# Tasks: User Preferences API

## Task Order (dependency sequence)

### T1: Domain layer - preferences entity, validation, and errors
- **Scope:** Create `UserPreferences` struct, preference key/value validation functions, and domain error definitions. Implement `ValidatePreferences`, `ValidatePreferenceKey`, and `ValidatePreferenceValue` with the closed key set (`theme`, `language`, `notifications_enabled`) and per-key value rules.
- **Files:**
  - Create `services/preferences-api/internal/domain/preferences.go`
  - Replace `services/preferences-api/internal/domain/errors.go`
- **Depends on:** None
- **Acceptance criteria:**
  - [ ] `UserPreferences` struct has `UserID`, `Preferences`, `CreatedAt`, `UpdatedAt` fields
  - [ ] `ValidatePreferences` rejects unknown keys with `ErrInvalidPreferenceKey`
  - [ ] `ValidatePreferenceValue` validates `theme` accepts only `"light"` and `"dark"`
  - [ ] `ValidatePreferenceValue` validates `language` matches `^[a-z]{2}$`
  - [ ] `ValidatePreferenceValue` validates `notifications_enabled` is a boolean
  - [ ] Error messages include the offending key/value for debuggability
  - [ ] `ErrInvalidPreferenceKey` and `ErrInvalidPreferenceValue` sentinel errors defined

### T2: Port layer - PreferencesRepository interface
- **Scope:** Define the `PreferencesRepository` interface with `Get` and `Upsert` methods. This is a thin interface file replacing the Example port.
- **Files:**
  - Create `services/preferences-api/internal/port/preferences.go`
- **Depends on:** T1
- **Acceptance criteria:**
  - [ ] `PreferencesRepository` interface defined with `Get(ctx, userID) (*UserPreferences, error)` and `Upsert(ctx, userID, prefs) (*UserPreferences, error)`
  - [ ] Uses domain types from `internal/domain`
  - [ ] Context parameter on all methods for cancellation/timeout support

### T3: Database migration and PostgreSQL adapter
- **Scope:** Create the SQL migration for the `user_preferences` table and implement the PostgreSQL repository adapter that satisfies the `PreferencesRepository` port.
- **Files:**
  - Create `services/preferences-api/migrations/001_create_user_preferences.sql`
  - Create `services/preferences-api/internal/adapter/postgres/preferences.go`
- **Depends on:** T2
- **Acceptance criteria:**
  - [ ] Migration creates `user_preferences` table with `user_id UUID PRIMARY KEY`, `preferences JSONB NOT NULL DEFAULT '{}'`, `created_at TIMESTAMPTZ`, `updated_at TIMESTAMPTZ`
  - [ ] Migration uses `IF NOT EXISTS` for idempotency
  - [ ] `Get` returns `nil` (not error) when no row found, so handler returns empty preferences
  - [ ] `Upsert` uses `INSERT ... ON CONFLICT (user_id) DO UPDATE` with JSONB merge (`preferences || $2`)
  - [ ] `Upsert` returns the full merged row after upsert
  - [ ] All queries use parameterized statements (no SQL injection)
  - [ ] Repository struct accepts `*sql.DB` or pool via constructor

### T4: Service layer - PreferencesService with Get and Update
- **Scope:** Implement `PreferencesService` with `Get` and `Update` methods. Get retrieves preferences (returning empty object for new users). Update validates input via domain layer, then delegates to repository upsert.
- **Files:**
  - Create `services/preferences-api/internal/service/preferences.go`
- **Depends on:** T1, T2
- **Acceptance criteria:**
  - [ ] `Get(ctx, userID)` returns `*UserPreferences` — empty preferences struct for new users (not nil, not error)
  - [ ] `Update(ctx, userID, prefs)` calls `domain.ValidatePreferences` before persisting
  - [ ] `Update` returns the full merged preferences after upsert
  - [ ] Validation errors from domain layer propagate to caller unchanged
  - [ ] Repository errors propagate to caller unchanged (will become 500s)
  - [ ] Structured logging with user_id context on operations

### T5: Service layer unit tests
- **Scope:** Write table-driven unit tests for `PreferencesService` with a mock repository. Cover valid operations, validation failures, and repository errors.
- **Files:**
  - Create `services/preferences-api/internal/service/preferences_test.go`
- **Depends on:** T4
- **Acceptance criteria:**
  - [ ] Tests use mock repository implementing `port.PreferencesRepository`
  - [ ] Test `Get` for existing user (returns preferences) and new user (returns empty)
  - [ ] Test `Update` with valid preferences succeeds
  - [ ] Test `Update` with unknown key returns `ErrInvalidPreferenceKey`
  - [ ] Test `Update` with invalid theme value returns `ErrInvalidPreferenceValue`
  - [ ] Test `Update` with invalid language format returns `ErrInvalidPreferenceValue`
  - [ ] Test `Update` with non-boolean `notifications_enabled` returns `ErrInvalidPreferenceValue`
  - [ ] Tests use `logging.Nop()` for no-op logger
  - [ ] All tests pass with `go test -v ./internal/service/...`

### T6: HTTP handlers - Get and Update preferences
- **Scope:** Implement `Preferences` handler struct with `Get` and `Update` methods. Include UUID validation on path params, ownership check against JWT user, request binding, domain error mapping, and response envelope formatting.
- **Files:**
  - Create `services/preferences-api/internal/api/handlers/preferences.go`
- **Depends on:** T4
- **Acceptance criteria:**
  - [ ] `Get` extracts `user_id` from `chi.URLParam`, validates UUID format
  - [ ] `Get` checks ownership via `auth.MustGetUser(ctx)` comparison
  - [ ] `Get` returns 200 with `{data, meta}` envelope via `httpresponse.OK`
  - [ ] `Update` binds request with `app.BindAndValidate`
  - [ ] `Update` checks ownership before calling service
  - [ ] `Update` returns 200 with full merged preferences
  - [ ] Invalid UUID returns 400 via `httperror.BadRequest`
  - [ ] Ownership mismatch returns 403 via `httperror.Forbidden`
  - [ ] Domain errors mapped: `ErrInvalidPreferenceKey` → 400, `ErrInvalidPreferenceValue` → 400
  - [ ] Unhandled errors bubble up as 500 via `app.Wrap`
  - [ ] `PreferencesResponse` DTO with `user_id`, `preferences`, `updated_at` (nullable)

### T7: Handler integration tests
- **Scope:** Write HTTP-level integration tests for the preferences handlers using `httptest` and chi router. Mock the repository at the port layer. Test all status codes, response shapes, and error cases.
- **Files:**
  - Create `services/preferences-api/internal/api/handlers/preferences_test.go`
- **Depends on:** T6
- **Acceptance criteria:**
  - [ ] Test `GET` returns 200 with preferences for existing user
  - [ ] Test `GET` returns 200 with empty preferences for new user
  - [ ] Test `GET` returns 400 for invalid UUID
  - [ ] Test `PUT` returns 200 with merged preferences on success
  - [ ] Test `PUT` returns 400 for unknown preference keys
  - [ ] Test `PUT` returns 400 for invalid preference values
  - [ ] Test `PUT` returns 400 for missing `preferences` field
  - [ ] All responses use `{data, meta}` envelope structure
  - [ ] Tests use table-driven pattern with subtests
  - [ ] All tests pass with `go test -v ./internal/api/handlers/...`

### T8: Routes, OpenAPI spec, and main.go wiring
- **Scope:** Update route registration to mount preferences endpoints under auth middleware, update OpenAPI spec with the two new endpoints, and wire the PostgreSQL adapter + service in `main.go` (DB connect, migrations, shutdown hook).
- **Files:**
  - Modify `services/preferences-api/internal/api/routes.go`
  - Modify `services/preferences-api/internal/api/spec.go`
  - Modify `services/preferences-api/cmd/server/main.go`
- **Depends on:** T3, T6
- **Acceptance criteria:**
  - [ ] Routes: `GET /api/preferences-api/preferences/{user_id}` and `PUT /api/preferences-api/preferences/{user_id}` registered
  - [ ] Both preference routes wrapped in `auth.Middleware()` group
  - [ ] URL parameters use `{user_id}` brace syntax (not colon)
  - [ ] Handlers wrapped with `app.Wrap()`
  - [ ] OpenAPI spec defines both endpoints with request/response schemas, security requirements, and error codes
  - [ ] `main.go` connects to PostgreSQL via `database.MustConnect()` with `DatabaseConfig`
  - [ ] `main.go` runs migrations via `database.MustRunMigrations()`
  - [ ] `main.go` creates `postgres.PreferencesRepository` and `PreferencesService`
  - [ ] `main.go` registers DB pool shutdown hook
  - [ ] Health endpoint remains functional

### T9: Remove Example scaffold code
- **Scope:** Delete all Example scaffold files that have been replaced by preferences code. Ensure no references to Example types remain in routes, spec, main, or tests.
- **Files:**
  - Delete `services/preferences-api/internal/domain/example.go`
  - Delete `services/preferences-api/internal/port/example.go`
  - Delete `services/preferences-api/internal/adapter/memory/example.go` (and `memory/` directory)
  - Delete `services/preferences-api/internal/service/example.go`
  - Delete `services/preferences-api/internal/service/example_test.go`
  - Delete `services/preferences-api/internal/api/handlers/example.go`
  - Delete `services/preferences-api/internal/api/handlers/example_test.go`
- **Depends on:** T8
- **Acceptance criteria:**
  - [ ] All Example files deleted
  - [ ] No remaining imports of Example types in any file
  - [ ] No remaining references to `/examples` routes
  - [ ] `go build ./...` succeeds with no compilation errors
  - [ ] `go test ./...` passes with no failures
  - [ ] Health endpoint still works
