initial webapp

README.md

@@ -53,3 +53,40 @@ State is only persisted once the input reaches EOF, so a crash or `Ctrl-C` befor
 All Euro values are rounded to cents (2 decimal places) but internal calculations use the statement values with full precision.
 There are no explicit rules or details about how to round Euro values in Anexo J.
 This application rounds according to `Portaria n.º 1180/2001, art. 2.º, alínea c) e d)` (Ministerial Order / Government Order) examples, which imply we should round to the 2nd decimal place by rounding up (ceiling) or down (floor) depending on whether the third decimal place is ≥ 5 or < 5, respectively.
+
+## Web app
+
+A minimal single-user web frontend is bundled in the `cmd/any2anexoj-web` binary. It reuses the existing `internal/trading212` parser, the `internal.BuildReport` pipeline, and the `internal/prettyprinter` formatter, so the rendered table is byte-for-byte identical to the CLI output.
+
+### Run
+
+```bash
+go run ./cmd/any2anexoj-web
+```
+
+The server listens on `:8080` by default. Override the port with the `PORT` environment variable:
+
+```bash
+PORT=9000 go run ./cmd/any2anexoj-web
+```
+
+Then open <http://localhost:8080> in a browser, pick a Trading212 CSV file, and click **Upload**. The rendered Anexo J table appears below the form along with the row count.
+
+### API
+
+The web app exposes two JSON endpoints. Auth is intentionally stubbed (a no-op middleware), and state is kept in process memory only — single user, no persistence.
+
+| Method | Path           | Description                                                                                       |
+|--------|----------------|---------------------------------------------------------------------------------------------------|
+| POST   | `/api/upload`  | `multipart/form-data` with a `csv` file field. Returns `{"table": "<rendered>", "rows": <int>}`. |
+| GET    | `/api/table`   | Returns the most recently rendered table (`{"table": "", "rows": 0}` if none uploaded yet).       |
+
+Example:
+
+```bash
+curl -F csv=@trading212-small.csv http://localhost:8080/api/upload
+curl http://localhost:8080/api/table
+```
+
+> [!NOTE]
+> The web app is single-user and in-memory. Uploads overwrite the previously stored table, and restarting the server clears all state. Auth is a stub — do not expose this service to the public internet without adding real authentication and per-user state first.