An ERP for a wholesale garments business, with real accounting underneath

Overview

A full ERP for a wholesale garments importer: purchases in supplier currency, landed-cost inventory, sales, invoicing, a general ledger and reporting. NestJS + Prisma + PostgreSQL behind a React 19 + Vite + shadcn front end.

The problem

Most 'ERPs' built by web teams store money as floats, cost inventory by average, and edit history in place. All three produce books that don't reconcile. This business trades in Omani Rial with three decimal places, buys in Bangladeshi Taka, and needed accounts an auditor could follow.

What I built

• Money as a value object: integer baisa (1 OMR = 1000 baisa), never floats, persisted to NUMERIC(18,3). Arithmetic that cannot silently lose a third decimal.
• FIFO lot costing: every shipment receipt is a StockLot with its own landed cost; sales consume lots oldest-first and record exact cost of goods sold.
• A double-entry ledger: every financial action posts a balanced LedgerTransaction against a seeded chart of accounts.
• Immutable history: ledgers, confirmed sales, invoices and stock movements are append-only; corrections are reversing records, never edits.
• Per-shipment FX: purchases entered in the supplier's currency with the exchange rate captured on the shipment.
• Fail-fast environment validation, strict ESLint where `any` is an error, Vitest, an ERD and data-model document, CI and deploy pipelines.

Outcome

Engineering decisions

• Integer money value object
• FIFO lot costing with landed cost
• Double-entry ledger, append-only
• Per-shipment foreign exchange