Retained — LeetCode → Google Drive

Manifest V3 Chrome extension that saves your accepted LeetCode solutions to a LeetCode-Solutions folder in Google Drive, and offers to restore a saved solution when you revisit a problem. Saving happens automatically once your submission is Accepted — you can also save manually at any time via the floating button. Pasting a previously saved solution back into the editor is still entirely on your terms, via explicit Yes/No buttons — nothing is ever pasted automatically.

Files

• manifest.template.json — tracked in git; the real manifest.json (with your OAuth client ID) is generated from this and is gitignored
• scripts/build-manifest.js — generates manifest.json from .env + the template
• .env.example — copy to .env and fill in your own OAuth client ID
• content.js — runs the bottom-right corner UI, the Drive lookup, and the manual save/paste flow
• background.js — authenticates with Google Drive and uploads/looks up solutions
• icons/ — toolbar icon

How it behaves

• On opening a problem page: the extension checks Drive for a saved solution. A small "Checking for a saved solution…" indicator appears in the bottom-right corner (never full-screen, never blocking the page).
  • Found: a bottom-right card says "Solution available" and asks "Paste it into the editor?" with Yes / No buttons. Nothing is pasted unless you click Yes.
  • Not found: a bottom-right card says "No saved solution found" with a 💾 Save Solution button.
• Autosave on Accepted. The extension watches for you clicking LeetCode's Submit button, then watches the verdict panel for a few seconds. If it comes back Accepted, your code is uploaded to Drive automatically — no click required. This only fires after a fresh Submit click, so it won't trigger from browsing your Submissions history or switching tabs.
• Manual save is still available. A 💾 Save Solution button is always available in the bottom-right corner (as a small floating pill once you've dismissed the lookup card), so you can save a draft at any point, even before submitting.
• On save (auto or manual): a "Saving…" indicator appears, followed by a success toast, both in the same corner. The autosave toast is labeled "Accepted" so you can tell it apart from a manual save.

Why it doesn't work "out of the box"

The code itself is complete and functional — the reason a freshly cloned copy of this repo won't work is that Google OAuth client IDs are tied to a specific extension ID. A client ID generated for one person's local unpacked copy will never authenticate for anyone else's install — Chrome's chrome.identity.getAuthToken call will silently fail (or show an "OAuth2 request failed" / "bad client id" error) because your unpacked extension gets a different auto-generated ID than theirs.

This isn't something that can be fixed by editing the code — you need to create your own OAuth client and keep it out of git (see setup below). It only takes a few minutes.

Setup (required, one-time)

1. Load the unpacked extension first (to get its ID)

You need a manifest.json to load the extension at all, even before OAuth works. Generate a placeholder one now:

cp .env.example .env
node scripts/build-manifest.js

This writes manifest.json (gitignored — it will contain your real client ID once you fill in .env, so it never gets committed). For now it'll have a placeholder value, which is fine for this step.

1. Open chrome://extensions/.
2. Enable Developer mode (top-right toggle).
3. Click Load unpacked and select this project folder.
4. It will load successfully (auth isn't wired up yet) and Chrome will assign it an Extension ID — a 32-character string shown on its card, e.g. abcdefghijklmnopqrstuvwxyzabcdef. Copy it.

2. Create a Google Cloud project + OAuth client

1. Go to Google Cloud Console and create a new project (or pick an existing one).
2. Enable the Google Drive API: APIs & Services → Library → search "Google Drive API" → Enable.
3. Configure the OAuth consent screen (APIs & Services → OAuth consent screen):
   • User type: External (unless you have a Workspace org) → Create.
   • Fill in app name, your email, etc. → Save and continue through the steps.
   • Under Scopes, you don't need to add anything manually here since the extension requests drive.file at runtime, but you can add it if prompted.
   • Under Test users, add the Google account(s) you'll actually use with the extension (required while the app is in "Testing" mode, which is fine for personal use — no Google verification needed).
4. Create the OAuth client: APIs & Services → Credentials → Create Credentials → OAuth client ID.
   • Application type: Chrome Extension.
   • Item ID: paste the Extension ID you copied in step 1.
   • Create → copy the generated Client ID (ends in .apps.googleusercontent.com).

3. Put the client ID in .env

Open .env (created in step 1) and set:

GOOGLE_OAUTH_CLIENT_ID=YOUR_REAL_CLIENT_ID.apps.googleusercontent.com

Then regenerate manifest.json:

node scripts/build-manifest.js

.env and manifest.json are both gitignored, so your client ID never gets committed.

4. Reload the extension

Back on chrome://extensions/, click the reload icon on the extension's card so it picks up the new manifest.json.

Note: the Extension ID normally stays stable for a given unpacked folder path on your machine, so you shouldn't need to redo step 1/2 after this — just rerun node scripts/build-manifest.js and reload after any .env or code changes. If you ever move the folder to a new path or a different machine, Chrome may assign a new ID and you'll need to add that ID to the same OAuth client (Credentials → your client → Item ID can only hold one ID, so create a new OAuth client instead, or reuse it by re-registering).

Using it

1. Go to any https://leetcode.com/problems/... page.
2. On first load, you'll see a small popup asking you to sign in with Google and grant Drive access — this happens automatically the first time the extension checks for or saves a solution.
3. The extension checks Drive for a saved solution (bottom-right indicator). If one exists, it asks whether to paste it into the editor — nothing is pasted without your say-so.
4. Write your solution and click Submit as normal. If it comes back Accepted, Retained saves it to Drive automatically. You can also click 💾 Save Solution (bottom-right) at any time to save a draft manually.

Notes

• Uses the narrower drive.file scope (not full drive access) — the extension can only see/manage files and folders it creates itself, not your entire Drive.
• If you ever revoke access, just reload the page and re-authenticate when prompted.
• If uploads/lookups stop working, open the extension's service worker console (chrome://extensions/ → "service worker" link on the card) to see the actual error — most issues at that point are auth-related (client ID / test user list) rather than code bugs.
• If you previously had a real OAuth client ID committed in manifest.json in git history, rotate it in Google Cloud Console (delete the old credential, create a new one) now that it's out of the tracked files.