Object> keyIt = keys.iterator();
            Iterator<Object> valIt = vals.iterator();

            while (keyIt.hasNext()) map.put(keyIt.next(), valIt.hasNext() ? valIt.next() : null);

            restReq0.values(map);
          }

          restReq = restReq0;

          break;
        }

      case TOPOLOGY:
      case NODE:
        {
          GridRestTopologyRequest restReq0 = new GridRestTopologyRequest();

          restReq0.includeMetrics(Boolean.parseBoolean((String) params.get("mtr")));
          restReq0.includeAttributes(Boolean.parseBoolean((String) params.get("attr")));

          restReq0.nodeIp((String) params.get("ip"));

          restReq0.nodeId(uuidValue("id", params));

          restReq = restReq0;

          break;
        }

      case EXE:
      case RESULT:
      case NOOP:
        {
          GridRestTaskRequest restReq0 = new GridRestTaskRequest();

          restReq0.taskId((String) params.get("id"));
          restReq0.taskName((String) params.get("name"));

          restReq0.params(values("p", params));

          restReq0.async(Boolean.parseBoolean((String) params.get("async")));

          restReq0.timeout(longValue("timeout", params, 0L));

          restReq = restReq0;

          break;
        }

      case LOG:
        {
          GridRestLogRequest restReq0 = new GridRestLogRequest();

          restReq0.path((String) params.get("path"));

          restReq0.from(intValue("from", params, -1));
          restReq0.to(intValue("to", params, -1));

          restReq = restReq0;

          break;
        }

      case VERSION:
        {
          restReq = new GridRestRequest();

          break;
        }

      default:
        throw new GridException("Invalid command: " + cmd);
    }

    restReq.address(new InetSocketAddress(req.getRemoteAddr(), req.getRemotePort()));

    restReq.command(cmd);

    if (params.containsKey("gridgain.login") || params.containsKey("gridgain.password")) {
      GridSecurityCredentials cred =
          new GridSecurityCredentials(
              (String) params.get("gridgain.login"), (String) params.get("gridgain.password"));

      restReq.credentials(cred);
    }

    String clientId = (String) params.get("clientId");

    try {
      if (clientId != null) restReq.clientId(UUID.fromString(clientId));
    } catch (Exception ignored) {
      // Ignore invalid client id. Rest handler will process this logic.
    }

    String destId = (String) params.get("destId");

    try {
      if (destId != null) restReq.destinationId(UUID.fromString(destId));
    } catch (IllegalArgumentException ignored) {
      // Don't fail - try to execute locally.
    }

    String sesTokStr = (String) params.get("sessionToken");

    try {
      if (sesTokStr != null) restReq.sessionToken(U.hexString2ByteArray(sesTokStr));
    } catch (IllegalArgumentException ignored) {
      // Ignore invalid session token.
    }

    return restReq;
  }