# Step 1: mesh-keyword-parser

## Read First

Read these files before editing:

- `/AGENTS.md`
- `/docs/PRD.md`
- `/docs/ARCHITECTURE.md`
- `/docs/ADR.md`
- `/docs/io-definitions/abaqus-input-parser-io.md`
- `/src/fesa/model/domain.hpp`
- `/src/fesa/model/node.hpp`
- `/src/fesa/model/element.hpp`
- `/tests/unit/model_domain_test.cpp`

Review step 0 output before implementing. Keep this step limited to parser API
and mesh keyword mapping.

## Task

Add the first C++ parser slice under `/src/fesa/io/abaqus/`.

Required behavior:

- Provide a small `InputParser` that accepts an in-memory `.inp` string and
  returns a parse result containing `fesa::model::Domain` and
  `fesa::core::Status`.
- Parse `*HEADING` as accepted but not yet stored.
- Parse `*NODE` data lines into `Domain::add_node`.
- Parse `*ELEMENT, TYPE=<type>` data lines into `Domain::add_element`.
- Support only two-node line/bar element names needed by the current model:
  `T2D2`, `T3D2`, `B31`, and `C3D2`.
- Map `T2D2`, `T3D2`, and `C3D2` to `ElementTopology::truss2`; map `B31` to
  `ElementTopology::bar2`.
- Use `PropertyId{0}` for elements in this first mesh-only slice because
  section parsing is introduced later.
- Treat keywords and parameter names case-insensitively.
- Skip blank lines and comment lines that begin with `**`.

Keep implementation C++17/MSVC-compatible. Do not introduce external
libraries, regex-heavy parser frameworks, JavaScript, TypeScript, or npm
fallbacks.

## Tests To Write First

Add `/tests/unit/abaqus_input_parser_mesh_test.cpp` before production code.

The test must first fail because `fesa/io/abaqus/input_parser.hpp` does not
exist, then pass after implementation. It should verify:

- a small input with `*HEADING`, `*NODE`, and `*ELEMENT, TYPE=T3D2` returns
  `Status::is_ok() == true`;
- the returned `Domain` contains the expected node ids and 3D coordinates;
- the returned `Domain` contains the expected element id, topology,
  connectivity, and `PropertyId{0}`;
- keyword and parameter casing are accepted case-insensitively.

## Acceptance Criteria

```powershell
ctest --test-dir build/msvc-debug --output-on-failure -C Debug -R abaqus_input_parser_mesh_test
python -m unittest discover -s scripts -p "test_*.py"
python scripts/validate_workspace.py
```

## Verification Procedure

1. Run the targeted CTest after writing the test and before production code;
   confirm the failure is due to the missing parser API.
2. Implement the minimum code needed for the test to pass.
3. Run all acceptance criteria commands.
4. Confirm C++ production changes have a related C++ test file.
5. Update `phases/abaqus-input-parser/index.json` step 1:
   - success: `"status": "completed"`, `"summary": "Mesh keyword parser maps NODE and ELEMENT data into Domain"`
   - error after three attempts: `"status": "error"`, `"error_message": "<specific error>"`
   - blocked: `"status": "blocked"`, `"blocked_reason": "<specific reason>"`

## Forbidden

- Do not add set, material, section, load, boundary condition, output request,
  include-file, or HDF5 behavior in this step.
- Do not mutate reference artifacts.