EnvelopeGenerator/EnvelopeGenerator.Application/Services/EnvelopeSmsHandler.cs

using EnvelopeGenerator.Application.Configurations;
using EnvelopeGenerator.Application.Contracts;
using EnvelopeGenerator.Application.DTOs.EnvelopeReceiver;
using EnvelopeGenerator.Application.DTOs.Messaging;
using EnvelopeGenerator.Application.Extensions;
using Microsoft.Extensions.Caching.Distributed;
using Microsoft.Extensions.Options;

namespace EnvelopeGenerator.Application.Services;

public class EnvelopeSmsHandler : IEnvelopeSmsHandler
{
    private readonly ISmsSender _sender;

    private readonly TotpSmsParams _totpSmsParams;

    private readonly IDistributedCache _dCache;

    private readonly IAuthenticator _authenticator;

    public EnvelopeSmsHandler(ISmsSender sender, IOptions<TotpSmsParams> totpSmsParamsOptions, IDistributedCache distributedCache, IAuthenticator authenticator)
    {
        _sender = sender;
        _totpSmsParams = totpSmsParamsOptions.Value;
        _dCache = distributedCache;
        _authenticator = authenticator;
    }

    /// <summary>
    /// If expiration is passed then, sends sms and returns smsResponse and up-to-date expiration; otherwise send expiration.
    /// </summary>
    /// <param name="er_secret"></param>
    /// <param name="cToken"></param>
    /// <returns></returns>
    public async Task<(SmsResponse? SmsResponse, DateTime Expiration)> SendTotpAsync(EnvelopeReceiverSecretDto er_secret, CancellationToken cToken = default)
    {
        var key = string.Format(_totpSmsParams.Expiration.CacheKeyFormat, er_secret.EnvelopeId, er_secret.ReceiverId);
        var expiration = await _dCache.GetDateTimeAsync(key, cToken);

        if(expiration is DateTime expirationDateTime && expirationDateTime >= DateTime.Now)
            return (null, expirationDateTime);
        else
        {
            var new_expiration = DateTime.Now.AddSeconds(_totpSmsParams.TotpStep);
            var totp = _authenticator.GenerateTotp(er_secret.Receiver!.TotpSecretkey!, _totpSmsParams.TotpStep);
            var msg = string.Format(_totpSmsParams.Format, totp, new_expiration.ToString(_totpSmsParams.Expiration.Format, _totpSmsParams.Expiration.CultureInfo));
            await _dCache.SetDateTimeAsync(key, new_expiration, cToken: cToken);
            return (await _sender.SendSmsAsync(er_secret.PhoneNumber!, msg), new_expiration);
        }
    }

    public bool VerifyTotp(string totpCode, string secretKey) => _authenticator
        .VerifyTotp(totpCode, secretKey, _totpSmsParams.TotpStep, _totpSmsParams.TotpVerificationWindow);
}