import { join } from 'path';
import fetch from 'node-fetch';
import execa from 'execa';
import { createWriteStream } from 'fs';
import { getWriteableDirectory } from '@now/build-utils';

const url = 'https://portableruby.s3.amazonaws.com/ruby-2.5.3.zip';

// downloads `ruby` and `gem` and returns their absolute paths
async function downloadPortableRuby(path: string) {
  console.log('downloading "ruby-2.5.5.zip"...');
  const res = await fetch(url);

  if (!res.ok || res.status !== 200) {
    throw new Error(`Could not download "ruby-2.5.3.zip" from "${url}"`);
  }

  const dir = await getWriteableDirectory();
  const filePath = join(dir, 'ruby-2.5.3.zip');
  const writeStream = createWriteStream(filePath);

  await new Promise<string>((resolve, reject) => {
    res.body
      .on('error', reject)
      .pipe(writeStream)
      .on('finish', resolve);
  });

  try {
    await execa('unzip', ['-q', '-d', path, filePath], { stdio: 'inherit' });
  } catch (err) {
    console.log('could not unzip ruby-2.5.3.zip');
    throw err;
  }

  return {
    rubyPath: join(path, 'bin', 'ruby'),
    gemPath: join(path, 'bin', 'gem'),
  }
}

// downloads and installs `bundler` (respecting
// process.env.GEM_HOME), and returns
// the absolute path to it
export async function downloadAndInstallBundler() {
  const { GEM_HOME } = process.env;
  if (!GEM_HOME) {
    // this is the directory in which `gem` will be
    // installed to. `--prefix` will assume `~` if this
    // is not set, and `~` is not writeable on AWS Lambda.
    // let's refuse to proceed
    throw new Error(
      'Could not install "bundler": "GEM_HOME" env var is not set',
    );
  }

  console.log('installing ruby...')
  const { rubyPath, gemPath } = await downloadPortableRuby(GEM_HOME);

  console.log('installing bundler...')
  await execa(gemPath, ['install', 'bundler', '--no-document'], { stdio: 'inherit' })

  return {
    rubyPath,
    gemPath,
    bundlerPath: join(GEM_HOME, 'bin', 'bundler'),
  };
}