# CHR Data Contracts

This project supports two CHR input contracts that are normalized into one internal `ChromoModel` representation before calling `RenderGRFF`.

## 1) IDL Contract (`.sav`)

Entry point: `GXRadioImageComputing.load_model_sav(path)`

Expected fields in `BOX` (current CHR format):
- `DR`, `DZ`
- `BCUBE`, `CHROMO_BCUBE`
- `CHROMO_LAYERS`, `CORONA_BASE`
- `CHROMO_IDX`, `CHROMO_N`, `N_P`, `N_HI`, `CHROMO_T`
- `BASE.CHROMO_MASK`
- `AVFIELD`, `PHYSLENGTH`, `STATUS`, `STARTIDX`, `ENDIDX`

Metadata source:
- `BOX.INDEX` (`CRVAL1`, `CRVAL2`, `DSUN_OBS`, `DATE_OBS`)

## 2) pyAMPP HDF5 Contract (`.h5`)

Entry point: `GXRadioImageComputing.load_model_hdf(path)`

Expected datasets (v0.2.0 canonical):
- `/corona/dr`, `/corona/corona_base`
- `/corona/bx`, `/corona/by`, `/corona/bz` (or legacy packed `/corona/bcube`)
- `/chromo/dz`, `/chromo/chromo_layers`
- `/chromo/chromo_idx`, `/chromo/chromo_n`, `/chromo/n_p`, `/chromo/n_hi`, `/chromo/chromo_t`
- `/chromo/bx`, `/chromo/by`, `/chromo/bz` (or legacy packed `/chromo/chromo_bcube`)
- `/lines/av_field`, `/lines/phys_length`, `/lines/voxel_status`
- `/lines/start_idx`, `/lines/end_idx`
- `/chromo/chromo_mask` (fallback: `/base/chromo_mask`)

Legacy-compatible fallbacks still supported:
- `/chromo/dr`, `/chromo/corona_base`
- `/chromo/bcube`
- line metadata under `/chromo/*` (`av_field`, `phys_length`, `voxel_status`, `start_idx`, `end_idx`)

Metadata source:
- `/chromo` attributes: `lon`, `lat`, `dsun_obs`, `obs_time`

## Normalized Internal Rules

- Both contracts are adapted to shared keys before rendering.
- `voxel_status` bitmask semantics are preserved.
- `start_idx`/`end_idx` are clamped to valid chromo-mask bounds.
- `obs_time` is normalized to `astropy.time.Time`.