Catch-Up Backend

Overview

Catch-Up Backend is a web application designed to assist with onboarding. This project represents only the backend part of the entire application. The complete system also includes:

• Frontend built with React + Vite (TypeScript)
• Mobile app developed using .NET MAUI

Features

• Authentication & Authorization: Secure JWT-based authentication with support for token validation and cookie-based access.

• Real-Time Communication: SignalR integration for real-time notifications and updates.

• Database Management: Entity Framework Core with SQL Server for database operations and migrations.

• Task Management: Models and services for managing tasks, categories, and related content.

• Event Management: Support for creating and managing events with descriptions.

• Notification System: Real-time notifications with SignalR hubs and DTOs for structured data transfer.

• Firebase Integration: Firebase support for additional services like push notifications.

• CORS Support: Configured to allow cross-origin requests for seamless frontend-backend communication.

• Swagger Documentation: Integrated Swagger/OpenAPI for API documentation and testing.

• File sharing/downloading.

• Archived and Deleted States.

  Example

  
  

  StateEnum State property is used to track the status (or lifecycle) of a FAQ entry using the StateEnum enum.

      public class FaqModel
      {
          [Key]
          public int Id { get; set; }
          public string Question { get; set; }
          public string Answer { get; set; }
          [ForeignKey("MaterialsId")]
          public int? MaterialId { get; set; }
          [ForeignKey("CreatorId")]
          public Guid CreatorId { get; set; }
          public StateEnum State { get; set; }
          public FaqModel(string question, string answer, int? materialId, Guid creatorId)
          {
              this.Question = question;
              this.Answer = answer;
              this.MaterialId = materialId;
              State = StateEnum.Active;
              CreatorId = creatorId;
          }
      }

  
  

  State Value Meaning:

  • Active (0) - The entry is visible and currently in use.
  • Archived (5) - The entry is no longer active, but kept for reference.
  • Deleted (10) - The entry is logically deleted (soft delete) and not shown to users.
    
    

      public enum StateEnum
      {
          Active = 0,
          Archived = 5,
          Deleted = 10
      }

  Example of soft Delete.

      public async Task<bool> DeleteAsync(int faqId)
      {
          var faq = await _context.Faqs.FindAsync(faqId);
          if (faq == null)
              return false;
          try
          {
              faq.State = StateEnum.Deleted;
              _context.Faqs.Update(faq);
              await _context.SaveChangesAsync();
          }
          catch (Exception ex)
          {
              throw new Exception("Error: Faq Delete: " + ex);
          }
          return true;
      }

Technologies Used

• .NET 8

• Entity Framework Core (SQL Server)

• SignalR for real-time communication

• Firebase Admin SDK

• JWT Authentication

  See more

  
  

  This code registers and configures JWT Bearer Authentication in an ASP.NET Core app

   //Authentication
   builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)   // this tells .NET to use JWT  bearer authentication as the default one
       .AddJwtBearer(options => {                                               // comapnySettings fot the JWT bearer authentication
               options.TokenValidationParameters = new TokenValidationParameters    // this object contains all of the rules for validating
           {
               ValidateIssuerSigningKey = true,                                 // this tells .NET to validate the issuer signing key
               IssuerSigningKey = new SymmetricSecurityKey(                     // this gets the secret key from the secret user config and converts it to a byte array
                   Encoding.ASCII.GetBytes(builder.Configuration["Jwt:AccessTokenSecret"])
               ),
               ValidateIssuer = true,                                           // tells .NET to validate who created the token 
               ValidIssuer = builder.Configuration["Jwt:Issuer"],               // sets the issuer to the one from the user secrets (Issuer)
               ValidateAudience = true,                                         // tells .NET to check who the token is intended for
               ValidAudience = builder.Configuration["Jwt:Audience"],           // sets the audience to the one from the user secrets (Audience)
               ClockSkew = TimeSpan.Zero                                        // sets a time window for the token to be valid (In production change to ~10sec), because there might be a situation when token is still valid on the                         client but not on the server.
         };
  
         options.Events = new JwtBearerEvents                                 // reading the token from the cookie
         {
             OnMessageReceived = context => {                                 // when a request comes in, this function will run
                 context.Token = context.Request.Cookies["accessToken"];      // get the token from the "accessToken" cookie insteaf of the Authorization header
                 return Task.CompletedTask;
             }
         };
     });

  This is a helper method to manually extract the userId from a JWT token found in the request.

      public static class TokenHelper
      {
          public static Guid GetUserIdFromTokenInRequest(HttpRequest request)
          {
              var jwtToken = new JwtSecurityTokenHandler().ReadJwtToken(
                  request.Headers["Authorization"].ToString().Substring("Bearer ".Length).Trim()
              );
              var userId = Guid.Parse(jwtToken.Claims.First(c => c.Type == "nameid").Value);
  
              return userId;
          }
      }

  Exmple of use

    [HttpGet]
    [Route("GetUserSchooling/{schoolingId:int}")]
    public async Task<IActionResult> GetUserSchooling(int schoolingId)
    {
        var userId = TokenHelper.GetUserIdFromTokenInRequest(Request);
        var schooling = await _schoolingService.GetById(schoolingId, userId);
  
        return schooling != null
            ? Ok(schooling)
            : NotFound(new { message = "Schooling not found." });
    }

• Swagger/OpenAPI

  Examples

  
  

• SMTP for email notifications

Project Structure

• Controllers: Handle API logic (e.g., NewbieMentorController for managing mentor assignments).

  Example

  
  

• Services: Contain business logic (e.g., EmailService, NotificationService).

  Example

  
  

• Repositories: Interfaces and implementations for data access.

  Example

  
  

• Models: Definitions of data structures (e.g., UserModel, NewbieMentorModel).

  Example

  
  

• Migrations: Handle changes to the database schema.

  Example

  
  

• Hubs: Handle real-time communication (e.g., NotificationHub).

  See more

  
  

      public class NotificationHub : Hub
      {
          private readonly IRefreshTokenRepository _refreshTokenRepository;
      
          public NotificationHub(IRefreshTokenRepository refreshTokenRepository)
          {
              _refreshTokenRepository = refreshTokenRepository;
          }
      
          public override async Task OnConnectedAsync() 
          {
      
              var accessToken = Context.GetHttpContext()?.Request?.Query["access_token"].ToString();
            
              Guid userId;
      
              if (string.IsNullOrEmpty(accessToken))
              {
                  userId = TokenHelper.GetUserIdFromTokenInRequest(Context.GetHttpContext()?.Request);
              }
              else
              {
                  var jwtToken = new JwtSecurityTokenHandler().ReadJwtToken(accessToken);
                  userId = Guid.Parse(jwtToken.Claims.First(c => c.Type == "nameid").Value);
              }
      
              await Groups.AddToGroupAsync(Context.ConnectionId, userId.ToString());
      
              await base.OnConnectedAsync();
          }
      
          public override async Task OnDisconnectedAsync(Exception exception)
          {
              var accessToken = Context.GetHttpContext()?.Request?.Query["access_token"].ToString();
              var jwtToken = new JwtSecurityTokenHandler().ReadJwtToken(accessToken);
              var userId = Guid.Parse(jwtToken.Claims.First(c => c.Type == "nameid").Value);
      
              await Groups.RemoveFromGroupAsync(Context.ConnectionId, userId.ToString());
      
              await base.OnDisconnectedAsync(exception);
          }
      }

• DTO (Data Transfer Object): Used for transferring data between layers of the application. Allow for the separation of business logic from the data transmitted via the API.

  Example

  
  

    public class RoadMapDto
    {
        public int Id { get; set; }
        public Guid NewbieId { get; set; }
        public Guid CreatorId { get; set; }
        public string? CreatorName { get; set; }
        public string? Title { get; set; }
        public string? Description { get; set; }
        public DateTime? AssignDate { get; set; }
        public DateTime? FinishDate { get; set; }
        public StatusEnum? Status { get; set; }
        public decimal? Progress { get; set; }
    }