From 6c93cbc9a2d462bcc1315a8fa1d8699145d3dc70 Mon Sep 17 00:00:00 2001
From: amhsirak <karishmashuklaa@gmail.com>
Date: Thu, 20 Nov 2025 02:42:44 +0530
Subject: [PATCH] feat: html -> markdown

---
 server/src/markdownify/markdown.ts | 141 +++++++++++++++++++++++++++++
 1 file changed, 141 insertions(+)
 create mode 100644 server/src/markdownify/markdown.ts

diff --git a/server/src/markdownify/markdown.ts b/server/src/markdownify/markdown.ts
new file mode 100644
index 00000000..8666f785
--- /dev/null
+++ b/server/src/markdownify/markdown.ts
@@ -0,0 +1,141 @@
+import koffi from "koffi";
+import dotenv from "dotenv";
+import { stat } from "fs/promises";
+import path from "node:path";
+import os from "node:os";
+
+const exts = {
+  win32: ".dll",
+  darwin: ".dylib",
+  default: ".so",
+};
+
+const ext =
+  exts[os.platform() as keyof typeof exts] || exts.default;
+
+// Build path to the binary **inside the same folder**
+export const GO_MARKDOWN_PARSER_PATH = path.join(
+  __dirname,
+  `html-to-markdown${ext}`
+);
+
+dotenv.config();
+
+// ---------------------------------------------
+// Native Go binding wrapper
+// ---------------------------------------------
+class NativeMarkdownBridge {
+  private static singleton: NativeMarkdownBridge;
+  private fnConvert: any;
+
+  private constructor() {
+    const lib = koffi.load(GO_MARKDOWN_PARSER_PATH);
+
+    const freeFn = lib.func("FreeCString", "void", ["string"]);
+    const trackedType = "CString:" + crypto.randomUUID();
+    const autoReleasedStr = koffi.disposable(trackedType, "string", freeFn);
+
+    this.fnConvert = lib.func("ConvertHTMLToMarkdown", autoReleasedStr, [
+      "string",
+    ]);
+  }
+
+  static async load(): Promise<NativeMarkdownBridge> {
+    if (!NativeMarkdownBridge.singleton) {
+      try {
+        await stat(GO_MARKDOWN_PARSER_PATH);
+      } catch {
+        throw new Error("Go shared library not found");
+      }
+      NativeMarkdownBridge.singleton = new NativeMarkdownBridge();
+    }
+    return NativeMarkdownBridge.singleton;
+  }
+
+  async run(html: string): Promise<string> {
+    return new Promise((resolve, reject) => {
+      this.fnConvert.async(html, (err: Error, output: string) => {
+        err ? reject(err) : resolve(output);
+      });
+    });
+  }
+}
+
+// ---------------------------------------------
+// Main exposed function
+// ---------------------------------------------
+export async function parseMarkdown(
+  html: string | null | undefined,
+): Promise<string> {
+  if (!html) return "";
+
+  // Try Go library first (if enabled)
+  try {
+      const engine = await NativeMarkdownBridge.load();
+      let md = await engine.run(html);
+
+      md = fixBrokenLinks(md);
+      md = stripSkipLinks(md);
+
+      return md;
+  } catch (err: any) {
+    if (err?.message !== "Go shared library not found") {
+        console.log("Go markdown parser failed, falling back to JS parser:", err);
+    } else {
+      console.log("Go parser missing.", { GO_MARKDOWN_PARSER_PATH });
+    }
+  }
+
+  // Fallback parser
+  const TurndownService = require("turndown");
+  const { gfm } = require("joplin-turndown-plugin-gfm");
+
+  const t = new TurndownService();
+  t.addRule("inlineLink", {
+    filter: (node: any, opts: any) =>
+      opts.linkStyle === "inlined" &&
+      node.nodeName === "A" &&
+      node.getAttribute("href"),
+    replacement: (content: string, node: any) => {
+      const href = node.getAttribute("href").trim();
+      const title = node.title ? ` "${node.title}"` : "";
+      return `[${content.trim()}](${href}${title})\n`;
+    },
+  });
+
+  t.use(gfm);
+
+  try {
+    let out = await t.turndown(html);
+    out = fixBrokenLinks(out);
+    out = stripSkipLinks(out);
+    return out;
+  } catch (err) {
+    console.error("HTML→Markdown failed", { err });
+    return "";
+  }
+}
+
+// ---------------------------------------------
+// Helpers
+// ---------------------------------------------
+function fixBrokenLinks(md: string): string {
+  let depth = 0;
+  let result = "";
+
+  for (const ch of md) {
+    if (ch === "[") depth++;
+    if (ch === "]") depth = Math.max(0, depth - 1);
+
+    if (depth > 0 && ch === "\n") {
+      result += "\\\n";
+    } else {
+      result += ch;
+    }
+  }
+  return result;
+}
+
+function stripSkipLinks(md: string): string {
+  return md.replace(/\[Skip to Content\]\(#[^\)]*\)/gi, "");
+}