Started testing a dx friendlier oauth2 handler

Moonlight.Client/UI/Components/OAuth2Handler.razor

@@ -0,0 +1,103 @@
+@using Microsoft.AspNetCore.WebUtilities
+
+@inject NavigationManager Navigation
+
+@if (IsAuthenticated)
+{
+    @AuthenticatedView
+}
+else if (IsCodeRequest)
+{
+    @PostAuthView
+}
+else
+{
+    if (IsAuthStateChecking)
+    {
+        if (Loader != null)
+        {
+            @Loader
+        }
+    }
+    else
+    {
+        @PreAuthView
+    }
+}
+
+@code
+{
+    [Parameter] public RenderFragment PreAuthView { get; set; }
+    [Parameter] public RenderFragment PostAuthView { get; set; }
+    [Parameter] public RenderFragment AuthenticatedView { get; set; }
+    [Parameter] public RenderFragment? Loader { get; set; }
+
+    [Parameter] public Func<Task<bool>> GetAuthState { get; set; }
+    [Parameter] public Func<Task<string>> GetLoginUrl { get; set; }
+    [Parameter] public Func<string, Task<bool>> HandleCode { get; set; }
+
+    private bool IsAuthStateChecking = true;
+    private bool IsCodeRequest = false;
+    private bool IsAuthenticated = false;
+
+    private string Code;
+
+    protected override async Task OnAfterRenderAsync(bool firstRender)
+    {
+        if (!firstRender)
+            return;
+
+        await Load();
+    }
+
+    private async Task Load()
+    {
+        IsAuthenticated = false;
+        IsAuthStateChecking = true;
+        
+        IsCodeRequest = HandleQueryCode();
+        await InvokeAsync(StateHasChanged);
+
+        if (IsCodeRequest)
+        {
+            var codeCorrect = await HandleCode.Invoke(Code);
+
+            if (codeCorrect)
+            {
+                IsAuthenticated = true;
+                await InvokeAsync(StateHasChanged);
+                return;
+            }
+        }
+
+        IsAuthenticated = await GetAuthState.Invoke();
+        IsAuthStateChecking = false;
+        await InvokeAsync(StateHasChanged);
+
+        var url = await GetLoginUrl.Invoke();
+        Navigation.NavigateTo(url, true);
+    }
+
+    public async Task Reload()
+        => await Load();
+
+    private bool HandleQueryCode()
+    {
+        var uri = new Uri(Navigation.Uri);
+        var query = QueryHelpers.ParseQuery(uri.Query);
+
+        if (!query.TryGetValue("code", out var codeValues))
+            return false;
+
+        if (codeValues.Count == 0)
+            return false;
+
+        var code = codeValues.First();
+
+        if (string.IsNullOrEmpty(code))
+            return false;
+
+        Code = code;
+        return true;
+    }
+}