Roomies Ledger 🏠💸

A modern expense-splitting app for roommates — track shared purchases, split bills (equal/custom/%), and settle up fast.
Built for hackathons, dorms, apartments, and anyone tired of “who owes who?” texts.

Inspiration

Roommates split groceries, utilities, random Target runs, and it always turns into:

“Did you Venmo me?”
“I paid last time”
“Wait how much do I owe?”

Roomies Ledger makes shared spending easy to track and easy to settle.

What it does

Roomies Ledger lets you:

Sign up / log in and get an auto-created profile
Create or join a household using an invite code
Add expenses with:
- title + date + optional place
- who paid
- split type: equal, custom amounts, percent split
- optional receipt upload
- optional recurring flag (daily/weekly/biweekly/monthly/yearly)
View a clean transaction feed with drill-down details
See net balances and who should pay whom to settle up

How we built it

Frontend: Next.js (App Router) + React + TypeScript
UI: Tailwind CSS + shadcn/ui + lucide-react
State: Central store (useStore) for group context, members, transactions, and UI flows
Backend: Supabase (Postgres + Auth + RLS)
- Auth + Profiles: a trigger creates a profiles row on signup (handle_new_user)
- Groups + Membership: groups + group_members connects users to households and permissions
- Transactions: stored per group with split metadata (equal/exact/percent)
- RPCs: SQL functions for creating groups and joining by invite code
- Security: RLS policies restrict reads/writes to members of a group
Demo mode: /api/seed creates sample users + households for quick judging

Key features

Groups + invite codes

Create a household, share the code, and roommates join in seconds.

3-step transaction flow

A guided add-expense flow: details → amount → split. Keeps the UX fast on mobile.

Multiple split modes

Equal split
Exact custom amounts
Percent split

Optional multi-currency input

Enter an expense in a different currency, store original amount/currency + exchange rate, normalize into the household currency so balances stay consistent.

Recurring expenses

Tag something like rent or utilities as recurring with a simple frequency setting.

Real security (RLS)

Members only see and modify data inside households they belong to.

Challenges we ran into

Getting split logic correct across equal/exact/percent
Keeping balances consistent when optional multi-currency metadata is present
Designing strict RLS policies that still allow smooth group creation/join flows

Accomplishments we’re proud of

Clean mobile-first UX with a fast, guided expense flow
Solid database design with normalized amounts + optional original currency fields
RLS across core tables so data access stays scoped to households
One-click demo seeding for judges