Generate property reference to uprn map from csv bytes 🟩

backend/condition/lookups/uprn_lookup.py

@@ -1,7 +1,9 @@
 from abc import ABC, abstractmethod
-from typing import Dict
+from typing import BinaryIO, Dict
 
 
 class UprnLookup(ABC):
-    def get_location_ref_to_uprn_map(self, lookup_filepath: str) -> Dict[str, int]:
+    def get_location_ref_to_uprn_map(
+        self, lookup_file_stream: BinaryIO
+    ) -> Dict[str, int]:
         pass

backend/condition/lookups/uprn_lookup_csv.py

@@ -1,4 +1,6 @@
-from typing import BinaryIO, Dict
+import csv
+from io import TextIOWrapper
+from typing import BinaryIO, Dict, TextIO
 from backend.condition.lookups.uprn_lookup import UprnLookup
 
 
@@ -6,4 +8,17 @@ class UprnLookupCsv(UprnLookup):
     def get_location_ref_to_uprn_map(
         self, lookup_file_stream: BinaryIO
     ) -> Dict[str, int]:
-        raise NotImplementedError
+        text_stream: TextIO = TextIOWrapper(lookup_file_stream, encoding="utf-8")
+        location_ref_to_uprn_map: Dict[str, int] = {}
+
+        reader = csv.DictReader(text_stream)
+        for row in reader:
+            if not row["reference"] or not row["out_uprn"]:
+                # skip empty rows
+                continue
+
+            ref = row["reference"].strip()
+            uprn = int(row["out_uprn"].strip())
+            location_ref_to_uprn_map[ref] = uprn
+
+        return location_ref_to_uprn_map

backend/condition/tests/lookups/test_uprn_lookup_csv.py

@@ -7,7 +7,7 @@ from backend.condition.lookups.uprn_lookup_csv import UprnLookupCsv
 
 @pytest.fixture
 def prop_ref_uprn_csv_bytes() -> BytesIO:
-    csv_bytes = b"""reference, out_uprn
+    csv_bytes = b"""reference,out_uprn
     ABC123,10000000001
     DEF456,10000000002
     GHI789,10000000003