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CP Arena — local backend

Local dev runs the Next.js app and its SQLite database natively on Node. The only containerised piece is the Piston code-execution sandbox.

Stack

Piece Where Notes
Web app + API routes Node (npm run dev) App Router route handlers under src/app/api
Database SQLite via libSQL + Drizzle file at ./data/arena.db (git-ignored)
Judge Piston in Docker docker-compose.yml, reached at PISTON_URL

Problems live in the database too — the challenges table (src/server/db/schema.ts), read by src/lib/challenges.ts. Statements are Markdown, rendered to sanitized HTML server-side. Seed the example problem locally with npm run challenges:seed.

First run

# 1. Start the judge (Docker)
npm run piston:up

# 2. Install language runtimes into Piston (one-time; persisted on a volume)
npm run piston:install        # c++, python, java

# 3. Run the app (migrations auto-apply on startup)
npm run dev

# 4. Seed the example problem into the DB (publishes it; re-run after edits)
npm run challenges:seed

# 5. Verify the whole stack
curl localhost:3000/api/health
# => { "ok": true, "db": true, "piston": true, "runtimes": ["c++@10.2.0", ...] }

No .env is required — the code defaults to file:./data/arena.db and http://localhost:2000. Copy .env.example to .env.local to override.

Database

Migrations live in ./migrations and are applied automatically on server start (src/instrumentation.ts → runMigrations). Manual control:

npm run db:generate   # after editing src/server/db/schema.ts
npm run db:migrate    # apply pending migrations
npm run db:studio     # browse the DB

Judge

npm run piston:up       # docker compose up -d
npm run piston:down     # stop

Piston runs privileged (sandbox isolation) and is published on 127.0.0.1:2000. Language runtimes install via its package API — see scripts/install-runtimes.sh.

Next

  • POST /api/submit — run a submission in Piston against hidden tests, record the server-authoritative verdict/time/flags, update standings.
  • GET /api/leaderboard — real standings from the DB.
  • A minimal dev login so submissions belong to a user.