EnvelopeGenerator/EnvelopeGenerator.Application/Envelopes/Queries/ReadSingleEnvelopeQuery.cs

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

namespace EnvelopeGenerator.Application.Envelopes.Queries;

/// <summary>
/// Repräsentiert eine Abfrage für einen einzelnen Umschlag.
/// </summary>
public record ReadSingleEnvelopeQuery : EnvelopeQueryBase, IRequest<EnvelopeDto>
{
    /// <summary>
    /// Optionaler Benutzerfilter; wenn gesetzt, werden nur Umschläge des Benutzers geladen.
    /// </summary>
    public int? UserId { get; init; }

    /// <summary>
    /// Setzt den Benutzerkontext für die Abfrage.
    /// </summary>
    public ReadSingleEnvelopeQuery Authorize(int userId) => this with { UserId = userId };
}

/// <summary>
/// Verarbeitet <see cref="ReadSingleEnvelopeQuery"/> und liefert ein einzelnes <see cref="EnvelopeDto"/>-Ergebnis.
/// </summary>
public class ReadSingleEnvelopeQueryHandler : IRequestHandler<ReadSingleEnvelopeQuery, EnvelopeDto>
{
    private readonly IRepository<Envelope> _repository;
    private readonly IMapper _mapper;

    /// <summary>
    /// 
    /// </summary>
    /// <param name="repository"></param>
    /// <param name="mapper"></param>
    public ReadSingleEnvelopeQueryHandler(IRepository<Envelope> repository, IMapper mapper)
    {
        _repository = repository;
        _mapper = mapper;
    }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="request"></param>
    /// <param name="cancel"></param>
    /// <returns></returns>
    public async Task<EnvelopeDto> Handle(ReadSingleEnvelopeQuery request, CancellationToken cancel)
    {
        var query = _repository.Query;

        if (request.UserId is int userId)
            query = query.Where(e => e.UserId == userId);

        if (request.Id is int id)
            query = query.Where(e => e.Id == id);

        if (request.Uuid is string uuid)
            query = query.Where(e => e.Uuid == uuid);
        
        var envelopes = await query
            .Include(e => e.Documents)
            .Take(2)
            .ToListAsync(cancel);

        if (envelopes.Count > 1)
            throw new BadRequestException($"Multiple envelopes found for the given criteria: Id={request.Id}, Uuid={request.Uuid}, UserId={request.UserId}");

        return envelopes.SingleOrDefault() is Envelope envelope
            ? _mapper.Map<EnvelopeDto>(envelope)
            : throw new NotFoundException($"Envelope with Id={request.Id}, Uuid={request.Uuid} not found");
    }
}