# Project Context for AI Agents

_This file contains critical rules and patterns that AI agents must follow when implementing code in this project. Focus on unobvious details that agents might otherwise miss._

---

## Project overview

**Grateful Journal** — A minimal, private-first gratitude journaling web app. Three main pages (Write, History/calendar, Settings/profile) plus Google auth. No feeds or algorithms; privacy by design with client-side encryption; daily use, even one sentence.

**User:** Jeet

---

## Technology stack & versions

| Layer    | Technology           | Notes                                                 |
| -------- | -------------------- | ----------------------------------------------------- |
| Frontend | React 19, TypeScript | Vite 7 build; port 8000                               |
| Routing  | react-router-dom 7   | Routes: `/`, `/history`, `/settings`, `/login`        |
| Auth     | Firebase 12          | Google sign-in only (no database)                     |
| Styling  | Plain CSS            | `src/index.css` (globals), `src/App.css` (components) |
| Backend  | FastAPI 0.104        | Python; port 8001; modular routes                     |
| Database | MongoDB 6.x          | Local instance; collections: users, entries, settings |

---

## Critical implementation rules

### Frontend

- **Colour palette (Coolors):** Use CSS variables from `src/index.css`. Primary green `#1be62c`, background soft `#f1eee1`, surface `#ffffff`, accent light `#cff2dc`, accent bright `#c3fd2f`. Do not introduce new palette colours without reason.
- **Layout:** Responsive for all screens. Breakpoints: `--bp-sm` 480px, `--bp-md` 768px, `--bp-lg` 1024px, `--bp-xl` 1280px. On laptop (1024px+), page is single-screen 100vh — no vertical scroll; fonts and spacing scaled so content fits one viewport.
- **Touch targets:** Minimum 44px (`--touch-min`) on interactive elements for small screens.
- **Safe areas:** Use `env(safe-area-inset-*)` for padding where the app can sit under notches or system UI. Viewport meta includes `viewport-fit=cover`.
- **Structure:** Main app layout: page container → header + main content + fixed `BottomNav`. Content max-width `min(680px, 100%)` (or `--content-max` 720px where appropriate).

### Backend (when implemented)

- **Framework:** FastAPI. APIs in Python only.
- **Modularity:** Separate file per route. Each feature (users, entries) has its own router module.
- **Database:** MongoDB. Setup instructions below.
- **Port:** 8001 (backend); 8000 (frontend). CORS configured between them.
- **Authentication:** Relies on Firebase Google Auth token from frontend (passed in Authorization header).

### Conventions

- **Fonts:** Inter for UI, Playfair Display for headings/editorial, Lora for body/entry text. Loaded via Google Fonts in `index.html`.
- **Naming:** CSS uses BEM-like class names (e.g. `.journal-card`, `.journal-prompt`). Keep the same pattern for new components.
- **Build:** Fixing the current TypeScript/ESLint build errors is deferred to a later step; do not assume a clean build when adding features.

---

## File layout (reference)

```
src/                          # Frontend
  App.tsx, App.css            # Root layout, routes, global page styles
  index.css                   # Resets, :root vars, base typography
  main.tsx
  pages/                      # HomePage, HistoryPage, SettingsPage, LoginPage
  components/                 # BottomNav, LoginCard, GoogleSignInButton, ProtectedRoute
  contexts/                   # AuthContext (Firebase Google Auth)
  lib/
    firebase.ts               # Firebase auth config (Google sign-in only)
    api.ts                    # API client for backend calls

backend/                      # FastAPI backend (Port 8001)
  main.py                     # FastAPI app, CORS, routes, lifespan
  config.py                   # Settings, environment variables
  db.py                       # MongoDB connection manager
  models.py                   # Pydantic models (User, JournalEntry, Settings)
  requirements.txt            # Python dependencies
  .env.example                # Environment variables template
  routers/
    users.py                  # User registration, update, delete endpoints
    entries.py                # Entry CRUD, date filtering endpoints
```

---

_Last updated: 2026-03-04_

## Recent Changes & Status

### Port Configuration (Updated)

✅ Frontend port changed to **8000** (was 5173)  
✅ Backend port remains **8001**  
✅ CORS configuration updated in FastAPI  
✅ Vite config updated with server port 8000

### Backend Setup (Completed)

✅ FastAPI backend initialized (port 8001)  
✅ MongoDB connection configured (local instance)  
✅ Pydantic models for User, JournalEntry, UserSettings  
✅ Route structure: `/api/users/*` and `/api/entries/*`  
✅ CORS enabled for frontend (localhost:8000)  
✅ Firebase Google Auth kept (Firestore completely removed)
✅ MongoDB as single source of truth

### API Ready

- User registration, profile updates, deletion
- Entry CRUD (create, read, update, delete)
- Entry filtering by date
- Pagination support

### Zero-Knowledge Encryption Implementation (Completed)

✅ **Crypto Module** — Created `src/lib/crypto.ts` with complete zero-knowledge privacy

- Libsodium.js integrated for cryptography (XSalsa20-Poly1305)
- Key derivation from Firebase credentials using Argon2i KDF
- Device key generation and localStorage persistence
- Encrypted secret key storage in IndexedDB
- Entry encryption/decryption utilities

✅ **Key Management Flow**

- **Login:** KDF derives master key from `firebaseUID + firebaseIDToken + salt`
- **Device Setup:** Random device key generated, stored in localStorage
- **Key Cache:** Master key encrypted with device key → IndexedDB
- **Memory:** Master key kept in memory during session only
- **Subsequent Login:** Cached encrypted key recovered via device key
- **New Device:** Full KDF derivation, new device key generated
- **Logout:** Master key cleared from memory; device key persists for next session

✅ **AuthContext Enhanced**

- Added `secretKey` state (in-memory only)
- Integrated encryption initialization on login
- Device key and IndexedDB cache management
- Automatic recovery of cached keys on same device

✅ **Backend Models Updated** — Zero-knowledge storage

- `JournalEntryCreate`: title/content optional (null if encrypted)
- `EncryptionMetadata`: stores ciphertext, nonce, algorithm
- Server stores **encryption metadata only**, never plaintext
- All entries encrypted with XSalsa20-Poly1305 (libsodium)

✅ **API Routes** — Encrypted entry flow

- POST `/api/entries/{userId}` accepts encrypted entries
- Validation ensures ciphertext and nonce present
- Entry retrieval returns full encryption metadata
- Update routes support re-encryption
- Server processes only encrypted data

✅ **HomePage** — Encrypted entry creation

- Entry and title combined: `title\n\n{entry}`
- Encrypted with master key before transmission
- Sends ciphertext, nonce, algorithm metadata to backend
- Success feedback confirms secure storage

✅ **HistoryPage** — Entry decryption & display

- Fetches encrypted entries from server
- Client-side decryption with master key
- Splits decrypted content: first line = title
- Graceful handling of decryption failures
- Displays original title or `[Encrypted]` on error

### Next Steps (Implementation)

🔄 Entry detail view with full decryption  
🔄 Edit encrypted entries (re-encrypt on changes)  
🔄 Search/filter encrypted entries (client-side only)  
🔄 Export/backup encrypted entries with device key
