EnvelopeGenerator/EnvelopeGenerator.Application/Envelopes/Queries/ReadReceiverNameQuery.cs

using DigitalData.Core.Abstraction.Application.Repository;
using EnvelopeGenerator.Application.Common.Query;
using MediatR;
using EnvelopeGenerator.Domain.Entities;
using Microsoft.EntityFrameworkCore;

namespace EnvelopeGenerator.Application.Envelopes.Queries;

/// <summary>
/// Eine Abfrage, um die zuletzt verwendete Anrede eines Empfängers zu ermitteln, 
/// damit diese für zukünftige Umschläge wiederverwendet werden kann.
/// </summary>
public record ReadReceiverNameQuery() : ReceiverQueryBase, IRequest<string?>;

/// <summary>
/// 
/// </summary>
public class ReadReceiverNameQueryHandler : IRequestHandler<ReadReceiverNameQuery, string?>
{
    private readonly IRepository<EnvelopeReceiver> _envelopeReceiverRepository;
    private readonly IRepository<Receiver> _receiverRepository;

    /// <summary>
    /// 
    /// </summary>
    /// <param name="envelopeReceiverRepository"></param>
    /// <param name="receiverRepository"></param>
    public ReadReceiverNameQueryHandler(IRepository<EnvelopeReceiver> envelopeReceiverRepository, IRepository<Receiver> receiverRepository)
    {
        _envelopeReceiverRepository = envelopeReceiverRepository;
        _receiverRepository = receiverRepository;
    }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="request"></param>
    /// <param name="cancellationToken"></param>
    /// <returns></returns>
    public async Task<string?> Handle(ReadReceiverNameQuery request, CancellationToken cancellationToken)
    {
        var receiverQuery = _receiverRepository.Query.AsNoTracking();

        if (request.Id is int id)
            receiverQuery = receiverQuery.Where(r => r.Id == id);
        if (request.EmailAddress is string email)
            receiverQuery = receiverQuery.Where(r => r.EmailAddress == email);
        if (request.Signature is string signature)
            receiverQuery = receiverQuery.Where(r => r.Signature == signature);

        var receiver = await receiverQuery.FirstOrDefaultAsync(cancellationToken);
        if (receiver is null)
            return null;

        var erName = await _envelopeReceiverRepository.Query
            .Where(er => er.ReceiverId == receiver.Id)
            .OrderByDescending(er => er.AddedWhen)
            .Select(er => er.Name)
            .FirstOrDefaultAsync(cancellationToken);

        return erName;
    }
}