Add Global Exception Handling

src/Imprink.Application/Exceptions/BaseApplicationException.cs

@@ -0,0 +1,7 @@
+namespace Imprink.Application.Exceptions;
+
+public abstract class BaseApplicationException : Exception
+{
+    protected BaseApplicationException(string message) : base(message) { }
+    protected BaseApplicationException(string message, Exception innerException) : base(message, innerException) { }
+}

src/Imprink.Application/Exceptions/NotFoundException.cs

@@ -0,0 +1,7 @@
+namespace Imprink.Application.Exceptions;
+
+public class NotFoundException : BaseApplicationException
+{
+    public NotFoundException(string message) : base(message) { }
+    public NotFoundException(string message, Exception innerException) : base(message, innerException) { }
+}

src/Imprink.Application/Users/DeleteUserRoleHandler.cs

@@ -1,3 +1,4 @@
+using Imprink.Application.Exceptions;
 using Imprink.Application.Users.Dtos;
 using Imprink.Domain.Entities.Users;
 using MediatR;
@@ -10,7 +11,8 @@ public class DeleteUserRoleHandler(IUnitOfWork uw) : IRequestHandler<DeleteUserR
 {
     public async Task<UserRoleDto?> Handle(DeleteUserRoleCommand request, CancellationToken cancellationToken)
     {
-        if (!await uw.UserRepository.UserExistsAsync(request.Sub, cancellationToken)) return null;
+        if (!await uw.UserRepository.UserExistsAsync(request.Sub, cancellationToken)) 
+            throw new NotFoundException("User with ID: " + request.Sub + " does not exist.");
 
         var userRole = new UserRole
         {

src/Imprink.Application/Users/GetUserRolesHandler.cs

@@ -1,3 +1,4 @@
+using Imprink.Application.Exceptions;
 using Imprink.Application.Users.Dtos;
 using MediatR;
 
@@ -9,7 +10,8 @@ public class GetUserRolesHandler(IUnitOfWork uw): IRequestHandler<GetUserRolesCo
 {
     public async Task<IEnumerable<RoleDto>> Handle(GetUserRolesCommand request, CancellationToken cancellationToken)
     {
-        if (!await uw.UserRepository.UserExistsAsync(request.Sub, cancellationToken)) return [];
+        if (!await uw.UserRepository.UserExistsAsync(request.Sub, cancellationToken)) 
+            throw new NotFoundException("User with ID: " + request.Sub + " does not exist.");
         
         var roles = await uw.UserRoleRepository.GetUserRolesAsync(request.Sub, cancellationToken);
 

src/Imprink.Application/Users/SetUserRoleHandler.cs

@@ -1,3 +1,4 @@
+using Imprink.Application.Exceptions;
 using Imprink.Application.Users.Dtos;
 using Imprink.Domain.Entities.Users;
 using MediatR;
@@ -10,7 +11,8 @@ public class SetUserRoleHandler(IUnitOfWork uw) : IRequestHandler<SetUserRoleCom
 {
     public async Task<UserRoleDto?> Handle(SetUserRoleCommand request, CancellationToken cancellationToken)
     {
-        if (!await uw.UserRepository.UserExistsAsync(request.Sub, cancellationToken)) return null;
+        if (!await uw.UserRepository.UserExistsAsync(request.Sub, cancellationToken))
+            throw new NotFoundException("User with ID: " + request.Sub + " does not exist.");
 
         var userRole = new UserRole
         {

src/Imprink.WebApi/Controllers/Users/UserRoleController.cs

@@ -11,7 +11,7 @@ namespace Imprink.WebApi.Controllers.Users;
 public class UserRoleController(IMediator mediator) : ControllerBase
 {
     [Authorize]
-    [HttpGet("/me")]
+    [HttpGet("me")]
     public async Task<IActionResult> GetMyRoles()
     {
         var claims = User.Claims as Claim[] ?? User.Claims.ToArray();
@@ -23,7 +23,7 @@ public class UserRoleController(IMediator mediator) : ControllerBase
     }
     
     [Authorize(Roles = "Admin")]
-    [HttpPost("/set")]
+    [HttpPost("set")]
     public async Task<IActionResult> SetUserRole(SetUserRoleCommand command)
     {
         var userRole = await mediator.Send(command);
@@ -35,7 +35,7 @@ public class UserRoleController(IMediator mediator) : ControllerBase
     }
     
     [Authorize(Roles = "Admin")]
-    [HttpPost("/unset")]
+    [HttpPost("unset")]
     public async Task<IActionResult> UnsetUserRole(DeleteUserRoleCommand command)
     {
         var userRole = await mediator.Send(command);

src/Imprink.WebApi/Middleware/ExceptionHandlingMiddleware.cs

@@ -0,0 +1,75 @@
+using System.Net;
+using System.Text.Json;
+using Imprink.Application.Exceptions;
+
+namespace Imprink.WebApi.Middleware;
+
+public class ExceptionHandlingMiddleware(
+    RequestDelegate next, 
+    ILogger<ExceptionHandlingMiddleware> logger)
+{
+    public async Task InvokeAsync(HttpContext context)
+    {
+        try
+        {
+            await next(context);
+        }
+        catch (Exception ex)
+        {
+            var (_, _, shouldLog) = GetStatusCodeAndMessage(ex);
+            
+             if (shouldLog)
+             {
+                 logger.LogError(ex, "An unhandled exception occurred: {Message}", ex.Message);
+             }
+             else
+             {
+                 logger.LogInformation("Handled: {Message}", ex.Message);
+             }
+                    
+            await HandleExceptionAsync(context, ex);
+        }
+    }
+
+    private static async Task HandleExceptionAsync(HttpContext context, Exception exception)
+    {
+        context.Response.ContentType = "application/json";
+
+        var (statusCode, message, _) = GetStatusCodeAndMessage(exception);
+        
+        context.Response.StatusCode = (int)statusCode;
+
+        var response = new
+        {
+            error = new
+            {
+                message,
+                timestamp = DateTime.UtcNow,
+            }
+        };
+
+        var jsonResponse = JsonSerializer.Serialize(response, new JsonSerializerOptions
+        {
+            PropertyNamingPolicy = JsonNamingPolicy.CamelCase
+        });
+
+        await context.Response.WriteAsync(jsonResponse);
+    }
+
+    private static (HttpStatusCode statusCode, string message, bool shouldLog) GetStatusCodeAndMessage(Exception exception)
+    {
+        return exception switch
+        {
+            NotFoundException => (HttpStatusCode.NotFound, exception.Message, false),
+            _ => (HttpStatusCode.InternalServerError, "An internal server error occurred", true)
+        };
+    }
+}
+
+public static class GlobalExceptionHandlingMiddlewareExtensions
+{
+    public static void UseGlobalExceptionHandling(this IApplicationBuilder builder)
+    {
+        builder.UseMiddleware<ExceptionHandlingMiddleware>();
+    }
+}

src/Imprink.WebApi/Startup.cs

@@ -140,13 +140,13 @@ public static class Startup
             }
         }
 
+        app.UseGlobalExceptionHandling();
         app.UseRequestTiming();
         
         if (env.IsDevelopment())
         {
             app.UseSwagger();
             app.UseSwaggerUI();
-            app.UseDeveloperExceptionPage();
         }
         else
         {