Pointfinity Case Study: High-Concurrency Rewards Engine for UAE Retail & FinTech

// Pointfinity Immutable Double-Entry Ledger Event
export interface JournalEntry {
  entryId: string;
  transactionHash: string;
  userId: string;         // UAE Pass Verified Identity GUID
  merchantId: string;     // Dubai Mall / Mall of the Emirates Partner ID
  timestamp: number;
  
  // Double-Entry Invariance: SUM(debits) MUST EQUAL SUM(credits)
  postings: Array<{
    accountType: 'CUSTOMER_POINTS' | 'MERCHANT_PAYABLE' | 'SYSTEM_RESERVE' | 'COMMISSION_REVENUE';
    accountNumber: string;
    debitAED: number;     // AED value of points debited
    creditAED: number;    // AED value of points credited
  }>;
  
  cbuaeAuditHash: string; // Cryptographic SHA-256 HMAC for Central Bank audit
}

// Invariance Validator executed on every ledger commit
export function validateEntryInvariance(entry: JournalEntry): boolean {
  const totalDebit = entry.postings.reduce((sum, p) => sum + p.debitAED, 0);
  const totalCredit = entry.postings.reduce((sum, p) => sum + p.creditAED, 0);
  
  // Math.abs check for micro-rounding floating point safety
  if (Math.abs(totalDebit - totalCredit) > 0.0001) {
    throw new Error(`LEDGER_UNBALANCED_ERROR: Debits (${totalDebit}) != Credits (${totalCredit})`);
  }
  return true;
}