Implement auto-saving

src/browser/components/AutoSaveIndicator.jsx

@@ -0,0 +1,33 @@
+const React = require('react');
+const {Alert} = require('react-bootstrap');
+
+function AutoSaveIndicator(props) {
+  const {savingState, errorMessage, ...rest} = props;
+  return (
+    <Alert
+      className='AutoSaveIndicator'
+      {...rest}
+      bsStyle={props.savingState === 'error' ? 'danger' : 'info'}
+    >
+      {(() => {
+        switch (props.savingState) {
+        case 'saving':
+          return 'Saving...';
+        case 'saved':
+          return 'Saved!';
+        case 'error':
+          return props.errorMessage;
+        default:
+          return '';
+        }
+      })()}
+    </Alert>
+  );
+}
+
+AutoSaveIndicator.propTypes = {
+  savingState: React.PropTypes.string.isRequired,
+  errorMessage: React.PropTypes.string
+};
+
+module.exports = AutoSaveIndicator;