Squashed commit of the following: (#12)

commit 989319906069c1cecf7ed5bd8cee454d87ebcd3f
Author: Sung Cho <sung.w.cho@pm.me>
Date:   Sat Oct 18 20:59:51 2025 -0700

    download spreadsheet

commit b4b833a9a0e8f04daf2896f131f4ea7398702612
Author: Sung Cho <sung.w.cho@pm.me>
Date:   Sat Oct 18 20:53:50 2025 -0700

    get spreadsheet with formulas

Author: dphoria

pdm.lock

@@ -28,7 +28,7 @@ description = "Split Bill Web Site"
 authors = [
     {name = "Sung Cho", email = "sung.w.cho@protonmail.com"},
 ]
-dependencies = ["flask", "pillow", "openai", "pydantic", "click"]
+dependencies = ["flask", "pillow", "openai", "pydantic", "click", "openpyxl"]
 requires-python = "==3.12.*"
 readme = "README.md"
 license = {text = "MIT"}

pyproject.toml

@@ -1,8 +1,9 @@
 import csv
-from io import StringIO
+from io import StringIO, BytesIO
 from typing import Iterable
 from bill.person import Person
 from bill.receipts import Items, Item
+from openpyxl import Workbook
 
 
 class Calculator:
@@ -195,3 +196,68 @@ def get_person_shares(get_share):
 
         output.seek(0)
         return output.getvalue()
+
+    def get_shares_spreadsheet(self):
+        """
+        Get an Excel spreadsheet (BytesIO) with formulas for calculating shares.
+        """
+        workbook = Workbook()
+        worksheet = workbook.active
+        worksheet.title = "Bill Split"
+
+        fieldnames = (
+            ["Item", "Receipt"] + [person.name for person in self.persons] + ["Check"]
+        )
+
+        worksheet.append(fieldnames)
+        current_row = 2
+
+        for item in self.items.items:
+            row_data = [item.name, item.price]
+            for person in self.persons:
+                share = self.get_person_share(item, person)
+                row_data.append(share if share else None)
+            row_data.append(None)
+            worksheet.append(row_data)
+            current_row += 1
+
+        subtotal_row = current_row
+        subtotal = self.items.get_sum()
+        person_count = len(self.persons)
+        last_person_col = chr(ord("C") + person_count - 1)
+
+        row_data = ["Subtotal", subtotal]
+        for col_idx in range(person_count):
+            col_letter = chr(ord("C") + col_idx)
+            formula = f"=SUM({col_letter}2:{col_letter}{current_row - 1})"
+            row_data.append(formula)
+        row_data.append(f"=SUM(C{current_row}:{last_person_col}{current_row})")
+        worksheet.append(row_data)
+        current_row += 1
+
+        for extra in self.extras.items:
+            row_data = [extra.name, extra.price]
+            for col_idx in range(person_count):
+                col_letter = chr(ord("C") + col_idx)
+                formula = (
+                    f"=({col_letter}{subtotal_row}/$B${subtotal_row})*$B{current_row}"
+                )
+                row_data.append(formula)
+            row_data.append(f"=SUM(C{current_row}:{last_person_col}{current_row})")
+            worksheet.append(row_data)
+            current_row += 1
+
+        total_row = current_row
+        row_data = ["Total"]
+        row_data.append(f"=SUM(B{subtotal_row}:B{current_row - 1})")
+        for col_idx in range(person_count):
+            col_letter = chr(ord("C") + col_idx)
+            formula = f"=SUM({col_letter}{subtotal_row}:{col_letter}{current_row - 1})"
+            row_data.append(formula)
+        row_data.append(f"=SUM(C{total_row}:{last_person_col}{total_row})")
+        worksheet.append(row_data)
+
+        output = BytesIO()
+        workbook.save(output)
+        output.seek(0)
+        return output

src/bill/calculator.py

@@ -72,21 +72,21 @@ def payments_page_view():
 
 
 @payments_page.route("/payments/download", methods=["GET"])
-def download_csv():
+def download_spreadsheet():
     items = get_current_items(session)
     extras = get_current_extras(session)
     persons = get_current_persons(session)
 
     calculator = Calculator(persons=persons, items=items, extras=extras)
 
     timestamp = datetime.now().strftime("%Y%m%d-%H%M%S")
-    filename = f"{timestamp}.csv"
+    filename = f"{timestamp}.xlsx"
 
-    csv_content = calculator.get_shares_csv()
+    spreadsheet_bytes = calculator.get_shares_spreadsheet()
 
     return Response(
-        csv_content,
-        mimetype="text/csv",
+        spreadsheet_bytes.getvalue(),
+        mimetype="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
         headers={"Content-Disposition": f"attachment; filename={filename}"},
     )
 

src/ui/payments.py

@@ -3,6 +3,7 @@
 from bill.person import Person
 from bill.receipts import Item, Items
 from tests.utils import EXPECTED_ITEMS
+from openpyxl import load_workbook
 
 SERVICE_CHARGE = "Service Charge"
 TAX = "Tax"
@@ -225,3 +226,91 @@ def test_person_update_item():
 
     person.update_item(5)
     assert person.items == [1, 7, 9], "Item 5 should be removed again"
+
+
+def test_spreadsheet(calculator, sample_persons):
+    spreadsheet_bytes = calculator.get_shares_spreadsheet()
+
+    workbook = load_workbook(spreadsheet_bytes)
+    worksheet = workbook.active
+
+    header = [cell.value for cell in worksheet[1]]
+    expected_header = ["Item", "Receipt", "A", "B", "C", "Check"]
+    assert header == expected_header
+
+    assert worksheet["A2"].value == "GL-Domaine Amido Cotes Du Rhone"
+    assert worksheet["B2"].value == 13.00
+    assert worksheet["C2"].value == 6.50
+    assert worksheet["D2"].value is None
+    assert worksheet["E2"].value == 6.50
+
+    assert worksheet["A16"].value == "Shahi tukda"
+    assert worksheet["B16"].value == 15.00
+    assert worksheet["C16"].value == 5.00
+    assert worksheet["D16"].value == 5.00
+    assert worksheet["E16"].value == 5.00
+
+    assert worksheet["A17"].value == "Jus d Manguir"
+    assert worksheet["B17"].value == 9.00
+    assert worksheet["C17"].value == 4.50
+    assert worksheet["D17"].value == 4.50
+    assert worksheet["E17"].value is None
+
+    subtotal_row = 18
+    assert worksheet[f"A{subtotal_row}"].value == "Subtotal"
+    subtotal = EXPECTED_ITEMS.get_sum()
+    assert worksheet[f"B{subtotal_row}"].value == subtotal
+
+    assert worksheet[f"C{subtotal_row}"].value == "=SUM(C2:C17)"
+    assert worksheet[f"D{subtotal_row}"].value == "=SUM(D2:D17)"
+    assert worksheet[f"E{subtotal_row}"].value == "=SUM(E2:E17)"
+    assert worksheet[f"F{subtotal_row}"].value == "=SUM(C18:E18)"
+
+    service_charge_row = 19
+    assert worksheet[f"A{service_charge_row}"].value == SERVICE_CHARGE
+    service_charge = subtotal * SERVICE_CHARGE_RATIO
+    assert worksheet[f"B{service_charge_row}"].value == service_charge
+
+    assert (
+        worksheet[f"C{service_charge_row}"].value
+        == f"=(C{subtotal_row}/$B${subtotal_row})*$B{service_charge_row}"
+    )
+    assert (
+        worksheet[f"D{service_charge_row}"].value
+        == f"=(D{subtotal_row}/$B${subtotal_row})*$B{service_charge_row}"
+    )
+    assert (
+        worksheet[f"E{service_charge_row}"].value
+        == f"=(E{subtotal_row}/$B${subtotal_row})*$B{service_charge_row}"
+    )
+    assert (
+        worksheet[f"F{service_charge_row}"].value
+        == f"=SUM(C{service_charge_row}:E{service_charge_row})"
+    )
+
+    tax_row = 20
+    assert worksheet[f"A{tax_row}"].value == TAX
+    tax = subtotal * TAX_RATIO
+    assert worksheet[f"B{tax_row}"].value == tax
+
+    assert (
+        worksheet[f"C{tax_row}"].value
+        == f"=(C{subtotal_row}/$B${subtotal_row})*$B{tax_row}"
+    )
+    assert (
+        worksheet[f"D{tax_row}"].value
+        == f"=(D{subtotal_row}/$B${subtotal_row})*$B{tax_row}"
+    )
+    assert (
+        worksheet[f"E{tax_row}"].value
+        == f"=(E{subtotal_row}/$B${subtotal_row})*$B{tax_row}"
+    )
+    assert worksheet[f"F{tax_row}"].value == f"=SUM(C{tax_row}:E{tax_row})"
+
+    total_row = 21
+    assert worksheet[f"A{total_row}"].value == "Total"
+    assert worksheet[f"B{total_row}"].value == f"=SUM(B{subtotal_row}:B{tax_row})"
+    assert worksheet[f"C{total_row}"].value == f"=SUM(C{subtotal_row}:C{tax_row})"
+    assert worksheet[f"D{total_row}"].value == f"=SUM(D{subtotal_row}:D{tax_row})"
+    assert worksheet[f"E{total_row}"].value == f"=SUM(E{subtotal_row}:E{tax_row})"
+    assert worksheet[f"F{total_row}"].value == f"=SUM(C{total_row}:E{total_row})"