feat(v2): add search page (#2756)

packages/docusaurus-theme-search-algolia/src/theme/hooks/useSearchQuery.js

@@ -0,0 +1,41 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {useHistory, useLocation} from '@docusaurus/router';
+import ExecutionEnvironment from '@docusaurus/ExecutionEnvironment';
+
+const SEARCH_PARAM_QUERY = 'q';
+
+function useSearchQuery() {
+  const history = useHistory();
+  const location = useLocation();
+
+  return {
+    searchValue:
+      (ExecutionEnvironment.canUseDOM &&
+        new URLSearchParams(location.search).get(SEARCH_PARAM_QUERY)) ||
+      '',
+    updateSearchPath: (searchValue) => {
+      const searchParams = new URLSearchParams(location.search);
+
+      if (searchValue) {
+        searchParams.set(SEARCH_PARAM_QUERY, searchValue);
+      } else {
+        searchParams.delete(SEARCH_PARAM_QUERY);
+      }
+
+      history.replace({
+        search: searchParams.toString(),
+      });
+    },
+    navigateToSearchPage: (searchValue) => {
+      history.push(`/search?q=${searchValue}`);
+    },
+  };
+}
+
+export default useSearchQuery;