feat: Auto update titles in linked documents (#1233)

* feat: Auto update titles in linked documents

* Add spec

server/services/backlinks.js

@@ -3,6 +3,7 @@ import { difference } from 'lodash';
 import type { DocumentEvent } from '../events';
 import { Document, Revision, Backlink } from '../models';
 import parseDocumentIds from '../../shared/utils/parseDocumentIds';
+import slugify from '../utils/slugify';
 
 export default class Backlinks {
   async on(event: DocumentEvent) {
@@ -50,6 +51,7 @@ export default class Backlinks {
         const addedLinkIds = difference(currentLinkIds, previousLinkIds);
         const removedLinkIds = difference(previousLinkIds, currentLinkIds);
 
+        // add any new backlinks that were created
         await Promise.all(
           addedLinkIds.map(async linkId => {
             const linkedDocument = await Document.findByPk(linkId);
@@ -67,6 +69,7 @@ export default class Backlinks {
           })
         );
 
+        // delete any backlinks that were removed
         await Promise.all(
           removedLinkIds.map(async linkId => {
             const document = await Document.findByPk(linkId);
@@ -78,6 +81,39 @@ export default class Backlinks {
             });
           })
         );
+
+        if (currentRevision.title === previousRevision.title) {
+          break;
+        }
+
+        // update any link titles in documents that lead to this one
+        const backlinks = await Backlink.findAll({
+          where: {
+            documentId: event.documentId,
+          },
+          include: [{ model: Document, as: 'reverseDocument' }],
+        });
+
+        await Promise.all(
+          backlinks.map(async backlink => {
+            const previousUrl = `/doc/${slugify(previousRevision.title)}-${
+              document.urlId
+            }`;
+
+            // find links in the other document that lead to this one and have
+            // the old title as anchor text. Go ahead and update those to the
+            // new title automatically
+            backlink.reverseDocument.text = backlink.reverseDocument.text.replace(
+              `[${previousRevision.title}](${previousUrl})`,
+              `[${document.title}](${document.url})`
+            );
+            await backlink.reverseDocument.save({
+              silent: true,
+              hooks: false,
+            });
+          })
+        );
+
         break;
       }
       case 'documents.delete': {