From 03a0ad238c70622fb0a3aec557986e8c44c218da Mon Sep 17 00:00:00 2001
From: Daniel Roth <daniel_roth@hotmail.co.uk>
Date: Wed, 4 Feb 2026 11:28:41 +0000
Subject: [PATCH] =?UTF-8?q?Generate=20property=20reference=20to=20uprn=20m?=
 =?UTF-8?q?ap=20from=20csv=20bytes=20=F0=9F=9F=A9?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 backend/condition/lookups/uprn_lookup.py      |  6 ++++--
 backend/condition/lookups/uprn_lookup_csv.py  | 19 +++++++++++++++++--
 .../tests/lookups/test_uprn_lookup_csv.py     |  2 +-
 3 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/backend/condition/lookups/uprn_lookup.py b/backend/condition/lookups/uprn_lookup.py
index 87cc54fa..b817445d 100644
--- a/backend/condition/lookups/uprn_lookup.py
+++ b/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
diff --git a/backend/condition/lookups/uprn_lookup_csv.py b/backend/condition/lookups/uprn_lookup_csv.py
index 5f84587a..43544ccd 100644
--- a/backend/condition/lookups/uprn_lookup_csv.py
+++ b/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
diff --git a/backend/condition/tests/lookups/test_uprn_lookup_csv.py b/backend/condition/tests/lookups/test_uprn_lookup_csv.py
index 67cb80b9..a2d66a94 100644
--- a/backend/condition/tests/lookups/test_uprn_lookup_csv.py
+++ b/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