ASP.NET Core Invoice Management System

Project Overview:
Develop an Invoice Management Web Application using Razor pages, React, Vue, or Angular (only one) for the frontend, with ASP.NET Core MVC as the backend. The application will have a single user type, Sales Person, who will manage customer invoices. The app should be optimized for offline functionality, allowing invoice creation and printing using the Epson TM-T82 thermal printer (3-inch roll).
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User Features:
1. User Authentication:
o Employees log in with username and password to access the system.
2. Invoice Creation Flow:
o Step 1: Enter the customer's mobile number.
o Step 2: Enter product details:
 Product Name
 MRP (Maximum Retail Price)
 Discounted Price
 Quantity
 Reward Points (manually input)
o Step 3: The invoice table updates dynamically with:
 Product
 MRP
 Quantity
 Discounted Price
 Rewards
 Total Discounted Price (Discounted Price × Quantity)
3. Draft Invoice Review:
o After adding all items, the Draft Invoice is displayed with the following auto-generated summary:
 Original Bill Amount: Sum of (MRP × Quantity)
 Total Reward Points: Sum of (Reward Points × Quantity)
 Total Discounted Price: Sum of total discounted price for each item
 Old Rewards Utilized: Manual input for old rewards deduction
 Final Amount to Pay: (Total Discounted Price) - (Old Rewards Utilized)
o Salesperson confirms the draft invoice before generating the final invoice.
4. Invoice Generation and Printing:
o After confirmation, the invoice will be printed using the Epson TM-T82 thermal printer.
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Additional Features:
1. Invoice Search:
o Search invoices by:
 Date Range
 Customer Mobile Number
 Invoice Amount
2. Invoice Reports:
o Generate reports based on:
 Daily/Monthly Sales
 Top-selling products
 Total rewards distributed
 Total discounts provided
3. Invoice Copy Printing:
o Allow reprinting of invoice copies upon request.
4. Invoice Editing & History:
o Edit invoices before confirmation and maintain an invoice history for future reference.
5. Export Functionality:
o Allow exporting sales data to CSV/Excel for offline access.
6. Error Handling & Validation:
o Input validation for:
 Mobile number format.
 MRP and Discounted Price (ensure valid prices).
 Quantity (only positive numbers).
o Clear and actionable error messages.
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Backend and Database Considerations (ASP.NET Core MVC):
• Backend: ASP.NET Core MVC with RESTful API architecture for invoice management.
• Database: A single Invoice Table to store invoice data, as there is no need to store customers or products separately.
o Key Fields for the Invoice Table:
 Invoice Number
 Customer Mobile Number
 List of products and their details (MRP, quantity, etc.)
 Date and Time of invoice creation
 Original Bill Amount, Rewards Earned, and Final Amount
• Ensure efficient indexing on fields like date, mobile number, and amount to enable fast search operations.
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Non-functional Requirements:
1. Responsiveness:
o The app should be responsive and work across desktop, tablet, and mobile devices, with an intuitive design that adapts to each screen size.
2. Performance:
o Optimize for low-latency interactions to ensure a smooth experience, particularly in invoice generation and search modules.
3. Offline Capability:
o Provide basic offline functionality for creating and printing invoices when the internet is not available.
o Store temporary data locally and sync with the server when back online.
4. Security:
o Secure login and session management using JWT (JSON Web Token) or ASP.NET Core Identity.
o Ensure that sensitive data such as invoice details is transmitted securely over HTTPS.
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Technology Stack:
1. Frontend:
o Razor pages, React, Vue, or Angular for dynamic user interaction.
o Axios or Fetch API for making HTTP requests to the backend.
2. Backend:
o ASP.NET Core MVC for creating APIs and handling server-side logic.
o Entity Framework Core for ORM to interact with the database.
3. Database:
o SQL Server or SQLite for storing invoices.
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Printing Considerations (Epson TM-T82):
• Ensure that the final invoice printout fits within the 3-inch width of the printer.
• Handle proper formatting for fields such as customer details, product information, and total amounts.
• Use JavaScript libraries such as Web Print or Epson's EPOS SDK for printing.
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Sample API Endpoints (ASP.NET Core MVC):
• User Authentication:
o POST /api/auth/login
o POST /api/auth/logout
• Invoice Management:
o POST /api/invoice/create
o GET /api/invoice/search
o GET /api/invoice/{id}
o PUT /api/invoice/{id}/edit
o GET /api/invoice/report/daily
• Printing:
o POST /api/invoice/{id}/print