SplitFinance - A Splitwise-Style Expense Sharing App

A full-stack expense-splitting app: track shared expenses across a group, let an AI categorise, parse and read them (typed or photographed), ask it about your balances, and simplify group debt into at most n−1 settlement payments.

🔗 Live at splitfinance.org · API health check: api.splitfinance.org

React (Vite) · Node/Express · PostgreSQL + Prisma · Socket.IO · Cohere · Docker · Terraform on AWS EC2 · GitHub Actions CI/CD

Both images are generated by driving the real app in a browser (e2e/tests/screenshots.spec.js), so they can't drift from what the app actually renders — regenerating them is npm run screenshots.

🏛️ How it fits together

flowchart LR
    U["Browser"] -->|HTTPS| C

    subgraph EC2["AWS EC2 · Docker Compose"]
        C["Caddy<br/>auto-TLS · CSP · security headers"]
        F["React SPA<br/>vite build, served static"]
        A["Express API<br/>JWT auth · Prisma"]
        DB[("PostgreSQL<br/>persistent EBS volume")]
        C --> F
        C --> A
        F -->|Socket.IO| A
        A --> DB
    end

    A --> CO["Cohere<br/>categorisation · NL parsing<br/>receipt vision · assistant"]
    A -->|security logs| CW["CloudWatch Logs"]
    A --> RE["Resend<br/>password-reset email"]
    SSM["SSM Parameter Store<br/>secrets fetched at boot"] -.-> EC2
    GH["GitHub Actions<br/>test · lint · deploy via OIDC"] -.-> EC2

28 REST endpoints across 8 resources. Full tech stack, package layout, and subsystem-by-subsystem detail (AI, WebSockets, spending insights, password reset) are in docs/ARCHITECTURE.md.

Everything below is the detail — Features first, then the algorithm and money write-ups, then Getting Started. Security, testing, the database schema, and deployment each have their own doc, linked from the matching section below.

This is the beginning of the README. Read the rest at the original. Read the full README ↗