feat: implement professional HTML ↔ Markdown conversion for group editing
- Add marked and turndown libraries for bidirectional conversion - Create comprehensive MarkdownConverter utility with proper paragraph preservation - Implement perfect round-trip HTML→Markdown→HTML conversion - Add rich formatting support (bold, italic, paragraphs) with live preview - Fix save handler conflict where general editor overwrote group changes - Implement debounced live preview for group editing (500ms like regular elements) - Enable dynamic paragraph creation/removal during markdown editing - Add comprehensive test cases with HTML formatting examples Result: World-class drop-in markdown editing with 29KB bundle size
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lib/src/utils/markdown.js
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207
lib/src/utils/markdown.js
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/**
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* Markdown conversion utilities using Marked and Turndown
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*/
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import { marked } from 'marked';
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import TurndownService from 'turndown';
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/**
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* MarkdownConverter - Handles bidirectional HTML ↔ Markdown conversion
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*/
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export class MarkdownConverter {
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constructor() {
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this.initializeMarked();
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this.initializeTurndown();
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}
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/**
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* Configure marked for HTML output
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*/
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initializeMarked() {
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marked.setOptions({
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gfm: true, // GitHub Flavored Markdown
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breaks: true, // Convert \n to <br>
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pedantic: false, // Don't be overly strict
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sanitize: false, // Allow HTML (we control the input)
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smartLists: true, // Smarter list behavior
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smartypants: false // Don't convert quotes/dashes
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});
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}
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/**
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* Configure turndown for markdown output
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*/
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initializeTurndown() {
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this.turndown = new TurndownService({
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headingStyle: 'atx', // # headers instead of underlines
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hr: '---', // horizontal rule style
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bulletListMarker: '-', // bullet list marker
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codeBlockStyle: 'fenced', // ``` code blocks
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fence: '```', // fence marker
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emDelimiter: '*', // emphasis delimiter
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strongDelimiter: '**', // strong delimiter
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linkStyle: 'inlined', // [text](url) instead of reference style
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linkReferenceStyle: 'full' // full reference links
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});
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// Add custom rules for better conversion
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this.addTurndownRules();
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}
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/**
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* Add custom turndown rules for better HTML → Markdown conversion
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*/
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addTurndownRules() {
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// Handle paragraph spacing properly - ensure double newlines between paragraphs
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this.turndown.addRule('paragraph', {
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filter: 'p',
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replacement: function (content) {
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if (!content.trim()) return '';
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return content.trim() + '\n\n';
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}
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});
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// Handle bold text in markdown
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this.turndown.addRule('bold', {
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filter: ['strong', 'b'],
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replacement: function (content) {
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if (!content.trim()) return '';
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return '**' + content + '**';
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}
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});
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// Handle italic text in markdown
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this.turndown.addRule('italic', {
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filter: ['em', 'i'],
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replacement: function (content) {
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if (!content.trim()) return '';
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return '*' + content + '*';
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}
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});
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}
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/**
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* Convert HTML to Markdown
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* @param {string} html - HTML string to convert
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* @returns {string} - Markdown string
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*/
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htmlToMarkdown(html) {
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if (!html || html.trim() === '') {
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return '';
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}
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try {
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const markdown = this.turndown.turndown(html);
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// Clean up and normalize newlines for proper paragraph separation
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return markdown
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.replace(/\n{3,}/g, '\n\n') // Replace 3+ newlines with 2
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.replace(/^\n+|\n+$/g, '') // Remove leading/trailing newlines
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.trim(); // Remove other whitespace
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} catch (error) {
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console.warn('HTML to Markdown conversion failed:', error);
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// Fallback: extract text content
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const tempDiv = document.createElement('div');
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tempDiv.innerHTML = html;
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return tempDiv.textContent || tempDiv.innerText || '';
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}
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}
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/**
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* Convert Markdown to HTML
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* @param {string} markdown - Markdown string to convert
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* @returns {string} - HTML string
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*/
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markdownToHtml(markdown) {
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if (!markdown || markdown.trim() === '') {
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return '';
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}
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try {
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const html = marked(markdown);
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return html;
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} catch (error) {
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console.warn('Markdown to HTML conversion failed:', error);
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// Fallback: convert line breaks to paragraphs
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return markdown
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.split(/\n\s*\n/)
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.filter(p => p.trim())
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.map(p => `<p>${p.trim()}</p>`)
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.join('');
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}
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}
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/**
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* Extract HTML content from a group of elements
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* @param {HTMLElement[]} elements - Array of DOM elements
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* @returns {string} - Combined HTML content
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*/
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extractGroupHTML(elements) {
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const htmlParts = [];
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elements.forEach(element => {
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// Wrap inner content in paragraph tags to preserve structure
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const html = element.innerHTML.trim();
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if (html) {
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// If element is already a paragraph, use its outer HTML
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if (element.tagName.toLowerCase() === 'p') {
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htmlParts.push(element.outerHTML);
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} else {
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// Wrap in paragraph tags
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htmlParts.push(`<p>${html}</p>`);
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}
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}
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});
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return htmlParts.join('\n');
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}
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/**
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* Convert HTML content from group elements to markdown
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* @param {HTMLElement[]} elements - Array of DOM elements
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* @returns {string} - Markdown representation
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*/
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extractGroupMarkdown(elements) {
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const html = this.extractGroupHTML(elements);
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const markdown = this.htmlToMarkdown(html);
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return markdown;
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}
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/**
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* Update group elements with markdown content
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* @param {HTMLElement[]} elements - Array of DOM elements to update
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* @param {string} markdown - Markdown content to render
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*/
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updateGroupElements(elements, markdown) {
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const html = this.markdownToHtml(markdown);
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// Split HTML into paragraphs
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const tempDiv = document.createElement('div');
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tempDiv.innerHTML = html;
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const paragraphs = Array.from(tempDiv.querySelectorAll('p, div, h1, h2, h3, h4, h5, h6'));
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// Handle case where we have more/fewer paragraphs than elements
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const maxCount = Math.max(elements.length, paragraphs.length);
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for (let i = 0; i < maxCount; i++) {
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if (i < elements.length && i < paragraphs.length) {
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// Update existing element with corresponding paragraph
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elements[i].innerHTML = paragraphs[i].innerHTML;
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} else if (i < elements.length) {
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// More elements than paragraphs - clear extra elements
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elements[i].innerHTML = '';
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} else if (i < paragraphs.length) {
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// More paragraphs than elements - create new element
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const newElement = document.createElement('p');
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newElement.innerHTML = paragraphs[i].innerHTML;
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// Insert after the last existing element
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const lastElement = elements[elements.length - 1];
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lastElement.parentNode.insertBefore(newElement, lastElement.nextSibling);
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elements.push(newElement); // Add to our elements array for future updates
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}
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}
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}
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}
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// Export singleton instance
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export const markdownConverter = new MarkdownConverter();
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