add delete application endpoint

Application/Application.Contracts/Applications/DeleteApplication.cs

@@ -0,0 +1,14 @@
+using MediatR;
+
+namespace Application.Contracts.Applications;
+
+public static class DeleteApplication
+{
+    public record struct Command(Guid Id) : IRequest<Response>;
+
+    public abstract record Response;
+
+    public sealed record Success(string Message) : Response;
+
+    public sealed record Failed(string Error) : Response;
+}

Application/Application/Applications/DeleteApplicationHandler.cs

@@ -0,0 +1,59 @@
+using Application.Abstractions.DataAccess;
+using MediatR;
+using Microsoft.EntityFrameworkCore;
+using static Application.Contracts.Applications.DeleteApplication;
+
+namespace Application.Applications;
+
+public class DeleteApplicationHandler : IRequestHandler<Command, Response>
+{
+    private readonly IDatabaseContext _databaseContext;
+
+    public DeleteApplicationHandler(IDatabaseContext databaseContext)
+    {
+        _databaseContext = databaseContext;
+    }
+
+    public async Task<Response> Handle(Command request, CancellationToken cancellationToken)
+    {
+        var unsubmittedApplication = await _databaseContext.UnsubmittedApplications
+            .Where(a => a.Id == request.Id)
+            .FirstOrDefaultAsync(cancellationToken);
+
+        if (unsubmittedApplication is not null)
+        {
+            _databaseContext.UnsubmittedApplications.Remove(unsubmittedApplication);
+            try
+            {
+                await _databaseContext.SaveChangesAsync(cancellationToken);
+            }
+            catch (DbUpdateException e)
+            {
+                return new Failed("Error while removing application from database");
+            }
+
+            return new Success("Ok");
+        }
+
+        var submittedApplication = await _databaseContext.SubmittedApplications
+            .Where(a => a.Id == request.Id)
+            .FirstOrDefaultAsync(cancellationToken);
+
+        if (submittedApplication is null)
+        {
+            return new Failed("No application with such id");
+        }
+
+        _databaseContext.SubmittedApplications.Remove(submittedApplication);
+        try
+        {
+            await _databaseContext.SaveChangesAsync(cancellationToken);
+        }
+        catch (DbUpdateException e)
+        {
+            return new Failed("Error while removing application from database");
+        }
+
+        return new Success("Ok");
+    }
+}

Application/Application/Applications/UpdateApplicationHandler.cs

@@ -60,7 +60,7 @@ await _databaseContext.ApplicationActivities.FirstOrDefaultAsync(x => x.Name ==
         }
         catch (DbUpdateException e)
         {
-            return new Failed("Error while changing application in   database");
+            return new Failed("Error while changing application in database");
         }
 
         return new Success(application.AsDto());

Presentation/Controllers/ApplicationsController.cs

@@ -54,4 +54,18 @@ public async Task<ActionResult<UnsubmittedApplicationDto>> UpdateAsync(
             _ => BadRequest()
         };
     }
+
+    [HttpDelete("{applicationId:guid}")]
+    public async Task<ActionResult<UnsubmittedApplicationDto>> DeleteAsync(Guid applicationId)
+    {
+        var command = new DeleteApplication.Command(applicationId);
+        var response = await _mediator.Send(command, CancellationToken);
+
+        return response switch
+        {
+            DeleteApplication.Success result => Ok(result.Message),
+            DeleteApplication.Failed result => BadRequest(result.Error),
+            _ => BadRequest()
+        };
+    }
 }