enh: add extractLinkParagraphs

Signed-off-by: Max <max@nextcloud.com>

src/plugins/extractLinkParagraphs.js

@@ -0,0 +1,70 @@
+/**
+ * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import { isLinkToSelfWithHash } from './../helpers/links.js'
+
+/**
+ * Get a list of all paragraphs that can be converted into a preview.
+ *
+ * @param {Document} doc - the prosemirror doc
+ * @return {Array} paragraphs with one link only found in the doc
+ */
+export default function extractLinkParagraphs(doc) {
+	const counter = new Map()
+	const paragraphs = []
+
+	doc.descendants((node, offset) => {
+		if (node.type.name !== 'paragraph') {
+			return
+		}
+		// ignore paragraphs that cannot be converted
+		if (!previewPossible(node)) return
+		paragraphs.push(Object.freeze({
+			offset,
+		}))
+	})
+
+	return paragraphs
+}
+
+/**
+ * Is it possible to convert the currently selected node into a preview?
+ * @param {object} state current editor state
+ * @param {object} state.selection current selection
+ * @return {boolean}
+ */
+function previewPossible(node) {
+	if (hasOtherContent(node)) {
+		return false
+	}
+	const href = extractHref(node.firstChild)
+	if (!href || isLinkToSelfWithHash(href)) {
+		return false
+	}
+	return true
+}
+
+/**
+ * Does the node contain more content than the first child
+ * @param {object} node node to inspect
+ * @return {boolean}
+ */
+function hasOtherContent(node) {
+	return node.childCount > 2
+		|| (node.childCount === 2 && node.lastChild.textContent.trim())
+}
+
+/**
+ * Get the link href of the given node
+ * @param {object} node to inspect
+ * @return {string} The href of the link mark of the node
+ */
+function extractHref(node) {
+	if (!node) {
+		return undefined
+	}
+	const link = node.marks.find(mark => mark.type.name === 'link')
+	return link?.attrs.href
+}

src/tests/plugins/extractLinkParagraphs.spec.js

@@ -0,0 +1,84 @@
+/**
+ * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+import extractLinkParagraphs from '../../plugins/extractLinkParagraphs.js'
+import Link from '../../marks/Link.js'
+import { createCustomEditor } from '../helpers.js'
+
+describe('extractLinkParagraphs', () => {
+
+	it('returns an empty array for an empty doc', () => {
+		const doc = prepareDoc('')
+		const paragraphs = extractLinkParagraphs(doc)
+		expect(paragraphs).toEqual([])
+	})
+
+	it('returns paragraphs with a single link', () => {
+		const content = '<p><a href="https://nextcloud.com">Link</a></p>'
+		const doc = prepareDoc(content)
+		const paragraphs = extractLinkParagraphs(doc)
+		expect(paragraphs).toEqual([
+			{ offset: 0 }
+		])
+	})
+
+	it('returns paragraphs with a single link and whitespace', () => {
+		const content = '<p><a href="https://nextcloud.com">Link</a> </p>'
+		const doc = prepareDoc(content)
+		const paragraphs = extractLinkParagraphs(doc)
+		expect(paragraphs).toEqual([
+			{ offset: 0 }
+		])
+	})
+
+	it('returns multiple paragraphs with a single link', () => {
+		const paragraph = '<p><a href="https://nextcloud.com">Link</a></p>'
+		const content = paragraph + paragraph
+		const doc = prepareDoc(content)
+		const paragraphs = extractLinkParagraphs(doc)
+		expect(paragraphs).toEqual([
+			{ offset: 0 },
+			{ offset: 6 }
+		])
+	})
+
+	it('ignores an empty paragraph', () => {
+		const content = '<p></p>'
+		const doc = prepareDoc(content)
+		const paragraphs = extractLinkParagraphs(doc)
+		expect(paragraphs).toEqual([])
+	})
+
+	it('ignores paragraphs with text after the link', () => {
+		const content = '<p><a href="https://nextcloud.com">Link</a> Hello</p>'
+		const doc = prepareDoc(content)
+		const paragraphs = extractLinkParagraphs(doc)
+		expect(paragraphs).toEqual([])
+	})
+
+	it('ignores paragraphs with text before the link', () => {
+		const content = '<p>bla <a href="https://nextcloud.com">Link</a></p>'
+		const doc = prepareDoc(content)
+		const paragraphs = extractLinkParagraphs(doc)
+		expect(paragraphs).toEqual([])
+	})
+
+	it('ignores paragraphs with multiple links', () => {
+		const link = '<a href="https://nextcloud.com">Link</a>'
+		const content = `<p>${link} ${link}</p>`
+		const doc = prepareDoc(content)
+		const paragraphs = extractLinkParagraphs(doc)
+		expect(paragraphs).toEqual([])
+	})
+
+})
+
+function prepareDoc(content) {
+	const editor = createCustomEditor({
+		content,
+		extensions: [ Link ]
+	})
+	return editor.state.doc
+}