core&ui: add new features about domain (#528)

Co-authored-by: undefined <i@undefined.moe>

- Add navigation hint
- Update homework/contest filter by assign
- Allow empty query for DomainSelectAutoComplete

packages/ui-default/pages/problem_sidebar.page.ts

@@ -1,4 +1,5 @@
 import $ from 'jquery';
+import DomainSelectAutoComplete from 'vj/components/autocomplete/DomainSelectAutoComplete';
 import { ActionDialog, ConfirmDialog } from 'vj/components/dialog';
 import Notification from 'vj/components/notification';
 import { NamedPage } from 'vj/misc/Page';
@@ -22,17 +23,31 @@ const page = new NamedPage([
     });
   });
   $(document).on('click', '[name="problem-sidebar__copy"]', () => {
-    new ActionDialog({
-      $body: tpl`
-        <div class="typo">
-          <label>
-            ${i18n('Target')}
-            <div class="textbox-container">
-              <input name="target" type="text" class="textbox" data-autofocus>
-            </div>
-          </label>
+    $(tpl`<div style="display: none" class="dialog__body--problem-copy">
+  <div class="row"><div class="columns">
+    <h1 name="select_user_hint">${i18n('Copy Problem')}</h1>
+  </div></div>
+  <div class="row">
+    <div class="columns">
+      <label>
+      ${i18n('Target')}
+        <div class="textbox-container">
+          <input name="target" type="text" class="textbox" data-autofocus>
         </div>
-      `,
+      </label>
+    </div>
+  </div>
+</div>`).appendTo(document.body);
+    const domainSelector = DomainSelectAutoComplete.getOrConstruct($('.dialog__body--problem-copy [name="target"]')) as any;
+    new ActionDialog({
+      $body: $('.dialog__body--problem-copy > div'),
+      onDispatch(action) {
+        if (action === 'ok' && domainSelector.value() === null) {
+          domainSelector.focus();
+          return false;
+        }
+        return true;
+      },
     }).open().then(async (action) => {
       if (action !== 'ok') return;
       const target = $('[name="target"]').val();