Retry interrupted thematic WCS tiles

backend/tests/test_sprint213_thematic_rasters.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from http.client import IncompleteRead
 from pathlib import Path
 from types import SimpleNamespace
 from uuid import uuid4
@@ -89,6 +90,11 @@ class FakeResponse:
         return self.content[:limit]
 
 
+class IncompleteResponse(FakeResponse):
+    def read(self, limit: int):
+        raise IncompleteRead(self.content[:limit])
+
+
 def payload(product_key: str = "space_occupation_2025", *, side_m: float = 1000.0) -> ThematicRasterAcquireRequest:
     transformer = Transformer.from_crs("EPSG:31370", "EPSG:4326", always_xy=True)
     min_x, min_y = transformer.transform(200_000, 210_000)
@@ -171,6 +177,52 @@ def test_complete_kempen_scope_fits_the_tiled_thematic_guardrails() -> None:
     assert exc_info.value.code == "THEMATIC_RASTER_SELECTION_TOO_LARGE"
 
 
+def test_wcs_fetch_retries_an_incomplete_tile_without_accepting_partial_bytes(monkeypatch) -> None:
+    content = b"II*\x00complete-geotiff"
+    responses = [IncompleteResponse(content), FakeResponse(content)]
+    attempts = 0
+
+    def opener(*_args, **_kwargs):
+        nonlocal attempts
+        response = responses[attempts]
+        attempts += 1
+        return response
+
+    monkeypatch.setattr("app.services.thematic_raster_acquisition_service.time.sleep", lambda _seconds: None)
+
+    result, content_type = ThematicRasterAcquisitionService._fetch(
+        "https://example.invalid/wcs",
+        Settings(_env_file=None),
+        opener,
+    )
+
+    assert attempts == 2
+    assert result == content
+    assert content_type == "image/tiff"
+
+
+def test_wcs_fetch_fails_closed_after_bounded_incomplete_tile_retries(monkeypatch) -> None:
+    attempts = 0
+
+    def opener(*_args, **_kwargs):
+        nonlocal attempts
+        attempts += 1
+        return IncompleteResponse(b"II*\x00partial")
+
+    monkeypatch.setattr("app.services.thematic_raster_acquisition_service.time.sleep", lambda _seconds: None)
+
+    with pytest.raises(AppError) as exc_info:
+        ThematicRasterAcquisitionService._fetch(
+            "https://example.invalid/wcs",
+            Settings(_env_file=None),
+            opener,
+        )
+
+    assert attempts == ThematicRasterAcquisitionService.WCS_FETCH_ATTEMPTS
+    assert exc_info.value.code == "THEMATIC_RASTER_PROVIDER_UNAVAILABLE"
+    assert exc_info.value.details["attempts"] == 3
+
+
 def test_binary_and_normalized_products_fail_closed_on_invalid_values() -> None:
     binary = ThematicRasterAcquisitionService._product("space_occupation_2025")
     score = ThematicRasterAcquisitionService._product("service_level_2022")