# Step 15: Generic DofManager

## 담당 역할과 필수 스킬

- 담당 역할: `implementation-agent`
- 필수 스킬: `harness`, `fesa-cpp-msvc-tdd`
- 이 Step만 `RED -> observed failure -> minimal GREEN -> focused/full VERIFY`로 수행한다.

## 읽어야 할 파일

- `/AGENTS.md`
- `/docs/CODINGSTYLE.md`
- `/docs/ARCHITECTURE.md`
- `/docs/ADR.md`
- `/docs/cpp-object-oriented-modular-refactoring/implementation-plan.md`
- Step 13 Domain/AnalysisModel files
- Step 14 `element.h`, `element_factory.h`, concrete runtime elements
- `/include/fesa/fem/dof_manager.h`, `/src/fesa/fem/dof_manager.cpp`
- `/tests/unit/fem/dof_manager_test.cpp`
- `/tests/unit/assembly/sparse_assembler_test.cpp`
- `/phases/cpp-object-oriented-modular-refactoring/index.json`
- `/phases/cpp-object-oriented-modular-refactoring/step15.md`

## 작업

Requirement `R-PIPELINE-001`의 DofManager portion과 `R-DUP-002`의 DOF invariant owner를
구현한다.

1. `dof_manager_test.cpp`에 `C-DOF-001`을 먼저 추가한다. A test-only fake `Element`
   supplies a layout not named B33 or MITC4; DofManager must number/scatter it in source order.
2. Tests also corrupt duplicate/full/free/constrained/equation mappings through an approved test seam
   and expect `ValidateInvariants()` to reject each exact inconsistency.
3. Current DofManager cannot consume fake base layouts or expose owner validation, producing RED.
4. Candidate API:

```cpp
Status DofManager::Build(
    const AnalysisModel& analysis_model,
    const ElementView& elements);

Result<std::vector<std::size_t>> DofManager::ElementScatter(
    const ElementDofLayout& layout) const;

Status DofManager::ValidateInvariants() const;
```

5. Replace B33/MITC4 concrete scatter/pattern branches with the ordered layout. Node DOF ownership,
   constrained/free mappings, equation numbering and sparse pattern remain solely in DofManager.
6. Preserve stable node/source/component order, no/mixed/all-constraint behavior, and valid 0 free
   equations. Do not store equation ids in Node/Element.
7. Remove same-meaning `ValidateDofOrder` helpers from other modules only after their callers use
   `ValidateInvariants()` or an owner-issued immutable mapping.

## Acceptance Criteria

```powershell
cmake --build .harness/build --config Debug --target fesa_unit_tests
ctest --test-dir .harness/build -C Debug `
  -R "DofManager|EssentialConstraints|SparseAssembly" --output-on-failure
$typeBranches = @(rg -n "EulerBeam3D|Mitc4Shell" src/fesa/fem/dof_manager.cpp)
if ($typeBranches.Count -ne 0) { $typeBranches; throw "Concrete element branch remains" }
rg -n "ValidateDofOrder" src/fesa
& "C:/Program Files/LLVM/bin/clang-format.exe" --dry-run --Werror `
  include/fesa/fem/dof_manager.h src/fesa/fem/dof_manager.cpp `
  tests/unit/fem/dof_manager_test.cpp
cmake --build .harness/build --config Debug
ctest --test-dir .harness/build -C Debug --show-only=json-v1
ctest --test-dir .harness/build -C Debug --output-on-failure
```

`ValidateDofOrder` scan must show no duplicate local definitions. Existing public compatibility
wrappers may remain temporarily only if they delegate to DofManager and are removed by Step 20.

## 검증 및 상태 갱신

- RED fake-element/invariant failures, focused stable ordering, branch scan and full CTest를 summary에 기록한다.
- Equation or sparse pattern ordering regression is `error`.
- 성공 시 현재 Step만 `completed`로 갱신한다.
- timestamp, retry, commit, advancement는 Executor 소유다.

## 금지사항

- Element에 equation ids or global CSR를 저장하지 마라.
- DOF component order를 element kind switch로 재구성하지 마라.
- Sparse assembly algorithm을 수정하지 마라. 이유: Step 16 소유다.
- 직접 commit하거나 hook script를 수동 실행하지 마라.