How to use the rulr.maybe function in rulr

import Config from '../../Config';
import catchErrors from '../../utils/catchErrors';
import { CREATED } from 'http-status-codes'; 
import getAuthUserAndPermissions from '../../../../utils/jwt/getAuthUserAndPermissions';
import hasPermission from '../../../../utils/jwt/hasPermission';
import { CAN_CREATE_COMMENT, TEXT_FIELD_LENGTH } from '../../../../utils/constants';
import { maxLength } from '../../../../utils/validate';
import { maybe, required, checkType, composeRules, restrictToSchema } from 'rulr';

const validateCreateComment = maybe(composeRules([
  restrictToSchema({
    user_id: required(checkType(Number)),
    post_id: required(checkType(Number)),
    body: required(maxLength(TEXT_FIELD_LENGTH)),
  })
]));
   
export default (config: Config) => {
  return catchErrors(config, async (req, res) => {
  
    const { permissions } = await getAuthUserAndPermissions({req, service: config.service});

    hasPermission({permissions, permissionName: CAN_CREATE_COMMENT});
 
    validateCreateComment(req.body, ['comment']);

import Config from '../../Config';
import catchErrors from '../../utils/catchErrors';
import { OK } from 'http-status-codes';
import getAuthUserAndPermissions from '../../../../utils/jwt/getAuthUserAndPermissions';
import hasPermission from '../../../../utils/jwt/hasPermission';
import { CAN_GET_USERS } from '../../../../utils/constants';
import { maybe, optional, checkType, restrictToSchema } from 'rulr';
import { isValidSortObject } from '../../../../utils/validate';

const validateGetUsers = maybe(
  restrictToSchema({
    limit: optional(checkType(String)),
    offset: optional(checkType(String)),
    sort: optional(isValidSortObject())
  }),
);

export default (config: Config) => {
  return catchErrors(config, async (req, res) => {
      
    const { permissions } = await getAuthUserAndPermissions({req, service: config.service});
    
    hasPermission({ permissions, permissionName: CAN_GET_USERS});

    validateGetUsers(req.query,['users']);

import Config from '../../Config';
import catchErrors from '../../utils/catchErrors';
import { OK } from 'http-status-codes';
import getAuthUserAndPermissions from '../../../../utils/jwt/getAuthUserAndPermissions';
import hasPermission from '../../../../utils/jwt/hasPermission';
import { CAN_UPDATE_USER } from '../../../../utils/constants';
import { minLength, isEmail, validateMatchingPasswords } from '../../../../utils/validate';
import { maybe, optional, checkType, composeRules, first, restrictToSchema }from 'rulr';
import * as R from 'ramda';

const validateUpdateUser = maybe(composeRules([
  restrictToSchema({
    firstname: optional(checkType(String)),
    lastname: optional(checkType(String)),
    bio: optional(checkType(String)),
    email: optional(isEmail),
    password: optional(minLength(6)),
    password_confirmation: optional(checkType(String)),
  }),
  first(checkType(Object), optional(validateMatchingPasswords))
]));

export default (config: Config) => {
  return catchErrors(config, async (req, res) => {
  
    const { permissions } = await getAuthUserAndPermissions({req, service: config.service});

import Config from '../../Config';
import catchErrors from '../../utils/catchErrors';
import { Request, Response } from 'express';
import { OK } from 'http-status-codes';
import getAuthUserAndPermissions from '../../../../utils/jwt/getAuthUserAndPermissions';
import hasPermission from '../../../../utils/jwt/hasPermission';
import { CAN_GET_POSTS } from '../../../../utils/constants';
import { maybe, optional, checkType, restrictToSchema }from 'rulr';
import { isValidSortObject } from '../../../../utils/validate';

const validateGetPosts = maybe(
  restrictToSchema({
    limit: optional(checkType(String)),
    offset: optional(checkType(String)),
    sort: optional(isValidSortObject())
  }),
);

export default (config: Config) => {
  return catchErrors(config, async (req, res) => {
      
    const { permissions } = await getAuthUserAndPermissions({req, service: config.service});
    
    hasPermission({ permissions, permissionName: CAN_GET_POSTS});

    validateGetPosts(req.query,['posts']);

if (ifi.key === 'mbox_sha1sum') {
    return validateSha1(ifi.value, valuePath);
  }
  if (ifi.key === 'openid') {
    return validateIri(ifi.value, valuePath);
  }
  if (ifi.key === 'account') {
    return restrictToSchema({
      homePage: required(validateIri),
      name: required(checkType(String))
    })(ifi.value, valuePath);
  }
  return ['invalid key'];
};

export default maybe(validateIfi);