Wallet — euro spending in CAD and USD

You spent €52.30 in Berlin. Your Canadian card billed you CA$85.94. Was that fair? This converts every purchase at the rate the European Central Bank published on the day you spent it — and shows what the card's markup cost.

▶ Try it now, no install

• The wallet — record purchases and convert them, entirely in your browser
• The capture page — photograph a receipt on your phone and it reads the figures

Running with no server. Watch the Sunday purchase (Deutsche Bahn, 6 Sep): the ECB published nothing that day, so it takes Friday's rate and says so — +2d.

Read the full write-up → — how the screenshot reader decides what an amount is, why "real time" is the wrong promise for a card rate, and every bug this has had. (Or open docs/index.html locally.)

What the conversion actually cost

A Canadian card used in Europe doesn't bill euros. CIBC converts at the Visa rate and adds 2.5%, so the export shows CAD already converted, at a rate you were never told. Because the ECB rate is stored per transaction date, the comparison is free:

2026-09-02  REWE SAGT DANKE     €52.30
            billed by the card  CA$85.94
            at the ECB rate     CA$83.85
            the conversion cost CA$ 2.09   (2.49%)

When the original euro figure can't be recovered from the description, the row is refused rather than guessed at — a 200 SEK lunch booked as EUR 200 is a twenty-fold error that looks entirely plausible.

The part that's easy to get wrong

The ECB publishes on business days only — no weekend rows at all, and the longest gap in the series is five days. So a Sunday purchase has no rate of its own. This walks back to the last published day and records which day it used:

Spent on	Rate from	Lag
Tue 8 Sep 2026	8 Sep	0
Sun 6 Sep 2026	4 Sep	2
Easter Sun 5 Apr 2026	2 Apr	3

It never reaches forward for a nearer rate. 5 April is one day from the 7th and three from the 2nd, but the 7th hadn't happened yet — using it would make a closed month's total change every time the file was refreshed.

Run it

pip install -r requirements.txt
python app.py                        # http://127.0.0.1:5004
pip install -r requirements-ocr.txt  # optional: read receipts from screenshots

The first run caches the ECB history — one 640 KB file back to 1999 — then works offline. No account, no API key, no bank connection.

Getting data in: a watched folder your phone already syncs, a .qfx export (which carries the bank's own rate and id), a CSV in any layout, or typed by hand. data/sample-statement.csv is included to try it.

Where the code is

Four packages and three files at the root. The packages are layered, and the layering is asserted by tests/test_structure.py rather than left to convention — nothing imports upward — so this is also the dependency order:

core/     money, paths, fetch,     the primitives; no first-party imports,
          auth                     and who is allowed in at all
fx/       fxrates, fxcost,         the euro series, what a conversion costs,
          fxlive, pounds           and the CAD->GBP side trip
domain/   db, ledger, cards,       the ledger, and everything derived from it
          budgets, goals, trends,
          upcoming, export
ingest/   layout, importers, ofx,  getting purchases in: files, folders and
          ocr, receipts, sources   screenshots
app.py    the routes, and nothing else
wsgi.py   the entry point a real server uses -- gunicorn wsgi:application

Those two stay at the root because they're named from outside the repo (the Dockerfile CMD, the Fly and Render configs) and Flask resolves templates/ relative to the module the app is built in.

Hosting it

It binds 127.0.0.1 with no password because it holds your spending history, and it refuses to start reachable without one. See DEPLOYMENT.md for the Fly.io walkthrough and what the protection is and isn't.

Tests

pytest -q

984 tests, 100% of 2,875 statements — and that figure is itself checked, so it can't quietly go stale.

License

MIT — see CONTRIBUTING.md for setup and conventions.