const proc = require('child_process');
const read = cmd => proc.execSync(cmd, { encoding: 'utf8' }).trim();
const run = cmd => { proc.execSync(cmd, { stdio: 'inherit' }); };
const tryRead = cmd => { try { return read(cmd); } catch (e) { return undefined; } };

const releaseBranchRegex = /^release-v(?<version>(?<major>\d+)\.(?<minor>\d+)(?:\.(?<patch>\d+))?)$/;

const currentBranch = read(`git rev-parse --abbrev-ref HEAD`);
const match = currentBranch.match(releaseBranchRegex);

if (!match) {
  console.error(`Not currently on a release branch`);
  process.exit(1);
}

if (/-.*$/.test(require('../package.json').version)) {
  console.error(`Refusing to update docs: prerelease detected`);
  process.exit(0);
}

const current = match.groups;
const docsBranch = `docs-v${current.major}.x`;

// Fetch remotes and find the docs branch if it exists
run(`git fetch --all --no-tags`);
const matchingDocsBranches = tryRead(`git rev-parse --glob='*/${docsBranch}'`);

if (!matchingDocsBranches) {
  // Create the branch
  run(`git checkout --orphan ${docsBranch}`);
} else {
  const [publishedRef, ...others] = new Set(matchingDocsBranches.split('\n'));
  if (others.length > 0) {
    console.error(
      `Found conflicting ${docsBranch} branches.\n`
      + `Either local branch is outdated or there are multiple matching remote branches.`
    );
    process.exit(1);
  }
  const publishedVersion = JSON.parse(read(`git show ${publishedRef}:package.json`)).version;
  const publishedMinor = publishedVersion.match(/\d+\.(?<minor>\d+)\.\d+/).groups.minor;
  if (current.minor < publishedMinor) {
    console.error(`Refusing to update docs: newer version is published`);
    process.exit(0);
  }

  run(`git checkout --quiet --detach`);
  run(`git reset --soft ${publishedRef}`);
  run(`git checkout ${docsBranch}`);
}

run(`npm run prepare-docs`);
run(`git add -f docs`); // --force needed because generated docs files are gitignored
run(`git commit -m "Update docs"`);
run(`git checkout ${currentBranch}`);