# Step 6: boundary-load-step-storage

## Read First

Read these files before editing:

- `/AGENTS.md`
- `/docs/AGENT_RULES.md`
- `/docs/ADR.md`
- `/docs/ARCHITECTURE.md`
- `/docs/implementation-plans/domain-model-foundation-implementation-plan.md`
- `/include/fesa/core/Domain.hpp`
- `/include/fesa/core/ModelTypes.hpp`
- `/tests/core/domain_storage_test.cpp`

## Task

Add boundary condition, nodal load, and analysis step definition storage.

Allowed files:

- Create `/include/fesa/core/BoundaryCondition.hpp`
- Create `/include/fesa/core/LoadDefinition.hpp`
- Create `/include/fesa/core/StepDefinition.hpp`
- Modify `/include/fesa/core/Domain.hpp`
- Modify `/src/core/Domain.cpp`
- Modify `/tests/core/domain_storage_test.cpp`

Required behavior:

- A boundary condition stores node id, constrained `Dof`, and prescribed value.
- A nodal load stores node id, `Dof`, and value.
- A linear static step definition stores step id, name, boundary condition indices or ids, and load indices or ids.
- Adding BC/load for a missing node throws `std::invalid_argument`.
- Duplicate step ids throw `std::invalid_argument`.
- Stored BCs, loads, and steps are returned as const data.

## Tests To Write First

Write failing tests before production changes:

- Add and retrieve a boundary condition on an existing node.
- Add and retrieve a nodal load on an existing node.
- Missing-node BC/load throws.
- Add a linear static step referencing stored BC/load entries.
- Duplicate step id throws.

Run targeted CTest and verify RED before implementation.

## Acceptance Criteria

Run:

```powershell
cmake --build build/msvc-debug --config Debug
ctest --test-dir build/msvc-debug --output-on-failure -C Debug -R domain
python scripts/validate_workspace.py
```

Update `/phases/domain-model-foundation/index.json` step 6 with `completed`, `error`, or `blocked`.

## Do Not

- Do not apply boundary conditions to matrices.
- Do not compute reactions.
- Do not add solver state, displacements, equation ids, or sparse matrix behavior.