Wallet

What the system does

• Bank account connection over Open Finance, with consent handled inside the aggregator's widget.
• Expenses and income from the connected account, alongside manual entries, in the same listing.
• Statement reconciliation: credit card purchases, bill payments and transfers between the holder's own accounts handled before anything counts as spending.
• Investment positions by type and subtype, with the issuing institution and the twelve-month rate.
• A monthly summary and spreadsheet export, by month, by category and by year.

Architecture

• A NestJS API with TypeORM over PostgreSQL, with a global prefix and Swagger documentation.
• Seven modules in the backend, with the bank connection split into three controllers, connect token, bank item and transactions, plus the investment submodule.
• Bank consent inside the aggregator's widget: the server exchanges client credentials for an API key and returns the connect token, and bank credentials are typed into the widget, never into the application.
• Authentication by a Firebase token verified on the server, in a route guard. The same guard provisions the user on the first authenticated request, with no signup route.
• A uniform response contract: an interceptor wraps every successful response and a global filter handles exceptions. On the way in, a ValidationPipe with a whitelist that refuses unknown fields.
• Spending comes in through two paths and goes out through one: the listing merges connected-account transactions and manual entries into the same response, each tagged with its origin, and the monthly summary adds both.
• Investments as their own domain: a position entity with twenty-eight subtypes and six types in enums, the institution as a separate entity, and an assembler that translates the aggregator's vocabulary at the response boundary.
• The schema versioned across five migrations, with no automatic synchronization.
• Structured logging with Pino, a health-check route and three spreadsheet exports with exceljs.
• The web app in Next.js with Recharts charts, consuming the API directly with the Firebase token in the header.

Implementation details

• Card reconciliation subtracts the bill payment and ten excluded categories, so a purchase is not counted twice.
• Synchronization is on demand: there is no schedule and no webhook, the bank item is refreshed when the client asks.
• Investment deduplication uses the asset's ISIN as its key.