1 files changed, 102 insertions, 0 deletions
diff --git a/Pages/Component/LinkAction.razor b/Pages/Component/LinkAction.razor
new file mode 100644
index 0000000..ee6d189
--- /dev/null
+++ b/Pages/Component/LinkAction.razor
@@ -0,0 +1,102 @@
+@using System.Timers
+@implements IDisposable
+@inject IJSRuntime js
+
+<a
+    class=@(isLoading || errorTimer.Enabled ? "disabled" : "")
+    @attributes=Attributes
+    @onclick=Trigger>
+
+    @if(errorTimer.Enabled) {
+        @("Error!")
+    } else if(isLoading) {
+        @(LoadingText + "...")
+    } else {
+        @Text
+    }
+</a>
+
+@code {
+    [Parameter]
+    public Func<Task> OnClick { get; set; }
+
+    [Parameter]
+    public string Text{ get; set; }
+
+    [Parameter]
+    public string LoadingText { get; set; }
+
+    private Dictionary<string, object?> Attributes => new() {
+        ["disabled"] = isLoading,
+    };
+
+    private Timer loadingTimer;
+    private Timer errorTimer;
+
+    private object triggerLock = new();
+    private bool   isRunning   = false;
+    private bool   isLoading   = false;
+
+    protected override void OnInitialized() {
+        loadingTimer = new(50) {
+            AutoReset = false
+        };
+        loadingTimer.Elapsed += LoadingTimerElapsed;
+
+        errorTimer = new(1000) {
+            AutoReset = false
+        };
+        errorTimer.Elapsed += ErrorTimerElapsed;
+    }
+
+    // Most link-click actions (e.g. triggering dialogs, page
+    // navigation, etc) complete very quickly (under 50ms).
+    // Triggering a render cycle to show a loading animation is
+    // usually pointless as doing so would waste resources and
+    // appear less seemless to the user who will see brief
+    // flickering while the browser quickly recalculates it's
+    // layout twice. To that end, a timer is used to only render
+    // the loading animation on the link if the delegate task
+    // takes longer than 50ms
+    private void LoadingTimerElapsed(object? sender, EventArgs e) {
+        lock(triggerLock) {
+            if(isRunning)
+                isLoading = true;
+            InvokeAsync(() => StateHasChanged());
+        }
+    }
+
+    private void ErrorTimerElapsed(object? sender, EventArgs e) =>
+        InvokeAsync(() => StateHasChanged());
+
+    private async Task Trigger() {
+        lock(triggerLock) {
+            if(isRunning)
+                return;
+            isRunning = true;
+            loadingTimer.Start();
+        }
+
+        bool error = false;
+
+        try {
+            await Task.Run(OnClick);
+        } catch {
+            error = true;
+        } finally {
+            lock(triggerLock) {
+                loadingTimer.Stop();
+                isRunning = false;
+                isLoading = false;
+            }
+        }
+
+        if(error)
+            errorTimer.Start();
+
+        await InvokeAsync(() => StateHasChanged());
+    }
+
+    public void Dispose() =>
+        loadingTimer.Dispose();
+}