feat: generate metadata from content on revision creation

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

backend/package.json

@@ -56,8 +56,10 @@
     "diff": "5.1.0",
     "express-session": "1.17.3",
     "file-type": "16.5.4",
+    "htmlparser2": "9.0.0",
     "joi": "17.9.2",
     "ldapauth-fork": "5.0.5",
+    "markdown-it": "13.0.1",
     "minio": "7.1.1",
     "mysql": "2.18.1",
     "node-fetch": "2.6.11",

backend/src/revisions/revisions.service.ts

@@ -11,10 +11,12 @@ import { Repository } from 'typeorm';
 import { NotInDBError } from '../errors/errors';
 import { ConsoleLoggerService } from '../logger/console-logger.service';
 import { Note } from '../notes/note.entity';
+import { Tag } from '../notes/tag.entity';
 import { EditService } from './edit.service';
 import { RevisionMetadataDto } from './revision-metadata.dto';
 import { RevisionDto } from './revision.dto';
 import { Revision } from './revision.entity';
+import { extractRevisionMetadataFromContent } from './utils/extract-revision-metadata-from-content';
 
 class RevisionUserInfo {
   usernames: string[];
@@ -121,6 +123,9 @@ export class RevisionsService {
       createdAt: revision.createdAt,
       authorUsernames: revisionUserInfo.usernames,
       anonymousAuthorCount: revisionUserInfo.anonymousUserCount,
+      title: revision.title,
+      description: revision.description,
+      tags: (await revision.tags).map((tag) => tag.name),
     };
   }
 
@@ -131,6 +136,9 @@ export class RevisionsService {
       content: revision.content,
       length: revision.length,
       createdAt: revision.createdAt,
+      title: revision.title,
+      tags: (await revision.tags).map((tag) => tag.name),
+      description: revision.description,
       authorUsernames: revisionUserInfo.usernames,
       anonymousAuthorCount: revisionUserInfo.anonymousUserCount,
       patch: revision.patch,
@@ -147,18 +155,35 @@ export class RevisionsService {
     newContent: string,
     yjsStateVector?: number[],
   ): Promise<Revision | undefined> {
-    // TODO: Save metadata
+    const latestRevision =
-    const latestRevision = await this.getLatestRevision(note);
+      note.id === undefined ? undefined : await this.getLatestRevision(note);
-    const oldContent = latestRevision.content;
+    const oldContent = latestRevision?.content;
     if (oldContent === newContent) {
       return undefined;
     }
     const patch = createPatch(
       note.publicId,
-      latestRevision.content,
+      latestRevision?.content ?? '',
       newContent,
     );
-    const revision = Revision.create(newContent, patch, note, yjsStateVector);
+    const { title, description, tags } =
+      extractRevisionMetadataFromContent(newContent);
+
+    const tagEntities = tags.map((tagName) => {
+      const entity = new Tag();
+      entity.name = tagName;
+      return entity;
+    });
+
+    const revision = Revision.create(
+      newContent,
+      patch,
+      note,
+      yjsStateVector ?? null,
+      title,
+      description,
+      tagEntities,
+    ) as Revision;
     return await this.revisionRepository.save(revision);
   }
 }

backend/src/revisions/utils/extract-revision-metadata-from-content.spec.ts

@@ -0,0 +1,77 @@
+/*
+ * SPDX-FileCopyrightText: 2023 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+import { extractRevisionMetadataFromContent } from './extract-revision-metadata-from-content';
+
+describe('revision entity', () => {
+  it('works without frontmatter without first heading', () => {
+    const { title, description, tags } = extractRevisionMetadataFromContent(
+      'This is a note content',
+    );
+    expect(title).toBe('');
+    expect(description).toBe('');
+    expect(tags).toStrictEqual([]);
+  });
+
+  it('works with broken frontmatter', () => {
+    const { title, description, tags } = extractRevisionMetadataFromContent(
+      '---\ntitle: \n  - 1\n  - 2\n---\nThis is a note content',
+    );
+
+    expect(title).toBe('');
+    expect(description).toBe('');
+    expect(tags).toStrictEqual([]);
+  });
+
+  it('works with frontmatter title', () => {
+    const { title, description, tags } = extractRevisionMetadataFromContent(
+      '---\ntitle: note title\n---\nThis is a note content',
+    );
+
+    expect(title).toBe('note title');
+    expect(description).toBe('');
+    expect(tags).toStrictEqual([]);
+  });
+
+  it('works with first heading title', () => {
+    const { title, description, tags } = extractRevisionMetadataFromContent(
+      '# Note Title Heading\nThis is a note content',
+    );
+
+    expect(title).toBe('Note Title Heading');
+    expect(description).toBe('');
+    expect(tags).toStrictEqual([]);
+  });
+
+  it('works with frontmatter description', () => {
+    const { title, description, tags } = extractRevisionMetadataFromContent(
+      '---\ndescription: note description\n---\nNote content',
+    );
+
+    expect(title).toBe('');
+    expect(description).toBe('note description');
+    expect(tags).toStrictEqual([]);
+  });
+
+  it('extracts tags as list', async () => {
+    const { title, description, tags } = extractRevisionMetadataFromContent(
+      '---\ntags: \n  - tag1\n  - tag2\n---\nNote content',
+    );
+
+    expect(title).toBe('');
+    expect(description).toBe('');
+    expect(tags).toStrictEqual(['tag1', 'tag2']);
+  });
+
+  it('extracts tags in legacy syntax', async () => {
+    const { title, description, tags } = extractRevisionMetadataFromContent(
+      '---\ntags: "tag1, tag2"\n---\nNote content',
+    );
+
+    expect(title).toBe('');
+    expect(description).toBe('');
+    expect(tags).toStrictEqual(['tag1', 'tag2']);
+  });
+});

backend/src/revisions/utils/extract-revision-metadata-from-content.ts

@@ -0,0 +1,87 @@
+/*
+ * SPDX-FileCopyrightText: 2023 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+import {
+  convertRawFrontmatterToNoteFrontmatter,
+  defaultNoteFrontmatter,
+  extractFirstHeading,
+  extractFrontmatter,
+  generateNoteTitle,
+  NoteFrontmatter,
+  parseRawFrontmatterFromYaml,
+} from '@hedgedoc/commons';
+import { parseDocument } from 'htmlparser2';
+import MarkdownIt from 'markdown-it';
+
+interface FrontmatterExtractionResult {
+  title: string;
+  description: string;
+  tags: string[];
+}
+
+interface FrontmatterParserResult {
+  frontmatter: NoteFrontmatter;
+  firstLineOfContentIndex: number;
+}
+
+/**
+ * Parses the frontmatter of the given content and extracts the metadata that are necessary to create a new revision..
+ *
+ * @param {string} content the revision content that contains the frontmatter.
+ */
+export function extractRevisionMetadataFromContent(
+  content: string,
+): FrontmatterExtractionResult {
+  const parserResult = parseFrontmatter(content);
+  const frontmatter = parserResult?.frontmatter;
+  const firstLineOfContentIndex = parserResult?.firstLineOfContentIndex;
+
+  const title = generateNoteTitle(frontmatter, () =>
+    extractFirstHeadingFromContent(
+      generateContentWithoutFrontmatter(firstLineOfContentIndex, content),
+    ),
+  );
+  const description = frontmatter?.description ?? '';
+  const tags = frontmatter?.tags ?? [];
+
+  return { title, description, tags };
+}
+
+function generateContentWithoutFrontmatter(
+  firstLineOfContentIndex: number | undefined,
+  content: string,
+): string {
+  return firstLineOfContentIndex === undefined
+    ? content
+    : content.split('\n').slice(firstLineOfContentIndex).join('\n');
+}
+
+function parseFrontmatter(
+  content: string,
+): FrontmatterParserResult | undefined {
+  const extractionResult = extractFrontmatter(content.split('\n'));
+  const rawText = extractionResult?.rawText;
+  if (!rawText) {
+    return undefined;
+  }
+
+  const firstLineOfContentIndex = extractionResult.lineOffset + 1;
+  const rawDataValidation = parseRawFrontmatterFromYaml(rawText);
+  const noteFrontmatter =
+    rawDataValidation.error !== undefined
+      ? defaultNoteFrontmatter
+      : convertRawFrontmatterToNoteFrontmatter(rawDataValidation.value);
+  return {
+    frontmatter: noteFrontmatter,
+    firstLineOfContentIndex: firstLineOfContentIndex,
+  };
+}
+
+function extractFirstHeadingFromContent(content: string): string | undefined {
+  const markdownIt = new MarkdownIt('default');
+  const html = markdownIt.render(content);
+  const document = parseDocument(html);
+  return extractFirstHeading(document);
+}

yarn.lock

@@ -2332,10 +2332,12 @@ __metadata:
     eslint-plugin-prettier: 4.2.1
     express-session: 1.17.3
     file-type: 16.5.4
+    htmlparser2: 9.0.0
     http-proxy-middleware: 2.0.6
     jest: 29.5.0
     joi: 17.9.2
     ldapauth-fork: 5.0.5
+    markdown-it: 13.0.1
     minio: 7.1.1
     mocked-env: 1.3.5
     mysql: 2.18.1