index.js

'use strict';

const gunzipMaybe = require('gunzip-maybe');
const fstream     = require('fstream');
const pify        = require('pify');
const pathExists  = require('path-exists');
const mem         = require('mem');
const mkdirp      = require('make-dir');

// rewired in test
let which = pify(require('which'));
let execa = require('execa');
let tar   = require('tar-fs');

/**
 * Check if the system has a tar binary.
 * @returns {Promise.<Boolean>}
 */
let hasBinaryTar = mem(function () {
    if (process.platform === 'win32') return Promise.resolve(false);
    else return which('tar').then(() => true, () => false);
});

/**
 * Extract using built-in tar binary with the node.js implementation as a fallback
 * @param {string} archive
 * @param {string} extractTo
 * @returns {Promise.<T>}
 */
const extrakt = function (archive, extractTo) {
    return Promise.all([
        pathExists(archive),
        hasBinaryTar()
    ]).then(([exists, hasBinaryTar]) => {
        if (!exists) throw new Error(`No file at ${archive}`);
        return hasBinaryTar;
    })
        .then(sys => sys ? extrakt.system(archive, extractTo) : extrakt.native(archive, extractTo));
};

/**
 * Extract using the system's built-in tar binary
 * @param {string} archive
 * @param {string} extractTo
 * @returns {Promise}
 */
extrakt.system = function (archive, extractTo) {
    return mkdirp(extractTo).then(() => execa('tar', ['-xf', archive, '-C', extractTo]));
};

/**
 * Extract using the tar-fs module
 * @param {string} archive
 * @param {string} extractTo
 * @returns {Promise}
 */
extrakt.native = function (archive, extractTo) {
    // note the tar module takes care of mkdirp'ing the destination directory
    let extract = tar.extract(extractTo);
    fstream
        .Reader(archive)
        .pipe(gunzipMaybe())
        .pipe(extract);
    return new Promise((resolve, reject) => {
        extract.on('finish', resolve);
        extract.on('error', reject);
    });
};

module.exports = extrakt;