Inject Hasher class and register as singleton service

The `Hasher` class is now being injected into the constructors of `CreateLinkBundle`, `DeleteLinkBundle`, `GetLinkBundlesForUser`, and `UpdateLinkBundle` classes, replacing the previous implementation where a new `Hasher` instance was created within these classes' methods. This change improves the testability and reusability of the `Hasher` class. The `Hasher` class is also registered as a singleton service in the `Program.cs` file, ensuring only one instance is used throughout the application's lifetime. It is initialized with `HASHER_KEY` and `HASHER_SALT` configuration values. The `Api` namespace, where `Hasher` is defined, is now being used in the `Program.cs` file. The creation of new `Hasher` instances has been removed from various places in the aforementioned classes due to the new injection approach.

Api/Functions/CreateLinkBundle.cs

@@ -12,7 +12,7 @@
 
 namespace Api.Functions
 {
-    public partial class CreateLinkBundle(CosmosClient cosmosClient)
+    public partial class CreateLinkBundle(CosmosClient cosmosClient, Hasher hasher)
     {
         protected const string CHARACTERS = "abcdefghijklmnopqrstuvwxyz0123456789";
         protected const string VANITY_REGEX = @"^([\w\d-])+(/([\w\d-])+)*$";
@@ -43,7 +43,6 @@ public async Task<HttpResponseData> Run([HttpTrigger(AuthorizationLevel.Anonymou
             if (clientPrincipal != null)
             {
                 string username = clientPrincipal.UserDetails;
-                Hasher hasher = new();
                 linkBundle.UserId = hasher.HashString(username);
                 linkBundle.Provider = clientPrincipal.IdentityProvider;
             }

Api/Functions/DeleteLinkBundle.cs

@@ -9,7 +9,7 @@
 
 namespace Api.Functions
 {
-    public class DeleteLinkBundle(ILoggerFactory loggerFactory, CosmosClient cosmosClient)
+    public class DeleteLinkBundle(ILoggerFactory loggerFactory, CosmosClient cosmosClient, Hasher hasher)
     {
         private readonly ILogger _logger = loggerFactory.CreateLogger<DeleteLinkBundle>();
 
@@ -30,7 +30,6 @@ public async Task<HttpResponseData> Run(
 
             if (result.Count != 0)
             {
-                Hasher hasher = new();
                 var hashedUsername = hasher.HashString(principal.UserDetails);
                 if (hashedUsername != result.First().UserId || principal.IdentityProvider != result.First().Provider)
                 {

Api/Functions/GetLinkBundlesForUser.cs

@@ -9,7 +9,7 @@
 
 namespace Api.Functions
 {
-    public class GetLinkBundlesForUser(CosmosClient cosmosClient)
+    public class GetLinkBundlesForUser(CosmosClient cosmosClient, Hasher hasher)
     {
         [Function(nameof(GetLinkBundlesForUser))]
         public async Task<HttpResponseData> Run([HttpTrigger(AuthorizationLevel.Anonymous, "get", Route = "user")] HttpRequestData req)
@@ -23,7 +23,6 @@ public async Task<HttpResponseData> Run([HttpTrigger(AuthorizationLevel.Anonymou
 
                 if (clientPrincipal != null)
                 {
-                    Hasher hasher = new();
                     string username = hasher.HashString(clientPrincipal.UserDetails);
                     string provider = clientPrincipal.IdentityProvider;
 

Api/Functions/UpdateLinkBundle.cs

@@ -11,7 +11,7 @@
 
 namespace Api
 {
-    public class UpdateLinkBundle(CosmosClient cosmosClient)
+    public class UpdateLinkBundle(CosmosClient cosmosClient, Hasher hasher)
     {
         [Function(nameof(UpdateLinkBundle))]
         public async Task<HttpResponseData> Run([HttpTrigger(AuthorizationLevel.Anonymous, "put", Route = "links/{vanityUrl}")] HttpRequestData req,
@@ -45,7 +45,6 @@ public async Task<HttpResponseData> Run([HttpTrigger(AuthorizationLevel.Anonymou
 
                 if (result.Count != 0)
                 {
-                    Hasher hasher = new();
                     var hashedUsername = hasher.HashString(principal.UserDetails);
                     if (hashedUsername != result.First().UserId || principal.IdentityProvider != result.First().Provider)
                     {

Api/Program.cs

@@ -1,3 +1,4 @@
+using Api;
 using Microsoft.Azure.Cosmos;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Hosting;
@@ -23,6 +24,9 @@
             context.Configuration["CosmosDb:Endpoint"],
             context.Configuration["CosmosDb:Key"],
             cosmosClientOptions));
+        services.AddSingleton<Hasher>(services => new Hasher(
+            context.Configuration["HASHER_KEY"],
+            context.Configuration["HASHER_SALT"]));
     })
     .ConfigureFunctionsWorkerDefaults()
     .Build();