# Story 1.2: Configuration Read/Write/Wipe

Status: ready-for-dev

## Story

As a provisioning system,
I want a single config module that reads, writes, and wipes `/etc/planemapper/config.json`,
So that all components share one reliable config boundary with no direct filesystem access elsewhere.

## Acceptance Criteria

1. **Given** no config file exists at `CONFIG_PATH` **When** `config.read()` is called **Then** it raises `FileNotFoundError`

2. **Given** a valid config dict with home lat/lon, coverage radius, WiFi SSID/password, and `provisioned` flag **When** `config.write(data)` is called **Then** the file is created at `CONFIG_PATH` with correct JSON content and all expected keys present

3. **Given** an existing config file **When** `config.wipe()` is called **Then** the config file is deleted and a subsequent `config.read()` raises `FileNotFoundError`

4. **Given** a test using `conftest.py` **When** `CONFIG_PATH` is patched to `tmp_path` **Then** all config operations work without touching `/etc/planemapper/`

## Tasks / Subtasks

- [ ] Task 1: Implement `config.read()` in `src/planemapper/provisioning/config.py` (AC: #1, #4)
  - [ ] 1.1 Import `CONFIG_PATH` from `planemapper.constants`
  - [ ] 1.2 Implement `read() -> dict` that opens `CONFIG_PATH` and parses JSON
  - [ ] 1.3 Let `FileNotFoundError` propagate naturally if the file does not exist — no bare `except`

- [ ] Task 2: Implement `config.write(data)` in `src/planemapper/provisioning/config.py` (AC: #2, #4)
  - [ ] 2.1 Implement `write(data: dict) -> None`
  - [ ] 2.2 Call `CONFIG_PATH.parent.mkdir(parents=True, exist_ok=True)` before writing to ensure `/etc/planemapper/` exists
  - [ ] 2.3 Write JSON to `CONFIG_PATH` with `indent=2`

- [ ] Task 3: Implement `config.wipe()` in `src/planemapper/provisioning/config.py` (AC: #3, #4)
  - [ ] 3.1 Implement `wipe() -> None` that deletes `CONFIG_PATH` if it exists
  - [ ] 3.2 Use `CONFIG_PATH.unlink(missing_ok=True)` so wipe is idempotent

- [ ] Task 4: Update `tests/conftest.py` with `CONFIG_PATH` patch fixture (AC: #4)
  - [ ] 4.1 Add a `monkeypatch` fixture (or autouse session fixture) that patches `planemapper.provisioning.config.CONFIG_PATH` to `tmp_path / "config.json"` for every test
  - [ ] 4.2 Confirm the fixture is applied so no test ever touches `/etc/planemapper/`

- [ ] Task 5: Write tests in `tests/provisioning/test_config.py` covering all 4 ACs (AC: #1, #2, #3, #4)
  - [ ] 5.1 Test AC1: call `config.read()` with no file present; assert `FileNotFoundError` is raised
  - [ ] 5.2 Test AC2: call `config.write(data)` with a valid dict; assert file exists and JSON round-trips correctly with all expected keys (`home_lat`, `home_lon`, `coverage_radius_nm`, `wifi_ssid`, `wifi_password`, `provisioned`)
  - [ ] 5.3 Test AC3: write a config, call `config.wipe()`, assert file is gone, then assert `config.read()` raises `FileNotFoundError`
  - [ ] 5.4 Test AC4: confirm `CONFIG_PATH` resolves inside `tmp_path` (not `/etc/planemapper/`) during test execution

- [ ] Task 6: Run quality gates
  - [ ] 6.1 `pytest tests/` — all tests pass, 0 failures
  - [ ] 6.2 `ruff check .` — zero violations
  - [ ] 6.3 `ruff format --check .` — no formatting issues

## Dev Notes

### CONFIG_PATH patching
`CONFIG_PATH` is a module-level `Path` constant defined in `planemapper.constants` and imported into `planemapper.provisioning.config`. Patch the name **in the config module's namespace** — `monkeypatch.setattr("planemapper.provisioning.config.CONFIG_PATH", tmp_path / "config.json")` — not in `planemapper.constants`, so that all three functions pick up the patched value.

### Directory creation in `config.write()`
The directory `/etc/planemapper/` will not exist in CI or on a fresh OS install. `config.write()` must call `CONFIG_PATH.parent.mkdir(parents=True, exist_ok=True)` before opening the file for writing. In tests, `tmp_path` already exists, so this call is a safe no-op.

### JSON formatting
Write config files with `json.dump(data, f, indent=2)` for human readability. No extra dependencies — use the Python stdlib `json` module only.

### Error handling policy
Do not catch any exceptions inside `read()`, `write()`, or `wipe()`. Let `FileNotFoundError`, `PermissionError`, `json.JSONDecodeError`, etc. propagate to callers. Provisioning code higher up the stack is responsible for user-facing error messages.

### Config schema
The canonical key set written by `config.write()` and expected by all consumers:

```
home_lat            float   — decimal degrees, WGS-84
home_lon            float   — decimal degrees, WGS-84
coverage_radius_nm  int     — display radius in nautical miles
wifi_ssid           str     — WiFi network name
wifi_password       str     — WiFi passphrase
provisioned         bool    — True once provisioning has completed
```

### File location constants
`CONFIG_PATH = Path("/etc/planemapper/config.json")` is defined in `src/planemapper/constants.py`. Do not hard-code the path string anywhere in `config.py` or test files; always reference the module-level `CONFIG_PATH` symbol so the monkeypatch can redirect it cleanly.