SDR → MNST

A one-screen PWA for turning deposit-return bottles into Monster Beverage (MNST) stock.

In Portugal a returned bottle is worth €0.10. This logs each batch of bottles, stacks the cash, and — once there's at least a whole euro — records it as a stock buy. Weekly target is shown on a ruler (€10/week). Single user, one Supabase project behind it, no build step.

Why whole euros (the one real design decision)

You can only buy stock in whole currency units, so an investment always floors to the euro. The leftover cents don't vanish and don't get rounded away: on "Mark as invested", floor(total) is written to the investments table, and total − floor(total) is written straight back into bottle_log as a row with source: 'carry' and that exact value.

That carry row:

• seeds next week's pot — it's already counted in the running total on the next load;
• does not count as a bottle — the "N bottles" counter and the weekly ruler both exclude source carry (and seed), so a €0.40 carry-over never looks like 4 bottles collected or inflates the week's progress.

So the running total is always honest about fractional amounts, and every euro that goes in is a euro you could actually have invested.

Sources

Each batch is tagged, and the split line separates them:

Source	Shown as	Meaning
found	profit	picked up from the street / a bin
scam	scam	machine trickery (over-counted a return)
own_deposit	reclaimed	returning bottles that were already yours
others	others	recycled on someone else's behalf

seed (opening balance) and carry (see above) are internal — they show on the history tape but never in the bottle count or the ruler.

Data model (Supabase)

Two tables:

• bottle_log — qty, source, value, unit_value, logged_date, created_at, invested_at (null until a batch is marked invested; all pending rows get the same invested_at timestamp when you invest).
• investments — invested_at, amount (the whole-euro part), share_price and shares (both optional — fill them in if you know the fill price).

Running it

It's a static site — index.html + sw.js + manifest.json + icons, nothing to build. Serve the folder from any static host (GitHub Pages, or python -m http.server locally) and open it.

On first load it asks for the Supabase project URL and an anon / publishable key. Those are kept in localStorage only — never in the code. The key needs read/write on bottle_log and investments; scope the project's RLS to that. Use the conn button in the header to change or clear the saved connection.

Stack

Vanilla JS, Supabase JS (ESM from esm.sh), a service worker (network-first for navigations so a deploy is picked up immediately, cache-first for the static shell). No framework, no bundler.

Known debt: the update lag

The service worker precaches the shell (./, ./index.html) with a plain fetch, which can be served from the browser HTTP cache. GitHub Pages sends HTML with Cache-Control: max-age=600, so right after a deploy a returning user can keep seeing the previous version for up to ~10 minutes (plus one reload) before the SW cache refills. It's short and self-healing, so it's left as-is; the fix is to precache with cache: 'reload' (c.addAll(SHELL.map(u => new Request(u, { cache: 'reload' }))) in sw.js).