Refactoring authentication to support server-side Blazor using a seamless login flow.

Oqtane.Client/Providers/IdentityAuthenticationStateProvider.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Net.Http;
+using System.Security.Claims;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Components;
+using Oqtane.Models;
+
+namespace Oqtane.Providers
+{
+    public class IdentityAuthenticationStateProvider : AuthenticationStateProvider
+    {
+        private readonly IUriHelper urihelper;
+
+        public IdentityAuthenticationStateProvider(IUriHelper urihelper)
+        {
+            this.urihelper = urihelper;
+        }
+
+        public override async Task<AuthenticationState> GetAuthenticationStateAsync()
+        {
+            // hack: create a new HttpClient rather than relying on the registered service as the AuthenticationStateProvider is initialized prior to IUriHelper ( https://github.com/aspnet/AspNetCore/issues/11867 )
+            HttpClient http = new HttpClient();
+            Uri uri = new Uri(urihelper.GetAbsoluteUri());
+            string apiurl = uri.Scheme + "://" + uri.Authority + "/~/api/User/authenticate";
+            User user = await http.GetJsonAsync<User>(apiurl);
+
+            var identity = user.IsAuthenticated
+                ? new ClaimsIdentity(new[] { new Claim(ClaimTypes.Name, user.Username) }, "Identity.Application")
+                : new ClaimsIdentity();
+            return new AuthenticationState(new ClaimsPrincipal(identity));
+        }
+
+        public void NotifyAuthenticationChanged()
+        {
+            NotifyAuthenticationStateChanged(GetAuthenticationStateAsync());
+        }
+    }
+}