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ApplicationLayer/Services/VisaApplications/Handlers/IVisaApplicationRequestsHandler.cs

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+using ApplicationLayer.Services.VisaApplications.Models;
+using ApplicationLayer.Services.VisaApplications.Requests;
+
+namespace ApplicationLayer.Services.VisaApplications.Handlers;
+
+public interface IVisaApplicationRequestsHandler
+{
+    /// Returns all applications for approving authorities
+    Task<List<VisaApplicationPreview>> GetPendingAsync(CancellationToken cancellationToken);
+
+    /// Returns all applications of one applicant
+    Task<List<VisaApplicationPreview>> GetForApplicantAsync(CancellationToken cancellationToken);
+
+    /// Returns one application with specific id
+    Task<VisaApplicationModel> GetApplicationForApplicantAsync(Guid id, CancellationToken cancellationToken);
+
+    /// Returns one application with specific id
+    Task<VisaApplicationModel> GetApplicationForAuthorityAsync(Guid id, CancellationToken cancellationToken);
+
+    /// Creates application for applicant with specific user identifier
+    Task HandleCreateRequestAsync(VisaApplicationCreateRequest request, CancellationToken cancellationToken);
+
+    /// Sets application status to closed
+    Task HandleCloseRequestAsync(Guid applicationId, CancellationToken cancellationToken);
+
+    /// Sets application status to approved or rejected
+    Task SetApplicationStatusFromAuthorityAsync(Guid applicationId, AuthorityRequestStatuses status, CancellationToken cancellationToken);
+
+    /// Returns stream with file with formatted application data to download
+    Task<Stream> ApplicationToStreamAsync(Guid applicationId, CancellationToken cancellationToken);
+}

ApplicationLayer/Services/VisaApplications/Handlers/VisaApplicationRequestsHandler.cs

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+using ApplicationLayer.InfrastructureServicesInterfaces;
+using ApplicationLayer.Services.Applicants.Models;
+using ApplicationLayer.Services.Applicants.NeededServices;
+using ApplicationLayer.Services.VisaApplications.Exceptions;
+using ApplicationLayer.Services.VisaApplications.Models;
+using ApplicationLayer.Services.VisaApplications.NeededServices;
+using ApplicationLayer.Services.VisaApplications.Requests;
+using AutoMapper;
+using Domains.VisaApplicationDomain;
+
+namespace ApplicationLayer.Services.VisaApplications.Handlers;
+
+/// Handles visa requests
+public class VisaApplicationRequestsHandler(
+    IVisaApplicationsRepository applications,
+    IApplicantsRepository applicants,
+    IUnitOfWork unitOfWork,
+    IMapper mapper,
+    IDateTimeProvider dateTimeProvider,
+    IUserIdProvider userIdProvider,
+    IEntityWriter entityWriter) : IVisaApplicationRequestsHandler
+{
+    async Task<List<VisaApplicationPreview>> IVisaApplicationRequestsHandler.GetPendingAsync(CancellationToken cancellationToken)
+    {
+        var applicationsList = await applications.GetPendingApplicationsAsync(cancellationToken);
+
+        var applicationModels = mapper.Map<List<VisaApplicationPreview>>(applicationsList);
+        return applicationModels;
+    }
+
+    async Task<List<VisaApplicationPreview>> IVisaApplicationRequestsHandler.GetForApplicantAsync(CancellationToken cancellationToken)
+    {
+        var applicantId = await applicants.GetApplicantIdByUserId(userIdProvider.GetUserId(), cancellationToken);
+        var visaApplications = await applications.GetOfApplicantAsync(applicantId, cancellationToken);
+        return mapper.Map<List<VisaApplicationPreview>>(visaApplications);
+    }
+
+    /// <inheritdoc cref="IVisaApplicationRequestsHandler.GetApplicationForApplicantAsync"/>
+    public async Task<VisaApplicationModel> GetApplicationForApplicantAsync(Guid id, CancellationToken cancellationToken)
+    {
+        var applicant = await applicants.FindByUserIdAsync(userIdProvider.GetUserId(), cancellationToken);
+        var application = await applications.GetByApplicantAndApplicationIdAsync(applicant.Id, id, cancellationToken);
+        var mapped = mapper.Map<VisaApplicationModel>(application);
+        mapped.Applicant = mapper.Map<ApplicantModel>(applicant);
+        return mapped;
+    }
+
+    async Task<VisaApplicationModel> IVisaApplicationRequestsHandler.GetApplicationForAuthorityAsync(Guid id, CancellationToken cancellationToken)
+    {
+        var pending = await applications.GetPendingApplicationsAsync(cancellationToken);
+        var application = pending.SingleOrDefault(a => a.Id == id) ?? throw new ApplicationAlreadyProcessedException();
+        var mapped = mapper.Map<VisaApplicationModel>(application);
+        var applicant = await applicants.GetByIdAsync(application.ApplicantId, cancellationToken);
+        mapped.Applicant = mapper.Map<ApplicantModel>(applicant);
+        return mapped;
+    }
+
+    async Task IVisaApplicationRequestsHandler.HandleCreateRequestAsync(VisaApplicationCreateRequest request, CancellationToken cancellationToken)
+    {
+        var applicant = await applicants.FindByUserIdAsync(userIdProvider.GetUserId(), cancellationToken);
+
+        var visaApplication = mapper.Map<VisaApplication>(request);
+        visaApplication.RequestDate = dateTimeProvider.Now();
+        visaApplication.ApplicantId = applicant.Id;
+
+        await applications.AddAsync(visaApplication, cancellationToken);
+
+        await unitOfWork.SaveAsync(cancellationToken);
+    }
+
+    async Task IVisaApplicationRequestsHandler.HandleCloseRequestAsync(Guid applicationId, CancellationToken cancellationToken)
+    {
+        var applicantId = await applicants.GetApplicantIdByUserId(userIdProvider.GetUserId(), cancellationToken);
+        var application = await applications.GetByApplicantAndApplicationIdAsync(applicantId, applicationId, cancellationToken);
+        if (application.Status is ApplicationStatus.Approved or ApplicationStatus.Rejected)
+        {
+            throw new ApplicationAlreadyProcessedException();
+        }
+
+        application.Status = ApplicationStatus.Closed;
+        await applications.UpdateAsync(application, cancellationToken);
+
+        await unitOfWork.SaveAsync(cancellationToken);
+    }
+
+    async Task IVisaApplicationRequestsHandler.SetApplicationStatusFromAuthorityAsync(
+        Guid applicationId,
+        AuthorityRequestStatuses status,
+        CancellationToken cancellationToken)
+    {
+        var application = await applications.GetByIdAsync(applicationId, cancellationToken);
+        if (application.Status != ApplicationStatus.Pending)
+        {
+            throw new ApplicationAlreadyProcessedException();
+        }
+
+        var statusToSet = status switch
+        {
+            AuthorityRequestStatuses.Approved => ApplicationStatus.Approved,
+            AuthorityRequestStatuses.Rejected => ApplicationStatus.Rejected,
+            _ => throw new ArgumentOutOfRangeException(nameof(status), status, null)
+        };
+
+        application.Status = statusToSet;
+        await applications.UpdateAsync(application, cancellationToken);
+
+        await unitOfWork.SaveAsync(cancellationToken);
+    }
+
+    async Task<Stream> IVisaApplicationRequestsHandler.ApplicationToStreamAsync(Guid applicationId, CancellationToken cancellationToken)
+    {
+        var application = await GetApplicationForApplicantAsync(applicationId, cancellationToken);
+        return await entityWriter.WriteEntityToStream(application, cancellationToken);
+    }
+}