MVCPostall/Postall.Infra/Services/FacebookTokenService.cs

using Microsoft.Extensions.Configuration;
using MongoDB.Driver;
using Postall.Domain.Dtos.Responses;
using Postall.Domain.Entities;
using Postall.Domain.Services;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http.Json;
using System.Text;
using System.Threading.Tasks;

namespace Postall.Infra.Services
{
    public class FacebookTokenService: IFacebookServices
    {
        private readonly IMongoCollection<UserSocialData> _tokens;
        private readonly IConfiguration _config;
        private readonly HttpClient _httpClient;

        public async Task<string> GetLongLivedToken(string shortLivedToken)
        {
            var appId = _config["Authentication:Facebook:AppId"];
            var appSecret = _config["Authentication:Facebook:AppSecret"];

            var response = await _httpClient.GetFromJsonAsync<FacebookTokenResponse>(
                $"https://graph.facebook.com/oauth/access_token?" +
                $"grant_type=fb_exchange_token&" +
                $"client_id={appId}&" +
                $"client_secret={appSecret}&" +
                $"fb_exchange_token={shortLivedToken}");

            return response.AccessToken;
        }

        public async Task SaveFacebookToken(string userId, string token)
        {
            var update = Builders<UserSocialData>.Update
                .Set(x => x.FacebookToken.AccessToken, token)
                .Set(x => x.FacebookToken.ExpiresAt, DateTime.UtcNow.AddDays(60));

            await _tokens.UpdateOneAsync(
                x => x.UserId == userId,
                update,
                new UpdateOptions { IsUpsert = true }
            );
        }
    }
}