MOSAIC ETC

Web-based Exposure Time Calculator for the MOSAIC spectrograph on the Extremely Large Telescope (ELT). All scientific computation (1D SNR across wavelengths, 2D SNR maps) runs in the browser; the server provides versioned file storage, admin tooling, and authentication.

Tech stack

• Next.js 16 (App Router) — TypeScript, React 19
• Prisma 7 + PostgreSQL 16 — schema, migrations, driver adapter (@prisma/adapter-pg)
• Auth.js v5 — credentials provider, JWT-embedded permissions (RBAC)
• Tailwind CSS 4 + Radix UI primitives (shadcn-style components)
• next-intl — i18n (pt-BR default, en-US, fr-FR)

Prerequisites

• Node.js 20+ and npm
• Docker (for local PostgreSQL) — or an existing Postgres 16 instance
• Git LFS — the MaNGA spectral cubes in prisma/seed-data/objects/**/cube.fits are stored via Git LFS (see below)

Cloning the repository

The MaNGA data cubes are large binaries tracked with Git LFS, so install the LFS client before cloning:

# Install the Git LFS client (once per machine)
#   Debian/Ubuntu:  sudo apt install git-lfs
#   macOS (brew):   brew install git-lfs
#   other:          https://git-lfs.com
git lfs install

# Clone — the cube.fits files are downloaded automatically
git clone [email protected]:MOSAIC-ETC/website.git

If you cloned before installing Git LFS, the cube.fits files will be ~130-byte text pointers instead of real data. Fetch the actual binaries with:

git lfs install
git lfs pull

CI / deployment: make sure git lfs is installed and run git lfs pull before npx prisma db seed — otherwise the seed imports the LFS pointer files instead of the cubes, and the ETC fails to parse them.

Quick start

# 1. Install dependencies
npm install

# 2. Start Postgres (Docker)
docker compose up -d

# 3. Copy env template and fill in values
cp .env.example .env.local
# Generate AUTH_SECRET:   openssl rand -base64 32
# For the Docker DB use:  DATABASE_URL="postgresql://mosaic:mosaic_dev@localhost:5433/mosaic_etc?schema=public"
# STORAGE_PATH can be a local path like "./storage" during dev

# 4. Apply migrations and seed initial data
npx prisma migrate dev
# The seed runs automatically on first migrate; if not, run it explicitly:
npx prisma db seed

# 5. Start the dev server
npm run dev

Open http://localhost:3000 in a browser. Sign in at /login with the ADMIN_EMAIL / ADMIN_PASSWORD from .env.local. The admin dashboard is at /admin.

Common commands

Command	Description
npm run dev	Start the dev server on localhost:3000
npm run build	Production build
npm start	Run the production build
npm run lint	ESLint
npx tsc --noEmit	Type-check without emitting
docker compose up -d	Start local Postgres
docker compose down	Stop Postgres (data is persisted in a named volume)
npx prisma migrate dev	Apply schema changes locally + regenerate the client
npx prisma migrate reset	Drop the DB and re-seed (destructive)
npx prisma db seed	Re-run the seed script
npx prisma studio	Browse the database in a GUI

Project layout

src/
  app/[locale]/(public)/etc/   ETC feature: form, calculation, visualizations
  app/[locale]/(admin)/admin/  Admin pages (filters, objects, tables, users, roles, …)
  app/[locale]/(auth)/         Sign-in, sign-out, accept-invite
  app/api/                     Route handlers (public + admin)
  lib/                         Server utilities (auth helpers, storage, validators)
  hooks/                       Client hooks (manifest, IndexedDB caches)
  components/                  Shared UI (shadcn primitives under ui/)
  i18n/                        next-intl routing configuration
locales/                       Translation JSONs (pt-BR, en-US, fr-FR)
prisma/
  schema.prisma                Database schema
  migrations/                  Versioned SQL migrations
  seed.ts                      Idempotent bootstrap script
  seed-data/                   Filter/table/object files imported by the seed
public/assets/                 Static runtime assets (images, logos)
storage/                       Local file storage (gitignored; created at runtime)

How files are served

The seed reads from prisma/seed-data/ and imports each file into the storage path defined by STORAGE_PATH, recording hash and metadata in Prisma. At runtime, the ETC client reads /api/manifest to discover available filters / objects / tables and the current instrument parameters, then fetches binaries from /api/files/<category>/<slug>[/<role>]. IndexedDB caches are keyed on the manifest hash so stale entries are evicted when admins upload new versions.

Internationalization

All user-visible strings live in locales/*.json. Use useTranslations / getTranslations from next-intl — never hardcode. Locale prefixes are /pt, /en, /fr (default Portuguese has no prefix on the root).

Further reading

• CLAUDE.md — architecture deep-dive for contributors / AI assistants
• TCC.md — design decisions, tradeoffs, and rationale (in Portuguese; companion to the author's undergraduate thesis)