@bernierllc/nevar-context-builder

Builds flat key-value evaluation context from trigger payload and registered context providers for the Nevar rules engine.

Installation

npm install @bernierllc/nevar-context-builder

Usage

import { ContextBuilder } from '@bernierllc/nevar-context-builder';

const builder = new ContextBuilder();

// Register a context provider
builder.registerProvider('user', async (payload) => {
  const userId = payload.userId as string;
  return { name: 'Alice', role: 'admin' };
});

// Build context from trigger payload
const context = await builder.build('order.created', { orderId: '123', userId: 'u1' }, ['user.name', 'user.role']);
// Result:
// {
//   'trigger.key': 'order.created',
//   'trigger.orderId': '123',
//   'trigger.userId': 'u1',
//   'user.name': 'Alice',
//   'user.role': 'admin'
// }

API

ContextBuilder

Builds flat key-value evaluation context from trigger payloads and registered context providers. Providers are only invoked when their prefix appears in the required fields list.

Constructor: new ContextBuilder()

• registerProvider(prefix, providerFn) - Registers a context provider under a prefix. The "trigger" prefix is reserved. Throws NevarEvaluationError on empty prefix, reserved prefix, or duplicate registration
• build(triggerKey, payload, requiredFields) - Builds the evaluation context. Auto-prefixes payload fields with trigger.*, sets trigger.key, and invokes only the providers whose prefixes appear in requiredFields. Returns Promise<Record<string, unknown>>
• listProviders() - Returns array of registered provider prefixes
• hasProvider(prefix) - Returns true if a provider is registered under the given prefix

Integration Documentation

Logger Integration

This package does not integrate with @bernierllc/logger. As a core package, logger integration is optional and not included by default. Consumers should handle logging at the service layer.

NeverHub Integration

This package does not integrate with @bernierllc/neverhub-adapter. As a core package, NeverHub integration is not applicable. NeverHub registration should be handled by service-layer packages that compose this package.

License

Copyright (c) 2025 Bernier LLC. All rights reserved.