DigitalData.MessagingService/src/infrastructure/DigitalData.MessagingService.Infrastructure/Services/Background/EmailSyncWorker.cs

using DigitalData.MessagingService.Application.Common.Dto.MailSearch;
using DigitalData.MessagingService.Application.Common.Interfaces;
using DigitalData.MessagingService.Application.Common.Interfaces.Repositories;
using DigitalData.MessagingService.Application.Common.Options;
using DigitalData.MessagingService.Domain.Entities;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Options;

namespace DigitalData.MessagingService.Infrastructure.Services.Background;

public class EmailSyncWorker(IImapEmailService imapService, IOptions<EmailAccountsOptions> Options, IServiceProvider Provider) : BackgroundService
{
    private DateFilter? _dateFilter = null;

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        await UpsertSeedEmailAccount(stoppingToken);

        if (imapService is not LimilabsImapEmailService limapService)
        {
            await Task.Delay(Timeout.Infinite, stoppingToken).ConfigureAwait(ConfigureAwaitOptions.SuppressThrowing);
            return;
        }

        var interval = TimeSpan.FromSeconds(Options.Value.SyncIntervalSeconds);

        while (!stoppingToken.IsCancellationRequested)
        {
            using var scope = Provider.CreateAsyncScope();

            var emailAccountRepo = scope.ServiceProvider.GetRequiredService<IRepository<EmailAccount>>();

            foreach (var account in await emailAccountRepo.GetAllAsync(stoppingToken))
                if (account.ImapServer is not null)
                {
                    // init or update last date filter
                    _dateFilter = _dateFilter is null
                        ? new DateFilter
                        {
                            After = null,
                            Before = DateTime.UtcNow
                        }
                        : new DateFilter
                        {
                            After = _dateFilter.Before,
                            Before = DateTime.UtcNow
                        };

                    await limapService.FetchEmailsAsync(account, new MailSearchFilter { Date = _dateFilter }, stoppingToken);
                }

            await Task.Delay(interval, stoppingToken).ConfigureAwait(ConfigureAwaitOptions.SuppressThrowing);
        }
    }

    public async Task UpsertSeedEmailAccount(CancellationToken stoppingToken)
    {
        using var scope = Provider.CreateAsyncScope();

        var emailAccountRepo = scope.ServiceProvider.GetRequiredService<IRepository<EmailAccount>>();

        // init seed email accounts if not exist
        foreach (var account in Options.Value.Accounts)
            await emailAccountRepo.UpsertAsync(a => a.Username == account.Username, account, stoppingToken);
    }
}