Merge pull request #152 from cloudscribe/feature/151

#151 Add nav suppressor support

Author: JimKerslake

src/cloudscribe.Web.Navigation/CachingNavigationViewComponent.cs

@@ -64,12 +64,17 @@ public CachingNavigationViewComponent(
         // In a simplecontent system I'd probably need to use the IHandlePageCreated (etc) 
         // hooks to clear a navcache of known name.
 
-        public async Task<IViewComponentResult> InvokeAsync(string viewName, 
-                                                            string filterName, 
-                                                            string startingNodeKey, 
+        public async Task<IViewComponentResult> InvokeAsync(string viewName,
+                                                            string filterName,
+                                                            string startingNodeKey,
                                                             int    expirationSeconds = 60,
                                                             bool   testMode = false)
         {
+            if (NavigationSuppressor.IsFilterSuppressed(Request.HttpContext, filterName))
+            {
+                return Content(string.Empty);
+            }
+
             NavigationViewModel model = null;
 
             string cacheKey = $"{viewName}_{filterName}_{startingNodeKey}";

src/cloudscribe.Web.Navigation/Constants.cs

@@ -9,5 +9,6 @@ namespace cloudscribe.Web.Navigation
     public static class Constants
     {
         public static readonly string TailCrumbsContexctKey = "navigationtailcrumbs";
+        public static readonly string NavigationSuppressContextKey = "navigation-suppress";
     }
 }

src/cloudscribe.Web.Navigation/NavigationSuppressor.cs

@@ -0,0 +1,43 @@
+// Copyright (c) Source Tree Solutions, LLC. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.AspNetCore.Http;
+using System;
+using System.Collections.Generic;
+
+namespace cloudscribe.Web.Navigation
+{
+    /// <summary>
+    /// Allows consuming applications to suppress specific navigation filters for the current request.
+    /// When a filter is suppressed, the NavigationViewComponent and CachingNavigationViewComponent
+    /// will return empty content immediately, avoiding all tree-building computation.
+    /// </summary>
+    public static class NavigationSuppressor
+    {
+        public static void SuppressFilter(HttpContext context, string filterName)
+        {
+            if (context == null) throw new ArgumentNullException(nameof(context));
+            if (string.IsNullOrEmpty(filterName)) return;
+
+            var key = Constants.NavigationSuppressContextKey;
+            if (context.Items[key] is not HashSet<string> suppressed)
+            {
+                suppressed = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
+                context.Items[key] = suppressed;
+            }
+            suppressed.Add(filterName);
+        }
+
+        public static bool IsFilterSuppressed(HttpContext context, string filterName)
+        {
+            if (context == null) return false;
+            if (string.IsNullOrEmpty(filterName)) return false;
+
+            if (context.Items[Constants.NavigationSuppressContextKey] is HashSet<string> suppressed)
+            {
+                return suppressed.Contains(filterName);
+            }
+            return false;
+        }
+    }
+}

src/cloudscribe.Web.Navigation/NavigationViewComponent.cs

@@ -47,6 +47,11 @@ public NavigationViewComponent(
 
         public async Task<IViewComponentResult> InvokeAsync(string viewName, string filterName, string startingNodeKey)
         {
+            if (NavigationSuppressor.IsFilterSuppressed(Request.HttpContext, filterName))
+            {
+                return Content(string.Empty);
+            }
+
             var rootNode = await _builder.GetTree();
             var urlHelper = _urlHelperFactory.GetUrlHelper(_actionContextAccesor.ActionContext);
             NavigationViewModel model = new NavigationViewModel(