import { BlockStart, Matched } from '../blockStarts';
import { BlockNode } from '../node';

// `---` for YAML, `+++` for TOML, `;;;` for JSON
export const reFrontMatter = /^(-{3}|\+{3}|;{3})$/;

export const frontMatter: BlockStart = (parser, container) => {
  const { currentLine, lineNumber, indented } = parser;

  if (
    lineNumber === 1 &&
    !indented &&
    container.type === 'document' &&
    reFrontMatter.test(currentLine)
  ) {
    parser.closeUnmatchedBlocks();
    const frontMatter = parser.addChild('frontMatter', parser.nextNonspace) as BlockNode;
    frontMatter.stringContent = currentLine;

    parser.advanceNextNonspace();
    parser.advanceOffset(currentLine.length, false);

    return Matched.Leaf;
  }
  return Matched.None;
};