docs/lib/remark-custom-blocks.js

const spaceSeparated = require('space-separated-tokens');

function escapeRegExp(str) {
  return str.replace(new RegExp(`[-[\\]{}()*+?.\\\\^$|/]`, 'g'), '\\$&');
}

const C_NEWLINE = '\n';
const C_FENCE = '|';

function compilerFactory(nodeType) {
  let text;
  let title;

  return {
    blockHeading(node) {
      title = this.all(node).join('');
      return '';
    },
    blockBody(node) {
      text = this.all(node)
        .map(s => s.replace(/\n/g, '\n| '))
        .join('\n|\n| ');
      return text;
    },
    block(node) {
      text = '';
      title = '';
      this.all(node);
      if (title) {
        return `[[${nodeType} | ${title}]]\n| ${text}`;
      } else {
        return `[[${nodeType}]]\n| ${text}`;
      }
    },
  };
}

module.exports = function blockPlugin(availableBlocks = {}) {
  const pattern = Object.keys(availableBlocks).map(escapeRegExp).join('|');

  if (!pattern) {
    throw new Error('remark-custom-blocks needs to be passed a configuration object as option');
  }

  const regex = new RegExp(`\\[\@(${pattern})(?: *\\| *(.*))?\]\n`);

  function blockTokenizer(eat, value, silent) {
    const now = eat.now();
    const keep = regex.exec(value);
    if (!keep) return;
    if (keep.index !== 0) return;
    const [eaten, blockType, blockTitle] = keep;

    /* istanbul ignore if - never used (yet) */
    if (silent) return true;

    const linesToEat = [];
    const content = [];

    let idx = 0;
    while ((idx = value.indexOf(C_NEWLINE)) !== -1) {
      const next = value.indexOf(C_NEWLINE, idx + 1);
      // either slice until next NEWLINE or slice until end of string
      const lineToEat = next !== -1 ? value.slice(idx + 1, next) : value.slice(idx + 1);
      if (lineToEat[0] !== C_FENCE) break;
      // remove leading `FENCE ` or leading `FENCE`
      const line = lineToEat.slice(lineToEat.startsWith(`${C_FENCE} `) ? 2 : 1);
      linesToEat.push(lineToEat);
      content.push(line);
      value = value.slice(idx + 1);
    }

    const contentString = content.join(C_NEWLINE);

    const stringToEat = eaten + linesToEat.join(C_NEWLINE);

    const potentialBlock = availableBlocks[blockType];
    const titleAllowed =
      potentialBlock.title && ['optional', 'required'].includes(potentialBlock.title);
    const titleRequired = potentialBlock.title && potentialBlock.title === 'required';

    if (titleRequired && !blockTitle) return;
    if (!titleAllowed && blockTitle) return;

    const add = eat(stringToEat);
    if (potentialBlock.details) {
      potentialBlock.containerElement = 'details';
      potentialBlock.titleElement = 'summary';
    }

    const exit = this.enterBlock();
    const contents = {
      type: `${blockType}CustomBlockBody`,
      data: {
        hName: potentialBlock.contentsElement ? potentialBlock.contentsElement : 'div',
        hProperties: {
          className: 'custom-block-body',
        },
      },
      children: this.tokenizeBlock(contentString, now),
    };
    exit();

    const blockChildren = [contents];
    if (titleAllowed && blockTitle) {
      const titleElement = potentialBlock.titleElement ? potentialBlock.titleElement : 'div';
      const titleNode = {
        type: `${blockType}CustomBlockHeading`,
        data: {
          hName: titleElement,
          hProperties: {
            className: 'custom-block-heading',
          },
        },
        children: this.tokenizeInline(blockTitle, now),
      };

      blockChildren.unshift(titleNode);
    }

    const classList = spaceSeparated.parse(potentialBlock.classes || '');

    return add({
      type: `${blockType}CustomBlock`,
      children: blockChildren,
      data: {
        hName: potentialBlock.containerElement ? potentialBlock.containerElement : 'div',
        hProperties: {
          className: ['custom-block', ...classList],
        },
      },
    });
  }

  const Parser = this.Parser;

  // Inject blockTokenizer
  const blockTokenizers = Parser.prototype.blockTokenizers;
  const blockMethods = Parser.prototype.blockMethods;
  blockTokenizers.customBlocks = blockTokenizer;
  blockMethods.splice(blockMethods.indexOf('fencedCode') + 1, 0, 'customBlocks');
  const Compiler = this.Compiler;
  if (Compiler) {
    const visitors = Compiler.prototype.visitors;
    if (!visitors) return;
    Object.keys(availableBlocks).forEach(key => {
      const compiler = compilerFactory(key);
      visitors[`${key}CustomBlock`] = compiler.block;
      visitors[`${key}CustomBlockHeading`] = compiler.blockHeading;
      visitors[`${key}CustomBlockBody`] = compiler.blockBody;
    });
  }
  // Inject into interrupt rules
  const interruptParagraph = Parser.prototype.interruptParagraph;
  const interruptList = Parser.prototype.interruptList;
  const interruptBlockquote = Parser.prototype.interruptBlockquote;
  interruptParagraph.splice(interruptParagraph.indexOf('fencedCode') + 1, 0, ['customBlocks']);
  interruptList.splice(interruptList.indexOf('fencedCode') + 1, 0, ['customBlocks']);
  interruptBlockquote.splice(interruptBlockquote.indexOf('fencedCode') + 1, 0, ['customBlocks']);
};