diff --git a/helpers/micromark-helpers.cjs b/helpers/micromark-helpers.cjs
new file mode 100644
index 00000000..89eca1be
--- /dev/null
+++ b/helpers/micromark-helpers.cjs
@@ -0,0 +1,462 @@
+// @ts-check
+
+"use strict";
+
+const { directive, gfmAutolinkLiteral, gfmFootnote, gfmTable, math, parse, postprocess, preprocess } =
+  require("markdownlint-micromark");
+const { newLineRe } = require("./shared.js");
+
+const flatTokensSymbol = Symbol("flat-tokens");
+const htmlFlowSymbol = Symbol("html-flow");
+
+/** @typedef {import("markdownlint-micromark").Event} Event */
+/** @typedef {import("markdownlint-micromark").ParseOptions} ParseOptions */
+/** @typedef {import("markdownlint-micromark").TokenType} TokenType */
+/** @typedef {import("../lib/markdownlint.js").MicromarkToken} Token */
+
+/**
+ * Determines if a Micromark token is within an htmlFlow type.
+ *
+ * @param {Token} token Micromark token.
+ * @returns {boolean} True iff the token is within an htmlFlow type.
+ */
+function inHtmlFlow(token) {
+  return Boolean(token[htmlFlowSymbol]);
+}
+
+/**
+ * Returns whether a token is an htmlFlow type containing an HTML comment.
+ *
+ * @param {Token} token Micromark token.
+ * @returns {boolean} True iff token is htmlFlow containing a comment.
+ */
+function isHtmlFlowComment(token) {
+  const { text, type } = token;
+  if (
+    (type === "htmlFlow") &&
+    text.startsWith("<!--") &&
+    text.endsWith("-->")
+  ) {
+    const comment = text.slice(4, -3);
+    return (
+      !comment.startsWith(">") &&
+      !comment.startsWith("->") &&
+      !comment.endsWith("-")
+      // The following condition from the CommonMark specification is commented
+      // to avoid parsing HTML comments that include "--" because that is NOT a
+      // condition of the HTML specification.
+      // https://spec.commonmark.org/0.30/#raw-html
+      // https://html.spec.whatwg.org/multipage/syntax.html#comments
+      // && !comment.includes("--")
+    );
+  }
+  return false;
+}
+
+/**
+ * Parses a Markdown document and returns Micromark events.
+ *
+ * @param {string} markdown Markdown document.
+ * @param {ParseOptions} [micromarkOptions] Options for micromark.
+ * @param {boolean} [referencesDefined] Treat references as defined.
+ * @returns {Event[]} Micromark events.
+ */
+function getMicromarkEvents(
+  markdown,
+  micromarkOptions = {},
+  referencesDefined = true
+) {
+
+  // Customize options object to add useful extensions
+  micromarkOptions.extensions = micromarkOptions.extensions || [];
+  micromarkOptions.extensions.push(
+    directive(),
+    gfmAutolinkLiteral(),
+    gfmFootnote(),
+    gfmTable(),
+    math()
+  );
+
+  // Use micromark to parse document into Events
+  const encoding = undefined;
+  const eol = true;
+  const parseContext = parse(micromarkOptions);
+  if (referencesDefined) {
+    // Customize ParseContext to treat all references as defined
+    parseContext.defined.includes = (searchElement) => searchElement.length > 0;
+  }
+  const chunks = preprocess()(markdown, encoding, eol);
+  const events = postprocess(parseContext.document().write(chunks));
+  return events;
+}
+
+/**
+ * Parses a Markdown document and returns (frozen) tokens.
+ *
+ * @param {string} markdown Markdown document.
+ * @param {ParseOptions} micromarkOptions Options for micromark.
+ * @param {boolean} referencesDefined Treat references as defined.
+ * @param {number} lineDelta Offset to apply to start/end line.
+ * @param {Token} [ancestor] Parent of top-most tokens.
+ * @returns {Token[]} Micromark tokens (frozen).
+ */
+function micromarkParseWithOffset(
+  markdown,
+  micromarkOptions,
+  referencesDefined,
+  lineDelta,
+  ancestor
+) {
+  // Use micromark to parse document into Events
+  const events = getMicromarkEvents(
+    markdown, micromarkOptions, referencesDefined
+  );
+
+  // Create Token objects
+  const document = [];
+  let flatTokens = [];
+  /** @type {Token} */
+  const root = {
+    "type": "data",
+    "startLine": -1,
+    "startColumn": -1,
+    "endLine": -1,
+    "endColumn": -1,
+    "text": "ROOT",
+    "children": document,
+    "parent": null
+  };
+  const history = [ root ];
+  let current = root;
+  // eslint-disable-next-line jsdoc/valid-types
+  /** @type ParseOptions | null */
+  let reparseOptions = null;
+  let lines = null;
+  let skipHtmlFlowChildren = false;
+  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;
+    const text = context.sliceSerialize(token);
+    if ((kind === "enter") && !skipHtmlFlowChildren) {
+      const previous = current;
+      history.push(previous);
+      current = {
+        type,
+        "startLine": startLine + lineDelta,
+        startColumn,
+        "endLine": endLine + lineDelta,
+        endColumn,
+        text,
+        "children": [],
+        "parent": ((previous === root) ? (ancestor || null) : previous)
+      };
+      if (ancestor) {
+        Object.defineProperty(current, htmlFlowSymbol, { "value": true });
+      }
+      previous.children.push(current);
+      flatTokens.push(current);
+      if ((current.type === "htmlFlow") && !isHtmlFlowComment(current)) {
+        skipHtmlFlowChildren = true;
+        if (!reparseOptions || !lines) {
+          reparseOptions = {
+            ...micromarkOptions,
+            "extensions": [
+              {
+                "disable": {
+                  "null": [ "codeIndented", "htmlFlow" ]
+                }
+              }
+            ]
+          };
+          lines = markdown.split(newLineRe);
+        }
+        const reparseMarkdown = lines
+          .slice(current.startLine - 1, current.endLine)
+          .join("\n");
+        const tokens = micromarkParseWithOffset(
+          reparseMarkdown,
+          reparseOptions,
+          referencesDefined,
+          current.startLine - 1,
+          current
+        );
+        current.children = tokens;
+        // Avoid stack overflow of Array.push(...spread)
+        // eslint-disable-next-line unicorn/prefer-spread
+        flatTokens = flatTokens.concat(tokens[flatTokensSymbol]);
+      }
+    } else if (kind === "exit") {
+      if (type === "htmlFlow") {
+        skipHtmlFlowChildren = false;
+      }
+      if (!skipHtmlFlowChildren) {
+        Object.freeze(current.children);
+        Object.freeze(current);
+        // @ts-ignore
+        current = history.pop();
+      }
+    }
+  }
+
+  // Return document
+  Object.defineProperty(document, flatTokensSymbol, { "value": flatTokens });
+  Object.freeze(document);
+  return document;
+}
+
+/**
+ * Parses a Markdown document and returns (frozen) tokens.
+ *
+ * @param {string} markdown Markdown document.
+ * @param {ParseOptions} [micromarkOptions] Options for micromark.
+ * @param {boolean} [referencesDefined] Treat references as defined.
+ * @returns {Token[]} Micromark tokens (frozen).
+ */
+function micromarkParse(
+  markdown,
+  micromarkOptions = {},
+  referencesDefined = true
+) {
+  return micromarkParseWithOffset(
+    markdown,
+    micromarkOptions,
+    referencesDefined,
+    0
+  );
+}
+
+/**
+ * Adds a range of numbers to a set.
+ *
+ * @param {Set<number>} set Set of numbers.
+ * @param {number} start Starting number.
+ * @param {number} end Ending number.
+ * @returns {void}
+ */
+function addRangeToSet(set, start, end) {
+  for (let i = start; i <= end; i++) {
+    set.add(i);
+  }
+}
+
+/**
+ * @callback AllowedPredicate
+ * @param {Token} token Micromark token.
+ * @returns {boolean} True iff allowed.
+ */
+
+/**
+ * @callback TransformPredicate
+ * @param {Token} token Micromark token.
+ * @returns {Token[]} Child tokens.
+ */
+
+/**
+ * Filter a list of Micromark tokens by predicate.
+ *
+ * @param {Token[]} tokens Micromark tokens.
+ * @param {AllowedPredicate} [allowed] Allowed token predicate.
+ * @param {TransformPredicate} [transformChildren] Transform predicate.
+ * @returns {Token[]} Filtered tokens.
+ */
+function filterByPredicate(tokens, allowed, transformChildren) {
+  allowed = allowed || (() => true);
+  const result = [];
+  const queue = [
+    {
+      "array": tokens,
+      "index": 0
+    }
+  ];
+  while (queue.length > 0) {
+    const current = queue[queue.length - 1];
+    const { array, index } = current;
+    if (index < array.length) {
+      const token = array[current.index++];
+      if (allowed(token)) {
+        result.push(token);
+      }
+      const { children } = token;
+      if (children.length > 0) {
+        const transformed =
+          transformChildren ? transformChildren(token) : children;
+        queue.push(
+          {
+            "array": transformed,
+            "index": 0
+          }
+        );
+      }
+    } else {
+      queue.pop();
+    }
+  }
+  return result;
+}
+
+/**
+ * Filter a list of Micromark tokens by type.
+ *
+ * @param {Token[]} tokens Micromark tokens.
+ * @param {TokenType[]} types Types to allow.
+ * @param {boolean} [htmlFlow] Whether to include htmlFlow content.
+ * @returns {Token[]} Filtered tokens.
+ */
+function filterByTypes(tokens, types, htmlFlow) {
+  const predicate = (token) =>
+    (htmlFlow || !inHtmlFlow(token)) && types.includes(token.type);
+  const flatTokens = tokens[flatTokensSymbol];
+  if (flatTokens) {
+    return flatTokens.filter(predicate);
+  }
+  return filterByPredicate(tokens, predicate);
+}
+
+/**
+ * Gets a list of nested Micromark token descendants by type path.
+ *
+ * @param {Token|Token[]} parent Micromark token parent or parents.
+ * @param {(TokenType|TokenType[])[]} typePath Micromark token type path.
+ * @returns {Token[]} Micromark token descendants.
+ */
+function getDescendantsByType(parent, typePath) {
+  let tokens = Array.isArray(parent) ? parent : [ parent ];
+  for (const type of typePath) {
+    tokens = tokens
+      .flatMap((t) => t.children)
+      .filter((t) => Array.isArray(type) ? type.includes(t.type) : (type === t.type));
+  }
+  return tokens;
+}
+
+/**
+ * Gets the heading level of a Micromark heading tokan.
+ *
+ * @param {Token} heading Micromark heading token.
+ * @returns {number} Heading level.
+ */
+function getHeadingLevel(heading) {
+  const headingSequence = filterByTypes(
+    heading.children,
+    [ "atxHeadingSequence", "setextHeadingLineSequence" ]
+  );
+  let level = 1;
+  const { text } = headingSequence[0];
+  if (text[0] === "#") {
+    level = Math.min(text.length, 6);
+  } else if (text[0] === "-") {
+    level = 2;
+  }
+  return level;
+}
+
+/**
+ * Gets the heading style of a Micromark heading tokan.
+ *
+ * @param {Token} heading Micromark heading token.
+ * @returns {"atx" | "atx_closed" | "setext"} Heading style.
+ */
+function getHeadingStyle(heading) {
+  if (heading.type === "setextHeading") {
+    return "setext";
+  }
+  const atxHeadingSequenceLength = filterByTypes(
+    heading.children,
+    [ "atxHeadingSequence" ]
+  ).length;
+  if (atxHeadingSequenceLength === 1) {
+    return "atx";
+  }
+  return "atx_closed";
+}
+
+/**
+ * Gets the heading text of a Micromark heading token.
+ *
+ * @param {Token} heading Micromark heading token.
+ * @returns {string} Heading text.
+ */
+function getHeadingText(heading) {
+  const headingTexts = getDescendantsByType(heading, [ [ "atxHeadingText", "setextHeadingText" ] ]);
+  return headingTexts[0]?.text.replace(/[\r\n]+/g, " ") || "";
+}
+
+/**
+ * HTML tag information.
+ *
+ * @typedef {Object} HtmlTagInfo
+ * @property {boolean} close True iff close tag.
+ * @property {string} name Tag name.
+ */
+
+/**
+ * Gets information about the tag in an HTML token.
+ *
+ * @param {Token} token Micromark token.
+ * @returns {HtmlTagInfo | null} HTML tag information.
+ */
+function getHtmlTagInfo(token) {
+  const htmlTagNameRe = /^<([^!>][^/\s>]*)/;
+  if (token.type === "htmlText") {
+    const match = htmlTagNameRe.exec(token.text);
+    if (match) {
+      const name = match[1];
+      const close = name.startsWith("/");
+      return {
+        close,
+        "name": close ? name.slice(1) : name
+      };
+    }
+  }
+  return null;
+}
+
+/**
+ * Gets the nearest parent of the specified type for a Micromark token.
+ *
+ * @param {Token} token Micromark token.
+ * @param {TokenType[]} types Types to allow.
+ * @returns {Token | null} Parent token.
+ */
+function getParentOfType(token, types) {
+  /** @type {Token | null} */
+  let current = token;
+  while ((current = current.parent) && !types.includes(current.type)) {
+    // Empty
+  }
+  return current;
+}
+
+/**
+ * Set containing token types that do not contain content.
+ *
+ * @type {Set<TokenType>}
+ */
+const nonContentTokens = new Set([
+  "blockQuoteMarker",
+  "blockQuotePrefix",
+  "blockQuotePrefixWhitespace",
+  "lineEnding",
+  "lineEndingBlank",
+  "linePrefix",
+  "listItemIndent"
+]);
+
+module.exports = {
+  "parse": micromarkParse,
+  addRangeToSet,
+  filterByPredicate,
+  filterByTypes,
+  getDescendantsByType,
+  getHeadingLevel,
+  getHeadingStyle,
+  getHeadingText,
+  getHtmlTagInfo,
+  getParentOfType,
+  getMicromarkEvents,
+  inHtmlFlow,
+  isHtmlFlowComment,
+  nonContentTokens
+};
diff --git a/helpers/micromark-parse.cjs b/helpers/micromark-parse.cjs
new file mode 100644
index 00000000..89eca1be
--- /dev/null
+++ b/helpers/micromark-parse.cjs
@@ -0,0 +1,462 @@
+// @ts-check
+
+"use strict";
+
+const { directive, gfmAutolinkLiteral, gfmFootnote, gfmTable, math, parse, postprocess, preprocess } =
+  require("markdownlint-micromark");
+const { newLineRe } = require("./shared.js");
+
+const flatTokensSymbol = Symbol("flat-tokens");
+const htmlFlowSymbol = Symbol("html-flow");
+
+/** @typedef {import("markdownlint-micromark").Event} Event */
+/** @typedef {import("markdownlint-micromark").ParseOptions} ParseOptions */
+/** @typedef {import("markdownlint-micromark").TokenType} TokenType */
+/** @typedef {import("../lib/markdownlint.js").MicromarkToken} Token */
+
+/**
+ * Determines if a Micromark token is within an htmlFlow type.
+ *
+ * @param {Token} token Micromark token.
+ * @returns {boolean} True iff the token is within an htmlFlow type.
+ */
+function inHtmlFlow(token) {
+  return Boolean(token[htmlFlowSymbol]);
+}
+
+/**
+ * Returns whether a token is an htmlFlow type containing an HTML comment.
+ *
+ * @param {Token} token Micromark token.
+ * @returns {boolean} True iff token is htmlFlow containing a comment.
+ */
+function isHtmlFlowComment(token) {
+  const { text, type } = token;
+  if (
+    (type === "htmlFlow") &&
+    text.startsWith("<!--") &&
+    text.endsWith("-->")
+  ) {
+    const comment = text.slice(4, -3);
+    return (
+      !comment.startsWith(">") &&
+      !comment.startsWith("->") &&
+      !comment.endsWith("-")
+      // The following condition from the CommonMark specification is commented
+      // to avoid parsing HTML comments that include "--" because that is NOT a
+      // condition of the HTML specification.
+      // https://spec.commonmark.org/0.30/#raw-html
+      // https://html.spec.whatwg.org/multipage/syntax.html#comments
+      // && !comment.includes("--")
+    );
+  }
+  return false;
+}
+
+/**
+ * Parses a Markdown document and returns Micromark events.
+ *
+ * @param {string} markdown Markdown document.
+ * @param {ParseOptions} [micromarkOptions] Options for micromark.
+ * @param {boolean} [referencesDefined] Treat references as defined.
+ * @returns {Event[]} Micromark events.
+ */
+function getMicromarkEvents(
+  markdown,
+  micromarkOptions = {},
+  referencesDefined = true
+) {
+
+  // Customize options object to add useful extensions
+  micromarkOptions.extensions = micromarkOptions.extensions || [];
+  micromarkOptions.extensions.push(
+    directive(),
+    gfmAutolinkLiteral(),
+    gfmFootnote(),
+    gfmTable(),
+    math()
+  );
+
+  // Use micromark to parse document into Events
+  const encoding = undefined;
+  const eol = true;
+  const parseContext = parse(micromarkOptions);
+  if (referencesDefined) {
+    // Customize ParseContext to treat all references as defined
+    parseContext.defined.includes = (searchElement) => searchElement.length > 0;
+  }
+  const chunks = preprocess()(markdown, encoding, eol);
+  const events = postprocess(parseContext.document().write(chunks));
+  return events;
+}
+
+/**
+ * Parses a Markdown document and returns (frozen) tokens.
+ *
+ * @param {string} markdown Markdown document.
+ * @param {ParseOptions} micromarkOptions Options for micromark.
+ * @param {boolean} referencesDefined Treat references as defined.
+ * @param {number} lineDelta Offset to apply to start/end line.
+ * @param {Token} [ancestor] Parent of top-most tokens.
+ * @returns {Token[]} Micromark tokens (frozen).
+ */
+function micromarkParseWithOffset(
+  markdown,
+  micromarkOptions,
+  referencesDefined,
+  lineDelta,
+  ancestor
+) {
+  // Use micromark to parse document into Events
+  const events = getMicromarkEvents(
+    markdown, micromarkOptions, referencesDefined
+  );
+
+  // Create Token objects
+  const document = [];
+  let flatTokens = [];
+  /** @type {Token} */
+  const root = {
+    "type": "data",
+    "startLine": -1,
+    "startColumn": -1,
+    "endLine": -1,
+    "endColumn": -1,
+    "text": "ROOT",
+    "children": document,
+    "parent": null
+  };
+  const history = [ root ];
+  let current = root;
+  // eslint-disable-next-line jsdoc/valid-types
+  /** @type ParseOptions | null */
+  let reparseOptions = null;
+  let lines = null;
+  let skipHtmlFlowChildren = false;
+  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;
+    const text = context.sliceSerialize(token);
+    if ((kind === "enter") && !skipHtmlFlowChildren) {
+      const previous = current;
+      history.push(previous);
+      current = {
+        type,
+        "startLine": startLine + lineDelta,
+        startColumn,
+        "endLine": endLine + lineDelta,
+        endColumn,
+        text,
+        "children": [],
+        "parent": ((previous === root) ? (ancestor || null) : previous)
+      };
+      if (ancestor) {
+        Object.defineProperty(current, htmlFlowSymbol, { "value": true });
+      }
+      previous.children.push(current);
+      flatTokens.push(current);
+      if ((current.type === "htmlFlow") && !isHtmlFlowComment(current)) {
+        skipHtmlFlowChildren = true;
+        if (!reparseOptions || !lines) {
+          reparseOptions = {
+            ...micromarkOptions,
+            "extensions": [
+              {
+                "disable": {
+                  "null": [ "codeIndented", "htmlFlow" ]
+                }
+              }
+            ]
+          };
+          lines = markdown.split(newLineRe);
+        }
+        const reparseMarkdown = lines
+          .slice(current.startLine - 1, current.endLine)
+          .join("\n");
+        const tokens = micromarkParseWithOffset(
+          reparseMarkdown,
+          reparseOptions,
+          referencesDefined,
+          current.startLine - 1,
+          current
+        );
+        current.children = tokens;
+        // Avoid stack overflow of Array.push(...spread)
+        // eslint-disable-next-line unicorn/prefer-spread
+        flatTokens = flatTokens.concat(tokens[flatTokensSymbol]);
+      }
+    } else if (kind === "exit") {
+      if (type === "htmlFlow") {
+        skipHtmlFlowChildren = false;
+      }
+      if (!skipHtmlFlowChildren) {
+        Object.freeze(current.children);
+        Object.freeze(current);
+        // @ts-ignore
+        current = history.pop();
+      }
+    }
+  }
+
+  // Return document
+  Object.defineProperty(document, flatTokensSymbol, { "value": flatTokens });
+  Object.freeze(document);
+  return document;
+}
+
+/**
+ * Parses a Markdown document and returns (frozen) tokens.
+ *
+ * @param {string} markdown Markdown document.
+ * @param {ParseOptions} [micromarkOptions] Options for micromark.
+ * @param {boolean} [referencesDefined] Treat references as defined.
+ * @returns {Token[]} Micromark tokens (frozen).
+ */
+function micromarkParse(
+  markdown,
+  micromarkOptions = {},
+  referencesDefined = true
+) {
+  return micromarkParseWithOffset(
+    markdown,
+    micromarkOptions,
+    referencesDefined,
+    0
+  );
+}
+
+/**
+ * Adds a range of numbers to a set.
+ *
+ * @param {Set<number>} set Set of numbers.
+ * @param {number} start Starting number.
+ * @param {number} end Ending number.
+ * @returns {void}
+ */
+function addRangeToSet(set, start, end) {
+  for (let i = start; i <= end; i++) {
+    set.add(i);
+  }
+}
+
+/**
+ * @callback AllowedPredicate
+ * @param {Token} token Micromark token.
+ * @returns {boolean} True iff allowed.
+ */
+
+/**
+ * @callback TransformPredicate
+ * @param {Token} token Micromark token.
+ * @returns {Token[]} Child tokens.
+ */
+
+/**
+ * Filter a list of Micromark tokens by predicate.
+ *
+ * @param {Token[]} tokens Micromark tokens.
+ * @param {AllowedPredicate} [allowed] Allowed token predicate.
+ * @param {TransformPredicate} [transformChildren] Transform predicate.
+ * @returns {Token[]} Filtered tokens.
+ */
+function filterByPredicate(tokens, allowed, transformChildren) {
+  allowed = allowed || (() => true);
+  const result = [];
+  const queue = [
+    {
+      "array": tokens,
+      "index": 0
+    }
+  ];
+  while (queue.length > 0) {
+    const current = queue[queue.length - 1];
+    const { array, index } = current;
+    if (index < array.length) {
+      const token = array[current.index++];
+      if (allowed(token)) {
+        result.push(token);
+      }
+      const { children } = token;
+      if (children.length > 0) {
+        const transformed =
+          transformChildren ? transformChildren(token) : children;
+        queue.push(
+          {
+            "array": transformed,
+            "index": 0
+          }
+        );
+      }
+    } else {
+      queue.pop();
+    }
+  }
+  return result;
+}
+
+/**
+ * Filter a list of Micromark tokens by type.
+ *
+ * @param {Token[]} tokens Micromark tokens.
+ * @param {TokenType[]} types Types to allow.
+ * @param {boolean} [htmlFlow] Whether to include htmlFlow content.
+ * @returns {Token[]} Filtered tokens.
+ */
+function filterByTypes(tokens, types, htmlFlow) {
+  const predicate = (token) =>
+    (htmlFlow || !inHtmlFlow(token)) && types.includes(token.type);
+  const flatTokens = tokens[flatTokensSymbol];
+  if (flatTokens) {
+    return flatTokens.filter(predicate);
+  }
+  return filterByPredicate(tokens, predicate);
+}
+
+/**
+ * Gets a list of nested Micromark token descendants by type path.
+ *
+ * @param {Token|Token[]} parent Micromark token parent or parents.
+ * @param {(TokenType|TokenType[])[]} typePath Micromark token type path.
+ * @returns {Token[]} Micromark token descendants.
+ */
+function getDescendantsByType(parent, typePath) {
+  let tokens = Array.isArray(parent) ? parent : [ parent ];
+  for (const type of typePath) {
+    tokens = tokens
+      .flatMap((t) => t.children)
+      .filter((t) => Array.isArray(type) ? type.includes(t.type) : (type === t.type));
+  }
+  return tokens;
+}
+
+/**
+ * Gets the heading level of a Micromark heading tokan.
+ *
+ * @param {Token} heading Micromark heading token.
+ * @returns {number} Heading level.
+ */
+function getHeadingLevel(heading) {
+  const headingSequence = filterByTypes(
+    heading.children,
+    [ "atxHeadingSequence", "setextHeadingLineSequence" ]
+  );
+  let level = 1;
+  const { text } = headingSequence[0];
+  if (text[0] === "#") {
+    level = Math.min(text.length, 6);
+  } else if (text[0] === "-") {
+    level = 2;
+  }
+  return level;
+}
+
+/**
+ * Gets the heading style of a Micromark heading tokan.
+ *
+ * @param {Token} heading Micromark heading token.
+ * @returns {"atx" | "atx_closed" | "setext"} Heading style.
+ */
+function getHeadingStyle(heading) {
+  if (heading.type === "setextHeading") {
+    return "setext";
+  }
+  const atxHeadingSequenceLength = filterByTypes(
+    heading.children,
+    [ "atxHeadingSequence" ]
+  ).length;
+  if (atxHeadingSequenceLength === 1) {
+    return "atx";
+  }
+  return "atx_closed";
+}
+
+/**
+ * Gets the heading text of a Micromark heading token.
+ *
+ * @param {Token} heading Micromark heading token.
+ * @returns {string} Heading text.
+ */
+function getHeadingText(heading) {
+  const headingTexts = getDescendantsByType(heading, [ [ "atxHeadingText", "setextHeadingText" ] ]);
+  return headingTexts[0]?.text.replace(/[\r\n]+/g, " ") || "";
+}
+
+/**
+ * HTML tag information.
+ *
+ * @typedef {Object} HtmlTagInfo
+ * @property {boolean} close True iff close tag.
+ * @property {string} name Tag name.
+ */
+
+/**
+ * Gets information about the tag in an HTML token.
+ *
+ * @param {Token} token Micromark token.
+ * @returns {HtmlTagInfo | null} HTML tag information.
+ */
+function getHtmlTagInfo(token) {
+  const htmlTagNameRe = /^<([^!>][^/\s>]*)/;
+  if (token.type === "htmlText") {
+    const match = htmlTagNameRe.exec(token.text);
+    if (match) {
+      const name = match[1];
+      const close = name.startsWith("/");
+      return {
+        close,
+        "name": close ? name.slice(1) : name
+      };
+    }
+  }
+  return null;
+}
+
+/**
+ * Gets the nearest parent of the specified type for a Micromark token.
+ *
+ * @param {Token} token Micromark token.
+ * @param {TokenType[]} types Types to allow.
+ * @returns {Token | null} Parent token.
+ */
+function getParentOfType(token, types) {
+  /** @type {Token | null} */
+  let current = token;
+  while ((current = current.parent) && !types.includes(current.type)) {
+    // Empty
+  }
+  return current;
+}
+
+/**
+ * Set containing token types that do not contain content.
+ *
+ * @type {Set<TokenType>}
+ */
+const nonContentTokens = new Set([
+  "blockQuoteMarker",
+  "blockQuotePrefix",
+  "blockQuotePrefixWhitespace",
+  "lineEnding",
+  "lineEndingBlank",
+  "linePrefix",
+  "listItemIndent"
+]);
+
+module.exports = {
+  "parse": micromarkParse,
+  addRangeToSet,
+  filterByPredicate,
+  filterByTypes,
+  getDescendantsByType,
+  getHeadingLevel,
+  getHeadingStyle,
+  getHeadingText,
+  getHtmlTagInfo,
+  getParentOfType,
+  getMicromarkEvents,
+  inHtmlFlow,
+  isHtmlFlowComment,
+  nonContentTokens
+};