EnvelopeGenerator/EnvelopeGenerator.Application/Services/ConfigService.cs

using AutoMapper;
using DigitalData.Core.Application;
using DigitalData.Core.DTO;
using EnvelopeGenerator.Application.Contracts.Services;
using EnvelopeGenerator.Application.DTOs;
using EnvelopeGenerator.Domain.Entities;
using EnvelopeGenerator.Application.Contracts.Repositories;
using Microsoft.Extensions.Caching.Memory;
using Microsoft.Extensions.Logging;
namespace EnvelopeGenerator.Application.Services;

public class ConfigService : ReadService<IConfigRepository, ConfigDto, Config, int>, IConfigService
{
		private static readonly Guid DefaultConfigCacheId = Guid.NewGuid();

		private readonly IMemoryCache _cache;
    private readonly ILogger<ConfigService> _logger;
		public ConfigService(IConfigRepository repository, IMapper mapper, IMemoryCache memoryCache, ILogger<ConfigService> logger) : base(repository, mapper)
    {
			_cache = memoryCache;
        _logger = logger;
    }

    public async Task<DataResult<ConfigDto>> ReadFirstAsync()
    {
        var config = await _repository.ReadFirstAsync();
        return config is null 
            ? Result.Fail<ConfigDto>().Notice(LogLevel.Error, Flag.DataIntegrityIssue, "There is no configuration in DB.")
            : Result.Success(_mapper.Map<ConfigDto>(config));
    }

		/// <summary>
		/// Reads the default configuration asynchronously.
		/// </summary>
		/// <remarks>
		/// The configuration is cached in memory upon the first retrieval. If the configuration is updated, 
		/// the application needs to be restarted for the changes to take effect as the memory cache will not be updated automatically.
		/// </remarks>
		/// <returns>
		/// A task that represents the asynchronous read operation. The task result contains the default configuration as a <see cref="ConfigDto"/>.
		/// </returns>
		/// <exception cref="InvalidOperationException">
		/// Thrown when the default configuration cannot be found.
		/// </exception>
		public async Task<ConfigDto> ReadDefaultAsync()
    {
        var config = await _cache.GetOrCreateAsync(DefaultConfigCacheId, _ => ReadFirstAsync().ThenAsync(
                Success: config => config,
                Fail: (mssg, ntc) =>
                {
                    _logger.LogNotice(ntc);
                    throw new InvalidOperationException("Default configuration cannot find.");
                }));

        return config!;
    }

    public async Task<string> ReadDefaultSignatureHost() => (await ReadDefaultAsync()).SignatureHost;
}