galaeth-draft/Galaeth.Services/Services/EmailDomainBlacklistService.cs

using System.Net.Mail;
using Galaeth.Core.Entities;
using Galaeth.Core.Extensions;
using Galaeth.Core.RepositoryInterfaces;
using Galaeth.Services.Configuration;
using Galaeth.Services.Interfaces;
using Injectio.Attributes;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

namespace Galaeth.Services.Services;

/// <inheritdoc/>
[RegisterScoped]
public class EmailDomainBlacklistService : IEmailDomainBlacklistService
{
    private readonly EmailDomainBlacklistConfiguration _configuration;
    private readonly IEmailDomainBlacklistRepository _repository;
    private readonly ILogger<EmailDomainBlacklistService> _logger;

    /// <summary>
    /// Initializes a new instance of the <see cref="EmailDomainBlacklistService"/> class.
    /// </summary>
    /// <param name="configuration">Instance of <see cref="IOptions{EmailDomainBlacklistConfiguration}"/>.</param>
    /// <param name="repository">Instance of <see cref="IEmailDomainBlacklistRepository"/>.</param>
    /// <param name="logger">Instance of <see cref="ILogger"/>.</param>
    public EmailDomainBlacklistService(
        IOptions<EmailDomainBlacklistConfiguration> configuration,
        IEmailDomainBlacklistRepository repository,
        ILogger<EmailDomainBlacklistService> logger)
    {
        _configuration = configuration.Value;
        _repository = repository;
        _logger = logger;
    }

    /// <inheritdoc/>
    public async Task UpdateBlacklist()
    {
        if (!_configuration.Enabled)
        {
            _logger.LogInformation("Email address domain blacklist disabled");
            return;
        }

        _logger.LogInformation("Updating email address domain blacklist");

        try
        {
            var client = new HttpClient();

            // Attempt to fetch master list.
            var result = await client.GetAsync(_configuration.MasterList);
            if (!result.IsSuccessStatusCode)
            {
                _logger.LogError(
                    "Failed to retrieve up-to-date blacklisted domains. Http status code: {code}",
                    result.StatusCode);
                return;
            }

            var content = await result.Content.ReadAsStringAsync();
            var entries = content.Split(
                    ["\r\n", "\r", "\n"],
                    StringSplitOptions.None)
                .Where(s => !string.IsNullOrWhiteSpace(s) && s.Trim()[..1] != "#" && s.Trim()[..1] != "[" &&
                            s.Trim()[..1] != "!");

            var existing = await _repository.GetAllAsync();

            var newDomains = entries.Except(existing.Select(e => e.Domain)).ToList();

            _logger.LogInformation("Adding {count} new domains to the blacklist", newDomains.Count);

            // Add new domains to blacklist
            var listChunks = newDomains.ChunkBy(1000);
            newDomains.Clear();

            foreach (var chunk in listChunks)
            {
                await _repository.AddAsync(chunk.Select(d => new EmailDomainBlacklist()
                {
                    Domain = d,
                    CreatedAt = DateTime.UtcNow,
                }));
            }

            GC.Collect(2, GCCollectionMode.Aggressive);
            GC.WaitForFullGCComplete();
        }
        catch (Exception exception)
        {
            _logger.LogError("Failed to retrieve up-to-date blacklisted domains: {exception}", exception);
        }

        var count = await _repository.CountEntries();
        _logger.LogInformation("Total email address domains in blacklist: {count}", count);
    }

    /// <inheritdoc/>
    public async Task<bool> CheckBlacklist(string emailAddress)
    {
        if (!_configuration.Enabled)
        {
            return false;
        }

        try
        {
            var mailAddress = new MailAddress(emailAddress.ToLowerInvariant());
            var domain = mailAddress.Host;
            var blacklisted = await _repository.FindByIdAsync(domain);
            return blacklisted is not null;
        }
        catch (Exception exception)
        {
            _logger.LogWarning(
                "Failed to determine if following email address is in the blacklist: {email}. {exception}",
                emailAddress.MaskEmailAddress(),
                exception);
            return false;
        }
    }
}