4 files changed, 78 insertions, 3 deletions

diff --git a/application/bookmark/LinkUtils.php b/application/bookmark/LinkUtils.php
index 88379430..98d9038a 100644
--- a/application/bookmark/LinkUtils.php
+++ b/application/bookmark/LinkUtils.php
@@ -220,7 +220,7 @@ function hashtag_autolink($description, $indexUrl = '')
      * \p{Mn} - any non marking space (accents, umlauts, etc)
      */
     $regex = '/(^|\s)#([\p{Pc}\p{N}\p{L}\p{Mn}]+)/mui';
-    $replacement = '$1<a href="'. $indexUrl .'?addtag=$2" title="Hashtag $2">#$2</a>';
+    $replacement = '$1<a href="'. $indexUrl .'./add-tag/$2" title="Hashtag $2">#$2</a>';
     return preg_replace($regex, $replacement, $description);
 }
 
diff --git a/application/container/ShaarliContainer.php b/application/container/ShaarliContainer.php
index af62e574..3995f669 100644
--- a/application/container/ShaarliContainer.php
+++ b/application/container/ShaarliContainer.php
@@ -18,6 +18,7 @@ use Slim\Container;
 /**
  * Extension of Slim container to document the injected objects.
  *
+ * @property mixed[]                  $environment     $_SERVER automatically injected by Slim
  * @property ConfigManager            $conf
  * @property SessionManager           $sessionManager
  * @property LoginManager             $loginManager
diff --git a/application/formatter/BookmarkMarkdownFormatter.php b/application/formatter/BookmarkMarkdownFormatter.php
index 077e5312..5d244d4c 100644
--- a/application/formatter/BookmarkMarkdownFormatter.php
+++ b/application/formatter/BookmarkMarkdownFormatter.php
@@ -114,7 +114,7 @@ class BookmarkMarkdownFormatter extends BookmarkDefaultFormatter
 
     /**
      * Replace hashtag in Markdown links format
-     * E.g. `#hashtag` becomes `[#hashtag](?addtag=hashtag)`
+     * E.g. `#hashtag` becomes `[#hashtag](./add-tag/hashtag)`
      * It includes the index URL if specified.
      *
      * @param string $description
@@ -133,7 +133,7 @@ class BookmarkMarkdownFormatter extends BookmarkDefaultFormatter
          * \p{Mn} - any non marking space (accents, umlauts, etc)
          */
         $regex = '/(^|\s)#([\p{Pc}\p{N}\p{L}\p{Mn}]+)/mui';
-        $replacement = '$1[#$2]('. $indexUrl .'?addtag=$2)';
+        $replacement = '$1[#$2]('. $indexUrl .'./add-tag/$2)';
 
         $descriptionLines = explode(PHP_EOL, $description);
         $descriptionOut = '';
diff --git a/application/front/controllers/TagController.php b/application/front/controllers/TagController.php
new file mode 100644
index 00000000..598275b0
--- /dev/null
+++ b/application/front/controllers/TagController.php
@@ -0,0 +1,74 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Shaarli\Front\Controller;
+
+use Slim\Http\Request;
+use Slim\Http\Response;
+
+/**
+ * Class TagController
+ *
+ * Slim controller handle tags.
+ *
+ * @package Front\Controller
+ */
+class TagController extends ShaarliController
+{
+    /**
+     * Add another tag in the current search through an HTTP redirection.
+     *
+     * @param array $args Should contain `newTag` key as tag to add to current search
+     */
+    public function addTag(Request $request, Response $response, array $args): Response
+    {
+        $newTag = $args['newTag'] ?? null;
+        $referer = $this->container->environment['HTTP_REFERER'] ?? null;
+
+        // In case browser does not send HTTP_REFERER, we search a single tag
+        if (null === $referer) {
+            if (null !== $newTag) {
+                return $response->withRedirect('./?searchtags='. urlencode($newTag));
+            }
+
+            return $response->withRedirect('./');
+        }
+
+        $currentUrl = parse_url($this->container->environment['HTTP_REFERER']);
+        parse_str($currentUrl['query'] ?? '', $params);
+
+        if (null === $newTag) {
+            return $response->withRedirect(($currentUrl['path'] ?? './') .'?'. http_build_query($params));
+        }
+
+        // Prevent redirection loop
+        if (isset($params['addtag'])) {
+            unset($params['addtag']);
+        }
+
+        // Check if this tag is already in the search query and ignore it if it is.
+        // Each tag is always separated by a space
+        $currentTags = isset($params['searchtags']) ? explode(' ', $params['searchtags']) : [];
+
+        $addtag = true;
+        foreach ($currentTags as $value) {
+            if ($value === $newTag) {
+                $addtag = false;
+                break;
+            }
+        }
+
+        // Append the tag if necessary
+        if (true === $addtag) {
+            $currentTags[] = trim($newTag);
+        }
+
+        $params['searchtags'] = trim(implode(' ', $currentTags));
+
+        // We also remove page (keeping the same page has no sense, since the results are different)
+        unset($params['page']);
+
+        return $response->withRedirect(($currentUrl['path'] ?? './') .'?'. http_build_query($params));
+    }
+}