116 lines
5.5 KiB
Markdown
116 lines
5.5 KiB
Markdown
# Feature Flags Library & Configuration — Brownfield Addition (FF-1)
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Story ID: FF-1
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Epic: Feature Flags Framework for Controlled Rollbacks — Brownfield Enhancement
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Date: 2025-09-18
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Owner: Product Manager (John)
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Related Docs:
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- docs/prd/epic-feature-flags-controlled-rollbacks.md
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- docs/prd/rollback-strategy.md
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- docs/brownfield-architecture-tech.md
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---
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Story Title
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Feature Flags Library & Configuration — Brownfield Addition
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User Story
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As an operator of the United Tattoo site,
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I want to control critical features via environment-driven flags,
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So that I can safely disable problematic areas without redeploying the application.
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Story Context
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Existing System Integration
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- Integrates with: Next.js 14 App Router (server/client), route handlers under app/api, Cloudflare Pages/Workers runtime via OpenNext.
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- Technology: TypeScript, environment variables via wrangler.toml ([env.preview.vars] / [env.production.vars]), Cloudflare bindings.
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- Follows pattern: Centralized lib utilities (e.g., lib/utils.ts), environment validation in lib/env.ts, defensive configuration.
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- Touch points:
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- New module lib/flags.ts (exporting typed, environment-driven booleans).
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- Documentation updates for wrangler env vars and operational usage.
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- Optional: non-breaking additions to lib/env.ts for boolean parsing.
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Acceptance Criteria
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Functional Requirements
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1. A new module lib/flags.ts exports a typed Flags object (or individual exports) for the following keys with safe defaults that preserve current behavior:
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- ADMIN_ENABLED
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- ARTISTS_MODULE_ENABLED
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- UPLOADS_ADMIN_ENABLED
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- BOOKING_ENABLED
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- PUBLIC_APPOINTMENT_REQUESTS_ENABLED
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- REFERENCE_UPLOADS_PUBLIC_ENABLED
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- DEPOSITS_ENABLED
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- PUBLIC_DB_ARTISTS_ENABLED
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- ADVANCED_NAV_SCROLL_ANIMATIONS_ENABLED
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- STRICT_CI_GATES_ENABLED
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- ISR_CACHE_R2_ENABLED
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2. Flags are derived from environment variables (string "true"/"false", case-insensitive) with robust parsing; missing or malformed values do not throw and fall back to defaults.
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3. Server-side usage (route handlers, server components) and client-side usage (components) can import the same typed flags safely (tree-shakeable, no runtime errors).
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Integration Requirements
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4. Existing functionality remains unchanged by default when no flag variables are defined (defaults reflect current behavior).
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5. The new module follows existing lib/* coding standards (TypeScript types, export conventions).
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6. Documentation added to an operations note (append to docs/prd/rollback-strategy.md or new doc referenced by it) including:
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- List of flags, default behavior, and how to toggle via wrangler dashboard/vars.
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- Example wrangler.toml snippets for preview/production vars (non-secret).
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- Post-toggle smoke checklist.
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Quality Requirements
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7. Unit tests cover boolean parsing and default behavior for at least three representative flags (true/false/undefined cases).
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8. Typecheck, lint, and unit tests pass (no suppression added).
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9. No regressions in existing functionality (smoke run of dev and preview builds).
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Technical Notes
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- Integration Approach:
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- Implement a pure-TS helper to parse env booleans: parseBool(str | undefined, defaultValue).
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- Export a const Flags object freezing evaluated booleans at module init time (OK for Workers model).
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- Client-side consumption: Ensure flags do not leak secrets (they are booleans only) and remain serializable if needed.
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- Existing Pattern Reference:
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- Align with lib/utils.ts coding style and export patterns.
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- Reference docs/prd/rollback-strategy.md “Feature Flags Operations” for operator guidance.
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- Key Constraints:
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- Do not introduce breaking changes or throw errors on missing envs.
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- Do not gate any routes/components in this story (wiring will be handled in a separate story).
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- Keep the module minimal; do not add runtime network calls or storage dependencies.
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Definition of Done
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- [ ] lib/flags.ts created with typed exports and safe defaults.
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- [ ] Tests added (Vitest) verifying parsing and defaults.
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- [ ] Documentation updated (rollback strategy ops section extended with flags list, toggling, smoke steps).
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- [ ] Lint, typecheck, and unit tests pass locally (npm run test).
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- [ ] Preview build succeeds (npm run pages:build && npm run preview).
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- [ ] No functional changes observed when flags are absent (baseline preserved).
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Risk and Compatibility Check
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Minimal Risk Assessment
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- Primary Risk: Misinterpretation of default behavior leading to unintended disablement.
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- Mitigation: Defaults preserve current behavior; explicit console.warn on server when critical flags are undefined (non-fatal).
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- Rollback: Delete or bypass imports of lib/flags.ts; defaults ensure no breakage when env flags are absent.
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Compatibility Verification
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- [x] No breaking changes to existing APIs.
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- [x] No database changes.
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- [x] UI unchanged in this story (no gating yet).
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- [x] Negligible performance impact (constant boolean checks).
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Validation Checklist
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Scope Validation
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- [x] Single-session implementable (library + tests + docs).
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- [x] Straightforward integration (new lib module).
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- [x] Follows existing patterns exactly (lib/* utilities, env-based config).
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- [x] No design/architecture work required.
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Clarity Check
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- [x] Requirements are unambiguous (module + keys + defaults + tests + docs).
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- [x] Integration points specified (lib, docs, env).
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- [x] Success criteria testable (unit tests, build/preview).
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- [x] Rollback approach simple (remove usage; defaults benign).
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References
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- Epic: docs/prd/epic-feature-flags-controlled-rollbacks.md
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- Ops: docs/prd/rollback-strategy.md (Feature Flags Operations section to be updated in this story)
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