Implement configuration getting

lib/AbstractSanitizer.php

@@ -510,6 +510,10 @@ abstract class AbstractSanitizer {
                                 // ignore any other value for the elements list (this is invalid)
                                 continue;
                             }
+                            if (!$list) {
+                                // an empty element list is non-functional, so we can skip the attribute
+                                continue;
+                            }
                             // create any structures which might be missing
                             if (!isset($out[$opt])) {
                                 $out[$opt] = [];
@@ -531,4 +535,71 @@ abstract class AbstractSanitizer {
             $this->config = $out;
         }
     }
+
+    /** Returns a normalized representation of the effective configuration */
+    public function getConfiguration(): array {
+        return $this->exportConfiguration($this->config);
+    }
+
+    /** Returns the default configuration */
+    public function getDefaultConfiguration(): array {
+        return $this->exportConfiguration(self::DEFAULT_CONF);
+    }
+
+    /** Converts a configuration from the internal representation to the external representation */
+    protected function exportConfiguration(array $config): array {
+        $out = [];
+        // start with the element lists
+        foreach (["allowElements", "blockElements", "dropElements"] as $opt) {
+            if (isset($config[$opt])) {
+                $out[$opt] = [];
+                ksort($config[$opt]);
+                foreach ($config[$opt] as $ns => $set) {
+                    ksort($set);
+                    foreach ($set as $el => $t) {
+                        if ($ns === self::HTML_NAMESPACE) {
+                            $out[$opt][] = $el;
+                        } else {
+                            $out[$opt][] = ['name' => $el, 'namespace' => $ns];
+                        }
+                    }
+                }
+            }
+        }
+        // continue with attribute lists
+        foreach (["allowAttributes", "dropAttributes"] as $opt) {
+            if (isset($config[$opt])) {
+                $out[$opt] = [];
+                ksort($config[$opt]);
+                foreach ($config[$opt] as $ns => $set) {
+                    ksort($set);
+                    foreach ($set as $attr => $elems) {
+                        $list = [];
+                        ksort($elems);
+                        foreach ($elems as $eNs => $eSet) {
+                            ksort($eSet);
+                            foreach ($eSet as $el => $t) {
+                                if ($eNs === self::HTML_NAMESPACE) {
+                                    $list[] = $el;
+                                } else {
+                                    $list[] = ['name' => $el, 'namespace' => $eNs];
+                                }
+                            }
+                        }
+                        if ($ns === self::NULL_NAMESPACE) {
+                            $out[$opt][] = ['name' => $attr, 'elements' => $list];
+                        } else {
+                            $out[$opt][] = ['name' => $attr, 'namespace' => $ns, 'elements' => $list];
+                        }
+                    }
+                }
+            }
+        }
+        // finally handle the boolean options
+        foreach (["allowCustomElements", "allowUnknownMarkup", "allowComments", "allowProcessingInstructions", "nullNamespaceAsHtml"] as $opt) {
+            $out[$opt] = $config[$opt];
+        }
+        // return the transformed configuration
+        return $out;
+    }
 }