trpc-shield/src/utils.ts

tRPC permissions as another layer of abstraction!

import { LogicRule, Rule } from './rules';
import { ILogicRule, IRule, IRuleFieldMap, ShieldRule } from './types';

/**
 *
 * @param x
 *
 * Makes sure that a certain field is a rule.
 *
 */
export function isRule<TContext extends Record<string, any>>(x: any): x is IRule<TContext> {
  return x instanceof Rule || (x?.constructor && x.constructor.name === 'Rule');
}

/**
 *
 * @param x
 *
 * Makes sure that a certain field is a logic rule.
 *
 */
export function isLogicRule<TContext extends Record<string, any>>(x: any): x is ILogicRule<TContext> {
  return (
    x instanceof LogicRule ||
    (x?.constructor &&
      (x.constructor.name === 'RuleOr' ||
        x.constructor.name === 'RuleAnd' ||
        x.constructor.name === 'RuleChain' ||
        x.constructor.name === 'RuleRace' ||
        x.constructor.name === 'RuleNot' ||
        x.constructor.name === 'RuleTrue' ||
        x.constructor.name === 'RuleFalse'))
  );
}

/**
 *
 * @param x
 *
 * Makes sure that a certain field is a rule or a logic rule.
 *
 */
export function isRuleFunction<TContext extends Record<string, any>>(x: any): x is ShieldRule<TContext> {
  return isRule(x) || isLogicRule(x);
}

/**
 *
 * @param x
 *
 * Determines whether a certain field is rule field map or not.
 *
 */
export function isRuleFieldMap<TContext extends Record<string, any>>(x: any): x is IRuleFieldMap<TContext> {
  return typeof x === 'object' && Object.values(x).every((rule) => isRuleFunction(rule));
}

/**
 *
 * @param obj
 * @param func
 *
 * Flattens object of particular type by checking if the leaf
 * evaluates to true from particular function.
 *
 */
export function flattenObjectOf<T>(obj: { [key: string]: any }, f: (x: any) => boolean): T[] {
  const values = Object.keys(obj).reduce<T[]>((acc, key) => {
    const val = obj[key];
    if (f(val)) {
      return [...acc, val];
    } else if (typeof val === 'object' && !f(val)) {
      return [...acc, ...flattenObjectOf(val, f)];
    } else {
      return acc;
    }
  }, []);
  return values;
}

/**
 *
 * Returns fallback is provided value is undefined
 *
 * @param fallback
 */
export function withDefault<T>(fallback: T): (value: T | undefined) => T {
  return (value) => {
    if (value === undefined) return fallback;
    return value;
  };
}