"""Regression tests from real-world invoices (anonymized).

Every test in this module originated from a production bug. When a new real
invoice reveals a service bug: anonymize the invoice XML into
tests/fixtures/real/, verify it contains no real-world data, and add a test
here that locks in the correct behavior.
"""

from io import BytesIO
from pathlib import Path

import pytest

from pypdf import PdfWriter

from src.extractor import extract_zugferd
from src.models import ValidateRequest
from src.validator import validate_invoice

REAL_FIXTURES = Path(__file__).parent / "fixtures" / "real"
ALL_CHECKS = ["pflichtfelder", "betraege", "ustid", "pdf_abgleich"]


def _pdf_with_attachment(xml_bytes: bytes) -> bytes:
    """Wrap invoice XML in a minimal PDF (no visual content)."""
    writer = PdfWriter()
    writer.add_blank_page(width=72, height=72)
    writer.add_attachment("factur-x.xml", xml_bytes)
    output = BytesIO()
    writer.write(output)
    return output.getvalue()


class TestFcTaxNumberBasisQuantityInvoice:
    """Anonymized EXTENDED invoice: FC-only tax registration (no VAT ID),
    unit price with basis quantity 100, spaced buyer VAT ID, seller email
    in DefinedTradeContact.

    Regressions locked in (found 2026-09 on a real workshop invoice):
    supplier tax_number never extracted, unit price off by factor 100,
    spaced VAT ID rejected as invalid format, contact email dropped.
    """

    XML_PATH = REAL_FIXTURES / "extended_fc_steuernummer_basisqty.xml"

    def test_extraction(self) -> None:
        pdf_bytes = _pdf_with_attachment(self.XML_PATH.read_bytes())
        result = extract_zugferd(pdf_bytes)

        assert result.is_zugferd is True
        data = result.xml_data

        assert data.invoice_number == "4711"
        assert data.supplier.tax_number == "1112223334444"
        assert data.supplier.vat_id is None
        assert data.supplier.email == "rechnung@beispielwerkstatt.example"
        assert data.buyer.vat_id == "DE 123 456 789"

        assert len(data.line_items) == 2
        first, second = data.line_items
        assert first.quantity == 140
        assert first.unit_price == pytest.approx(0.7585)
        assert first.line_total == pytest.approx(106.19)
        assert second.quantity == 50
        assert second.unit_price == pytest.approx(0.7585)
        assert second.line_total == pytest.approx(37.93)

        assert data.totals.net == pytest.approx(144.12)
        assert data.totals.vat_total == pytest.approx(10.09)
        assert data.totals.gross == pytest.approx(154.21)

    def test_validation_all_checks_pass(self) -> None:
        pdf_bytes = _pdf_with_attachment(self.XML_PATH.read_bytes())
        result = extract_zugferd(pdf_bytes)

        request = ValidateRequest(
            xml_data=result.xml_data.model_dump(),
            pdf_text=result.pdf_text,
            checks=ALL_CHECKS,
        )
        validation = validate_invoice(request)

        assert validation.is_valid is True
        assert validation.errors == []