Extract mention-aware link node helper and add tests

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/src/lib/mention-aware-link-node.ts

@@ -0,0 +1,67 @@
+import {
+  LinkNode,
+  type LinkAttributes,
+  type SerializedLinkNode,
+} from "@lexical/link";
+
+const CUSTOM_MENTION_URL_RE = /^(agent|project):\/\//;
+
+export class MentionAwareLinkNode extends LinkNode {
+  static getType(): string {
+    return "mention-aware-link";
+  }
+
+  static clone(node: MentionAwareLinkNode): MentionAwareLinkNode {
+    return new MentionAwareLinkNode(
+      node.getURL(),
+      {
+        rel: node.getRel(),
+        target: node.getTarget(),
+        title: node.getTitle(),
+      },
+      node.getKey(),
+    );
+  }
+
+  static importJSON(serializedNode: SerializedLinkNode): MentionAwareLinkNode {
+    return new MentionAwareLinkNode(
+      serializedNode.url ?? "",
+      {
+        rel: serializedNode.rel ?? null,
+        target: serializedNode.target ?? null,
+        title: serializedNode.title ?? null,
+      },
+    );
+  }
+
+  constructor(url?: string, attributes?: LinkAttributes, key?: string) {
+    super(url, attributes, key);
+  }
+
+  sanitizeUrl(url: string): string {
+    if (CUSTOM_MENTION_URL_RE.test(url)) return url;
+    return super.sanitizeUrl(url);
+  }
+}
+
+type MentionAwareLinkSource = Pick<LinkNode, "getURL" | "getRel" | "getTarget" | "getTitle">;
+
+export function getMentionAwareLinkNodeInit(node: MentionAwareLinkSource) {
+  return {
+    url: node.getURL(),
+    attributes: {
+      rel: node.getRel(),
+      target: node.getTarget(),
+      title: node.getTitle(),
+    },
+  };
+}
+
+export const mentionAwareLinkNodeReplacement = {
+  replace: LinkNode,
+  with: (node: LinkNode) => {
+    const { url, attributes } = getMentionAwareLinkNodeInit(node);
+    return new MentionAwareLinkNode(url, attributes);
+  },
+  withKlass: MentionAwareLinkNode,
+} as const;