Fix Category widget URLs

The category widget template expects a URL without any query params, as
it appends `/?cat=<selected category>` to the base URL passed to it.

The Widget code tried to preserve any query param passed to it except
for the `cat` query param. When passed to the template, this caused the
invalid URLs to be generated.

Example input url:

    https://example.com/channel/user?f=&tag=pasta

The URL generated for the "Dinner" category would then be:

    https://example.com/channel/user&tag=pasta&tag=pasta/?cat=Dinner

Which is troublesome in more than one way, and cause at least some
search bots to go wild by sending requests with increasingly long URLs.

This patch will simply discard the existing query params in the URL, so
with the same input url, the generated URL for the "Dinner" category
will now be:

    https://example.com/channel/user/?cat=Dinner

This is comparable to what the Category Cloud and Tag Cloud widgets
already do.

1 files changed, 6 insertions, 5 deletions

diff --git a/Zotlabs/Widget/Categories.php b/Zotlabs/Widget/Categories.php
index b31856e48..b0eda253b 100644
--- a/Zotlabs/Widget/Categories.php
+++ b/Zotlabs/Widget/Categories.php
@@ -24,15 +24,16 @@ class Categories {
 		}
 
 		$cat = ((x($_REQUEST, 'cat')) ? htmlspecialchars($_REQUEST['cat'], ENT_COMPAT, 'UTF-8') : '');
-		$srchurl = App::$query_string;
-		$srchurl = rtrim(preg_replace('/cat\=[^\&].*?(\&|$)/is', '', $srchurl), '&');
-		$srchurl = str_replace(['?f=','&f=', '/?'], ['', '', ''], $srchurl);
+
+		// Discard queries from the current URL, as the template expects a base
+		// URL without any queries.
+		$base = substr(App::$query_string, 0, strcspn(App::$query_string, '?'));
 
 		if($files) {
-			return filecategories_widget($srchurl, $cat);
+			return filecategories_widget($base, $cat);
 		}
 
-		return categories_widget($srchurl, $cat);
+		return categories_widget($base, $cat);
 
 	}
 }