festipod/.project/knowledge/data-layer.md

Data Layer

NextGraph-backed local-first data with fallback to local state for demo/disconnected mode.

Overview

The app has two data modes:

1. Connected — NextGraph ORM shapes (P2P, encrypted, local-first)
2. Disconnected/Demo — Local React state seeded from seedData.ts

All screens use useFestipodData() hook regardless of mode.

NextGraph Stack

@ng-org/web          # Browser WASM runtime
@ng-org/orm          # RDF shape-based ORM
@ng-org/shex-orm     # SHEX → TypeScript code generation
@ng-org/alien-deepsignals  # Reactive signals bridge

Packages installed from npm (@ng-org/* alpha versions). For local development against an unreleased nextgraph-rs build, scripts/build-ng-packages.sh packs the monorepo into .ng-tarballs/ and updates package.json to point at those paths.

SHEX Shapes

src/shared/shapes/shex/festipodShapes.shex defines:

• Event — title, description, dates, location, themes, participants
• UserProfile — name, username, bio, city, visibility
• Participation — links event + user, confirmation status

ORM bindings in src/shared/shapes/orm/:

• festipodShapes.schema.ts — Schema registration
• festipodShapes.shapeTypes.ts — Shape type constants
• festipodShapes.typings.ts — TypeScript interfaces

Regenerate with bun run build:orm.

NextGraph Read/Write Pattern

The app follows the same pattern as the official expense-tracker-rdf example:

• Scope: useShape(shapeType, did🆖${session.private_store_id}) — opens the private store repo in the verifier
• @graph: did:ng:${session.private_store_id} — writes target the same NURI

This is critical: orm_start_graph with the private store NURI explicitly opens the repo in the verifier's self.repos HashMap. Without this, orm_frontend_update fails with RepoNotFound.

Do NOT use did:ng:i as scope — it subscribes to the entire user site via a special code path that doesn't open individual repos, breaking all writes.

Deleting Objects

ngSet.delete(item) updates the local reactive set but does not persist to the broker. Use ng.sparql_update() with SPARQL DELETE instead:

import { ng } from '@ng-org/web';
import { sessionPromise } from '../utils/ngSession';

const session = await sessionPromise;
await ng.sparql_update(
  session.session_id,
  `DELETE WHERE { GRAPH <${item["@graph"]}> { <${item["@id"]}> ?p ?o } }`,
  item["@graph"],
);

The broker sends back a GraphOrmUpdate with op: "remove" that reactively removes the item from the ORM set. Do NOT combine with ngSet.delete() — the two operations conflict in the CRDT.

See decision record for details.

Key files

• src/shared/hooks/useShapeWithDefaults.ts — Accepts storeNuri param, passes to useShape
• src/shared/utils/ngGraph.ts — ensureGraphNuri() returns @graph for entity creation
• src/shared/utils/ngBootstrap.ts — Seeds test data using ensureGraphNuri() for @graph

See decision record for why.

Context Providers

NextGraphContext (src/shared/context/NextGraphContext.tsx)

• Connection lifecycle: disconnected → connecting → connected | error
• Provides session with store IDs (private, protected, public)
• Conditional auto-init: Only auto-calls initNg() when running inside the broker iframe (window.self !== window.top). Outside the iframe, initNgWeb() would redirect the page to the broker — so connection waits for explicit connect() call.
• connect(): Called by user clicking "Se connecter". When outside broker, triggers the redirect flow.

@ng-org/web redirect behavior

initNgWeb() checks window.self === window.top. If the app is NOT in an iframe, it redirects to nextgraph.net/redir/ with the current URL encoded as a return parameter. The broker then loads the app back in an iframe after auth. This means the app must NOT auto-init NG when loaded standalone.

FestipodDataContext (src/shared/context/FestipodDataContext.tsx)

• Wraps NextGraph shapes with useShapeWithDefaults() hook
• CRUD: createEvent(), updateEvent(), joinEvent(), leaveEvent(), etc.
• Exposes useFestipodData() hook consumed by all screens
• selectedEventId state for cross-screen event navigation
• loadTestData(): Calls bootstrapWallet() to seed test data into NG wallet — only triggered by explicit user action
• Provider states based on NG status:
  • disconnected → LocalDataProvider with seed data (demo mode)
  • connecting → LocalDataProvider with empty data (avoids flashing seed data before wallet loads)
  • connected → NgDataProvider with real wallet data
  • error → LocalDataProvider with seed data (graceful fallback)

Data Types

src/shared/data/types.ts:

• FpEventData — id, title, date, location, distance, themes, etc.
• FpUserData — id, name, username, bio, city, counts
• FpParticipationData — eventId + userId + confirmed
• FpMeetingPointData — eventId, location, time, host (local-only)
• FpFriendshipData — userId + friendId (local-only)

Seed Data

src/shared/data/seedData.ts:

• 10 users (Marie Dupont = current user, user-1)
• Multiple events with dates, locations, themes
• Participations, meeting points, friendships
• CURRENT_USER_ID = 'user-1'