EnvelopeGenerator/EnvelopeGenerator.Application/Configs/DefaultReadConfigQuery.cs

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

namespace EnvelopeGenerator.Application.Configs;

/// <summary>
/// 
/// </summary>
public class DefaultReadConfigQuery : IRequest<ConfigDto>
{
    /// <summary>
    /// 
    /// </summary>
    public static readonly Guid MemoryCacheKey = Guid.NewGuid();
}

/// <summary>
/// 
/// </summary>
public static class DefaultReadConfigQueryExtensions
{
    /// <summary>
    /// 
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="cancel"></param>
    /// <returns></returns>
    public static Task<ConfigDto> ReadDefaultConfigAsync(this ISender sender, CancellationToken cancel = default) 
        => sender.Send(new DefaultReadConfigQuery(), cancel);
}

/// <summary>
/// 
/// </summary>
public class DefaultReadConfigQueryHandler : IRequestHandler<DefaultReadConfigQuery, 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 DefaultReadConfigQueryHandler(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="NotImplementedException"></exception>
    public async Task<ConfigDto> Handle(DefaultReadConfigQuery request, CancellationToken cancel)
    {
        var config = await _cache.GetOrCreateAsync(DefaultReadConfigQuery.MemoryCacheKey, async entry =>
        {
            entry.AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(5);
            var configs = await _repo.GetAllAsync(cancel);
            var defaultConfig = configs.FirstOrDefault();
            var defaultConfigDto = _mapper.Map<ConfigDto>(defaultConfig);
            return defaultConfigDto;
        });

        if(config is null)
        {
            _cache.Remove(DefaultReadConfigQuery.MemoryCacheKey);
            throw new NotFoundException("No configuration record is found.");
        }

        return config;
    }
}