📒 Bahhi Khata — Backend-First Expense Tracker

Bahhi Khata is a backend-first expense tracker built as a proof-of-work engineering project. The focus is on correct backend design, schema ownership, authentication, and real-world evolution, with the frontend intentionally kept simple until the data layer is solid.

This project is meant to resemble a digital khata (ledger) — reliable, structured, and honest — rather than a flashy dashboard.

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🎯 Project Philosophy

• Backend correctness first — APIs, auth, and schema before UI polish
• Schema evolves with features — migrations over guesswork
• No premature abstraction — clarity > cleverness
• Real-world constraints — production DB, cloud hosting, auth flows

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🌟 Live Demo

• Backend API: https://bahhi-khata-backend.onrender.com (Render free tier — may cold start)
• Frontend: Local / in progress

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🚀 Quick Start

Prerequisites

• Node.js 18+
• PostgreSQL 16+ (local or Neon)
• Git

Backend Setup

git clone https://github.com/BahhiKhata/BahhiKhata.git
cd BahhiKhata/backend
npm install
cp .env.example .env

Initialize database:

psql <DATABASE_URL> -f database/schema.sql

Start server:

npm run dev
# or
npm start

Frontend Setup

cd frontend
npm install
npm run dev

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🏗️ Architecture Overview

Frontend (Next.js)
        │
        ▼
Backend API (Express + JWT)
        │
        ▼
PostgreSQL (Neon)

• Stateless JWT authentication
• Strict user-level data ownership
• Hosted on Render + Neon

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📁 Project Structure

Backend

backend/
├── server.js
├── config/db.js
├── routes/
│   ├── auth.js
│   ├── expenses.js
│   └── expenseTypes.js
├── middleware/auth.js
├── database/
│   ├── schema.sql
│   └── migrations/
└── utils/

Frontend

frontend/
├── pages/
│   ├── login.jsx
│   ├── register.jsx
│   ├── expenses.jsx
│   ├── add-expense.jsx
│   └── edit-expense/[id].jsx
├── components/
│   └── Layout.jsx
├── utils/api.js

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📊 Database Schema (Phase 3 — Final)

CREATE EXTENSION IF NOT EXISTS "pgcrypto";

CREATE TABLE users (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    name VARCHAR(100) NOT NULL,
    email VARCHAR(100) UNIQUE NOT NULL,
    password_hash TEXT NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE expense_types (
    id SERIAL PRIMARY KEY,
    name VARCHAR(50) UNIQUE NOT NULL,
    description TEXT,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE expenses (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
    expense_type_id INTEGER NOT NULL REFERENCES expense_types(id),
    amount NUMERIC(10,2) NOT NULL CHECK (amount > 0),
    description TEXT,
    expense_date DATE NOT NULL DEFAULT CURRENT_DATE,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

CREATE INDEX idx_expenses_user_id ON expenses(user_id);
CREATE INDEX idx_expenses_date ON expenses(expense_date);
CREATE INDEX idx_expenses_type ON expenses(expense_type_id);

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🔌 API Overview

Auth

• POST /api/auth/register
• POST /api/auth/login

Expenses (Phase 3)

• GET /api/expenses (supports filters)
• POST /api/expenses
• PUT /api/expenses/:id
• DELETE /api/expenses/:id

Filtering supported via query params:

/api/expenses?from=YYYY-MM-DD&to=YYYY-MM-DD&min=100&max=500

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✅ Phase 3 — Completed Features

• JWT-based authentication
• Expense CRUD (add / edit / delete)
• User-scoped data access
• Date & amount filtering
• Production DB on Neon
• Schema migration experience
• Minimal but functional frontend

Phase 3 intentionally focuses on correctness over polish.

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🛣️ Roadmap

Phase 4 — Analytics & Statistics

• Monthly spending summary
• Category-wise totals
• Daily averages
• Dedicated /stats pages

Phase 5 — UX & Efficiency

• Better edit flows (inline / modal)
• Debounced filters
• Pagination
• Performance improvements

Phase 6 — Bahhi Khata UI Identity

• Ledger-style layout
• Date-grouped expenses
• Calm, paper-like design language

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📝 License

MIT License

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⭐ *This repository represents real backend learning: schema drift, migrations, auth, and production debugging — not just UI