simpleRulesEngine.js

import {every, filter} from 'lodash'


export const numericComparisons = {
	lte: (a, b) => a <= b,
	lt: (a, b) => a < b,
	gt: (a, b) => a > b,
	gte: (a, b) => a >= b,
	eq: (a, b) => a === b,
	neq: (a, b) => a !== b
}

export function evalRules(n, {name, description, ...classRules}, rules) {
	return every(classRules, (classVal, ruleName) => rules[ruleName](n, classVal))
}

export function classify(n, classes, rules) {
	return filter(classes, classDef => evalRules(n, classDef, rules))
}

export function numericClassification(n, classes) {
	let c = classify(n, classes, numericComparisons)
	return c[0] || {}
}

/* e.g.
let aucClasses = [
	{gte: 0.0, lt: 0.6, name: 'Failed'},
	{gte: 0.6, lt: 0.7, name: 'Marginal'},
	{gte: 0.7, lt: 0.8, name: 'Satisfactory'},
	{gte: 0.8, lte: 1.0, name: 'Good'}
]

aucRating = numericClassification(auc, aucClasses)
 */