import { mkdir, stat, readFile, writeFile } from 'fs';
import * as glob from 'glob';
import * as path from 'path';
import {promisify} from 'util';
import { ChildProcess, ForkOptions, fork, SpawnOptions, spawn } from 'child_process';
import * as once from 'once';
import * as tmp from 'tmp';

export const BUILD_DIRECTORY = 'build';

export const globP = promisify(glob);
export const mkdirP = promisify(mkdir);
export const readFileP = promisify(readFile);
export const writeFileP = promisify(writeFile);
export const statP = promisify(stat);
export const tmpDirP = promisify(tmp.dir) as () => Promise<string>;

export function nodule(nodule: string) {
  return path.relative(BUILD_DIRECTORY, `node_modules/${nodule}`);
}

export function flatten<T>(arr: Array<Array<T>>): Array<T> {
  return arr.reduce((acc, e) => acc.concat(e), []);
}

export function existsP(path: string): Promise<boolean> {
  return statP(path).then(
    () => Promise.resolve(true),
    () => Promise.resolve(false)
  );
}

function promisifyChildProcess(childProcess: ChildProcess): Promise<void> {
  return new Promise((resolve, reject) => {
    const exit = (err?: Error) => once(() => err ? reject(err) : resolve())();
    childProcess.on('error', exit);
    childProcess.on('close', (code) => {
      if (code === 0) {
        exit();
      } else {
        exit(new Error(`Process ${childProcess.pid} exited with code ${code}.`));
      }
    });
  });
}

export function spawnP(command: string, args?: string[], options?: SpawnOptions): Promise<void> {
  const stringifiedCommand = `\`${command}${args ? (' ' + args.join(' ')) : ''}\``;
  console.log(`> Running: ${stringifiedCommand}`);
  return promisifyChildProcess(spawn(command, args, Object.assign({
    stdio: 'inherit',
    shell: true
  }, options)));
}

export function forkP(moduleName: string, args?: string[], options?: ForkOptions): Promise<void> {
  const stringifiedCommand = `\`${moduleName}${args ? (' ' + args.join(' ')) : ''}\``;
  console.log(`> Running: ${stringifiedCommand}`);
  return promisifyChildProcess(fork(moduleName, args, Object.assign({
    stdio: 'inherit',
    execArgv: []
  }, options)));
}