feat(ingest): country-focused seeding (collect domestic CN products)

Add a market-focused seeding path so the catalogue can be built from
domestic products rather than the English-heavy global default:

- adapter.fetch_by_country(country): OFF search filtered by
  countries_tags_en, sorted by unique_scans_n (most-scanned first),
  de-duplicated across pages since OFF popularity ordering is unstable.
- is_cn_gs1(code): True for GS1-China company prefixes (690-699),
  i.e. genuinely domestic items vs. imports merely sold in China.
- seed_off --country <slug> [--domestic-only] [--page-size/--max-pages]:
  e.g. 'seed_off --country china --domestic-only' loads only 69x
  barcodes.

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

ingestion/opengoods/adapters/openfoodfacts.py

@@ -157,6 +157,60 @@ class OpenFoodFactsAdapter:
             if reached_old or len(products) < page_size:
                 return
 
+    def fetch_by_country(
+        self,
+        country: str,
+        *,
+        page_size: int = 100,
+        max_pages: int = 10,
+        sort_by: str = "unique_scans_n",
+    ) -> Iterator[dict]:
+        """Yield products sold in ``country`` (an OFF ``countries_tags_en`` slug).
+
+        Used to seed a market-specific catalogue (e.g. ``china``). Results are
+        sorted by ``sort_by`` (default ``unique_scans_n`` so the most-scanned,
+        best-known products come first) and de-duplicated across pages, since
+        OFF's popularity ordering is not stable between page requests.
+        """
+        seen: set[str] = set()
+        for page in range(1, max_pages + 1):
+            resp = self._get(
+                _SEARCH_URL,
+                params={
+                    "fields": _SEARCH_FIELDS,
+                    "countries_tags_en": country,
+                    "sort_by": sort_by,
+                    "page": page,
+                    "page_size": page_size,
+                },
+            )
+            products = resp.json().get("products") or []
+            if not products:
+                return
+            new_on_page = 0
+            for prod in products:
+                code = str(prod.get("code") or "")
+                if code and code in seen:
+                    continue
+                if code:
+                    seen.add(code)
+                new_on_page += 1
+                yield prod
+            if len(products) < page_size or new_on_page == 0:
+                return
+
+
+def is_cn_gs1(code: str | None) -> bool:
+    """Return True for a GS1 China company prefix (barcodes starting 690-699).
+
+    These identify products registered with GS1 China, i.e. genuinely domestic
+    items, as opposed to imported goods merely tagged as sold in China.
+    """
+    if not code:
+        return False
+    code = code.strip()
+    return len(code) >= 3 and code[:2] == "69" and code[2].isdigit()
+
 
 def read_dump(path: str | Path) -> Iterator[dict]:
     """Yield raw product records from an OFF JSONL dump file.

ingestion/opengoods/jobs/seed_off.py

@@ -7,6 +7,11 @@ Usage:
     # from a downloaded OFF JSONL dump (optionally .gz), limited to N records
     python -m opengoods.jobs.seed_off --dump products.jsonl.gz --limit 1000
 
+    # market-focused: the most-scanned products sold in China, restricted to
+    # genuine GS1-China (69x) barcodes
+    python -m opengoods.jobs.seed_off --country china --domestic-only \
+        --max-pages 20 --limit 1000
+
 The OFF read API is rate-limited client-side; for large imports use a dump.
 """
 
@@ -18,20 +23,33 @@ from collections.abc import Iterator
 
 import psycopg
 
-from opengoods.adapters.openfoodfacts import OpenFoodFactsAdapter, read_dump
+from opengoods.adapters.openfoodfacts import (
+    OpenFoodFactsAdapter,
+    is_cn_gs1,
+    read_dump,
+)
 from opengoods.etl.load import default_dsn, ensure_source, load_record_safe
 from opengoods.etl.transform import transform
 
 
 def _raw_records(args: argparse.Namespace) -> Iterator[dict]:
     if args.dump:
-        records = read_dump(args.dump)
+        records: Iterator[dict] = read_dump(args.dump)
+    elif args.country:
+        adapter = OpenFoodFactsAdapter(min_interval=args.min_interval)
+        records = adapter.fetch_by_country(
+            args.country, page_size=args.page_size, max_pages=args.max_pages
+        )
     else:
         adapter = OpenFoodFactsAdapter(min_interval=args.min_interval)
         records = adapter.fetch(args.barcodes)
-    for i, rec in enumerate(records):
-        if args.limit and i >= args.limit:
+    yielded = 0
+    for rec in records:
+        if args.domestic_only and not is_cn_gs1(str(rec.get("code") or "")):
+            continue
+        if args.limit and yielded >= args.limit:
             break
+        yielded += 1
         yield rec
 
 
@@ -58,7 +76,18 @@ def main(argv: list[str] | None = None) -> int:
     src = parser.add_mutually_exclusive_group(required=True)
     src.add_argument("--barcodes", nargs="+", help="barcodes to fetch via the OFF API")
     src.add_argument("--dump", help="path to an OFF JSONL dump (.jsonl or .jsonl.gz)")
+    src.add_argument(
+        "--country",
+        help="OFF countries_tags_en slug to seed from, e.g. 'china' (most-scanned first)",
+    )
+    parser.add_argument(
+        "--domestic-only",
+        action="store_true",
+        help="keep only genuine GS1-China (69x) barcodes; drop imported goods",
+    )
     parser.add_argument("--limit", type=int, default=0, help="max records to load (0 = all)")
+    parser.add_argument("--page-size", type=int, default=100, help="search page size")
+    parser.add_argument("--max-pages", type=int, default=10, help="max search pages (country mode)")
     parser.add_argument("--min-interval", type=float, default=4.0, help="API throttle seconds")
     parser.add_argument("--dsn", default=default_dsn(), help="PostgreSQL DSN")
     return run(parser.parse_args(argv))

ingestion/tests/test_off_country.py

@@ -0,0 +1,57 @@
+import httpx
+
+from opengoods.adapters.openfoodfacts import OpenFoodFactsAdapter, is_cn_gs1
+
+
+def _adapter(handler, **kwargs):
+    client = httpx.Client(transport=httpx.MockTransport(handler))
+    return OpenFoodFactsAdapter(client=client, min_interval=0, backoff_base=0, **kwargs)
+
+
+def test_is_cn_gs1():
+    assert is_cn_gs1("6901234567892")  # GS1 China prefix
+    assert is_cn_gs1("690")
+    assert not is_cn_gs1("3017624010701")  # France
+    assert not is_cn_gs1("5449000000996")  # Belgium
+    assert not is_cn_gs1("")
+    assert not is_cn_gs1(None)
+    assert not is_cn_gs1("69")  # too short to carry a prefix digit
+
+
+def test_fetch_by_country_passes_filter_and_paginates():
+    seen_params = []
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        seen_params.append(dict(request.url.params))
+        page = int(request.url.params.get("page", "1"))
+        if page == 1:
+            return httpx.Response(
+                200,
+                json={"products": [{"code": "6901"}, {"code": "6902"}]},
+            )
+        return httpx.Response(200, json={"products": []})
+
+    adapter = _adapter(handler)
+    out = list(adapter.fetch_by_country("china", page_size=2, max_pages=5))
+    assert [p["code"] for p in out] == ["6901", "6902"]
+    assert seen_params[0]["countries_tags_en"] == "china"
+    assert seen_params[0]["sort_by"] == "unique_scans_n"
+
+
+def test_fetch_by_country_dedupes_across_pages():
+    def handler(request: httpx.Request) -> httpx.Response:
+        page = int(request.url.params.get("page", "1"))
+        if page == 1:
+            return httpx.Response(
+                200, json={"products": [{"code": "6901"}, {"code": "6902"}]}
+            )
+        if page == 2:
+            # OFF popularity ordering is unstable; a repeat appears on page 2
+            return httpx.Response(
+                200, json={"products": [{"code": "6902"}, {"code": "6903"}]}
+            )
+        return httpx.Response(200, json={"products": []})
+
+    adapter = _adapter(handler)
+    out = [p["code"] for p in adapter.fetch_by_country("china", page_size=2, max_pages=5)]
+    assert out == ["6901", "6902", "6903"]