import yaml from "js-yaml";
import { Release, VersionType } from "@changesets/types";

const mdRegex = /\s*---([^]*?)\n\s*---(\s*(?:\n|$)[^]*)/;

export default function parseChangesetFile(contents: string): {
  summary: string;
  releases: Release[];
} {
  const execResult = mdRegex.exec(contents);
  if (!execResult) {
    throw new Error(
      `could not parse changeset - invalid frontmatter: ${contents}`
    );
  }
  let [, roughReleases, roughSummary] = execResult;
  let summary = roughSummary.trim();

  let releases: Release[];
  try {
    const yamlStuff: { [key: string]: VersionType } =
      yaml.safeLoad(roughReleases);
    if (yamlStuff) {
      releases = Object.entries(yamlStuff).map(([name, type]) => ({
        name,
        type,
      }));
    } else {
      releases = [];
    }
  } catch (e) {
    throw new Error(
      `could not parse changeset - invalid frontmatter: ${contents}`
    );
  }

  if (!releases) {
    throw new Error(`could not parse changeset - unknown error: ${contents}`);
  }

  return { releases, summary };
}