Add linkification cache for stdout/stderr rendering

packages/rendermime/src/renderers.ts

@@ -787,6 +787,24 @@ function* alignedNodes<T extends Node, U extends Node>(
  * @returns A promise which resolves when rendering is complete.
  */
 export function renderText(options: renderText.IRenderOptions): Promise<void> {
+  renderTextual(options, {
+    checkWeb: true,
+    checkPaths: false
+  });
+
+  // Return the rendered promise.
+  return Promise.resolve(undefined);
+}
+
+/**
+ * Render the textual representation into a host node.
+ *
+ * Implements the shared logic for `renderText` and `renderError`.
+ */
+function renderTextual(
+  options: renderText.IRenderOptions,
+  autoLinkOptions: IAutoLinkOptions
+) {
   // Unpack the options.
   const { host, sanitizer, source } = options;
 
@@ -801,16 +819,57 @@ export function renderText(options: renderText.IRenderOptions): Promise<void> {
 
   const preTextContent = pre.textContent;
 
+  let cacheStoreOptions = [];
+  if (autoLinkOptions.checkWeb) {
+    cacheStoreOptions.push('web');
+  }
+  if (autoLinkOptions.checkPaths) {
+    cacheStoreOptions.push('paths');
+  }
+  const cacheStoreKey = cacheStoreOptions.join('-');
+  let cacheStore = Private.autoLinkCache.get(cacheStoreKey);
+  if (!cacheStore) {
+    cacheStore = new WeakMap();
+    Private.autoLinkCache.set(cacheStoreKey, cacheStore);
+  }
+
   let ret: HTMLPreElement;
   if (preTextContent) {
     // Note: only text nodes and span elements should be present after sanitization in the `<pre>` element.
-    const linkedNodes =
-      sanitizer.getAutolink?.() ?? true
-        ? autolink(preTextContent, {
-            checkWeb: true,
-            checkPaths: false
-          })
-        : [document.createTextNode(content)];
+    let linkedNodes: (HTMLAnchorElement | Text)[];
+    if (sanitizer.getAutolink?.() ?? true) {
+      const cache = getApplicableLinkCache(
+        cacheStore.get(host),
+        preTextContent
+      );
+      if (cache) {
+        const { cachedNodes, addedText } = cache;
+        const fromCache = cachedNodes;
+        const newAdditions = autolink(addedText, autoLinkOptions);
+        const lastInCache = fromCache[fromCache.length - 1];
+        const firstNewNode = newAdditions[0];
+
+        if (lastInCache instanceof Text && firstNewNode instanceof Text) {
+          const joiningNode = lastInCache;
+          joiningNode.data += firstNewNode.data;
+          linkedNodes = [
+            ...fromCache.slice(0, -1),
+            joiningNode,
+            ...newAdditions.slice(1)
+          ];
+        } else {
+          linkedNodes = [...fromCache, ...newAdditions];
+        }
+      } else {
+        linkedNodes = autolink(preTextContent, autoLinkOptions);
+      }
+      cacheStore.set(host, {
+        preTextContent,
+        linkedNodes
+      });
+    } else {
+      linkedNodes = [document.createTextNode(content)];
+    }
 
     const preNodes = Array.from(pre.childNodes) as (Text | HTMLSpanElement)[];
     ret = mergeNodes(preNodes, linkedNodes);
@@ -819,9 +878,6 @@ export function renderText(options: renderText.IRenderOptions): Promise<void> {
   }
 
   host.appendChild(ret);
-
-  // Return the rendered promise.
-  return Promise.resolve(undefined);
 }
 
 /**
@@ -854,6 +910,67 @@ export namespace renderText {
   }
 }
 
+interface IAutoLinkCacheEntry {
+  preTextContent: string;
+  linkedNodes: (HTMLAnchorElement | Text)[];
+}
+
+/**
+ * Return the information from the cache that can be used given the cache entry and current text.
+ * If the cache is invalid given the current text (or cannot be used) `null` is returned.
+ */
+function getApplicableLinkCache(
+  cachedResult: IAutoLinkCacheEntry | undefined,
+  preTextContent: string
+): {
+  cachedNodes: IAutoLinkCacheEntry['linkedNodes'];
+  addedText: string;
+} | null {
+  if (!cachedResult) {
+    return null;
+  }
+  if (preTextContent.length < cachedResult.preTextContent.length) {
+    // If the new content is shorter than the cached content
+    // we cannot use the cache as we only support appending.
+    return null;
+  }
+  let addedText = preTextContent.substring(cachedResult.preTextContent.length);
+  let cachedNodes = cachedResult.linkedNodes;
+  const lastCachedNode =
+    cachedResult.linkedNodes[cachedResult.linkedNodes.length - 1];
+
+  // Only use cached nodes if:
+  // - the last cached node is a text node
+  // - the new content starts with a new line
+  // - the old content ends with a new line
+  if (
+    cachedResult.preTextContent.endsWith('\n') ||
+    addedText.startsWith('\n')
+  ) {
+    // continue
+  } else if (lastCachedNode instanceof Text) {
+    // Remove the Text node to re-analyse this text.
+    // This is required when we cached `aaa www.one.com bbb www.`
+    // and the incoming addition is `two.com`. We can still
+    // use text node `aaa ` and anchor node `www.one.com`, but
+    // we need to pass `bbb www.` + `two.com` through linkify again.
+    cachedNodes = cachedNodes.slice(0, -1);
+    addedText = lastCachedNode.textContent + addedText;
+    // continue
+  } else {
+    return null;
+  }
+
+  // Finally check if text has not changed.
+  if (!preTextContent.startsWith(cachedResult.preTextContent)) {
+    return null;
+  }
+  return {
+    cachedNodes,
+    addedText
+  };
+}
+
 /**
  * Render error into a host node.
  *
@@ -865,37 +982,13 @@ export function renderError(
   options: renderError.IRenderOptions
 ): Promise<void> {
   // Unpack the options.
-  const { host, linkHandler, sanitizer, resolver, source } = options;
+  const { host, linkHandler, resolver } = options;
 
-  // Create the HTML content.
-  const content = sanitizer.sanitize(Private.ansiSpan(source), {
-    allowedTags: ['span']
+  renderTextual(options, {
+    checkWeb: true,
+    checkPaths: true
   });
 
-  // Set the sanitized content for the host node.
-  const pre = document.createElement('pre');
-  pre.innerHTML = content;
-
-  const preTextContent = pre.textContent;
-
-  let ret: HTMLPreElement;
-  if (preTextContent) {
-    // Note: only text nodes and span elements should be present after sanitization in the `<pre>` element.
-    const linkedNodes =
-      sanitizer.getAutolink?.() ?? true
-        ? autolink(preTextContent, {
-            checkWeb: true,
-            checkPaths: true
-          })
-        : [document.createTextNode(content)];
-
-    const preNodes = Array.from(pre.childNodes) as (Text | HTMLSpanElement)[];
-    ret = mergeNodes(preNodes, linkedNodes);
-  } else {
-    ret = document.createElement('pre');
-  }
-  host.appendChild(ret);
-
   // Patch the paths if a resolver is available.
   let promise: Promise<void>;
   if (resolver) {
@@ -1012,6 +1105,14 @@ export namespace renderError {
  * The namespace for module implementation details.
  */
 namespace Private {
+  /**
+   * Cache for auto-linking results to provide better performance when streaming outputs.
+   */
+  export const autoLinkCache = new Map<
+    string,
+    WeakMap<HTMLElement, IAutoLinkCacheEntry>
+  >();
+
   /**
    * Eval the script tags contained in a host populated by `innerHTML`.
    *