Work / Mizan
Mizan · ميزان
Live at mizan.arzlabs.cloudAn Arabic-first web app that prices gold, silver and cash conversions at your actual dealer's margins, tracks the resulting ledger by karat, and tells you where you stand, built on an exact-integer money engine with a 201-test correctness contract.
201
Tests, money-math contract
0
Floats in storage: bigint everywhere
12
Routes, RTL throughout
5
Alert kinds on a 30-min price loop
The problem
Screen prices are not the prices you get. International spot quotes fine metal per troy ounce; a real trade is a physical weight at a real karat, priced by a dealer who adds his own absolute margin, quoted in whatever unit you asked in. Every step moves the number, and none of them are visible in a generic portfolio tracker.
What it does
Price a swap first
Bidirectional gold / silver / cash quotes at a chosen dealer's margins, with break-even and round-trip cost stated plainly. Public, no login.
Record the real deal
Swaps freeze the spot prices and margins actually applied; deposits and withdrawals are separate movements. The ledger stays reconstructable forever.
See where you stand
Holdings bucketed by metal and karat, valued by liquidating through the dealer, contributions subtracted, so added money never shows as profit.
Dealer commission cards
A dealer quotes by the unit you ask in, so each carries two metals × three units × buy/sell, with cheaper-category detection and per-deal overrides.
Ratio charts & alerts
The gold/silver ratio plotted from the app's own price history with your trades marked; five alert kinds delivered by email.
Arabic-native, RTL
Written in Arabic, not translated, right-to-left from the locale, with domain vocabulary as first-class terms rather than English words in translation. Arabic-Indic digits are accepted as input. Examples: صائغ، عيار، العالمي زائد/ناقص، ليرة ذهب.
Engineering notes
Nothing is stored as a float
Metal is bigint milligrams, cash is bigint cents, margins are integer cents per ounce. Rounding never manufactures value: conversions floor in the direction that cannot invent metal or cash.
A dated, documented correction
The purity model was corrected mid-project: face weight stays physical, purity scales the price. The earlier model overvalued 875 jewelry by 12.5 percent: the bug, the reasoning and the migration are all recorded in the repo.
Append-and-void ledger
Transactions are never edited or deleted: a void is a timestamp, and holdings are always a fold over the ledger. Idempotency keys make a double-submit unable to insert a second row.
An advisor that refuses to advise
The advisory layer states facts, where today's ratio sits, what the round trip costs, and deliberately emits no direction and no confidence. Below 300 samples over 14 days, it says so instead of guessing.
Stack
- Framework
- Next.js 16 App Router · React 19 · TypeScript strict
- Data
- PostgreSQL · Drizzle ORM · versioned migrations
- Money math
- decimal.js-light in a pure, framework-free domain layer
- Prices
- metals.dev → gold-api.com → Swissquote fallback chain
Status: live and early, weeks old, solo-built, no usage metrics claimed. Its value is rigor per line, and we say that plainly.