EnvelopeGenerator/EnvelopeGenerator.Application/Configuration/Queries/ReadDefaultConfigQuery.cs

using AutoMapper;
using DigitalData.Core.Abstraction.Application.Repository;
using DigitalData.Core.Exceptions;
using EnvelopeGenerator.Application.Common;
using EnvelopeGenerator.Application.Common.Dto;
using EnvelopeGenerator.Domain.Entities;
using MediatR;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Caching.Distributed;
using Microsoft.Extensions.Caching.Memory;

namespace EnvelopeGenerator.Application.Configuration.Queries;

/// <summary>
/// 
/// </summary>
public record ReadDefaultConfigQuery : IRequest<ConfigDto>
{
    /// <summary>
    /// 
    /// </summary>
    public bool EnforceSingleResult { get; init; }
}

/// <summary>
/// 
/// </summary>
public class ReadDefaultConfigQueryHandler : IRequestHandler<ReadDefaultConfigQuery, ConfigDto>
{
    private readonly IRepository<Config> _repo;

    private readonly IMapper _mapper;

    private readonly IMemoryCache _cache;

    /// <summary>
    /// 
    /// </summary>
    /// <param name="repo"></param>
    /// <param name="mapper"></param>
    /// <param name="cache"></param>
    public ReadDefaultConfigQueryHandler(IRepository<Config> repo, IMapper mapper, IMemoryCache cache)
    {
        _repo = repo;
        _mapper = mapper;
        _cache = cache;
    }

    /// <summary>
    /// 
    /// </summary>
    /// <param name="request"></param>
    /// <param name="cancel"></param>
    /// <returns></returns>
    /// <exception cref="InvalidOperationException"></exception>
    public async Task<ConfigDto> Handle(ReadDefaultConfigQuery request, CancellationToken cancel)
    {
        var config = await _cache.GetOrCreateAsync(CacheKey.DefaultConfig, entry =>
        {
            entry.AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(30);
            return request.EnforceSingleResult
            ? _repo.Query.SingleOrDefaultAsync(cancel)
            : _repo.Query.FirstOrDefaultAsync(cancel)
            ?? throw new NotFoundException("Default configuration could not be found. Ensure at least one configuration record exists in the database.");
        });

        return _mapper.Map<ConfigDto>(config);
    }
}