"""SAP 10.2 (14-03-2025 amendment) Table 12 value-correctness tests.

Locks the CO2 emission factors and primary energy factors against the
published SAP 10.2 specification at
`domain/sap10_calculator/docs/specs/sap-10-2-full-specification-2025-03-14.pdf`, page 189.

The price column (`UNIT_PRICE_P_PER_KWH`) was already SAP 10.2-correct
when the calculator code was authored; the CO2 column was authored
against SAP 10.3 (13-01-2026) values by mistake. ADR-0010 retargets the
calculator to SAP 10.2 (14-03-2025) until the corpus migrates, so the
CO2 column was corrected during P2.4. These tests lock the corrected
values.
"""
from __future__ import annotations

import pytest

from domain.sap10_calculator.tables.table_12 import (
    co2_factor_kg_per_kwh,
    primary_energy_factor,
    unit_price_p_per_kwh,
)


@pytest.mark.parametrize(
    "fuel_code, expected_co2_kg_per_kwh, fuel_name",
    [
        # Most-common cases first — gas + electricity dominate the corpus.
        (1, 0.210, "mains gas"),
        (30, 0.136, "standard tariff electricity"),
        # Sanity: heating oil is unchanged between SAP 10.2 and SAP 10.3.
        (4, 0.298, "heating oil"),
        # Off-peak electricity tariffs all share the annual-average factor.
        (31, 0.136, "7-hour low rate electricity"),
        (35, 0.136, "24-hour heating tariff"),
        # Bulk LPG — SAP 10.2 says 0.241 (file had 0.24 rounded).
        (2, 0.241, "bulk LPG"),
    ],
)
def test_co2_factor_matches_sap_10_2_table_12(
    fuel_code: int, expected_co2_kg_per_kwh: float, fuel_name: str
) -> None:
    # Arrange — table_12.co2_factor_kg_per_kwh is the only CO2 source
    # in the calculator pipeline (see cert_to_inputs._co2_factor_kg_per_kwh).
    # Act
    actual = co2_factor_kg_per_kwh(fuel_code)

    # Assert
    assert actual == pytest.approx(expected_co2_kg_per_kwh, abs=1e-6), (
        f"{fuel_name} (code {fuel_code}): expected SAP 10.2 CO2 factor "
        f"{expected_co2_kg_per_kwh}, got {actual}. See SAP 10.2 PDF p.189."
    )


def test_default_co2_factor_is_mains_gas_baseline() -> None:
    # Arrange — unknown fuel codes fall back to mains gas (the SAP 10.2
    # convention; see table_12._DEFAULT_CO2_KG_PER_KWH).
    # Act
    actual = co2_factor_kg_per_kwh(None)

    # Assert
    assert actual == pytest.approx(0.210, abs=1e-6)


def test_mains_gas_unit_price_unchanged_at_sap_10_2_value() -> None:
    # Arrange — sanity: prices were already SAP 10.2-correct before P2.4.
    # This locks that we didn't accidentally regress them while fixing CO2.
    # Act
    actual = unit_price_p_per_kwh(1)

    # Assert
    assert actual == pytest.approx(3.64, abs=1e-6)


def test_standard_electricity_primary_energy_factor_unchanged() -> None:
    # Arrange — sanity: PE factor for electricity is 1.501 in both SAP
    # 10.2 and SAP 10.3; locks that P2.4 didn't touch the PEF column.
    # Act
    actual = primary_energy_factor(30)

    # Assert
    assert actual == pytest.approx(1.501, abs=1e-6)