Policy Engine API

Complete API reference for the @guardrail-sim/policy-engine package.

PolicyEngine

The main class for policy evaluation.

import { PolicyEngine, defaultPolicy } from '@guardrail-sim/policy-engine';
 
const engine = new PolicyEngine(defaultPolicy);

Constructor

new PolicyEngine(policy: Policy)

Creates a new policy engine instance with the given policy.

evaluate

Evaluate a discount request against the policy.

async evaluate(order: Order, proposedDiscount: number): Promise<EvaluationResult>

Parameters:

order: Order details including value, quantity, margin, and customer segment
proposedDiscount: Discount as decimal (0.15 = 15%)

Returns: EvaluationResult with approval status, violations, and calculated margin.

Example:

const result = await engine.evaluate(
  { order_value: 5000, quantity: 100, product_margin: 0.4 },
  0.12
);
 
if (result.approved) {
  console.log(`Approved! Margin: ${result.calculated_margin}`);
} else {
  console.log('Violations:', result.violations);
}

getPolicy

Get the current policy.

getPolicy(): Policy

calculateAllocations

Calculate how a discount should be allocated across line items.

function calculateAllocations(
  discountAmount: number,
  lineItems: LineItem[],
  method?: 'across' | 'each'
): Allocation[]

Parameters:

discountAmount: Total discount amount
lineItems: Array of line items with subtotals
method: Allocation method ('across' proportionally, 'each' evenly)

Returns: Array of allocations per line item.

Example:

import { calculateAllocations } from '@guardrail-sim/policy-engine';
 
const allocations = calculateAllocations(
  100, // $100 discount
  [
    { item_id: 'A', subtotal: 300 },
    { item_id: 'B', subtotal: 200 },
  ],
  'across'
);
// [{ item_id: 'A', amount: 60 }, { item_id: 'B', amount: 40 }]

calculateMaxDiscount

Calculate the maximum allowed discount for an order.

function calculateMaxDiscount(
  order: Order,
  options?: { policy?: Policy }
): number

Returns: Maximum discount as decimal.

defaultPolicy

Pre-configured policy with standard B2B pricing rules.

import { defaultPolicy } from '@guardrail-sim/policy-engine';

Includes:

margin_floor: 15% minimum margin
max_discount: 25% maximum discount
volume_tier: 10% base, 15% for orders >= 100 units

getUCPErrorCode

Map a policy violation to a UCP-compatible error code.

function getUCPErrorCode(violationRule: string): UCPErrorCode

Example:

import { getUCPErrorCode } from '@guardrail-sim/policy-engine';
 
const code = getUCPErrorCode('margin_floor');
// 'discount_code_invalid'

VIOLATION_TO_UCP_ERROR

Mapping of violation rules to UCP error codes.

const VIOLATION_TO_UCP_ERROR: Record<string, UCPErrorCode> = {
  max_discount: 'discount_code_invalid',
  margin_floor: 'discount_code_invalid',
  volume_tier: 'discount_code_user_ineligible',
  stacking_not_allowed: 'discount_code_combination_disallowed',
  discount_expired: 'discount_code_expired',
  login_required: 'discount_code_user_not_logged_in',
  // ...
};

Policy Engine API

On this page