feat: add component preview to library authoring

src/library-authoring/LibraryBlock/LibraryBlock.tsx

@@ -0,0 +1,153 @@
+import React, {
+  useCallback, useEffect, useRef, useState,
+} from 'react';
+import { ensureConfig, getConfig } from '@edx/frontend-platform';
+
+import wrapBlockHtmlForIFrame from './wrap';
+
+// FixMe: This works????
+ensureConfig(['LMS_BASE_URL', 'SECURE_ORIGIN_XBLOCK_BOOTSTRAP_HTML_URL'], 'library block component');
+
+interface LibraryBlockProps {
+  getHandlerUrl: (usageId: string) => Promise<string>;
+  onBlockNotification?: (notification: any) => void;
+  view: {
+    content: string;
+    resources: any[];
+  };
+}
+
+/**
+ * React component that displays an XBlock in a sandboxed IFrame.
+ *
+ * The IFrame is resized responsively so that it fits the content height.
+ *
+ * We use an IFrame so that the XBlock code, including user-authored HTML,
+ * cannot access things like the user's cookies, nor can it make GET/POST
+ * requests as the user. However, it is allowed to call any XBlock handlers.
+ */
+const LibraryBlock = ({ getHandlerUrl, onBlockNotification, view } : LibraryBlockProps) => {
+  const iframeRef = useRef<HTMLIFrameElement>(null);
+  const [html, setHtml] = useState<string | null>(null);
+  const [iFrameHeight, setIFrameHeight] = useState(400);
+  const [iFrameKey, setIFrameKey] = useState(0);
+
+  /**
+   * Handle any messages we receive from the XBlock Runtime code in the IFrame.
+   * See wrap.ts to see the code that sends these messages.
+   */
+  const receivedWindowMessage = useCallback(async (event) => {
+    if (!iframeRef.current || event.source !== iframeRef.current.contentWindow) {
+      return; // This is some other random message.
+    }
+
+    const { method, replyKey, ...args } = event.data;
+    const frame = iframeRef.current.contentWindow;
+    const sendReply = async (data: any) => {
+      frame?.postMessage({ ...data, replyKey }, '*');
+    };
+
+    if (method === 'bootstrap') {
+      sendReply({ initialHtml: html });
+    } else if (method === 'get_handler_url') {
+      const handlerUrl = await getHandlerUrl(args.usageId);
+      sendReply({ handlerUrl });
+    } else if (method === 'update_frame_height') {
+      setIFrameHeight(args.height);
+    } else if (method?.indexOf('xblock:') === 0) {
+      // This is a notification from the XBlock's frontend via 'runtime.notify(event, args)'
+      if (onBlockNotification) {
+        onBlockNotification({
+          eventType: method.substr(7), // Remove the 'xblock:' prefix that we added in wrap.ts
+          ...args,
+        });
+      }
+    }
+  }, [html]);
+
+  const processView = useCallback(() => {
+    if (!view) {
+      return;
+    }
+
+    const newHtml = wrapBlockHtmlForIFrame(
+      view.content,
+      view.resources,
+      getConfig().LMS_BASE_URL,
+    );
+
+    // Load the XBlock HTML into the IFrame:
+    //   iframe will only re-render in react when its property changes (key here)
+    setHtml(newHtml);
+    setIFrameKey(prevValue => prevValue + 1);
+  }, [view]);
+
+  /**
+   * Load the XBlock data from the LMS and then inject it into our IFrame.
+   */
+  useEffect(() => {
+    // Prepare to receive messages from the IFrame.
+    // Messages are the only way that the code in the IFrame can communicate
+    // with the surrounding UI.
+    window.addEventListener('message', receivedWindowMessage);
+
+    processView();
+
+    return () => {
+      window.removeEventListener('message', receivedWindowMessage);
+    };
+  }, [view, html]);
+
+  /* Only draw the iframe if the HTML has already been set.  This is because xblock-bootstrap.html will only request
+   * HTML once, upon being rendered. */
+  if (!html) {
+    return null;
+  }
+
+  return (
+    <div style={{
+      height: `${iFrameHeight}px`,
+      boxSizing: 'content-box',
+      position: 'relative',
+      overflow: 'hidden',
+      minHeight: '200px',
+      margin: '12px',
+      border: '1px solid #ccc',
+    }}
+    >
+      <iframe
+        key={iFrameKey}
+        ref={iframeRef}
+        title="block"
+        src={getConfig().SECURE_ORIGIN_XBLOCK_BOOTSTRAP_HTML_URL || 'https://metadata-test233.s3.amazonaws.com/xblock-bootstrap.html'}
+        data-testid="block-preview"
+        style={{
+          position: 'absolute',
+          left: 0,
+          top: 0,
+          width: '100%',
+          height: '100%',
+          minHeight: '200px',
+          border: '0 none',
+          backgroundColor: 'white',
+        }}
+        // allowing 'autoplay' is required to allow the video XBlock to control the YouTube iframe it has.
+        allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture"
+        sandbox={[
+          'allow-forms',
+          'allow-modals',
+          'allow-popups',
+          'allow-popups-to-escape-sandbox',
+          'allow-presentation',
+          'allow-same-origin', // This is only secure IF the IFrame source
+          // is served from a completely different domain name
+          // e.g. labxchange-xblocks.net vs www.labxchange.org
+          'allow-scripts',
+          'allow-top-navigation-by-user-activation',
+        ].join(' ')}
+      />
+    </div>
+  );
+};
+
+export default LibraryBlock;

src/library-authoring/LibraryBlock/index.ts

@@ -0,0 +1,2 @@
+/* eslint-disable-next-line import/prefer-default-export */
+export { default as LibraryBlock } from './LibraryBlock';