import path from 'path';
import child_process from 'child_process';
import fs from 'fs-extra';

/**
 * write a template to a file
 *
 * @param {string} contents file contents
 * @param {string} destination file destination
 */
async function apply_template (
  contents: string,
  destination: string
): Promise<void> {
  const dst = path.join (process.cwd (), destination);
  if (!await fs.pathExists (dst))
    await fs.writeFile (dst, contents);
}

type JSONMutator = {
  (json: object): Promise<object>;
}

/**
 * modify a json file
 *
 * @param {Function} func function that modifies the object
 * @param {string} json_path path of json file
 */
async function modify_json (
  func: JSONMutator,
  json_path = 'package.json'
): Promise<void> {
  const file_path = path.join (process.cwd (), json_path);
  const content = JSON.parse (await fs.readFile (file_path, 'utf-8'));
  const new_obj = await func (content);
  await fs.writeFile (file_path, JSON.stringify (new_obj, null, 2));
}

/**
 * run a command
 *
 * @param {string} command command to run
 * @param {string} folder folder to run in
 * @returns {Promise<void>} promise
 */
function run_command (command: string, folder = ''): Promise<void> {
  return new Promise ((res) => {
    const exec = child_process.exec (
      command,
      { cwd: path.join (process.cwd (), folder), stdio: 'inherit' }
    );
    exec.on ('close', res);
  });
}

export { modify_json, apply_template, run_command };