feat: auto recognize magnet uri (#230)

ui/flutter/lib/app/modules/create/controllers/create_controller.dart

@@ -13,6 +13,7 @@ class CreateController extends GetxController
   final isResolving = false.obs;
   final showAdvanced = false.obs;
   late TabController advancedTabController;
+  final oldUrl = "".obs;
   final fileDataUri = "".obs;
 
   @override

ui/flutter/lib/app/modules/create/views/create_view.dart

@@ -55,7 +55,10 @@ class CreateView extends GetView<CreateController> {
             _urlController.text = value!.text!;
             _urlController.selection = TextSelection.fromPosition(
                 TextPosition(offset: _urlController.text.length));
+            return;
           }
+
+          recognizeMagnetUri(value!.text!);
         }
       });
     }
@@ -117,6 +120,10 @@ class CreateView extends GetView<CreateController> {
                           },
                           onChanged: (v) async {
                             controller.clearFileDataUri();
+                            if (controller.oldUrl.value.isEmpty) {
+                              recognizeMagnetUri(v);
+                            }
+                            controller.oldUrl.value = v;
                           },
                         ),
                       ),
@@ -237,6 +244,20 @@ class CreateView extends GetView<CreateController> {
     );
   }
 
+  // recognize magnet uri, if length == 40, auto add magnet prefix
+  recognizeMagnetUri(String text) {
+    if (text.length != 40) {
+      return;
+    }
+    final exp = RegExp(r"[0-9a-fA-F]+");
+    if (exp.hasMatch(text)) {
+      final uri = "magnet:?xt=urn:btih:$text";
+      _urlController.text = uri;
+      _urlController.selection = TextSelection.fromPosition(
+          TextPosition(offset: _urlController.text.length));
+    }
+  }
+
   Future<void> _doResolve() async {
     if (controller.isResolving.value) {
       return;