block.ts

import type MarkdownIt from 'markdown-it/lib/index.js';
import type StateBlock from 'markdown-it/lib/rules_block/state_block.js';
import type Token from 'markdown-it/lib/token.js';

/** Parse MyST targets (``(name)=``), blockquotes (``% comment``) and block breaks (``+++``).
 *
 * Adapted from: mdit_py_plugins/myst_blocks/index.py
 */
export function blockPlugin(md: MarkdownIt): void {
  md.block.ruler.before('blockquote', 'myst_line_comment', parse_line_comment, {
    alt: ['paragraph', 'reference', 'blockquote', 'list', 'footnote_def'],
  });
  md.block.ruler.before('hr', 'myst_block_break', parse_block_break, {
    alt: ['paragraph', 'reference', 'blockquote', 'list', 'footnote_def'],
  });
  md.block.ruler.before('hr', 'myst_target', parse_target, {
    alt: ['paragraph', 'reference', 'blockquote', 'list', 'footnote_def'],
  });
  md.renderer.rules.myst_line_comment = render_myst_line_comment;
  md.renderer.rules.myst_target = render_myst_target;
}

function parse_line_comment(
  state: StateBlock,
  startLine: number,
  endLine: number,
  silent: boolean,
): boolean {
  let pos = state.bMarks[startLine] + state.tShift[startLine];
  let maximum = state.eMarks[startLine];

  // if it's indented more than 3 spaces, it should be a code block
  if (state.sCount[startLine] - state.blkIndent >= 4) {
    return false;
  }

  if (state.src[pos] !== '%') {
    return false;
  }

  if (silent) {
    return true;
  }

  const token = state.push('myst_line_comment', '', 0);
  token.attrSet('class', 'myst-line-comment');
  token.content = state.src.slice(pos + 1, maximum).replace(/\s+$/gm, ''); // rstrip
  token.markup = '%';

  // search end of block while appending lines to `token.content`
  let nextLine: number;
  for (nextLine = startLine + 1; nextLine < endLine; nextLine++) {
    pos = state.bMarks[nextLine] + state.tShift[nextLine];
    maximum = state.eMarks[nextLine];
    if (state.src[pos] !== '%') {
      break;
    }
    token.content += '\n' + state.src.slice(pos + 1, maximum).replace(/\s+$/gm, ''); // rstrip
  }
  state.line = nextLine;
  token.map = [startLine, nextLine];

  return true;
}

function parse_block_break(
  state: StateBlock,
  startLine: number,
  endLine: number,
  silent: boolean,
): boolean {
  let pos = state.bMarks[startLine] + state.tShift[startLine];
  const maximum = state.eMarks[startLine];

  // if it's indented more than 3 spaces, it should be a code block
  if (state.sCount[startLine] - state.blkIndent >= 4) {
    return false;
  }

  const marker = state.src.charCodeAt(pos);
  pos += 1;

  // Check block marker /* + */
  if (marker !== 0x2b) {
    return false;
  }

  // markers can be mixed with spaces, but there should be at least 3 of them

  let cnt = 1;
  while (pos < maximum) {
    const ch = state.src.charCodeAt(pos);
    if (ch !== marker && !state.md.utils.isSpace(ch)) {
      break;
    }
    if (ch === marker) {
      cnt += 1;
    }
    pos += 1;
  }

  if (cnt < 3) {
    return false;
  }

  if (silent) {
    return true;
  }

  state.line = startLine + 1;

  const token = state.push('myst_block_break', 'hr', 0);
  token.attrSet('class', 'myst-block');
  token.content = state.src.slice(pos, maximum).trim();
  token.map = [startLine, state.line];
  token.markup = state.md.utils.fromCodePoint(marker).repeat(cnt);

  return true;
}

const TARGET_PATTERN = /^\((?<label>[a-zA-Z0-9|@<>*./_\-+:]{1,100})\)=\s*$/;

function parse_target(
  state: StateBlock,
  startLine: number,
  endLine: number,
  silent: boolean,
): boolean {
  const pos = state.bMarks[startLine] + state.tShift[startLine];
  const maximum = state.eMarks[startLine];

  // if it's indented more than 3 spaces, it should be a code block
  if (state.sCount[startLine] - state.blkIndent >= 4) {
    return false;
  }
  const match = TARGET_PATTERN.exec(state.src.slice(pos, maximum));
  if (!match) {
    return false;
  }
  if (silent) {
    return true;
  }

  state.line = startLine + 1;

  const token = state.push('myst_target', '', 0);
  token.attrSet('class', 'myst-target');
  token.content = match && match.groups ? match.groups['label'] : '';
  token.map = [startLine, state.line];

  return true;
}

function escapeHtml(unsafe: string) {
  return unsafe
    .replace(/&/g, '&amp;')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')
    .replace(/"/g, '&quot;')
    .replace(/'/g, '&#039;');
}

function render_myst_line_comment(tokens: Token[], idx: number): string {
  const token = tokens[idx];
  const content = token.content;
  return `<!-- ${escapeHtml(content).trim()} -->`;
}

function render_myst_target(tokens: Token[], idx: number) {
  const token = tokens[idx];
  const className = 'myst-target';
  const label = token.content;
  const target = `<a href="#${label}">(${label})=</a>`;
  return `<div class="${className}">${target}</div>`;
}