Add google authentication

Core.Thalos.BFF.Api/Services/IGoogleAuthorization.cs

@@ -0,0 +1,42 @@
+using Google.Apis.Auth.OAuth2;
+using Google.Apis.Auth.OAuth2.Flows;
+
+namespace Core.Thalos.BFF.Api.Services
+{
+    public interface IGoogleAuthorization
+    {
+        string GetAuthorizationUrl();
+        Task<UserCredential> ExchangeCodeForToken(string code);
+    }
+
+    public class GoogleAuthorizationService(
+        IGoogleAuthHelper googleHelper, IConfiguration config) : IGoogleAuthorization
+    {
+        private string RedirectUrl = config["Authentication:Google:RedirectUri"]!;
+
+        public async Task<UserCredential> ExchangeCodeForToken(string code)
+        {
+            var flow = new GoogleAuthorizationCodeFlow(
+                new GoogleAuthorizationCodeFlow.Initializer
+                {
+                    ClientSecrets = googleHelper.GetClientSecrets(),
+                    Scopes = googleHelper.GetScopes()
+                });
+
+            var token = await flow.ExchangeCodeForTokenAsync(
+                "user", code, RedirectUrl, CancellationToken.None);
+
+            return new UserCredential(flow, "user", token);
+        }
+
+        public string GetAuthorizationUrl() =>
+            new GoogleAuthorizationCodeFlow(
+                new GoogleAuthorizationCodeFlow.Initializer
+                {
+
+                    ClientSecrets = googleHelper.GetClientSecrets(),
+                    Scopes = googleHelper.GetScopes(),
+                    Prompt = "consent"
+                }).CreateAuthorizationCodeRequest(RedirectUrl).Build().ToString();
+    }
+}