Split Four Ways — Google Sheets backed

A shared expense splitter whose data lives in your own Google Sheet. The frontend (index.html) is a static page you deploy to Vercel or Render. It talks to the Sheet through a free Google Apps Script web app — so you never run a server, and nothing gets lost.

  Browser (index.html on Vercel/Render)
        │  fetch()
        ▼
  Google Apps Script web app  ──►  your Google Sheet (People / Expenses / Settings)

Why Apps Script and not "frontend straight to Sheets"? A browser-only page can't hold a Google credential safely — it would be visible to anyone who opens the page. The Apps Script is a tiny gatekeeper that Google hosts for free and that keeps the write access on its side.

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Part 1 — Create the Sheet + backend (10 min, once)

1. Go to https://sheets.google.com and create a blank spreadsheet. Name it e.g. Split Four Ways. You don't need to add any tabs — the script makes them.
2. In the Sheet: Extensions → Apps Script.
3. Delete the sample function myFunction() {}, then paste the entire Code.gs file from this folder. Click the Save icon.
4. Click Deploy → New deployment.
   • Click the gear next to "Select type" → choose Web app.
   • Description: anything (e.g. v1).
   • Execute as: Me.
   • Who has access: Anyone.
   • Click Deploy.
5. The first time, Google asks you to Authorize access → pick your account → "Advanced" → "Go to (project) (unsafe)" → Allow. (It's your own script touching your own Sheet; this screen is normal for personal scripts.)
6. Copy the Web app URL it shows. It ends in /exec. Keep it handy.

Test it: paste YOUR_EXEC_URL?action=load into a browser tab. You should see JSON with Akshay, Praney, Vivek, Logesh. If you do, the backend works.

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Part 2 — Point the frontend at your Sheet

Open index.html and edit the two lines near the top of the <script>:

var API_URL   = "https://script.google.com/macros/s/XXXXX/exec";  // your /exec URL
var API_TOKEN = "";                                               // leave "" for now

Save. That's the only change needed.

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Part 3 — Deploy the frontend

Option A — Vercel (easiest)

1. Put this folder in a GitHub repo (or just the index.html).
2. Go to https://vercel.com → Add New → Project → import the repo.
3. Framework preset: Other. No build command, no output dir needed — it's a static file. Click Deploy.
4. You get a URL like https://split-four-ways.vercel.app. Share it with the other three.

No GitHub? Install the CLI (npm i -g vercel), run vercel inside this folder, follow the prompts.

Option B — Render

1. Push this folder to a GitHub repo.
2. Render dashboard → New → Static Site → connect the repo.
3. Build command: leave blank. Publish directory: . (a single dot).
4. Create Static Site → you get a URL to share.

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How it works day to day

• Everyone opens the same deployed URL. Each expense they add writes a row to the Expenses tab; the page re-reads the Sheet every ~10 seconds so all four see updates within a few seconds.
• Each expense can have a category, a date, and multiple items (the total is the sum of the items). Use the month filter at the top of the Expenses list to see a month's spending and the by-category breakdown ("we spent ₹8k on food this month").
• Rename people, add a person, or change currency under People & currency — it all saves to the Sheet.
• Tap any person's balance tile to open their profile: how much they paid out, their share, their overall net, and a person-by-person breakdown — for each other person, who owes whom (mutual debts are netted / subtracted).
• Settle up: when someone pays a debt back, tap Mark paid on the settle-up row (or record it manually under Payments & settle-ups). The payment clears that much of the balance so old debts don't linger. Every payment is logged in the Settlements tab and can be deleted.

Tabs the sheet keeps

People, Expenses, Settings, and Settlements. New columns (category, date, items on Expenses) are added automatically — an older sheet keeps working and just gains the new columns.

Updating the backend

After pasting a new Code.gs, you must Deploy → Manage deployments → (edit the pencil) → Deploy to publish it to the same /exec URL. Just saving in the editor is not enough.

• You can open the Google Sheet directly any time to see or fix the raw data. Columns: Expenses = id, desc, amount, paidBy, splitAmong, createdAt; People = id, name, order.

Security — PINs and roles live on the server

Logins are enforced by the backend, not the webpage:

• The 4 PINs are stored only as one-way hashes inside the Apps Script project (in Script Properties) — they are not in index.html, so no one can read them from "View Source".
• When someone enters the right PIN, the server hands the browser a signed token (stamped with a secret only the script knows). Every change must carry a valid token, and the token's role has to allow that action:
  • admin (Vivek): everything, incl. add/remove/rename people and reset PINs
  • editor (Akshay, Praney): add/edit/delete expenses, settle up, currency
  • viewer (Logesh): read-only — the server refuses every write
• A view-only person therefore cannot write even if they tamper with the page, and you can't gain powers by creating a second profile with someone's name (roles are tied to the real account, not the display name).

Changing PINs

• Anyone can change their own PIN in the app under Your PIN → Change your PIN.
• The admin can reset anyone's PIN there too (admin-only panel).
• Forgot a PIN / locked out? In the Apps Script editor open Code.gs, edit the id and pin at the top of resetPinManual_(), press Run once.
• To force everyone to log in again, delete the AUTH_SECRET row in Project Settings → Script Properties.

Honest limits: reads (the load endpoint) are still open to anyone with the /exec URL — that's fine, the expense data isn't sensitive. And once you are logged in, your own browser holds your own token; that's expected. What's now impossible: reading other people's PINs, logging in as someone else, or a viewer making any change.

Updating the backend later

If you change Code.gs, you must Deploy → Manage deployments → (edit) → Deploy to publish the new version to the same /exec URL. Just saving isn't enough.

Troubleshooting

• Page says "Couldn't reach the Google Sheet" — the API_URL is wrong, or the web app wasn't deployed to Anyone. Re-check Part 1 steps 4–6.
• Changes don't appear for others — they will within ~10s; a hard refresh forces it. Make sure everyone uses the same deployed URL.
• "Your session ended — please log in again" — your login token expired (they last 30 days) or you rotated AUTH_SECRET. Just log in again.
• A friend can't log in after the security update — make sure you redeployed Code.gs (Deploy → Manage deployments → Edit → Deploy). The new login only works once the new backend is live.
• Everyone's PINs start at the originals (Akshay 2005, Praney 3699, Vivek 7733, Logesh 1234). Because those were public before, change them after the update (Your PIN → Change your PIN).