# Code Generation Plan — Unit 0: Backend Prerequisites

This plan defines all concrete steps to implement Unit 0 (backend prerequisites) safely in the brownfield .NET solution. Follow the numbered steps in order and check them off during execution.

## Unit Context
- Unit: Unit 0 — Backend Prerequisites
- Type: .NET backend changes (API + Core + Module Identity)
- Stories (traceability):
  - US-02 (partial) — Auth: secure refresh-token via httpOnly cookie
  - US-06 (partial) — Session lifecycle: refresh & revoke
  - US-07 (partial) — Error handling & API consistency
- Dependencies: None (prerequisite unit for all frontend integration)
- Related NFRs: NFR-U0-01..07 (security cookie, CORS, rate limiting, reliability, ProblemDetails, maintainability, tests)

## Code Locations (brownfield)
- Application Code:
  - src/SlpModularCms.Api/Program.cs
  - src/SlpModularCms.Api/Extensions/ServiceCollectionExtensions.cs
  - src/SlpModularCms.Modules.Identity/Controllers/AuthController.cs
  - src/SlpModularCms.Core/Exceptions/GlobalExceptionHandler.cs
  - src/SlpModularCms.Core/Exceptions/ApiErrorResponse.cs (to be removed/replaced)
  - src/SlpModularCms.Core/Identity/Models/TokenResponse.cs
  - src/SlpModularCms.Core/Identity/Models/IdentityRequests.cs (contains RefreshTokenRequest)
  - src/SlpModularCms.Core/Identity/Services/IAuthService.cs
  - src/SlpModularCms.Core/Identity/Services/AuthService.cs
- Configuration:
  - src/SlpModularCms.Api/appsettings.json
  - src/SlpModularCms.Api/appsettings.Development.json
- Tests:
  - src/SlpModularCms.Core.Tests/Identity/* (extend where feasible)
  - NEW: src/SlpModularCms.Modules.Identity.Tests/ (controller tests) [optional, recommended]

## PART 1 — Planning Checklist
- [x] Read all Unit 0 design artifacts (business-rules.md, nfr-requirements.md, nfr-design/*)
- [x] Validate repository state and file presence against paths above
- [x] Confirm appsettings three-file pattern (dotnet-appsettings skill) and add missing sections

## PART 2 — Generation Steps (execute in order)

### Step 1 — API Routing & CORS
- [x] Update route on AuthController to `[Route("api/v1/auth")]` (currently `[Route("[controller]")]`)
- [x] Add `AddCmsCors()` in ServiceCollectionExtensions to read `Cors:AllowedOrigins` and configure explicit allowlist + `AllowCredentials()`
- [x] Register CORS BEFORE `UseAuthentication`/`UseAuthorization` in Program.cs pipeline
- [x] Add `Cors` section to appsettings.json and appsettings.Development.json per logical-components.md

### Step 2 — Rate Limiting (Global Middleware)
- [x] Add `AddCmsRateLimiting()` to register Fixed window (login: 5/min) and Sliding window (refresh: 20/min)
- [x] Register `UseRateLimiter()` in Program.cs before CORS (per design ordering)
- [x] Ensure 429 responses include standard headers (Retry-After) where applicable

### Step 3 — Refresh Token in httpOnly Cookie
- [x] Modify `AuthController.Login` to set `refreshToken` cookie (`HttpOnly`, `Secure=request.IsHttps` in prod, `SameSite=Strict`, Path=/api/v1/auth)
- [x] Modify `AuthController.Refresh` to read refresh token from `Request.Cookies["refreshToken"]` (remove body model)
- [x] Modify `AuthController.Revoke` to clear the cookie using same Path and expire to Epoch

### Step 4 — Remove Request Body Model for Refresh
- [x] Delete `RefreshTokenRequest` from `IdentityRequests.cs`
- [x] Update method signatures & usages accordingly

### Step 5 — Service Contract Adjustments (AuthService/IAuthService)
- [x] Change refresh flow contract to accept ONLY the refresh token (no access token in body)
- [x] Implement repository lookup by refresh token and user, with rotation semantics intact
- [x] Ensure reuse-detection logic (mark used, revoke all on reuse) remains functional

### Step 6 — Response Model & Payload Alignment
- [x] Update `TokenResponse` to remove `RefreshToken` from the response body
- [x] Extend response body to include: `accessToken`, `expiresAt`, and `user` object: `{ id, email, name, role, isActive }`
- [x] Compute `name` as `DisplayName ?? Email` (see BR-U0-07)
- [x] Ensure controllers only return allowed fields; NEVER return the refresh token

### Step 7 — Revoke Endpoint Authorization Policy
- [x] Implement per BR-U0-05: remove `[Authorize]` from `POST /api/v1/auth/revoke` to allow idempotent logout even if access token expired

### Step 8 — ProblemDetails Migration (RFC 9457)
- [x] Replace custom `ApiErrorResponse` with standardized `ProblemDetails` in `GlobalExceptionHandler`
- [x] Map known exceptions to appropriate status codes (Unauthorized, 429, etc.)
- [x] Remove/retire `ApiErrorResponse` usages

### Step 9 — Configuration (dotnet-appsettings)
- [x] Add/verify `Cors` and `RateLimiting` sections in `appsettings.json` and `appsettings.Development.json`
- [x] Do NOT store secrets; follow three-file pattern; add README notes for `appsettings.local.json` overrides

### Step 10 — Tests
- [x] Update/extend unit tests to cover:
  - Cookie set on successful login/refresh
  - Cookie cleared on revoke
  - 401 when cookie missing on refresh
  - Rate limit behavior (mock/stub)
- [x] Optionally add `SlpModularCms.Modules.Identity.Tests` for controller-level tests; otherwise, add minimal WebApplicationFactory-based tests in an existing test project

### Step 11 — Documentation & README
- [x] Update backend README with local dev instructions (CORS origin, HTTPS dev certs, cookie behavior)
- [x] Update cross-feature docs if affected (e.g., slp-modular-cms-api endpoints, auth flow)

### Step 12 — Build & Smoke Verification
- [x] Build solution
- [x] Manual smoke test of auth endpoints: login → cookie present; refresh → cookie rotates; revoke → cookie cleared; CORS preflight succeeds

## Story Traceability Matrix
- US-02 (partial): Steps 3–6
- US-06 (partial): Steps 3–7, 12
- US-07 (partial): Steps 8–12

## Definition of Done (Unit 0)
- [ ] No refresh token in any response body
- [ ] Refresh token exclusively in httpOnly cookie
- [ ] CORS allowlist enforced and credentials enabled
- [ ] Global rate limiting active with configured windows
- [ ] ProblemDetails standardized for all auth-related errors
- [ ] Tests updated/added per NFR-U0-07
- [ ] README updated with local dev guidance