import YAML from "yaml";
const FRONTMATTER_REGEX = /^---[\s\S]*?---/gm;

/**
 * Parse a markdown document with optional YAML frontmatter into an object
 * with the markdown content and any frontmatter as keys.
 * @param content The raw markdown content
 * @param markdownKey The key to use for the markdown content
 * @returns The parsed markdown content and frontmatter
 */
function parse(
  content: string,
  markdownKey = "content",
): Record<string, unknown> {
  const markdown = content.trim().replace(FRONTMATTER_REGEX, "").trim();
  let frontmatter: Record<string, unknown> = {};

  if (FRONTMATTER_REGEX.test(content)) {
    const frontmatterString = content.match(FRONTMATTER_REGEX)?.[0] ?? "";
    const cleanFrontmatter = frontmatterString.replaceAll("---", "").trim();
    frontmatter = YAML.parse(cleanFrontmatter);
  }

  return {
    [markdownKey]: markdown,
    ...frontmatter,
  };
}

/**
 * Serialize an object with markdown content and optional frontmatter into a
 * Markdown document. Uses the `content` key for the markdown content by default.
 * @param data The object to serialize
 * @param markdownKey The key to use for the markdown content
 * @returns The parsed markdown content and frontmatter
 */
function stringify(
  data: Record<string, unknown>,
  markdownKey = "content",
): string {
  const markdown = String(data[markdownKey] ?? "");
  const frontmatter = { ...data };
  delete frontmatter[markdownKey];

  const remainingKeys = Object.keys(frontmatter).length;

  if (remainingKeys === 0) {
    return markdown;
  }

  const stringifiedFrontmatter = YAML.stringify(frontmatter).trim();

  return `---\n${stringifiedFrontmatter}\n---\n${markdown}`;
}

const EMDY = {
  parse,
  stringify,
} as const;

export default EMDY;