Add GET /stats/top (most-clicked links leaderboard)

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Business impact

Right now the only way to see how a link is performing is GET /:code/stats, one code at a time -- you have to already know which short code you're asking about. There's no way to answer "which of our links are actually getting clicked?" without querying the database by hand. That's a real gap for anyone using this service to track campaign links, social posts, or anything where "what's working?" is the whole point of tracking clicks in the first place -- right now that question requires direct DB access, not the API.

Problem

GET /stats/top is registered as a stub in src/routes/redirect.js (right before GET /:code). It compiles and the route exists, but its handler unconditionally throws -- hitting it always returns a 500, regardless of query parameters.

Current behavior

GET /stats/top?limit=2 always returns HTTP 500 instead of a ranked list of links.

Expected behavior

GET /stats/top?limit=N returns a JSON array of the N links with the highest clicks count, sorted descending by clicks (most-clicked first). limit is optional, defaulting to 10 if omitted, and clamped to a sane range (e.g. 1–100) rather than trusting an arbitrary client-supplied number directly. Each entry has the shape { shortCode, longUrl, clicks } -- no need to include createdAt/expiresAt, this is intentionally a lighter-weight response than GET /:code/stats. An empty database (no links at all) returns 200 [], not an error.

Steps to reproduce

npm run dev curl -s "http://localhost:3003/stats/top?limit=2"

-> 500 Internal Server Error

Why this matters

This is a straightforward read: one Prisma query with orderBy: { clicks: 'desc' } and a take: limit. The part actually worth thinking through is the limit query parameter -- it arrives as a string (or is absent entirely), and it's client-controlled, so it needs to be parsed and clamped defensively (an unbounded or non-numeric limit should never reach Prisma's take unvalidated).

Suggested approach

Look at how GET /:code/stats (right below where you'll add this) already shapes a Prisma response into a small JSON object -- you want the same idea, but for many rows instead of one, using prisma.link.findMany with an orderBy and a take instead of findUnique. Parse req.query.limit with Number(...), and think about what should happen if it's missing, non-numeric, zero, negative, or absurdly large.

Acceptance criteria

GET /stats/top?limit=2 with 3+ links of differing click counts returns exactly 2 entries, the two highest, in descending order.
GET /stats/top with no limit still returns a sensible default number of results (not an error, not all rows unbounded).
GET /stats/top on a database with zero links returns 200 [].
The route never mutates any Link row (read-only).

Verification

npx jest --config practice-tickets/jest.config.js practice-tickets/tests/05-top-links-leaderboard.test.js

Hints (0/2)

Try it without hints first — the reading is the exercise.

Working on this ticket

Work on a branch named for the ticket — that's what you'll submit.

Branch off your fork

$git checkout -b feat/top-links-leaderboard

Fix it and commit

Meet every acceptance criterion, and add a test that would have caught this.

Push the branch

$git push -u origin feat/top-links-leaderboard

Submit it below

Paste your fork URL and the branch name, with a short write-up of the root cause.

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Questions

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The project

URL Shortener — Redirect Latency vs. Click-Count Correctness

A production-quality Express/Prisma/Redis URL shortener whose central engineering problem is keeping the redirect path fast while still counting every click correctly -- async, fire-and-forget click logging that never adds latency, backed by a single atomic SQL increment instead of a read-then-write.

Fork on GitHub

Download

Setup

URL Shortener — Redirect Latency vs. Click-Count Correctness

git clone <your-fork>
cd url_shortener
cp .env.example .env
npm install                       # also runs `prisma generate` via postinstall
docker compose up -d postgres redis   # or point .env at Postgres/Redis you already run
npm run prisma:migrate:dev        # applies prisma/migrations, creates the db schema
npm run dev                       # nodemon, http://localhost:3003