link-unlink/dist/esm/link.js

Link and unlink with saving and restoring the previous file or directory

import fs from 'fs';
import { Lock } from 'lock';
import mkdirp from 'mkdirp-classic';
import path from 'path';
import tempSuffix from 'temp-suffix';
const lock = Lock();
const isWindows = process.platform === 'win32' || /^(msys|cygwin)$/.test(process.env.OSTYPE);
const dirSymlinkType = isWindows ? 'junction' : 'dir';
function saveLink(target, callback) {
    const movedPath = path.join(path.dirname(target), `${path.basename(target)}.${tempSuffix()}`);
    fs.rename(target, movedPath, callback);
}
function createLink(src, target, callback) {
    fs.stat(src, (err, stat)=>{
        if (err) return callback(err);
        mkdirp(path.dirname(target), ()=>{
            fs.symlink(src, target, stat.isFile() ? 'file' : dirSymlinkType, (err)=>{
                if (!err) return callback(null, target);
                // already exists, move and try to link again
                return saveLink(target, (err)=>{
                    err ? callback(err) : createLink(src, target, callback);
                });
            });
        });
    });
}
function worker(src, target, callback) {
    lock([
        src,
        target
    ], (release)=>{
        callback = release(callback);
        fs.stat(target, (_, stat)=>{
            // doesn't exist, create
            if (!stat) return createLink(src, target, callback);
            // exists so move it
            return saveLink(target, (err)=>{
                err ? callback(err) : createLink(src, target, callback);
            });
        });
    });
}
export default function link(src, target, callback) {
    if (typeof callback === 'function') return worker(src, target, callback);
    return new Promise((resolve, reject)=>worker(src, target, (err, restore)=>err ? reject(err) : resolve(restore)));
}