Move micromark.cjs helpers from lib to helpers so it can be used by code in both locations.

helpers/micromark.cjs

@@ -0,0 +1,84 @@
+// @ts-check
+
+"use strict";
+
+/* eslint-disable n/no-unpublished-require */
+
+// @ts-ignore
+const { parse, postprocess, preprocess } = require("../micromark/micromark.cjs");
+
+/**
+ * Markdown token.
+ *
+ * @typedef {Object} Token
+ * @property {string} type Token type.
+ * @property {number} startLine Start line (1-based).
+ * @property {number} startColumn Start column (1-based).
+ * @property {number} endLine End line (1-based).
+ * @property {number} endColumn End column (1-based).
+ * @property {string} text Token text.
+ * @property {Token[]} tokens Child tokens.
+ */
+
+/**
+ * Parses a Markdown document and returns (frozen) tokens.
+ *
+ * @param {string} markdown Markdown document.
+ * @returns {Token[]} Markdown tokens (frozen).
+ */
+function micromarkParse(markdown) {
+
+  // Use micromark to parse document into Events
+  const encoding = undefined;
+  const eol = true;
+  const options = undefined;
+  const chunks = preprocess()(markdown, encoding, eol);
+  const parseContext = parse(options).document().write(chunks);
+  const events = postprocess(parseContext);
+
+  // Create Token objects
+  const document = [];
+  let current = {
+    "tokens": document
+  };
+  const history = [ current ];
+  for (const event of events) {
+    const [ kind, token, context ] = event;
+    const { type, start, end } = token;
+    const { "column": startColumn, "line": startLine } = start;
+    const { "column": endColumn, "line": endLine } = end;
+    let text = null;
+    try {
+      text = context.sliceSerialize(token);
+    } catch {
+      // https://github.com/micromark/micromark/issues/131
+    }
+    if (kind === "enter") {
+      const previous = current;
+      history.push(previous);
+      current = {
+        type,
+        startLine,
+        startColumn,
+        endLine,
+        endColumn,
+        text,
+        "tokens": []
+      };
+      previous.tokens.push(current);
+    } else if (kind === "exit") {
+      Object.freeze(current.tokens);
+      Object.freeze(current);
+      // @ts-ignore
+      current = history.pop();
+    }
+  }
+
+  // Return document
+  Object.freeze(document);
+  return document;
+}
+
+module.exports = {
+  "parse": micromarkParse
+};