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Feature Specification Document: Chat App with Expense Tracking and Bill Splitting

1. Overview

This feature integrates a chat application designed for team members and roommates, combining real-time communication with expense tracking and bill splitting functionality. The web app will allow users to communicate seamlessly while managing shared expenses, simplifying the process of tracking debts and settling bills among roommates or team collaborators.

2. Goals

Problems Solved

• Eliminate confusion and miscommunication around shared expenses among roommates or team members.
• Provide a straightforward way to log, track, and split expenses without requiring external spreadsheets or separate apps.
• Facilitate transparent and real-time updates on debts and payments.

Opportunities Created

• Increase team/roommate cohesion through transparent financial interactions.
• Encourage timely settlements of shared bills.
• Expand into a broader financial collaboration tool integrated with communication features.

Success Metrics

• User Engagement: Number of active users interacting with expense features weekly.
• Feature Usage: Percentage of chats utilizing the expense tracking feature.
• Settlement Rate: Frequency and timeliness of bill settlements recorded in the app.
• User Satisfaction: Feedback collected via surveys or app ratings related to expense management.

3. User Stories

• As a team member, I want to add an expense in the chat so that everyone is aware of shared costs.
• As a roommate, I want to split the bill automatically among participants so that I do not have to calculate individual shares manually.
• As a user, I want to see the real-time expense updates in the chat so that I am always aware of the current balances.
• As a user, I want to mark an expense as paid so that debts are accurately updated and visible in the group.
• As a team member, I want to receive notifications about new expenses and payments so that I stay informed without constantly checking the chat.

4. Acceptance Criteria

User Story 1: Add an Expense

• Users can input expense amount, description, and select involved participants.
• The expense is posted as a message in the chat visible to all participants.
• The total amount and individual shares (if splitting) are displayed.

User Story 2: Automatic Bill Splitting

• Upon adding an expense, the app computes each participant’s share evenly or by custom amounts.
• Participants can view individual owed amounts per expense.
• The splits are adjustable before confirmation.

User Story 3: Real-Time Expense Updates

• Expense and payment updates appear instantly in the chat without page reload.
• Users see current balances with each participant, updated live.

User Story 4: Mark Expense as Paid

• Users can mark their share of an expense as paid.
• Payment status updates in real-time for all participants.
• Paid balances update accordingly.

User Story 5: Notifications

• Users receive notifications (in-app and optionally email) when a new expense is added or payment status changes.
• Notifications include relevant details and link back to the chat.

5. Technical Design

Architecture

• Frontend: React.js web application with real-time UI updates using WebSocket or similar technology (e.g., Socket.IO).
• Backend: Node.js + Express REST API combined with WebSocket server for push updates.
• Database: NoSQL (e.g., MongoDB) or relational DB (e.g., PostgreSQL) to store users, chats, expenses, and payment records.
• Authentication: JWT-based user authentication with secure login sessions.
• Notifications: Push notifications using Web Push API and optional email notifications via an external service (e.g., SendGrid).

Performance & Scalability

• WebSocket connections managed through scalable infrastructure (e.g., Redis Pub/Sub for multi-server message broadcasting).
• Database indexing on users and expenses to optimize read/write performance.
• Caching frequently accessed data at frontend or CDN layer.

Security

• HTTPS enforced for all communications.
• Input validation and sanitation to prevent injection attacks.
• Authentication and authorization checks for all expense management endpoints.
• Data encryption at rest and in transit.
• Audit logging for expense and payment actions.

6. Future Considerations

• Mobile Apps: Native Android/iOS apps or Progressive Web App (PWA) support.
• Multi-Currency Support: Allow users in different countries to split bills with currency conversion.
• Advanced Expense Types: Support for recurring expenses, installment payments, and expense categories.
• Integration: Sync with bank accounts, payment gateways (e.g., PayPal, Venmo) for automatic settlements.
• Analytics Dashboard: Visual summaries of expenses, spending trends, and payment history.
• Role-Based Permissions: Admin controls to approve expenses or manage participants.
• AI Assistant: Automated expense suggestions or reminders for upcoming bills.

Estimated Development Effort: 30 days (including design, implementation, testing, and deployment)

This specification provides a comprehensive guide enabling developers to initiate build phases with clear targets and measurable outcomes.