From ba8671ac0372c50e46d548fc4dd5e8a84e133044 Mon Sep 17 00:00:00 2001
From: YuviPanda <yuvipanda@gmail.com>
Date: Wed, 9 Jun 2021 02:18:24 +0530
Subject: [PATCH] Add an 'interface switcher' to the toolbar

Fixes https://github.com/jupyterlab/retrolab/issues/157
---
 packages/notebook-extension/src/index.ts    |   5 +-
 packages/notebook-extension/src/toolbar.tsx | 144 ++++++++++++++++++++
 2 files changed, 148 insertions(+), 1 deletion(-)
 create mode 100644 packages/notebook-extension/src/toolbar.tsx

diff --git a/packages/notebook-extension/src/index.ts b/packages/notebook-extension/src/index.ts
index 17913804..25861244 100644
--- a/packages/notebook-extension/src/index.ts
+++ b/packages/notebook-extension/src/index.ts
@@ -20,6 +20,8 @@ import { Poll } from '@lumino/polling';
 
 import { Widget } from '@lumino/widgets';
 
+import { addNotebookToolbarItems } from './toolbar';
+
 /**
  * The class for kernel status errors.
  */
@@ -241,7 +243,8 @@ const shell: JupyterFrontEndPlugin<IRetroShell> = {
 const plugins: JupyterFrontEndPlugin<any>[] = [
   checkpoints,
   kernelLogo,
-  kernelStatus
+  kernelStatus,
+  addNotebookToolbarItems
 ];
 
 export default plugins;
diff --git a/packages/notebook-extension/src/toolbar.tsx b/packages/notebook-extension/src/toolbar.tsx
new file mode 100644
index 00000000..96ac8434
--- /dev/null
+++ b/packages/notebook-extension/src/toolbar.tsx
@@ -0,0 +1,144 @@
+import {
+  JupyterFrontEnd,
+  JupyterFrontEndPlugin
+} from '@jupyterlab/application';
+import { ICommandPalette, ReactWidget } from '@jupyterlab/apputils';
+import { PageConfig } from '@jupyterlab/coreutils';
+import { DocumentRegistry } from '@jupyterlab/docregistry';
+import { IMainMenu } from '@jupyterlab/mainmenu';
+import {
+  INotebookModel,
+  INotebookTracker,
+  NotebookPanel
+} from '@jupyterlab/notebook';
+import { HTMLSelect } from '@jupyterlab/ui-components';
+import { CommandRegistry } from '@lumino/commands';
+import { IDisposable } from '@lumino/disposable';
+import * as React from 'react';
+
+/**
+ * Command IDs used by notebook toolbar items
+ */
+namespace CommandIDs {
+  /**
+   * Open current notebook in classic notebook
+   */
+  export const openClassic = 'retro:open-classic';
+  /**
+   * Open current notebook in JupyterLab
+   */
+  export const openLab = 'retro:open-lab';
+}
+
+class InterfaceSwitcher extends ReactWidget {
+  constructor(private commands: CommandRegistry) {
+    super();
+    this.addClass('jp-Notebook-toolbarCellType');
+  }
+
+  onChange = (event: React.ChangeEvent<HTMLSelectElement>) => {
+    const target = event.target.value;
+    if (target === '-') {
+      return;
+    }
+    this.commands.execute(target);
+  };
+
+  render = () => {
+    return (
+      <HTMLSelect
+        onChange={this.onChange}
+        className="jp-Notebook-toolbarCellTypeDropdown"
+      >
+        <option value="-">Interface</option>
+        <option value={CommandIDs.openClassic}>Classic</option>
+        <option value={CommandIDs.openLab}>JupyterLab</option>
+      </HTMLSelect>
+    );
+  };
+}
+
+/**
+ * A notebook widget extension that adds a open in classic notebook button to the toolbar.
+ */
+class InterfaceSwitcherButton
+  implements DocumentRegistry.IWidgetExtension<NotebookPanel, INotebookModel> {
+  constructor(commands: CommandRegistry) {
+    this._commands = commands;
+  }
+
+  createNew(panel: NotebookPanel): IDisposable {
+    const switcher = new InterfaceSwitcher(this._commands);
+    panel.toolbar.insertBefore('kernelName', 'switch-interface', switcher);
+    return switcher;
+  }
+
+  private _commands: CommandRegistry;
+}
+
+/**
+ * A plugin to add custom toolbar items to the notebook page
+ */
+const notebookToolbarItems: JupyterFrontEndPlugin<void> = {
+  id: '@retrolab/notebook-extension:open-classic',
+  autoStart: true,
+  optional: [INotebookTracker, ICommandPalette, IMainMenu],
+  activate: (
+    app: JupyterFrontEnd,
+    notebookTracker: INotebookTracker | null,
+    palette: ICommandPalette | null,
+    menu: IMainMenu | null
+  ) => {
+    if (!notebookTracker) {
+      // to prevent showing the toolbar button in RetroLab
+      return;
+    }
+
+    const { commands, docRegistry, shell } = app;
+    const baseUrl = PageConfig.getBaseUrl();
+
+    const isEnabled = () => {
+      return (
+        notebookTracker.currentWidget !== null &&
+        notebookTracker.currentWidget === shell.currentWidget
+      );
+    };
+
+    commands.addCommand(CommandIDs.openClassic, {
+      label: 'Open in Classic Notebook',
+      execute: () => {
+        const current = notebookTracker.currentWidget;
+        if (!current) {
+          return;
+        }
+        window.open(`${baseUrl}tree/${current.context.path}`);
+      },
+      isEnabled
+    });
+
+    commands.addCommand(CommandIDs.openLab, {
+      label: 'Open in JupyterLab',
+      execute: () => {
+        const current = notebookTracker.currentWidget;
+        if (!current) {
+          return;
+        }
+        window.open(`${baseUrl}lab/tree/${current.context.path}`);
+      },
+      isEnabled
+    });
+
+    if (palette) {
+      palette.addItem({ command: CommandIDs.openClassic, category: 'Other' });
+    }
+
+    if (menu) {
+      menu.viewMenu.addGroup([{ command: CommandIDs.openClassic }], 1);
+    }
+
+    const interfaceSwitcher = new InterfaceSwitcherButton(commands);
+    docRegistry.addWidgetExtension('Notebook', interfaceSwitcher);
+  }
+};
+
+export { notebookToolbarItems as addNotebookToolbarItems };