🎓 Attend-ED | Core API & Geospatial Backend

The robust, highly secure ASP.NET Core backend powering the Attend-ED student portal. Designed to solve modern academic challenges like proxy-attendance and location-spoofing, this API leverages PostGIS spatial querying and hardware-level device binding to ensure absolute academic integrity.

✨ Core System Architecture

1. Geospatial Verification Engine

Built on top of NetTopologySuite and PostgreSQL's PostGIS extension, the system utilizes high-accuracy coordinate math (SRID 4326) to enforce physical attendance.

• Evaluates incoming mobile GPS coordinates against dynamically generated lecture geofences.
• Accommodates GPS jitter and indoor signal degradation with configurable margin-of-error radii (e.g., 50-100m).

2. Hardware-Level Device Binding

Eliminates proxy sign-ins (students logging in for their friends) by permanently binding a user's database record to a unique cryptographic hardware token generated by their primary device.

• First-time logins silently register the device's hardware UUID.
• Subsequent logins from unrecognized devices are blocked at the middleware level with a 401 Unauthorized strict proxy-prevention alert.

3. Role-Based Access Control (RBAC)

Secured via short-lived JSON Web Tokens (JWT). The API strictly segregates endpoints using [Authorize(Roles = "Student")] and [Authorize(Roles = "Lecturer")] attributes, ensuring zero cross-pollution of data or capabilities.

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🛠️ Tech Stack & Infrastructure

• Framework: ASP.NET Core Web API (C#)
• ORM: Entity Framework Core
• Database: Serverless PostgreSQL via Neon DB
• Spatial Data: Npgsql.EntityFrameworkCore.PostgreSQL.NetTopologySuite
• Deployment: Render / AWS

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🚀 Local Setup & Development

Prerequisites

• .NET 8.0 SDK (or higher)
• PostgreSQL running locally or a Neon DB connection string.

Configuration

1. Clone the repository.
2. Update the appsettings.Development.json with your database connection string.

Note on Neon DB / Pooling: Use the ADO.NET standard Key-Value format to ensure EF Core CLI compatibility: "DefaultConnection": "Host=ep-...;Database=neondb;Username=...;Password=...;Ssl Mode=Require;"

Database Migrations

The schema is code-first. Apply the migrations to build your database:

dotnet ef database update

Running the Server

dotnet run

The API will be available at https://localhost:7042. Test endpoints via the automatically generated Swagger UI.

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📡 Key API Endpoints

Method	Endpoint	Description	Auth Required
POST	/api/Auth/login	Authenticates user & validates hardware token	No
POST	/api/Student/attendance	Verifies GPS coordinates against class geofence	Yes (Student)
GET	/api/Student/schedule	Fetches active classes created in the last 24h	Yes (Student)
GET	/api/Student/reports/summary	Aggregates attendance data for dashboard	Yes (Student)

🛡️ Edge Cases Handled

• PostGIS Coordinate Trap: Correctly maps incoming front-end (Lat, Lng) data to the NetTopologySuite (X: Longitude, Y: Latitude) standard to prevent spatial translation errors.
• Database Compute Sleep: Configured resilience for Neon DB's serverless cold-starts during EF Core Migrations.