Restore vanilla components

app/javascript/mastodon/components/collapsable.js

@@ -0,0 +1,22 @@
+import React from 'react';
+import Motion from '../features/ui/util/optional_motion';
+import spring from 'react-motion/lib/spring';
+import PropTypes from 'prop-types';
+
+const Collapsable = ({ fullHeight, isVisible, children }) => (
+  <Motion defaultStyle={{ opacity: !isVisible ? 0 : 100, height: isVisible ? fullHeight : 0 }} style={{ opacity: spring(!isVisible ? 0 : 100), height: spring(!isVisible ? 0 : fullHeight) }}>
+    {({ opacity, height }) =>
+      <div style={{ height: `${height}px`, overflow: 'hidden', opacity: opacity / 100, display: Math.floor(opacity) === 0 ? 'none' : 'block' }}>
+        {children}
+      </div>
+    }
+  </Motion>
+);
+
+Collapsable.propTypes = {
+  fullHeight: PropTypes.number.isRequired,
+  isVisible: PropTypes.bool.isRequired,
+  children: PropTypes.node.isRequired,
+};
+
+export default Collapsable;