feat: add md<->html document converters

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/converters/document.js

@@ -2,7 +2,9 @@ import fs from 'node:fs/promises';
 import mammoth from 'mammoth';
 import puppeteer from 'puppeteer';
 import * as pdfjsLib from 'pdfjs-dist/legacy/build/pdf.mjs';
-import { Document, Paragraph, TextRun, Packer } from 'docx';
+import { Document, Paragraph, TextRun, HeadingLevel, Packer } from 'docx';
+import MarkdownIt from 'markdown-it';
+import TurndownService from 'turndown';
 import { register } from './registry.js';
 
 async function renderHtmlToPdf(html, outputPath) {
@@ -44,6 +46,18 @@ async function convertDocxToPdf(inputPath, outputPath) {
   await renderHtmlToPdf(result.value, outputPath);
 }
 
+async function convertMdToHtml(inputPath, outputPath) {
+  const markdown = await fs.readFile(inputPath, 'utf8');
+  const html = new MarkdownIt().render(markdown);
+  await fs.writeFile(outputPath, html);
+}
+
+async function convertHtmlToMd(inputPath, outputPath) {
+  const html = await fs.readFile(inputPath, 'utf8');
+  const markdown = new TurndownService({ headingStyle: 'atx' }).turndown(html);
+  await fs.writeFile(outputPath, markdown);
+}
+
 async function extractPdfPageTexts(inputPath) {
   const data = new Uint8Array(await fs.readFile(inputPath));
   const doc = await pdfjsLib.getDocument({ data }).promise;
@@ -85,6 +99,8 @@ export function registerDocumentConverters() {
   register({ family: 'document', sourceFormat: 'docx', targetFormat: 'html', convert: convertDocxToHtml });
   register({ family: 'document', sourceFormat: 'txt', targetFormat: 'pdf', convert: convertTxtToPdf });
   register({ family: 'document', sourceFormat: 'html', targetFormat: 'pdf', convert: convertHtmlToPdf });
+  register({ family: 'document', sourceFormat: 'md', targetFormat: 'html', convert: convertMdToHtml });
+  register({ family: 'document', sourceFormat: 'html', targetFormat: 'md', convert: convertHtmlToMd });
   register({ family: 'document', sourceFormat: 'docx', targetFormat: 'pdf', convert: convertDocxToPdf });
   register({ family: 'document', sourceFormat: 'pdf', targetFormat: 'txt', convert: convertPdfToTxt });
   register({ family: 'document', sourceFormat: 'pdf', targetFormat: 'html', convert: convertPdfToHtml });

test/converters/document.test.js

@@ -74,4 +74,30 @@ describe('document converters', () => {
     const detected = await detectInputMime(outputPath);
     expect(detected.mime).toBe('application/pdf');
   }, 20000);
+
+  it('converts MD to HTML', async () => {
+    const inputPath = path.join(tmpDir, 'fixture.md');
+    await fs.writeFile(inputPath, '# Heading\n\nSome **bold** text.');
+    const outputPath = path.join(tmpDir, 'from-md.html');
+    const entry = resolve('md', 'html');
+
+    await entry.convert(inputPath, outputPath);
+
+    const html = await fs.readFile(outputPath, 'utf8');
+    expect(html).toContain('<h1>Heading</h1>');
+    expect(html).toContain('<strong>bold</strong>');
+  });
+
+  it('converts HTML to MD', async () => {
+    const inputPath = path.join(tmpDir, 'fixture-for-md.html');
+    await fs.writeFile(inputPath, '<h1>Heading</h1><p>Some <strong>bold</strong> text.</p>');
+    const outputPath = path.join(tmpDir, 'from-html.md');
+    const entry = resolve('html', 'md');
+
+    await entry.convert(inputPath, outputPath);
+
+    const markdown = await fs.readFile(outputPath, 'utf8');
+    expect(markdown).toContain('# Heading');
+    expect(markdown).toContain('**bold**');
+  });
 });