Money as Integer Minor Units

Specify how we store and display money. Integers in minor units. One currency per row. No binary floats. DOMAIN Currencies: [USD, OR A LIST] What we store: [PRICES, BALANCES, TAX LINES] Display locales: [LIST] Rounding rule for tax: [HALF UP OR THE RULE I NAME] DELIVER 1) The column type: integer minor units plus a currency code. The check constraint that the currency is one we support. 2) The TypeScript type that does not allow a number of dollars to be added to cents by accident. A function to format for display using Intl, and a parse function for input that rejects "1.2.3" and handles currencies with zero decimals if I listed one. 3) Addition and allocation: how we split a discount across lines without losing a cent. Show the remainder going to the last line. 4) The bugs you will comment on in review: float columns, money math in the client as the source of truth, formatting with a hardcoded "$". 5) A test set: $0.10 + $0.20, a 10% discount on $0.05, and a zero-decimal currency if applicable. Do not use JavaScript number arithmetic for the ledger. Integer math only.