# Core Function Gap Check

## Goal

Check the current MZH Library Management implementation against the documented
core modules and complete the highest-confidence missing core feature slice
without broad redesign.

## What I Already Know

* The user asked to check whether core functionality is still missing and to
  complete it.
* The app is a Java 11 Maven WAR using JSP + Servlet + MySQL and JDBC DAOs.
* Existing implemented slices cover login/permissions, dashboard navigation,
  book catalog/search, book CRUD, reader management, borrowing circulation,
  reader loan history, reports, administrator user management, and system-log
  viewing.
* Existing lightweight checks pass with `javac -Xlint:all` for non-Servlet
  layers and all service check mains.
* Maven is available in this workspace at
  `/home/sjy/.sdkman/candidates/maven/current/bin/mvn`.
* The clearest missing core requirement is book category maintenance. The
  schema and selectors already have `book_categories`, but there is no route,
  controller, JSP, DAO/service mutation API, or test coverage for maintaining
  categories.

## Requirements

* Preserve the existing JSP -> Servlet -> Service -> DAO -> MySQL layering.
* Keep category maintenance under the existing `MANAGE_BOOKS` permission.
* Add a staff-only category management flow for listing, creating, editing, and
  deleting book categories.
* Validate required category name, name length, description length, duplicate
  names, and invalid IDs with field-level service errors.
* Prevent deleting categories that still have book records, returning a safe
  validation message instead of surfacing a database constraint failure.
* Reuse the existing book management visual patterns, flash messages, and
  table/form conventions.
* Link category maintenance from the book management surface and staff
  navigation where appropriate.
* Update focused service checks and fallback validation commands.

## Acceptance Criteria

* [x] A user with `MANAGE_BOOKS` can open a category management page.
* [x] Staff can create and update category names/descriptions.
* [x] Duplicate category names are rejected with a field error.
* [x] Categories used by books cannot be deleted.
* [x] Readers or unauthenticated users cannot mutate categories.
* [x] Book forms/search continue to load categories from the shared DAO/service
  path.
* [x] JSPs do not contain SQL/JDBC/scriptlet logic.
* [x] Existing lightweight checks pass and Maven package succeeds through the
  workspace Maven path.

## Definition of Done

* Tests/checks updated where practical.
* Lint/type-check/compile equivalent checks pass in this environment.
* Docs/notes updated if behavior changes.
* No broad framework or visual redesign.

## Out of Scope

* Role/permission editor UI.
* Full database dump/restore execution from the web app.
* Audit logging expansion for every non-user operation.
* Automatic reader-account/profile linking changes.

## Technical Notes

* Relevant specs:
  `.trellis/spec/backend/index.md`,
  `.trellis/spec/backend/database-guidelines.md`,
  `.trellis/spec/backend/error-handling.md`,
  `.trellis/spec/backend/logging-guidelines.md`,
  `.trellis/spec/backend/quality-guidelines.md`,
  `.trellis/spec/frontend/index.md`,
  `.trellis/spec/frontend/component-guidelines.md`,
  `.trellis/spec/frontend/quality-guidelines.md`.
* Current files most likely affected:
  `BookDao`, `JdbcBookDao`, `BookService`, `BookServiceImpl`,
  `BookManagementServlet`, `web.xml`, book JSPs, shared CSS, and
  `BookServiceCheck`.
* Initial verification before implementation:
  `javac -Xlint:all` over non-Servlet app layers and tests passed; all eight
  service check mains passed.
* Final verification after implementation:
  `javac -Xlint:all` over non-Servlet app layers and tests passed;
  `PermissionPolicyCheck`, `AuthServiceCheck`, `BookServiceCheck`,
  `ReaderServiceCheck`, `BorrowingServiceCheck`, `ReportServiceCheck`,
  `UserAccountServiceCheck`, and `SystemLogServiceCheck` passed;
  JSP/static scriptlet and SQL/JDBC scan returned no matches;
  `git diff --check` passed.
* Maven verification on 2026-04-27:
  `/home/sjy/.sdkman/candidates/maven/current/bin/mvn clean package` passed and
  produced `target/library-management.war`.
