Rule Decision Library

This library aims to provide an agnostic and reliable mechanism to decide the applicable value based on defined rules given at a specific moment.

Installation

yarn add @dev-vortex/rule-decision

or

npm install @dev-vortex/rule-decision

Rule definition

A rule RuleCase is composed by:

| Attribute | Description | Default | |:---------:|:------------|:-------:| |validation|Key/Value object where the key represents the validator name and the value is the expected value to validate|| |active|(Optional) boolean value, when false it will set the current case as inactive|undefined| |cases|(optional) An array of RuleCase object type. This will set the sub-rules to be checked.|undefined| |resolve|(optional) The return value in case the case is valid (if not defined the service will return true)|true|

Validators

A validator is a callable function that will return the value to validate.

The return value will be verified against the expected value set in the rule.validation object

Quick Start

1. Prepare the validator functions to provide them to the validation service function

import type { ValidatorSet } from '@dev-vortex/rule-decision'

...

const getValidators = (values: Record<string, any>): ValidatorSet => ({
   currentMarket: () => values.market || undefined,
   currentCountry: () => values.country || undefined,
   isCreditCard: () => values.cardNumber.indexOf('3') === 0,
   isMastercard: () => values.cardNumber.indexOf('35') === 0,
   isVisa: () => values.cardNumber.indexOf('34') === 0,
})

2. Define youur rules

import type { RuleCasesCollection } from '@dev-vortex/rule-decision'

...

const creditCardAcceptanceSimple: RuleCasesCollection = [
   {
       active: false,
       validation: { isCreditCard: false },
       resolve: { fee: 0.5 },
   },
   {
       validation: { currentCountry: 'NO', isVisa: true },
       resolve: { availability: false },
   },
   {
       validation: { currentCountry: 'NO', isMastercard: true },
   },
   {
       validation: { currentMarket: 'EU', isMastercard: true },
       resolve: { fee: 0.01 },
   },
   {
       validation: { currentCountry: 'SE', isMastercard: true },
       resolve: { fee: 0.02 },
   },
   {
       validation: { isMastercard: true },
       resolve: { fee: 0.03 },
   },
   {
       validation: { isVisa: true },
       resolve: { fee: 0.04 },
   },
   {
       validation: { isCreditCard: true },
       resolve: { fee: 0.05 },
   },
]

3. When needed, call the validation service providing the rule collection and the validator set.

import { decideOn } from '@dev-vortex/rule-decision'

...

const decision = decideOn(
    creditCardAcceptanceSimple,
    getValidators({
        market: 'EU',
        cardNumber: '3546367126490263',
    }),
)

4. Check if the decision is valid (true) or just use the resolved value for the first found case.

How to prepare/read the rule correction

The service will check your collection top to bottom and it will stop on the first successfully validated case.

For this reason, the rule priority matters. and the returned value will either be the resolve value present in the case or the value true (showiing that a case was found).

Any case with active attribute as false will be ignored.

If sub-cases are present in a valiid parent-case, the service will follow and check them returning the resolve value from the validated rule/sub-case.

If the sub-case does not have a resolve value set, the service will return the parent resolve value or true if none exist.