atari-engine

Lightweight rule evaluation engine for A/B testing, feature flags, and user targeting.

Highlights

• Zero runtime dependencies — @atari-engine/core has no external dependencies for minimal bundle size and cold starts.
• Edge-native — Runs on Cloudflare Workers, Node.js, and in the browser.
• Infinite nesting — AND/OR rule groups with arbitrary depth.
• Type-safe — Full TypeScript support and type definitions.
• Isomorphic — Same code and behavior across all supported environments.
• React Rule Builder — Optional UI components with dark mode and validation.

Packages

This monorepo publishes two packages:

Package	Description
@atari-engine/core	Rule evaluation engine: evaluate(), validate(), and shared types.
@atari-engine/react	React Rule Builder UI for creating and editing rule groups.

Quick Start — Core

Install the core engine:

npm install @atari-engine/core
# or
pnpm add @atari-engine/core
# or
yarn add @atari-engine/core

Define a rule, validate it, and evaluate against context:

import {
  evaluate,
  validate,
  FIELD_TYPES,
  LOGICAL_OPERATORS,
  OPERATORS,
  type RuleGroup,
  type UserProperties,
} from "@atari-engine/core";

const rule: RuleGroup = {
  logicalOperator: LOGICAL_OPERATORS.AND,
  conditions: [
    {
      fieldName: "age",
      fieldType: FIELD_TYPES.NUMBER,
      operator: OPERATORS.GREATER_THAN_OR_EQUAL_TO,
      value: 18,
    },
    {
      fieldName: "country",
      fieldType: FIELD_TYPES.STRING,
      operator: OPERATORS.IN,
      value: ["KR", "JP", "US"],
    },
  ],
};

const validation = validate(rule);
if (!validation.valid) {
  console.error(validation.errors);
  process.exit(1);
}

const user: UserProperties = { age: 25, country: "KR" };
const matched = evaluate(rule, user);
console.log(matched); // true

Quick Start — React

Install the React package and peer dependencies:

npm install @atari-engine/react @atari-engine/core react react-dom
# or
pnpm add @atari-engine/react @atari-engine/core react react-dom

Use the Rule Builder in your app:

import { useState } from "react";
import { RuleBuilder, createEmptyRuleGroup } from "@atari-engine/react";
import "@atari-engine/react/styles.css";

function App() {
  const [value, setValue] = useState(() => createEmptyRuleGroup("AND"));

  return (
    <RuleBuilder
      value={value}
      onChange={setValue}
      fields={[
        { name: "age", type: "number", label: "Age" },
        { name: "country", type: "string", label: "Country" },
      ]}
      showValidation
    />
  );
}

For dark mode, set data-theme="dark" on the wrapper or rely on prefers-color-scheme: dark.

Compatibility

Environment	Supported
Cloudflare Workers	Yes (primary target)
Node.js >= 18	Yes
Browser (ES2022+)	Yes
Deno / Bun	Yes (ESM)

Documentation

• @atari-engine/core API and usage
• @atari-engine/react components and props

Feedback

Issues and feedback are welcome.

License

MIT © JammyTheDreamer