Probook

The product

Probook is an all-in-one management tool for freelancers and small businesses: clients, a product catalogue, quotes that turn into invoices, delivery notes, credit notes, payments, expenses, suppliers and purchase orders, stock across several locations, and a point-of-sale mode for in-store sales.

The main market is Algeria: dinars, local tax identifiers (NIF, RC, NIS), 0/9/19% VAT, stamp duty. A French tax profile exists too. The interface is in French, English and Arabic. Probook is in production with its first customers.

From desktop app to SaaS

Probook started in January 2026 as a Tauri desktop app (React + Rust): a database, multiple users with roles, a point of sale with a thermal printer, an offline queue and a signed licence system (Ed25519).

In March 2026 I rewrote it as a Next.js SaaS. The features were ported, then the SaaS layer was added: trials, subscriptions, à-la-carte plans, a platform admin panel. One trace of its origins remains: ~180 Tauri command names mapped to REST routes.

What I built

• The full document flow: quote → invoice → delivery note → credit note, partial payments, client statements.
• Multi-location stock with transfers, a per-location ledger and weighted-average cost.
• Point of sale: sessions, split payments, refunds, receipt printing (WebUSB), offline sales.
• Branded PDFs with embedded fonts and amounts written out in words.
• Multi-tenant with roles, per-action permissions and two-factor authentication.
• Encrypted backups, CSV and Excel import / export, GDPR export and deletion.
• Subscriptions, trials, plan-based feature gating and a platform admin panel.

Technical challenges

• Algerian stamp duty, implemented from the law itself (Stamp Code, 2025 finance law) and checked against the ministry's official example: 35,000 DA → 525 DA. Only the cash part is taxed, recomputed on the server.
• Money correctness: two audits led to decimal amounts, atomic invoice numbering (required in Algeria), idempotency keys and row locks on stock.
• Arabic PDFs: the default font had no Arabic glyphs. I embedded IBM Plex Sans Arabic, with a test that checks fonts per language.
• Offline: three independent mechanisms replaced by a single sync queue with per-item conflict resolution.
• Tests as documentation: Playwright films the video guide in three languages, and twelve CI "barriers" check translation parity, no overflow at 390 px and dark-mode contrast.