Title: App-wide Settings Page — Design

Summary

Add an admin-only Settings page where operators can change app-wide configuration that affects server functions and runtime behavior (feature flags, execution modes, thresholds, API keys for integrations). Settings are persisted in the database and reflected immediately via an in-process cache + event broadcaster so server functions read updated values without restart.

Goals

- Provide a single UI for operators to view and change app-wide settings.
- Persist settings reliably and safely (DB-backed) and version/track changes.
- Ensure changes propagate to server functions quickly and predictably.
- Secure the UI and APIs (admin-only).
- Test coverage (unit + E2E).

Chosen approach (Recommended)

DB-backed settings with a Settings Service:
- Persist settings in a new Prisma model/table (AppSetting).
- Expose server-side SettingsService with get/set/getAll, an in-memory cache, and an EventEmitter to notify subscribers on change.
- Admin UI: route at /settings (app/routes/settings.tsx) with a guarded admin page to edit values.
- Server functions import SettingsService.get("key") or subscribe to change events when they need dynamic behavior.

Why DB-backed

- Atomic persistence, multi-instance safe when coupled with a small invalidation strategy (see below).
- Auditable (store updatedAt, updatedBy, description).
- Fits existing repo (prisma/ exists).

Data model (Prisma example)

model AppSetting {
  id         Int      @id @default(autoincrement())
  key        String   @unique
  value      Json
  description String?
  updatedAt  DateTime @updatedAt
  updatedBy  String?  // optional admin id/email
}

Backend: SettingsService

- File: app/lib/settings.server.ts
- Exports:
  - async getSetting(key: string): Promise<any>
  - async setSetting(key: string, value: any, opts?: { updatedBy?: string })
  - async getAllSettings(): Promise<Record<string, any>>
  - subscribe(cb: (key,value)=>void) => unsubscribe

Implementation notes:
- On startup, load all settings into an in-memory Map cache.
- getSetting reads from cache (fast). setSetting updates DB then cache and emits event.
- To support multiple instances, setSetting also writes a lightweight "manifest" or uses DB trigger; for now plan: setSetting updates DB and callers of getSetting should tolerate eventual consistency, or a periodic poll (1s) or Redis pub/sub can be added later.

API endpoints

- GET /api/admin/settings -> list all settings (admin-only)
- PUT /api/admin/settings/:key -> update a single setting (admin-only)
- POST /api/admin/settings -> create/replace settings (admin-only)

Server route files: app/routes/api/admin/settings/index.ts (GET, POST), app/routes/api/admin/settings/[key].ts (PUT)

Frontend: Settings page

- File: app/routes/settings.tsx (route available only to admins).
- UI: table/list of settings (key, value editor (text/json/toggle), description, last updated, updatedBy) and a Save button.
- Support types: boolean toggles, numeric inputs, string inputs, JSON editor for advanced values.
- Client calls API endpoints and displays toasts on success/failure.
- When updated, UI will optimistically update local state; eventual confirmation comes from API.

Security

- Protect API endpoints and the /settings route with admin guard. If the app has user sessions with roles, require isAdmin. Otherwise gate with an env-based ADMIN_TOKEN for now.
- Validate input server-side: schema for known keys; generic JSON allowed for advanced keys but validated.

Testing

- Unit tests for SettingsService (get/set/cache behavior). New tests under app/lib/__tests__.
- Integration test for API endpoints (app/routes/api/admin/settings tests).
- E2E Playwright test: toggling a setting that affects behavior (e.g., feature flag that hides/shows a UI element) should reflect immediately.

Migration

- Add Prisma model and generate migration: `npx prisma migrate dev --name add_app_setting`
- Run `npx prisma generate` and deploy migration.

Rollout

- Start with critical settings (e.g., ENABLE_TRADING=false, ANALYSIS_BACKGROUND=true, PRICE_STREAM_URL).
- Add a feature flag toggle to hide advanced JSON edits behind "advanced" switch.

Next steps after approval

1) Write this spec file into docs (done). (current step)
2) Create PR: add Prisma model, SettingsService, API routes, UI route + components, tests.
3) Run migrations locally and in staging, verify behavior.
4) Add audit logging for changes.

Notes

- Multi-instance real-time propagation: simple approach (polling or Redis pub/sub) is deferred to future work if needed.
- Keep settings small and typed where possible to avoid fragile JSON edits.

Files to create/change (implementation plan will enumerate exact edits)

- prisma/schema.prisma (add AppSetting model)
- app/lib/settings.server.ts (service)
- app/routes/api/admin/settings/index.ts
- app/routes/api/admin/settings/[key].ts
- app/routes/settings.tsx
- tests: unit + integration + e2e

Please review and confirm; after approval I'll: 1) commit this spec, 2) produce an implementation plan (writing-plans skill) and then implement if you ask.