Add dynamic category part.

lib/foundation/comic_source/category.dart

@@ -97,6 +97,43 @@ class RandomCategoryPart extends BaseCategoryPart {
   );
 }
 
+class DynamicCategoryPart extends BaseCategoryPart {
+  final JSAutoFreeFunction loader;
+
+  final String sourceKey;
+
+  @override
+  List<CategoryItem> get categories {
+    var data = loader([]);
+    print(data);
+    if (data is! List) {
+      throw "DynamicCategoryPart loader must return a List";
+    }
+    var res = <CategoryItem>[];
+    for (var item in data) {
+      if (item is! Map) {
+        throw "DynamicCategoryPart loader must return a List of Map";
+      }
+      var label = item['label'];
+      var target = PageJumpTarget.parse(sourceKey, item['target']);
+      if (label is! String) {
+        throw "Category label must be a String";
+      }
+      res.add(CategoryItem(label, target));
+    }
+    return res;
+  }
+
+  @override
+  bool get enableRandom => false;
+
+  @override
+  final String title;
+
+  /// A [BaseCategoryPart] that show dynamic tags on category page.
+  const DynamicCategoryPart(this.title, this.loader, this.sourceKey);
+}
+
 CategoryData getCategoryDataWithKey(String key) {
   for (var source in ComicSource.all()) {
     if (source.categoryData?.key == key) {

lib/foundation/comic_source/parser.dart

@@ -403,27 +403,40 @@ class ComicSourceParser {
     var categoryParts = <BaseCategoryPart>[];
 
     for (var c in doc["parts"]) {
-      if (c["categories"] is! List || c["categories"].isEmpty) {
+      if (c["categories"] != null && c["categories"] is! List) {
         continue;
       }
-      List categories = c["categories"];
-      if (categories[0] is Map) {
+      List? categories = c["categories"];
+      if (categories == null || categories[0] is Map) {
         // new format
         final String name = c["name"];
         final String type = c["type"];
         final cs = categories
-            .map(
+            ?.map(
               (e) => CategoryItem(
                 e['label'],
                 PageJumpTarget.parse(_key!, e['target']),
               ),
             )
             .toList();
+        if (type != "dynamic" && (cs == null || cs.isEmpty)) {
+          continue;
+        }
         if (type == "fixed") {
-          categoryParts.add(FixedCategoryPart(name, cs));
+          categoryParts.add(FixedCategoryPart(name, cs!));
         } else if (type == "random") {
           categoryParts
-              .add(RandomCategoryPart(name, cs, c["randomNumber"] ?? 1));
+              .add(RandomCategoryPart(name, cs!, c["randomNumber"] ?? 1));
+        } else if (type == "dynamic" && categories == null) {
+          var loader = c["loader"];
+          if (loader is! JSInvokable) {
+            throw "DynamicCategoryPart loader must be a function";
+          }
+          categoryParts.add(DynamicCategoryPart(
+            name,
+            JSAutoFreeFunction(loader),
+            _key!,
+          ));
         }
       } else {
         // old format