feat: add invoice row details, tax summary fields, and fix XML element ordering (#36)

- Fix: Nazwa element placement — Moved buyer name (Nazwa) inside
DaneIdentyfikacyjne where the FA(3) schema requires it, instead of
directly under Podmiot2
- Fix: XML element ordering — Moved Adres before Nazwa in Podmiot2, and
P_13/P_14 tax summary before P_15 in Fa
- Add: Invoice row fields — InvoiceRow now supports unit_of_measure
(P_8A), quantity (P_8B), unit_net_price (P_9A), net_value (P_11), and
delivery_date (P_6A)
- Add: Tax rate type safety — Replaced int tax field with TaxRate
literal type covering all 14 valid TStawkaPodatku enum values. Added
constants (TAX_23, TAX_0_WDT, TAX_NP_I, etc.)
- Add: OSS/IOSS support — InvoiceRow.tax_oss field (P_12_XII) for EU
consumer VAT rates not in the standard enum (e.g. 21%, 19%)
- Add: Tax summary — TaxSummary model with all P_13_*/P_14_* fields for
net/VAT totals per rate group, added as optional field on InvoiceData

Author: samupl

src/ksef/models/invoice.py

@@ -10,6 +10,52 @@
 from ksef.models.invoice_rows import InvoiceRows
 
 
+class TaxSummary(BaseModel):
+    """Tax summary totals per rate for the Fa section.
+
+    Each field pair (net + vat) corresponds to a tax rate group.
+    All fields are optional — only include those that apply to the invoice.
+    """
+
+    # 23% or 22% (standard rate)
+    net_standard: Optional[Decimal] = None  # P_13_1
+    vat_standard: Optional[Decimal] = None  # P_14_1
+    vat_standard_pln: Optional[Decimal] = None  # P_14_1W (foreign currency)
+
+    # 8% or 7% (first reduced rate)
+    net_reduced_1: Optional[Decimal] = None  # P_13_2
+    vat_reduced_1: Optional[Decimal] = None  # P_14_2
+    vat_reduced_1_pln: Optional[Decimal] = None  # P_14_2W
+
+    # 5% (second reduced rate)
+    net_reduced_2: Optional[Decimal] = None  # P_13_3
+    vat_reduced_2: Optional[Decimal] = None  # P_14_3
+    vat_reduced_2_pln: Optional[Decimal] = None  # P_14_3W
+
+    # 4% or 3% (taxi flat-rate)
+    net_flat_rate: Optional[Decimal] = None  # P_13_4
+    vat_flat_rate: Optional[Decimal] = None  # P_14_4
+
+    # OSS/IOSS procedure tax
+    net_oss: Optional[Decimal] = None
+    vat_oss: Optional[Decimal] = None
+
+    # 0% rates (no VAT fields — VAT is zero)
+    net_zero_domestic: Optional[Decimal] = None
+    net_zero_wdt: Optional[Decimal] = None
+    net_zero_export: Optional[Decimal] = None
+
+    # Exempt from tax
+    net_exempt: Optional[Decimal] = None
+
+    # Not subject to taxation
+    net_not_subject: Optional[Decimal] = None  # P_13_8 (np I)
+    net_not_subject_art100: Optional[Decimal] = None  # P_13_9 (np II)
+
+    # Reverse charge (oo)
+    net_reverse_charge: Optional[Decimal] = None  # P_13_10
+
+
 class IssuerIdentificationData(BaseModel):
     """
     Subject identification data.
@@ -132,6 +178,7 @@ class InvoiceData(BaseModel):
     issue_number: str
     sell_date: date
     total_amount: Decimal
+    tax_summary: Optional[TaxSummary] = None
     invoice_annotations: InvoiceAnnotations
     invoice_type: InvoiceType
     invoice_rows: InvoiceRows

src/ksef/models/invoice_rows.py

@@ -1,5 +1,6 @@
 """Models for individual invoice rows/positions."""
 
+from datetime import date
 from decimal import Decimal
 from typing import Literal, Optional, Sequence
 
@@ -45,9 +46,14 @@
 class InvoiceRow(BaseModel):
     """Single individual invoice position."""
 
-    name: str  # P_7, nazwa (rodzaj) towaru lub usługi
+    name: str  # P_7, product/service name
+    unit_of_measure: Optional[str] = None  # P_8A, unit of measure (e.g. "szt", "C62")
+    quantity: Optional[Decimal] = None  # P_8B, quantity
+    unit_net_price: Optional[Decimal] = None  # P_9A, unit net price
+    net_value: Optional[Decimal] = None  # P_11, net sales value
     tax: Optional[TaxRate] = None  # P_12, standard tax rate
     tax_oss: Optional[Decimal] = None  # P_12_XII, OSS/IOSS procedure tax rate (arbitrary %)
+    delivery_date: Optional[date] = None  # P_6A, delivery/service completion date
 
 
 class InvoiceRows(BaseModel):

src/ksef/xml_converters.py

@@ -171,19 +171,56 @@ def _build_invoice_data_annotations(invoice_data: ElementTree.Element, invoice:
         p_pmn.text = "1"
 
 
+def _build_tax_summary(parent: ElementTree.Element, invoice: Invoice) -> None:
+    """Emit P_13_*/P_14_* tax summary fields. Must be called before P_15."""
+    ts = invoice.invoice_data.tax_summary
+    if ts is None:
+        return
+
+    paired_fields = [
+        (ts.net_standard, "P_13_1", ts.vat_standard, "P_14_1", ts.vat_standard_pln, "P_14_1W"),
+        (ts.net_reduced_1, "P_13_2", ts.vat_reduced_1, "P_14_2", ts.vat_reduced_1_pln, "P_14_2W"),
+        (ts.net_reduced_2, "P_13_3", ts.vat_reduced_2, "P_14_3", ts.vat_reduced_2_pln, "P_14_3W"),
+        (ts.net_flat_rate, "P_13_4", ts.vat_flat_rate, "P_14_4", None, None),
+        (ts.net_oss, "P_13_5", ts.vat_oss, "P_14_5", None, None),
+    ]
+    for net_val, net_tag, vat_val, vat_tag, vat_pln_val, vat_pln_tag in paired_fields:
+        if net_val is not None:
+            ElementTree.SubElement(parent, net_tag).text = str(net_val)
+        if vat_val is not None:
+            ElementTree.SubElement(parent, vat_tag).text = str(vat_val)
+        if vat_pln_val is not None and vat_pln_tag is not None:
+            ElementTree.SubElement(parent, vat_pln_tag).text = str(vat_pln_val)
+
+    net_only_fields = [
+        (ts.net_zero_domestic, "P_13_6_1"),
+        (ts.net_zero_wdt, "P_13_6_2"),
+        (ts.net_zero_export, "P_13_6_3"),
+        (ts.net_exempt, "P_13_7"),
+        (ts.net_not_subject, "P_13_8"),
+        (ts.net_not_subject_art100, "P_13_9"),
+        (ts.net_reverse_charge, "P_13_10"),
+    ]
+    for val, tag in net_only_fields:
+        if val is not None:
+            ElementTree.SubElement(parent, tag).text = str(val)
+
+
 def _build_invoice_data(root: ElementTree.Element, invoice: Invoice) -> None:
     invoice_data = ElementTree.SubElement(root, "Fa")
-    invoice_data_currency_code = ElementTree.SubElement(invoice_data, "KodWaluty")
-    invoice_data_issue_date = ElementTree.SubElement(invoice_data, "P_1")
-    invoice_data_invoice_number = ElementTree.SubElement(invoice_data, "P_2")
-    invoice_data_sell_date = ElementTree.SubElement(invoice_data, "P_6")
-    invoice_data_total_amount = ElementTree.SubElement(invoice_data, "P_15")
-
-    invoice_data_currency_code.text = invoice.invoice_data.currency_code
-    invoice_data_issue_date.text = invoice.invoice_data.issue_date.strftime("%Y-%m-%d")
-    invoice_data_invoice_number.text = invoice.invoice_data.issue_number
-    invoice_data_sell_date.text = invoice.invoice_data.sell_date.strftime("%Y-%m-%d")
-    invoice_data_total_amount.text = str(invoice.invoice_data.total_amount)
+
+    ElementTree.SubElement(invoice_data, "KodWaluty").text = invoice.invoice_data.currency_code
+    ElementTree.SubElement(invoice_data, "P_1").text = invoice.invoice_data.issue_date.strftime(
+        "%Y-%m-%d"
+    )
+    ElementTree.SubElement(invoice_data, "P_2").text = invoice.invoice_data.issue_number
+    ElementTree.SubElement(invoice_data, "P_6").text = invoice.invoice_data.sell_date.strftime(
+        "%Y-%m-%d"
+    )
+
+    _build_tax_summary(invoice_data, invoice)
+
+    ElementTree.SubElement(invoice_data, "P_15").text = str(invoice.invoice_data.total_amount)
 
     _build_invoice_data_annotations(invoice_data, invoice)
 
@@ -193,18 +230,39 @@ def _build_invoice_data(root: ElementTree.Element, invoice: Invoice) -> None:
 
     for index, row in enumerate(invoice.invoice_data.invoice_rows.rows, start=1):
         invoice_data_row = ElementTree.SubElement(invoice_data, "FaWiersz")
-        invoice_data_row_number = ElementTree.SubElement(invoice_data_row, "NrWierszaFa")
-        invoice_data_row_name = ElementTree.SubElement(invoice_data_row, "P_7")
 
-        invoice_data_row_number.text = str(index)
-        invoice_data_row_name.text = row.name
+        nr = ElementTree.SubElement(invoice_data_row, "NrWierszaFa")
+        nr.text = str(index)
+
+        if row.delivery_date is not None:
+            p_6a = ElementTree.SubElement(invoice_data_row, "P_6A")
+            p_6a.text = row.delivery_date.strftime("%Y-%m-%d")
+
+        p_7 = ElementTree.SubElement(invoice_data_row, "P_7")
+        p_7.text = row.name
+
+        if row.unit_of_measure is not None:
+            p_8a = ElementTree.SubElement(invoice_data_row, "P_8A")
+            p_8a.text = row.unit_of_measure
+
+        if row.quantity is not None:
+            p_8b = ElementTree.SubElement(invoice_data_row, "P_8B")
+            p_8b.text = str(row.quantity)
+
+        if row.unit_net_price is not None:
+            p_9a = ElementTree.SubElement(invoice_data_row, "P_9A")
+            p_9a.text = str(row.unit_net_price)
+
+        if row.net_value is not None:
+            p_11 = ElementTree.SubElement(invoice_data_row, "P_11")
+            p_11.text = str(row.net_value)
 
         if row.tax_oss is not None:
-            invoice_data_row_tax_oss = ElementTree.SubElement(invoice_data_row, "P_12_XII")
-            invoice_data_row_tax_oss.text = str(row.tax_oss)
+            p_12_xii = ElementTree.SubElement(invoice_data_row, "P_12_XII")
+            p_12_xii.text = str(row.tax_oss)
         elif row.tax is not None:
-            invoice_data_row_tax_rate = ElementTree.SubElement(invoice_data_row, "P_12")
-            invoice_data_row_tax_rate.text = str(row.tax)
+            p_12 = ElementTree.SubElement(invoice_data_row, "P_12")
+            p_12.text = str(row.tax)
 
 
 def convert_invoice_to_xml(invoice: Invoice, invoicing_software_name: str = "python-ksef") -> bytes: