chore: Refactor backlinks and revisions (#1611)

* Update backlinks service to not rely on revisions

* fix: Add missing index for finding backlinks

* Debounce revision creation (#1616)

* refactor debounce logic to service

* Debounce slack notification

* Revisions created by service

* fix: Revision sidebar latest

* test: Add tests for notifications

server/services/backlinks.js

@@ -1,15 +1,17 @@
 // @flow
-import { difference } from "lodash";
-import type { DocumentEvent } from "../events";
-import { Document, Revision, Backlink } from "../models";
+import type { DocumentEvent, RevisionEvent } from "../events";
+import { Document, Backlink } from "../models";
+import { Op } from "../sequelize";
 import parseDocumentIds from "../utils/parseDocumentIds";
 import slugify from "../utils/slugify";
 
 export default class Backlinks {
-  async on(event: DocumentEvent) {
+  async on(event: DocumentEvent | RevisionEvent) {
     switch (event.name) {
       case "documents.publish": {
         const document = await Document.findByPk(event.documentId);
+        if (!document) return;
+
         const linkIds = parseDocumentIds(document.text);
 
         await Promise.all(
@@ -32,36 +34,18 @@ export default class Backlinks {
         break;
       }
       case "documents.update": {
-        // no-op for now
-        if (event.data.autosave) return;
-
-        // no-op for drafts
         const document = await Document.findByPk(event.documentId);
+        if (!document) return;
+
+        // backlinks are only created for published documents
         if (!document.publishedAt) return;
 
-        const [currentRevision, previousRevision] = await Revision.findAll({
-          where: { documentId: event.documentId },
-          order: [["createdAt", "desc"]],
-          limit: 2,
-        });
+        const linkIds = parseDocumentIds(document.text);
+        const linkedDocumentIds = [];
 
-        // before parsing document text we must make sure it's been migrated to
-        // the latest version or the parser may fail on version differences
-        await currentRevision.migrateVersion();
-        if (previousRevision) {
-          await previousRevision.migrateVersion();
-        }
-
-        const previousLinkIds = previousRevision
-          ? parseDocumentIds(previousRevision.text)
-          : [];
-        const currentLinkIds = parseDocumentIds(currentRevision.text);
-        const addedLinkIds = difference(currentLinkIds, previousLinkIds);
-        const removedLinkIds = difference(previousLinkIds, currentLinkIds);
-
-        // add any new backlinks that were created
+        // create or find existing backlink records for referenced docs
         await Promise.all(
-          addedLinkIds.map(async (linkId) => {
+          linkIds.map(async (linkId) => {
             const linkedDocument = await Document.findByPk(linkId);
             if (!linkedDocument || linkedDocument.id === event.documentId) {
               return;
@@ -73,35 +57,31 @@ export default class Backlinks {
                 reverseDocumentId: event.documentId,
               },
               defaults: {
-                userId: currentRevision.userId,
+                userId: document.lastModifiedById,
               },
             });
+            linkedDocumentIds.push(linkedDocument.id);
           })
         );
 
-        // delete any backlinks that were removed
-        await Promise.all(
-          removedLinkIds.map(async (linkId) => {
-            const document = await Document.findByPk(linkId, {
-              paranoid: false,
-            });
-            if (document) {
-              await Backlink.destroy({
-                where: {
-                  documentId: document.id,
-                  reverseDocumentId: event.documentId,
-                },
-              });
-            }
-          })
-        );
+        // delete any backlinks that no longer exist
+        await Backlink.destroy({
+          where: {
+            documentId: {
+              [Op.notIn]: linkedDocumentIds,
+            },
+            reverseDocumentId: event.documentId,
+          },
+        });
+        break;
+      }
+      case "documents.title_change": {
+        const document = await Document.findByPk(event.documentId);
+        if (!document) return;
 
-        if (
-          !previousRevision ||
-          currentRevision.title === previousRevision.title
-        ) {
-          break;
-        }
+        // might as well check
+        const { title, previousTitle } = event.data;
+        if (!previousTitle || title === previousTitle) break;
 
         // update any link titles in documents that lead to this one
         const backlinks = await Backlink.findAll({
@@ -113,7 +93,7 @@ export default class Backlinks {
 
         await Promise.all(
           backlinks.map(async (backlink) => {
-            const previousUrl = `/doc/${slugify(previousRevision.title)}-${
+            const previousUrl = `/doc/${slugify(previousTitle)}-${
               document.urlId
             }`;
 
@@ -121,8 +101,8 @@ export default class Backlinks {
             // 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})`
+              `[${previousTitle}](${previousUrl})`,
+              `[${title}](${document.url})`
             );
             await backlink.reverseDocument.save({
               silent: true,
@@ -136,12 +116,10 @@ export default class Backlinks {
       case "documents.delete": {
         await Backlink.destroy({
           where: {
-            reverseDocumentId: event.documentId,
-          },
-        });
-        await Backlink.destroy({
-          where: {
-            documentId: event.documentId,
+            [Op.or]: [
+              { reverseDocumentId: event.documentId },
+              { documentId: event.documentId },
+            ],
           },
         });
         break;