# Step 1: analysis-state-core

## Read First

Read these files before editing:

- `/AGENTS.md`
- `/docs/PLAN.md`
- `/docs/PROGRESS.md`
- `/docs/WORKNOTE.md`
- `/docs/AGENT_RULES.md`
- `/docs/ADR.md`
- `/docs/ARCHITECTURE.md`
- `/docs/implementation-plans/analysis-state-analysis-base-implementation-plan.md`
- `/include/fesa/core/ModelTypes.hpp`
- `/include/fesa/core/Domain.hpp`
- `/CMakeLists.txt`

## Task

Add `fesa::core::AnalysisState`.

Candidate files:

- Create `/include/fesa/core/AnalysisState.hpp`
- Create `/src/core/AnalysisState.cpp`
- Create `/tests/core/analysis_state_test.cpp`
- Modify `/CMakeLists.txt`

Required initial contract:

- `AnalysisState()` starts with zero DOFs and empty vectors.
- `explicit AnalysisState(std::size_t dof_count)` allocates zero-filled vectors.
- `dofCount()` returns the current vector size.
- `displacement()`, `externalForce()`, `internalForce()`, `residual()`, and `reaction()` return const vector references.
- All state vectors have the same size as `dofCount()`.
- State is mutable analysis data only. Do not store node ids, element ids, equation ids, sparse data, solver handles, writer handles, or references to `Domain`.

## Tests To Write First

Write tests in `/tests/core/analysis_state_test.cpp` before creating production code:

- default state has zero DOFs and all vectors empty.
- sized state creates zero-filled displacement, external force, internal force, residual, and reaction vectors.
- `dofCount()` matches vector sizes.

Run the targeted test and confirm it fails because `AnalysisState` does not exist:

```powershell
ctest --test-dir build/msvc-debug --output-on-failure -C Debug -R analysis
```

Then implement the minimum code needed to pass.

## Acceptance Criteria

Run:

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

Update `/phases/analysis-state-analysis-base/index.json` step 1 with `completed`, `error`, or `blocked`.

## Do Not

- Do not implement `AnalysisModel`, `DofManager`, assembly, solver, or result output.
- Do not add mutable solver state to `Domain`, `Node`, `Element`, `Material`, `Property`, `Load`, or `BoundaryCondition`.