server/src/SharedWeb/Utilities/ServiceCollectionExtensions.cs

using System.Reflection;
using System.Security.Claims;
using System.Security.Cryptography.X509Certificates;
using AspNetCoreRateLimit;
using AspNetCoreRateLimit.Redis;
using Bit.Core.Entities;
using Bit.Core.Enums;
using Bit.Core.HostedServices;
using Bit.Core.Identity;
using Bit.Core.IdentityServer;
using Bit.Core.Models.Business.Tokenables;
using Bit.Core.OrganizationFeatures;
using Bit.Core.Repositories;
using Bit.Core.Resources;
using Bit.Core.Services;
using Bit.Core.Settings;
using Bit.Core.Tokens;
using Bit.Core.Utilities;
using Bit.Infrastructure.Dapper;
using Bit.Infrastructure.EntityFramework;
using IdentityModel;
using IdentityServer4.AccessTokenValidation;
using IdentityServer4.Configuration;
using Microsoft.AspNetCore.Authentication.Cookies;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.DataProtection;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.HttpOverrides;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Mvc.Localization;
using Microsoft.Extensions.Caching.Distributed;
using Microsoft.Extensions.Caching.StackExchangeRedis;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection.Extensions;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Options;
using Serilog.Context;
using StackExchange.Redis;
using NoopRepos = Bit.Core.Repositories.Noop;
using Role = Bit.Core.Entities.Role;
using TableStorageRepos = Bit.Core.Repositories.TableStorage;

namespace Bit.SharedWeb.Utilities;

public static class ServiceCollectionExtensions
{
    public static void AddSqlServerRepositories(this IServiceCollection services, GlobalSettings globalSettings)
    {
        var selectedDatabaseProvider = globalSettings.DatabaseProvider;
        var provider = SupportedDatabaseProviders.SqlServer;
        var connectionString = string.Empty;
        if (!string.IsNullOrWhiteSpace(selectedDatabaseProvider))
        {
            switch (selectedDatabaseProvider.ToLowerInvariant())
            {
                case "postgres":
                case "postgresql":
                    provider = SupportedDatabaseProviders.Postgres;
                    connectionString = globalSettings.PostgreSql.ConnectionString;
                    break;
                case "mysql":
                case "mariadb":
                    provider = SupportedDatabaseProviders.MySql;
                    connectionString = globalSettings.MySql.ConnectionString;
                    break;
                default:
                    break;
            }
        }

        var useEf = (provider != SupportedDatabaseProviders.SqlServer);

        if (useEf)
        {
            services.AddEFRepositories(globalSettings.SelfHosted, connectionString, provider);
        }
        else
        {
            services.AddDapperRepositories(globalSettings.SelfHosted);
        }

        if (globalSettings.SelfHosted)
        {
            services.AddSingleton<IInstallationDeviceRepository, NoopRepos.InstallationDeviceRepository>();
            services.AddSingleton<IMetaDataRepository, NoopRepos.MetaDataRepository>();
        }
        else
        {
            services.AddSingleton<IEventRepository, TableStorageRepos.EventRepository>();
            services.AddSingleton<IInstallationDeviceRepository, TableStorageRepos.InstallationDeviceRepository>();
            services.AddSingleton<IMetaDataRepository, TableStorageRepos.MetaDataRepository>();
        }
    }

    public static void AddBaseServices(this IServiceCollection services, IGlobalSettings globalSettings)
    {
        services.AddScoped<ICipherService, CipherService>();
        services.AddScoped<IUserService, UserService>();
        services.AddOrganizationServices(globalSettings);
        services.AddScoped<ICollectionService, CollectionService>();
        services.AddScoped<IGroupService, GroupService>();
        services.AddScoped<IPolicyService, PolicyService>();
        services.AddScoped<IEventService, EventService>();
        services.AddScoped<IEmergencyAccessService, EmergencyAccessService>();
        services.AddSingleton<IDeviceService, DeviceService>();
        services.AddSingleton<IAppleIapService, AppleIapService>();
        services.AddScoped<ISsoConfigService, SsoConfigService>();
        services.AddScoped<ISendService, SendService>();
    }

    public static void AddTokenizers(this IServiceCollection services)
    {
        services.AddSingleton<IDataProtectorTokenFactory<EmergencyAccessInviteTokenable>>(serviceProvider =>
            new DataProtectorTokenFactory<EmergencyAccessInviteTokenable>(
                EmergencyAccessInviteTokenable.ClearTextPrefix,
                EmergencyAccessInviteTokenable.DataProtectorPurpose,
                serviceProvider.GetDataProtectionProvider())
        );
        services.AddSingleton<IDataProtectorTokenFactory<HCaptchaTokenable>>(serviceProvider =>
            new DataProtectorTokenFactory<HCaptchaTokenable>(
                HCaptchaTokenable.ClearTextPrefix,
                HCaptchaTokenable.DataProtectorPurpose,
                serviceProvider.GetDataProtectionProvider())
        );
        services.AddSingleton<IDataProtectorTokenFactory<SsoTokenable>>(serviceProvider =>
            new DataProtectorTokenFactory<SsoTokenable>(
                SsoTokenable.ClearTextPrefix,
                SsoTokenable.DataProtectorPurpose,
                serviceProvider.GetDataProtectionProvider()));
    }

    public static void AddDefaultServices(this IServiceCollection services, GlobalSettings globalSettings)
    {
        // Required for UserService
        services.AddWebAuthn(globalSettings);
        // Required for HTTP calls
        services.AddHttpClient();

        services.AddSingleton<IStripeAdapter, StripeAdapter>();
        services.AddSingleton<Braintree.IBraintreeGateway>((serviceProvider) =>
        {
            return new Braintree.BraintreeGateway
            {
                Environment = globalSettings.Braintree.Production ?
                    Braintree.Environment.PRODUCTION : Braintree.Environment.SANDBOX,
                MerchantId = globalSettings.Braintree.MerchantId,
                PublicKey = globalSettings.Braintree.PublicKey,
                PrivateKey = globalSettings.Braintree.PrivateKey
            };
        });
        services.AddSingleton<IPaymentService, StripePaymentService>();
        services.AddSingleton<IStripeSyncService, StripeSyncService>();
        services.AddSingleton<IMailService, HandlebarsMailService>();
        services.AddSingleton<ILicensingService, LicensingService>();
        services.AddTokenizers();

        if (CoreHelpers.SettingHasValue(globalSettings.ServiceBus.ConnectionString) &&
            CoreHelpers.SettingHasValue(globalSettings.ServiceBus.ApplicationCacheTopicName))
        {
            services.AddSingleton<IApplicationCacheService, InMemoryServiceBusApplicationCacheService>();
        }
        else
        {
            services.AddSingleton<IApplicationCacheService, InMemoryApplicationCacheService>();
        }

        var awsConfigured = CoreHelpers.SettingHasValue(globalSettings.Amazon?.AccessKeySecret);
        if (awsConfigured && CoreHelpers.SettingHasValue(globalSettings.Mail?.SendGridApiKey))
        {
            services.AddSingleton<IMailDeliveryService, MultiServiceMailDeliveryService>();
        }
        else if (awsConfigured)
        {
            services.AddSingleton<IMailDeliveryService, AmazonSesMailDeliveryService>();
        }
        else if (CoreHelpers.SettingHasValue(globalSettings.Mail?.Smtp?.Host))
        {
            services.AddSingleton<IMailDeliveryService, MailKitSmtpMailDeliveryService>();
        }
        else
        {
            services.AddSingleton<IMailDeliveryService, NoopMailDeliveryService>();
        }

        services.AddSingleton<IPushNotificationService, MultiServicePushNotificationService>();
        if (globalSettings.SelfHosted &&
            CoreHelpers.SettingHasValue(globalSettings.PushRelayBaseUri) &&
            globalSettings.Installation?.Id != null &&
            CoreHelpers.SettingHasValue(globalSettings.Installation?.Key))
        {
            services.AddSingleton<IPushRegistrationService, RelayPushRegistrationService>();
        }
        else if (!globalSettings.SelfHosted)
        {
            services.AddSingleton<IPushRegistrationService, NotificationHubPushRegistrationService>();
        }
        else
        {
            services.AddSingleton<IPushRegistrationService, NoopPushRegistrationService>();
        }

        if (!globalSettings.SelfHosted && CoreHelpers.SettingHasValue(globalSettings.Storage?.ConnectionString))
        {
            services.AddSingleton<IBlockIpService, AzureQueueBlockIpService>();
        }
        else if (!globalSettings.SelfHosted && CoreHelpers.SettingHasValue(globalSettings.Amazon?.AccessKeySecret))
        {
            services.AddSingleton<IBlockIpService, AmazonSqsBlockIpService>();
        }
        else
        {
            services.AddSingleton<IBlockIpService, NoopBlockIpService>();
        }

        if (!globalSettings.SelfHosted && CoreHelpers.SettingHasValue(globalSettings.Mail.ConnectionString))
        {
            services.AddSingleton<IMailEnqueuingService, AzureQueueMailService>();
        }
        else
        {
            services.AddSingleton<IMailEnqueuingService, BlockingMailEnqueuingService>();
        }

        if (!globalSettings.SelfHosted && CoreHelpers.SettingHasValue(globalSettings.Events.ConnectionString))
        {
            services.AddSingleton<IEventWriteService, AzureQueueEventWriteService>();
        }
        else if (globalSettings.SelfHosted)
        {
            services.AddSingleton<IEventWriteService, RepositoryEventWriteService>();
        }
        else
        {
            services.AddSingleton<IEventWriteService, NoopEventWriteService>();
        }

        if (CoreHelpers.SettingHasValue(globalSettings.Attachment.ConnectionString))
        {
            services.AddSingleton<IAttachmentStorageService, AzureAttachmentStorageService>();
        }
        else if (CoreHelpers.SettingHasValue(globalSettings.Attachment.BaseDirectory))
        {
            services.AddSingleton<IAttachmentStorageService, LocalAttachmentStorageService>();
        }
        else
        {
            services.AddSingleton<IAttachmentStorageService, NoopAttachmentStorageService>();
        }

        if (CoreHelpers.SettingHasValue(globalSettings.Send.ConnectionString))
        {
            services.AddSingleton<ISendFileStorageService, AzureSendFileStorageService>();
        }
        else if (CoreHelpers.SettingHasValue(globalSettings.Send.BaseDirectory))
        {
            services.AddSingleton<ISendFileStorageService, LocalSendStorageService>();
        }
        else
        {
            services.AddSingleton<ISendFileStorageService, NoopSendFileStorageService>();
        }

        if (globalSettings.SelfHosted)
        {
            services.AddSingleton<IReferenceEventService, NoopReferenceEventService>();
        }
        else
        {
            services.AddSingleton<IReferenceEventService, AzureQueueReferenceEventService>();
        }

        if (CoreHelpers.SettingHasValue(globalSettings.Captcha?.HCaptchaSecretKey) &&
            CoreHelpers.SettingHasValue(globalSettings.Captcha?.HCaptchaSiteKey))
        {
            services.AddSingleton<ICaptchaValidationService, HCaptchaValidationService>();
        }
        else
        {
            services.AddSingleton<ICaptchaValidationService, NoopCaptchaValidationService>();
        }
    }

    public static void AddOosServices(this IServiceCollection services)
    {
        services.AddScoped<IProviderService, NoopProviderService>();
    }

    public static void AddNoopServices(this IServiceCollection services)
    {
        services.AddSingleton<IMailService, NoopMailService>();
        services.AddSingleton<IMailDeliveryService, NoopMailDeliveryService>();
        services.AddSingleton<IPushNotificationService, NoopPushNotificationService>();
        services.AddSingleton<IBlockIpService, NoopBlockIpService>();
        services.AddSingleton<IPushRegistrationService, NoopPushRegistrationService>();
        services.AddSingleton<IAttachmentStorageService, NoopAttachmentStorageService>();
        services.AddSingleton<ILicensingService, NoopLicensingService>();
        services.AddSingleton<IEventWriteService, NoopEventWriteService>();
    }

    public static IdentityBuilder AddCustomIdentityServices(
        this IServiceCollection services, GlobalSettings globalSettings)
    {
        services.AddSingleton<IOrganizationDuoWebTokenProvider, OrganizationDuoWebTokenProvider>();
        services.Configure<PasswordHasherOptions>(options => options.IterationCount = 100000);
        services.Configure<TwoFactorRememberTokenProviderOptions>(options =>
        {
            options.TokenLifespan = TimeSpan.FromDays(30);
        });

        var identityBuilder = services.AddIdentityWithoutCookieAuth<User, Role>(options =>
        {
            options.User = new UserOptions
            {
                RequireUniqueEmail = true,
                AllowedUserNameCharacters = null // all
            };
            options.Password = new PasswordOptions
            {
                RequireDigit = false,
                RequireLowercase = false,
                RequiredLength = 8,
                RequireNonAlphanumeric = false,
                RequireUppercase = false
            };
            options.ClaimsIdentity = new ClaimsIdentityOptions
            {
                SecurityStampClaimType = "sstamp",
                UserNameClaimType = JwtClaimTypes.Email,
                UserIdClaimType = JwtClaimTypes.Subject
            };
            options.Tokens.ChangeEmailTokenProvider = TokenOptions.DefaultEmailProvider;
        });

        identityBuilder
            .AddUserStore<UserStore>()
            .AddRoleStore<RoleStore>()
            .AddTokenProvider<DataProtectorTokenProvider<User>>(TokenOptions.DefaultProvider)
            .AddTokenProvider<AuthenticatorTokenProvider>(
                CoreHelpers.CustomProviderName(TwoFactorProviderType.Authenticator))
            .AddTokenProvider<EmailTokenProvider>(
                CoreHelpers.CustomProviderName(TwoFactorProviderType.Email))
            .AddTokenProvider<YubicoOtpTokenProvider>(
                CoreHelpers.CustomProviderName(TwoFactorProviderType.YubiKey))
            .AddTokenProvider<DuoWebTokenProvider>(
                CoreHelpers.CustomProviderName(TwoFactorProviderType.Duo))
            .AddTokenProvider<TwoFactorRememberTokenProvider>(
                CoreHelpers.CustomProviderName(TwoFactorProviderType.Remember))
            .AddTokenProvider<EmailTokenProvider<User>>(TokenOptions.DefaultEmailProvider)
            .AddTokenProvider<WebAuthnTokenProvider>(
                CoreHelpers.CustomProviderName(TwoFactorProviderType.WebAuthn));

        return identityBuilder;
    }

    public static Tuple<IdentityBuilder, IdentityBuilder> AddPasswordlessIdentityServices<TUserStore>(
        this IServiceCollection services, GlobalSettings globalSettings) where TUserStore : class
    {
        services.TryAddTransient<ILookupNormalizer, LowerInvariantLookupNormalizer>();
        services.Configure<DataProtectionTokenProviderOptions>(options =>
        {
            options.TokenLifespan = TimeSpan.FromMinutes(15);
        });

        var passwordlessIdentityBuilder = services.AddIdentity<IdentityUser, Role>()
            .AddUserStore<TUserStore>()
            .AddRoleStore<RoleStore>()
            .AddDefaultTokenProviders();

        var regularIdentityBuilder = services.AddIdentityCore<User>()
            .AddUserStore<UserStore>();

        services.TryAddScoped<PasswordlessSignInManager<IdentityUser>, PasswordlessSignInManager<IdentityUser>>();

        services.ConfigureApplicationCookie(options =>
        {
            options.LoginPath = "/login";
            options.LogoutPath = "/";
            options.AccessDeniedPath = "/login?accessDenied=true";
            options.Cookie.Name = $"Bitwarden_{globalSettings.ProjectName}";
            options.Cookie.HttpOnly = true;
            options.ExpireTimeSpan = TimeSpan.FromDays(2);
            options.ReturnUrlParameter = "returnUrl";
            options.SlidingExpiration = true;
        });

        return new Tuple<IdentityBuilder, IdentityBuilder>(passwordlessIdentityBuilder, regularIdentityBuilder);
    }

    public static void AddIdentityAuthenticationServices(
        this IServiceCollection services, GlobalSettings globalSettings, IWebHostEnvironment environment,
        Action<AuthorizationOptions> addAuthorization)
    {
        services
            .AddAuthentication(IdentityServerAuthenticationDefaults.AuthenticationScheme)
            .AddIdentityServerAuthentication(options =>
            {
                options.Authority = globalSettings.BaseServiceUri.InternalIdentity;
                options.RequireHttpsMetadata = !environment.IsDevelopment() &&
                    globalSettings.BaseServiceUri.InternalIdentity.StartsWith("https");
                options.TokenRetriever = TokenRetrieval.FromAuthorizationHeaderOrQueryString();
                options.NameClaimType = ClaimTypes.Email;
                options.SupportedTokens = SupportedTokens.Jwt;
            });

        if (addAuthorization != null)
        {
            services.AddAuthorization(config =>
            {
                addAuthorization.Invoke(config);
            });
        }

        if (environment.IsDevelopment())
        {
            Microsoft.IdentityModel.Logging.IdentityModelEventSource.ShowPII = true;
        }
    }

    public static void AddCustomDataProtectionServices(
        this IServiceCollection services, IWebHostEnvironment env, GlobalSettings globalSettings)
    {
        var builder = services.AddDataProtection(options => options.ApplicationDiscriminator = "Bitwarden");
        if (env.IsDevelopment())
        {
            return;
        }

        if (globalSettings.SelfHosted && CoreHelpers.SettingHasValue(globalSettings.DataProtection.Directory))
        {
            builder.PersistKeysToFileSystem(new DirectoryInfo(globalSettings.DataProtection.Directory));
        }

        if (!globalSettings.SelfHosted && CoreHelpers.SettingHasValue(globalSettings.Storage?.ConnectionString))
        {
            X509Certificate2 dataProtectionCert = null;
            if (CoreHelpers.SettingHasValue(globalSettings.DataProtection.CertificateThumbprint))
            {
                dataProtectionCert = CoreHelpers.GetCertificate(
                    globalSettings.DataProtection.CertificateThumbprint);
            }
            else if (CoreHelpers.SettingHasValue(globalSettings.DataProtection.CertificatePassword))
            {
                dataProtectionCert = CoreHelpers.GetBlobCertificateAsync(globalSettings.Storage.ConnectionString, "certificates",
                    "dataprotection.pfx", globalSettings.DataProtection.CertificatePassword)
                    .GetAwaiter().GetResult();
            }
            //TODO djsmith85 Check if this is the correct container name
            builder
                .PersistKeysToAzureBlobStorage(globalSettings.Storage.ConnectionString, "aspnet-dataprotection", "keys.xml")
                .ProtectKeysWithCertificate(dataProtectionCert);
        }
    }

    public static IIdentityServerBuilder AddIdentityServerCertificate(
        this IIdentityServerBuilder identityServerBuilder, IWebHostEnvironment env, GlobalSettings globalSettings)
    {
        var certificate = CoreHelpers.GetIdentityServerCertificate(globalSettings);
        if (certificate != null)
        {
            identityServerBuilder.AddSigningCredential(certificate);
        }
        else if (env.IsDevelopment())
        {
            identityServerBuilder.AddDeveloperSigningCredential(false);
        }
        else
        {
            throw new Exception("No identity certificate to use.");
        }
        return identityServerBuilder;
    }

    public static GlobalSettings AddGlobalSettingsServices(this IServiceCollection services,
        IConfiguration configuration, IWebHostEnvironment environment)
    {
        var globalSettings = new GlobalSettings();
        ConfigurationBinder.Bind(configuration.GetSection("GlobalSettings"), globalSettings);

        if (environment.IsDevelopment() && configuration.GetValue<bool>("developSelfHosted"))
        {
            // Override settings with selfHostedOverride settings
            ConfigurationBinder.Bind(configuration.GetSection("Dev:SelfHostOverride:GlobalSettings"), globalSettings);
        }

        services.AddSingleton(s => globalSettings);
        services.AddSingleton<IGlobalSettings, GlobalSettings>(s => globalSettings);
        return globalSettings;
    }

    public static void UseDefaultMiddleware(this IApplicationBuilder app,
        IWebHostEnvironment env, GlobalSettings globalSettings)
    {
        string GetHeaderValue(HttpContext httpContext, string header)
        {
            if (httpContext.Request.Headers.ContainsKey(header))
            {
                return httpContext.Request.Headers[header];
            }
            return null;
        }

        // Add version information to response headers
        app.Use(async (httpContext, next) =>
        {
            using (LogContext.PushProperty("IPAddress", httpContext.GetIpAddress(globalSettings)))
            using (LogContext.PushProperty("UserAgent", GetHeaderValue(httpContext, "user-agent")))
            using (LogContext.PushProperty("DeviceType", GetHeaderValue(httpContext, "device-type")))
            using (LogContext.PushProperty("Origin", GetHeaderValue(httpContext, "origin")))
            {
                httpContext.Response.OnStarting((state) =>
                {
                    httpContext.Response.Headers.Append("Server-Version", CoreHelpers.GetVersion());
                    return Task.FromResult(0);
                }, null);
                await next.Invoke();
            }
        });
    }

    public static void UseForwardedHeaders(this IApplicationBuilder app, GlobalSettings globalSettings)
    {
        var options = new ForwardedHeadersOptions
        {
            ForwardedHeaders = ForwardedHeaders.XForwardedFor | ForwardedHeaders.XForwardedProto
        };
        if (!string.IsNullOrWhiteSpace(globalSettings.KnownProxies))
        {
            var proxies = globalSettings.KnownProxies.Split(',');
            foreach (var proxy in proxies)
            {
                if (System.Net.IPAddress.TryParse(proxy.Trim(), out var ip))
                {
                    options.KnownProxies.Add(ip);
                }
            }
        }
        if (options.KnownProxies.Count > 1)
        {
            options.ForwardLimit = null;
        }
        app.UseForwardedHeaders(options);
    }

    public static void AddCoreLocalizationServices(this IServiceCollection services)
    {
        services.AddTransient<II18nService, I18nService>();
        services.AddLocalization(options => options.ResourcesPath = "Resources");
    }

    public static IApplicationBuilder UseCoreLocalization(this IApplicationBuilder app)
    {
        var supportedCultures = new[] { "en" };
        return app.UseRequestLocalization(options => options
            .SetDefaultCulture(supportedCultures[0])
            .AddSupportedCultures(supportedCultures)
            .AddSupportedUICultures(supportedCultures));
    }

    public static IMvcBuilder AddViewAndDataAnnotationLocalization(this IMvcBuilder mvc)
    {
        mvc.Services.AddTransient<IViewLocalizer, I18nViewLocalizer>();
        return mvc.AddViewLocalization(options => options.ResourcesPath = "Resources")
            .AddDataAnnotationsLocalization(options =>
                options.DataAnnotationLocalizerProvider = (type, factory) =>
                {
                    var assemblyName = new AssemblyName(typeof(SharedResources).GetTypeInfo().Assembly.FullName);
                    return factory.Create("SharedResources", assemblyName.Name);
                });
    }

    public static IServiceCollection AddDistributedIdentityServices(this IServiceCollection services, GlobalSettings globalSettings)
    {
        services.AddOidcStateDataFormatterCache();
        services.AddSession();
        services.ConfigureApplicationCookie(configure => configure.CookieManager = new DistributedCacheCookieManager());
        services.ConfigureExternalCookie(configure => configure.CookieManager = new DistributedCacheCookieManager());
        services.AddSingleton<IPostConfigureOptions<CookieAuthenticationOptions>>(
            svcs => new ConfigureOpenIdConnectDistributedOptions(
                svcs.GetRequiredService<IHttpContextAccessor>(),
                globalSettings,
                svcs.GetRequiredService<IdentityServerOptions>())
        );

        return services;
    }

    public static void AddWebAuthn(this IServiceCollection services, GlobalSettings globalSettings)
    {
        services.AddFido2(options =>
        {
            options.ServerDomain = new Uri(globalSettings.BaseServiceUri.Vault).Host;
            options.ServerName = "Bitwarden";
            options.Origins = new HashSet<string> { globalSettings.BaseServiceUri.Vault, };
            options.TimestampDriftTolerance = 300000;
        });
    }

    /// <summary>
    ///     Adds either an in-memory or distributed IP rate limiter depending if a Redis connection string is available.
    /// </summary>
    /// <param name="services"></param>
    /// <param name="globalSettings"></param>
    public static void AddIpRateLimiting(this IServiceCollection services,
        GlobalSettings globalSettings)
    {
        services.AddHostedService<IpRateLimitSeedStartupService>();
        services.AddSingleton<IRateLimitConfiguration, RateLimitConfiguration>();

        if (string.IsNullOrEmpty(globalSettings.Redis.ConnectionString))
        {
            services.AddInMemoryRateLimiting();
        }
        else
        {
            services.AddRedisRateLimiting(); // Requires a registered IConnectionMultiplexer 
        }
    }

    /// <summary>
    ///     Adds an implementation of <see cref="IDistributedCache"/> to the service collection. Uses a memory
    /// cache if self hosted or no Redis connection string is available in GlobalSettings.
    /// </summary>
    public static void AddDistributedCache(
        this IServiceCollection services,
        GlobalSettings globalSettings)
    {
        if (globalSettings.SelfHosted || string.IsNullOrEmpty(globalSettings.Redis.ConnectionString))
        {
            services.AddDistributedMemoryCache();
            return;
        }

        // Register the IConnectionMultiplexer explicitly so it can be accessed via DI
        // (e.g. for the IP rate limiting store)
        services.AddSingleton<IConnectionMultiplexer>(
            _ => ConnectionMultiplexer.Connect(globalSettings.Redis.ConnectionString));

        // Explicitly register IDistributedCache to re-use existing IConnectionMultiplexer 
        // to reduce the number of redundant connections to the Redis instance
        services.AddSingleton<IDistributedCache>(s =>
        {
            return new RedisCache(new RedisCacheOptions
            {
                // Use "ProjectName:" as an instance name to namespace keys and avoid conflicts between projects
                InstanceName = $"{globalSettings.ProjectName}:",
                ConnectionMultiplexerFactory = () =>
                    Task.FromResult(s.GetRequiredService<IConnectionMultiplexer>())
            });
        });
    }
}