# age-injector (AZ-407)

Clones a `tile-cache-fixture` tree and mutates ONLY the manifest's
`capture_date` field (and the per-tile sidecar JSON's matching field)
to age every entry by a target number of months.

## Output volumes

| Volume | Age shift | Triggers |
|--------|-----------|----------|
| `synth-age-7mo`  | now - 7 mo  | > AC-8.2 active-conflict threshold (6 mo) — FT-N-05 |
| `synth-age-13mo` | now - 13 mo | > AC-8.2 rear threshold (12 mo) — FT-N-06 |

## Reproducibility

* Tile JPEG bodies are copied bit-identical (`shutil.copytree`).
* Manifest CSV row order is preserved from the source manifest (the
  builder already sorts rows by `(zoom, x, y)`).
* The shifted date is `now - age_months × 30.44 days`, rounded — the
  AC-3 tolerance is `± 1 day`, well within the 30.44-day floor.
* The descriptors.index (if present in the source) is copied
  bit-identical.

## Provenance

The injector itself is fully synthetic. The aged volumes are derivative
works of `tile-cache-fixture` (same license — see
`e2e/fixtures/tile-cache-builder/README.md` § Provenance).

## Usage

```bash
# Production (Docker volumes):
e2e/fixtures/age-injector/inject.sh

# Local mode (used by AZ-407 unit test):
e2e/fixtures/age-injector/inject.sh --local /tmp/src /tmp/out-7mo /tmp/out-13mo
```

The unit test `e2e/_unit_tests/fixtures/test_age_injector.py` verifies
AC-3 by:

1. Building a small tile-cache fixture from a synthetic 4-still input
2. Running the injector with `--age-months=7` and `--age-months=13`
3. Asserting the manifest `capture_date` shifts ±1 day from `now - N*30.44 days`
4. Asserting every tile JPEG body byte-equals the source

## Owned by

AZ-407 (this task).