add wildcard fallback handlers

SimpleHttpServer/HttpServer.cs

@@ -89,6 +89,7 @@ public sealed class HttpServer {
     private readonly Dictionary<string, PathTree<EndpointInvocationInfo>> pathEndpointMethodInfosTrees = new(); // reqmethod : pathtree
     private static readonly Type[] expectedEndpointParameterTypes = new[] { typeof(RequestContext) };
     internal static readonly int expectedEndpointParameterPrefixCount = expectedEndpointParameterTypes.Length;
+    private readonly Dictionary<string, Func<RequestContext, Task<bool>>> wildcardFallbackHandlers = new(); // reqmethod : handler
 
     public void RegisterEndpointsFromType<T>(Func<T>? instanceFactory = null) where T : class { // T cannot be static, as generic args must be nonstatic
         if (stringToTypeParameterConverters.Count == 0)
@@ -267,8 +268,9 @@ public sealed class HttpServer {
             /* Finding the endpoint that should process the request:
              * 1. Try to see if there is a simple endpoint where request method and path match
              * 2. Otherwise, try to see if a path-parameter-endpoint matches (duplicates throw an error on startup)
-             * 3. Otherwise, check if it is inside a static serve path
+             * 3. Otherwise, check if wildcardFallbackHandlers contains a handler for the current requestMethod. If this method returns false 'request was not handled', continue, otherwise skip all future steps.
-             * 4. Otherwise, show 404 page */
+             * 4. Otherwise, check if it is inside a static serve path
+             * 5. Otherwise, show 404 page */
 
             EndpointInvocationInfo? pathEndpointInvocationInfo = null;
             if (simpleEndpointMethodInfos.TryGetValue(requestMethod, reqPath, out var simpleEndpointInvocationInfo) ||
@@ -354,7 +356,17 @@ public sealed class HttpServer {
                 // todo read and convert pathparams
 
                 await (Task) (mi.Invoke(endpointInvocationInfo.typeInstanceReference, convertedMParamValues) ?? throw new NullReferenceException("Website func returned null unexpectedly"));
-            } else { // try to find suitable static serve path
+            } else {
+                // ---------------- check for fallback wildcard handler ----------------
+                if (wildcardFallbackHandlers.TryGetValue(requestMethod, out var handler)) {
+                    var handledByWildcard = await handler.Invoke(rc);
+                    if (handledByWildcard) { // if that handler was able to handle the request, end execution
+                        return;
+                    }
+                }
+                // ---------------------------------------------------------------------
+
+                // try to find suitable static serve path
                 if (requestMethod == "GET")
                     foreach (var (k, v) in staticServePaths) {
                         if (reqPath.StartsWith(k)) { // do a static serve
@@ -415,4 +427,14 @@ public sealed class HttpServer {
             }
         } catch (ObjectDisposedException) { }
     }
+
+    /// <summary>
+    /// Adds a wildcard fallback handler that receives any request that was not matched by a more explicit endpoint. 
+    /// The handler is supposed to return 'true' if the request was handled correctly and thus execution shall end. Return 'false' to try to serve the file from a static-serve path.
+    /// </summary>
+    /// <param name="reqMethod"></param>
+    /// <param name="requestHandler">This method must return whether the reuqest was handled; returning false makes handling act as if this handler never ran</param>
+    public void RegisterWildcardFallbackHandler(HttpRequestType reqMethod, Func<RequestContext, Task<bool>> requestHandler) {
+        wildcardFallbackHandlers.Add(Enum.GetName(reqMethod) ?? throw new NotImplementedException(), requestHandler);
+    }
 }