Attach Costco discounts to purchase rows

build_purchases.py

@@ -33,6 +33,8 @@ PURCHASE_FIELDS = [
     "measure_type",
     "line_total",
     "unit_price",
+    "matched_discount_amount",
+    "net_line_total",
     "store_name",
     "store_number",
     "store_city",
@@ -94,7 +96,7 @@ def decimal_or_zero(value):
 
 
 def derive_metrics(row):
-    line_total = to_decimal(row.get("line_total"))
+    line_total = to_decimal(row.get("net_line_total") or row.get("line_total"))
     qty = to_decimal(row.get("qty"))
     pack_qty = to_decimal(row.get("pack_qty"))
     size_value = to_decimal(row.get("size_value"))
@@ -292,6 +294,8 @@ def build_purchase_rows(
                 "measure_type": row["measure_type"],
                 "line_total": row["line_total"],
                 "unit_price": row["unit_price"],
+                "matched_discount_amount": row.get("matched_discount_amount", ""),
+                "net_line_total": row.get("net_line_total", ""),
                 "store_name": order_row.get("store_name", ""),
                 "store_number": order_row.get("store_number", ""),
                 "store_city": order_row.get("store_city", ""),

enrich_costco.py

@@ -1,6 +1,7 @@
 import csv
 import json
 import re
+from collections import defaultdict
 from pathlib import Path
 
 import click
@@ -29,6 +30,7 @@ HASH_SIZE_RE = re.compile(r"(?<![A-Z0-9])(\d+(?:\.\d+)?)#\b")
 PACK_DASH_RE = re.compile(r"(?<![A-Z0-9])(\d+)\s*-\s*PACK\b")
 PACK_WORD_RE = re.compile(r"(?<![A-Z0-9])(\d+)\s*PACK\b")
 SIZE_RE = re.compile(r"(?<![A-Z0-9])(\d+(?:\.\d+)?)\s*(OZ|LB|LBS|CT|KG|G)\b")
+DISCOUNT_TARGET_RE = re.compile(r"^/\s*(\d+)\b")
 
 
 def clean_costco_name(name):
@@ -156,6 +158,13 @@ def is_discount_item(item):
     return amount < 0 or unit < 0 or description.startswith("/")
 
 
+def discount_target_id(raw_name):
+    match = DISCOUNT_TARGET_RE.match(normalize_whitespace(raw_name))
+    if not match:
+        return ""
+    return match.group(1)
+
+
 def parse_costco_item(order_id, order_date, raw_path, line_no, item):
     raw_name = combine_description(item)
     cleaned_name = clean_costco_name(raw_name)
@@ -190,6 +199,8 @@ def parse_costco_item(order_id, order_date, raw_path, line_no, item):
         "reward_savings": "",
         "coupon_savings": str(item.get("amount", "")) if is_discount_line else "",
         "coupon_price": "",
+        "matched_discount_amount": "",
+        "net_line_total": str(item.get("amount", "")) if not is_discount_line else "",
         "image_url": "",
         "raw_order_path": raw_path.as_posix(),
         "item_name_norm": item_name_norm,
@@ -211,6 +222,51 @@ def parse_costco_item(order_id, order_date, raw_path, line_no, item):
     }
 
 
+def match_costco_discounts(rows):
+    rows_by_order = defaultdict(list)
+    for row in rows:
+        rows_by_order[row["order_id"]].append(row)
+
+    for order_rows in rows_by_order.values():
+        purchase_rows_by_item_id = defaultdict(list)
+        for row in order_rows:
+            if row.get("is_discount_line") == "true":
+                continue
+            retailer_item_id = row.get("retailer_item_id", "")
+            if retailer_item_id:
+                purchase_rows_by_item_id[retailer_item_id].append(row)
+
+        for row in order_rows:
+            if row.get("is_discount_line") != "true":
+                continue
+            target_id = discount_target_id(row.get("item_name", ""))
+            if not target_id:
+                continue
+            matches = purchase_rows_by_item_id.get(target_id, [])
+            if len(matches) != 1:
+                row["parse_notes"] = normalize_whitespace(
+                    f"{row.get('parse_notes', '')};discount_target_unmatched={target_id}"
+                ).strip(";")
+                continue
+
+            purchase_row = matches[0]
+            matched_discount = to_decimal(row.get("line_total"))
+            gross_total = to_decimal(purchase_row.get("line_total"))
+            existing_discount = to_decimal(purchase_row.get("matched_discount_amount")) or 0
+            if matched_discount is None or gross_total is None:
+                continue
+
+            total_discount = existing_discount + matched_discount
+            purchase_row["matched_discount_amount"] = format_decimal(total_discount)
+            purchase_row["net_line_total"] = format_decimal(gross_total + total_discount)
+            purchase_row["parse_notes"] = normalize_whitespace(
+                f"{purchase_row.get('parse_notes', '')};matched_discount={target_id}"
+            ).strip(";")
+            row["parse_notes"] = normalize_whitespace(
+                f"{row.get('parse_notes', '')};matched_to_item={target_id}"
+            ).strip(";")
+
+
 def iter_costco_rows(raw_dir):
     for path in discover_json_files(raw_dir):
         if path.name in {"summary.json", "summary_requests.json"}:
@@ -238,6 +294,7 @@ def discover_json_files(raw_dir):
 
 def build_items_enriched(raw_dir):
     rows = list(iter_costco_rows(raw_dir))
+    match_costco_discounts(rows)
     rows.sort(key=lambda row: (row["order_date"], row["order_id"], int(row["line_no"])))
     return rows
 

enrich_giant.py

@@ -33,6 +33,8 @@ OUTPUT_FIELDS = [
     "reward_savings",
     "coupon_savings",
     "coupon_price",
+    "matched_discount_amount",
+    "net_line_total",
     "image_url",
     "raw_order_path",
     "item_name_norm",
@@ -371,6 +373,8 @@ def parse_item(order_id, order_date, raw_path, line_no, item):
         "reward_savings": stringify(item.get("rewardSavings")),
         "coupon_savings": stringify(item.get("couponSavings")),
         "coupon_price": stringify(item.get("couponPrice")),
+        "matched_discount_amount": "",
+        "net_line_total": stringify(item.get("totalPrice")),
         "image_url": extract_image_url(item),
         "raw_order_path": raw_path.as_posix(),
         "item_name_norm": normalized_name,

tests/test_costco_pipeline.py

@@ -279,6 +279,57 @@ class CostcoPipelineTests(unittest.TestCase):
         self.assertEqual("true", discount["is_discount_line"])
         self.assertEqual("true", discount["is_coupon_line"])
 
+    def test_build_items_enriched_matches_discount_to_item(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            raw_dir = Path(tmpdir) / "raw"
+            raw_dir.mkdir()
+            payload = {
+                "data": {
+                    "receiptsWithCounts": {
+                        "receipts": [
+                            {
+                                "transactionBarcode": "abc",
+                                "transactionDate": "2026-03-12",
+                                "itemArray": [
+                                    {
+                                        "itemNumber": "4873222",
+                                        "itemDescription01": "ALL F&C",
+                                        "itemDescription02": "200OZ 160LOADS P104",
+                                        "itemDepartmentNumber": 14,
+                                        "transDepartmentNumber": 14,
+                                        "unit": 1,
+                                        "itemIdentifier": "E",
+                                        "amount": 19.99,
+                                        "itemUnitPriceAmount": 19.99,
+                                    },
+                                    {
+                                        "itemNumber": "374664",
+                                        "itemDescription01": "/ 4873222",
+                                        "itemDescription02": None,
+                                        "itemDepartmentNumber": 14,
+                                        "transDepartmentNumber": 14,
+                                        "unit": -1,
+                                        "itemIdentifier": None,
+                                        "amount": -5,
+                                        "itemUnitPriceAmount": 0,
+                                    },
+                                ],
+                            }
+                        ]
+                    }
+                }
+            }
+            (raw_dir / "abc.json").write_text(json.dumps(payload), encoding="utf-8")
+
+            rows = enrich_costco.build_items_enriched(raw_dir)
+
+            purchase_row = next(row for row in rows if row["is_discount_line"] == "false")
+            discount_row = next(row for row in rows if row["is_discount_line"] == "true")
+            self.assertEqual("-5", purchase_row["matched_discount_amount"])
+            self.assertEqual("14.99", purchase_row["net_line_total"])
+            self.assertIn("matched_discount=4873222", purchase_row["parse_notes"])
+            self.assertIn("matched_to_item=4873222", discount_row["parse_notes"])
+
     def test_cross_retailer_validation_writes_proof_example(self):
         with tempfile.TemporaryDirectory() as tmpdir:
             giant_csv = Path(tmpdir) / "giant_items_enriched.csv"