sysadmin reconstruct user page (#4030)

* sysadmin reconstruct user page

* [system admin] users: refactored it

frontend/src/components/dialog/sysadmin-dialog/sysadmin-import-user-dialog.js

@@ -0,0 +1,68 @@
+
+import React from 'react';
+import PropTypes from 'prop-types';
+import { Alert, Modal, ModalHeader, ModalBody, ModalFooter, Button } from 'reactstrap';
+import { gettext, siteRoot } from '../../../utils/constants';
+
+const propTypes = {
+  toggle: PropTypes.func.isRequired,
+  importUserInBatch: PropTypes.func.isRequired,
+};
+
+class SysAdminImportUserDialog extends React.Component {
+  constructor(props) {
+    super(props);
+    this.fileInputRef = React.createRef();
+    this.state = {
+      errorMsg: ''
+    };
+  }
+
+  toggle = () => {
+    this.props.toggle();
+  }
+
+  openFileInput = () => {
+    this.fileInputRef.current.click();
+  }
+
+  uploadFile = (e) => {
+    // no file selected
+    if (!this.fileInputRef.current.files.length) {
+      return;
+    }
+    // check file extension
+    let fileName = this.fileInputRef.current.files[0].name;
+    if(fileName.substr(fileName.lastIndexOf('.') + 1) != 'xlsx') {
+      this.setState({
+        errorMsg: gettext('Please choose a .xlsx file.')
+      });
+      return;
+    }
+    const file = this.fileInputRef.current.files[0];
+    this.props.importUserInBatch(file);
+  }
+
+  render() {
+    let { errorMsg } = this.state;
+    return (
+      <Modal isOpen={true} toggle={this.toggle}>
+        <ModalHeader toggle={this.toggle}>{gettext('Import users from a .xlsx file')}</ModalHeader>
+        <ModalBody>
+          <a href={`${siteRoot}useradmin/batchadduser/example/`}>{gettext('Download an example file')}</a>
+          <br/>
+          <button className="btn btn-outline-primary" onClick={this.openFileInput}>{gettext('Upload file')}</button>
+          <input className="d-none" type="file" onChange={this.uploadFile} ref={this.fileInputRef} />
+          {errorMsg && <Alert color="danger">{errorMsg}</Alert>}
+        </ModalBody>
+        <ModalFooter>
+          <Button color="secondary" onClick={this.toggle}>{gettext('Cancel')}</Button>
+        </ModalFooter>
+      </Modal>
+    );
+  }
+}
+
+SysAdminImportUserDialog.propTypes = propTypes;
+
+export default SysAdminImportUserDialog;