File Organizer

import { readdir, stat, rename, mkdir, writeFile, readFile } from "fs/promises";
import { join, extname, basename } from "path";

export const CATEGORIES = {
  Images:    [".jpg",".jpeg",".png",".gif",".webp",".svg",".ico"],
  Documents: [".pdf",".doc",".docx",".txt",".md",".csv",".xlsx",".pptx"],
  Videos:    [".mp4",".mov",".avi",".mkv",".webm"],
  Audio:     [".mp3",".wav",".flac",".aac",".ogg"],
  Code:      [".js",".mjs",".ts",".py",".html",".css",".json",".sh"],
  Archives:  [".zip",".tar",".gz",".rar",".7z"],
};

export function getCategory(filename) {
  const ext = extname(filename).toLowerCase();
  return Object.entries(CATEGORIES).find(([, exts]) => exts.includes(ext))?.[0] ?? "Other";
}

export async function organise(dir, { dryRun = false, undoLog = "undo.json" } = {}) {
  const entries = await readdir(dir);
  const moves   = [];

  for (const entry of entries) {
    const srcPath = join(dir, entry);
    const info    = await stat(srcPath);
    if (!info.isFile()) continue;               // skip directories
    if (entry.startsWith(".")) continue;         // skip hidden files
    if (entry === basename(undoLog)) continue;   // skip our own undo log

    const category = getCategory(entry);
    const destDir  = join(dir, category);
    const destPath = join(destDir, entry);

    moves.push({ from: srcPath, to: destPath, category });

    if (!dryRun) {
      await mkdir(destDir, { recursive: true });
      await rename(srcPath, destPath);
    }
  }

  if (!dryRun && moves.length > 0) {
    await writeFile(join(dir, undoLog), JSON.stringify(moves, null, 2));
  }

  return moves;
}

export async function undo(dir, undoLog = "undo.json") {
  const logPath = join(dir, undoLog);
  const moves   = JSON.parse(await readFile(logPath, "utf-8"));
  for (const { from, to } of moves.reverse()) {
    await rename(to, from).catch(() => {});   // ignore if already moved back
  }
  return moves.length;
}

// ── CLI ─────────────────────────────────────────────────────────────────────
const [,, targetDir = ".", ...flags] = process.argv;
const dryRun  = flags.includes("--dry-run");
const doUndo  = flags.includes("--undo");

if (doUndo) {
  const count = await undo(targetDir);
  console.log(`Undone: ${count} file(s) moved back.`);
} else {
  const moves = await organise(targetDir, { dryRun });
  if (!moves.length) { console.log("No files to organise."); process.exit(0); }
  const byCategory = {};
  moves.forEach(m => { byCategory[m.category] = (byCategory[m.category] || 0) + 1; });
  console.log(dryRun ? "
Dry run — no files moved:" : "
Organised:");
  Object.entries(byCategory).sort().forEach(([cat, n]) =>
    console.log(`  ${cat}/  ← ${n} file${n !== 1 ? "s" : ""}`)
  );
  if (!dryRun) console.log(`
Undo with: node organizer.mjs ${targetDir} --undo`);
}

import { getCategory, CATEGORIES } from "./organizer.mjs";
let p=0,f=0;
function test(d,fn){try{fn();console.log("  ✓",d);p++;}catch(e){console.log("  ✗",d,"—",e.message);f++;}}
test("jpg → Images",     () => { if(getCategory("photo.jpg")!=="Images") throw new Error(); });
test("PDF → Documents",  () => { if(getCategory("report.PDF")!=="Documents") throw new Error(); });
test("mp4 → Videos",     () => { if(getCategory("clip.mp4")!=="Videos") throw new Error(); });
test("js  → Code",       () => { if(getCategory("app.js")!=="Code") throw new Error(); });
test("zip → Archives",   () => { if(getCategory("backup.zip")!=="Archives") throw new Error(); });
test("unknown → Other",  () => { if(getCategory("file.xyz")!=="Other") throw new Error(); });
test("case-insensitive", () => { if(getCategory("IMG.PNG")!=="Images") throw new Error(); });
test("all extensions covered", () => {
  const allExts = Object.values(CATEGORIES).flat();
  const dupes = allExts.filter((e,i,a) => a.indexOf(e)!==i);
  if(dupes.length) throw new Error("Duplicate extensions: " + dupes);
});
console.log(`
${p} passed, ${f} failed`);

node organizer.mjs . --dry-run    # preview on current dir
node organizer.mjs ~/Downloads    # actually move files
node organizer.test.mjs