feat: move title extraction into commons package

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

commons/package.json

@@ -38,6 +38,7 @@
     "url": "https://github.com/hedgedoc/hedgedoc.git"
   },
   "dependencies": {
+    "domhandler": "5.0.3",
     "eventemitter2": "6.4.9",
     "isomorphic-ws": "5.0.0",
     "reveal.js": "4.5.0",

commons/src/index.ts

@@ -32,3 +32,5 @@ export * from './title-extraction/generate-note-title.js'
 export * from './title-extraction/types/iso6391.js'
 export * from './title-extraction/types/frontmatter.js'
 export * from './title-extraction/types/slide-show-options.js'
+
+export { extractFirstHeading } from './title-extraction/extract-first-heading.js'

commons/src/title-extraction/extract-first-heading.spec.ts

@@ -0,0 +1,60 @@
+/*
+ * SPDX-FileCopyrightText: 2023 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+import { extractFirstHeading } from './extract-first-heading.js'
+import { describe, expect, it } from '@jest/globals'
+import { Document, Element, Text } from 'domhandler'
+
+describe('extract first heading', () => {
+  describe.each([1, 2, 3, 4, 5, 6])('h%d', (headlineIndex) => {
+    it('extracts plain text', () => {
+      const content = `headline${headlineIndex}`
+      const headline = new Element(`h${headlineIndex}`, {}, [new Text(content)])
+      const document = new Document([headline])
+      expect(extractFirstHeading(document)).toBe(content)
+    })
+
+    it("doesn't extract heading-anchor", () => {
+      const headline = new Element(`h${headlineIndex}`, {}, [
+        new Element('a', { class: 'class1 heading-anchor class2' }, [
+          new Text('invalid link content')
+        ])
+      ])
+      const document = new Document([headline])
+      expect(extractFirstHeading(document)).toBe('')
+    })
+
+    it('extracts nested texts', () => {
+      const headline = new Element(`h${headlineIndex}`, {}, [
+        new Element('a', {}, [
+          new Text('Valid'),
+          new Element('div', {}, [new Text('Text')]),
+          new Text(`${headlineIndex}`)
+        ])
+      ])
+      const document = new Document([headline])
+      expect(extractFirstHeading(document)).toBe(`ValidText${headlineIndex}`)
+    })
+
+    it('extracts image alt texts', () => {
+      const headline = new Element(`h${headlineIndex}`, {}, [
+        new Element('img', { alt: 'Image Alt' })
+      ])
+      const document = new Document([headline])
+      expect(extractFirstHeading(document)).toBe('Image Alt')
+    })
+
+    it('extracts only the first found headline', () => {
+      const headline1 = new Element(`h${headlineIndex}`, {}, [
+        new Text(`headline${headlineIndex}`)
+      ])
+      const headline2 = new Element(`h${headlineIndex}`, {}, [
+        new Text('headline1')
+      ])
+      const document = new Document([headline1, headline2])
+      expect(extractFirstHeading(document)).toBe(`headline${headlineIndex}`)
+    })
+  })
+})

commons/src/title-extraction/extract-first-heading.ts

@@ -0,0 +1,57 @@
+/*
+ * SPDX-FileCopyrightText: 2023 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+import { Element, isTag, isText, Node, NodeWithChildren } from 'domhandler'
+
+const headlineTagRegex = /^h[1-6]$/gi
+
+/**
+ * Extracts the text content of the first top level headline tag.
+ *
+ * @param nodes The node whose children should be checked for the headline
+ * @return the plain text representation of the first headline. {@code undefined} if no headline has been found.
+ */
+export function extractFirstHeading(
+  nodes: NodeWithChildren
+): string | undefined {
+  const foundHeadlineNode = checkNodesForHeadline(nodes.children)
+  if (!foundHeadlineNode) {
+    return
+  }
+  return extractInnerTextFromNode(foundHeadlineNode).trim()
+}
+
+function checkNodesForHeadline(nodes: Node[]): Node | undefined {
+  return nodes.find((node) => isTag(node) && node.name.match(headlineTagRegex))
+}
+
+function extractInnerTextFromNode(node: Node): string {
+  if (isText(node)) {
+    return node.nodeValue
+  } else if (isTag(node)) {
+    return extractInnerTextFromTag(node)
+  } else {
+    return ''
+  }
+}
+
+function extractInnerTextFromTag(node: Element): string {
+  if (
+    node.name === 'a' &&
+    findAttribute(node, 'class')?.value.split(' ').includes('heading-anchor')
+  ) {
+    return ''
+  } else if (node.name === 'img') {
+    return findAttribute(node, 'alt')?.value ?? ''
+  } else {
+    return node.children.reduce((state, child) => {
+      return state + extractInnerTextFromNode(child)
+    }, '')
+  }
+}
+
+function findAttribute(node: Element, attributeName: string) {
+  return node.attributes.find((attribute) => attribute.name === attributeName)
+}

frontend/src/components/markdown-renderer/extensions/extract-first-headline/extract-first-headline-node-processor.ts

@@ -4,13 +4,11 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 import { NodeProcessor } from '../../node-preprocessors/node-processor'
+import { extractFirstHeading } from '@hedgedoc/commons'
 import { Optional } from '@mrdrogdrog/optional'
-import type { Document, Node, Element } from 'domhandler'
+import type { Document } from 'domhandler'
-import { isTag, isText } from 'domhandler'
 import type { EventEmitter2 } from 'eventemitter2'
 
-const headlineTagRegex = /^h[1-6]$/gi
-
 /**
  * Searches for the first headline tag and extracts its plain text content.
  */
@@ -22,40 +20,9 @@ export class ExtractFirstHeadlineNodeProcessor extends NodeProcessor {
   }
 
   process(nodes: Document): Document {
-    Optional.ofNullable(this.checkNodesForHeadline(nodes.children))
+    Optional.ofNullable(extractFirstHeading(nodes))
-      .map((foundHeadlineNode) => this.extractInnerTextFromNode(foundHeadlineNode).trim())
       .filter((text) => text !== '')
       .ifPresent((text) => this.eventEmitter.emit(ExtractFirstHeadlineNodeProcessor.EVENT_NAME, text))
     return nodes
   }
-
-  private checkNodesForHeadline(nodes: Node[]): Node | undefined {
-    return nodes.find((node) => isTag(node) && node.name.match(headlineTagRegex))
-  }
-
-  private extractInnerTextFromNode(node: Node): string {
-    if (isText(node)) {
-      return node.nodeValue
-    } else if (isTag(node)) {
-      return this.extractInnerTextFromTag(node)
-    } else {
-      return ''
-    }
-  }
-
-  private extractInnerTextFromTag(node: Element): string {
-    if (node.name === 'a' && this.findAttribute(node, 'class')?.value.includes('heading-anchor')) {
-      return ''
-    } else if (node.name === 'img') {
-      return this.findAttribute(node, 'alt')?.value ?? ''
-    } else {
-      return node.children.reduce((state, child) => {
-        return state + this.extractInnerTextFromNode(child)
-      }, '')
-    }
-  }
-
-  private findAttribute(node: Element, attributeName: string) {
-    return node.attributes.find((attribute) => attribute.name === attributeName)
-  }
 }

yarn.lock

@@ -2323,6 +2323,7 @@ __metadata:
     "@types/ws": 8.5.4
     "@typescript-eslint/eslint-plugin": 5.58.0
     "@typescript-eslint/parser": 5.58.0
+    domhandler: 5.0.3
     eslint: 8.38.0
     eslint-config-prettier: 8.8.0
     eslint-plugin-jest: 27.2.1