"""Tests for the PCDB Table 172 (postcode weather) lookup module.

The lookup parses pcdb10.dat at first use and caches it as a
`{(area, district): PostcodeClimate}` dict. Callers invoke
`postcode_climate(postcode_str)` to obtain the per-district monthly
weather (temp, wind, solar) used by the demand-side cascade for EPC
emissions / primary energy.

Reference: BRE PCDB pcdb10.dat Table 172 (Postcodes).
"""
from __future__ import annotations

from domain.sap10_calculator.tables.pcdb.postcode_weather import (
    PostcodeClimate,
    postcode_climate,
)


def test_postcode_climate_returns_bd3_record() -> None:
    """Bradford district 3 (BD3) is the postcode for Elmhurst fixture 000474.
    Verified against U985 Block 2 wind speed (5.2, 5.2, 5.0, ..., 4.9) which
    is the EPC demand-cascade climate."""
    # Arrange
    # Act
    climate = postcode_climate("bd3 8aq")

    # Assert
    assert climate is not None
    assert climate.area == "BD"
    assert climate.district == 3
    assert climate.region == 11  # East Pennines
    # Block 2 of U985-0001-000474.txt: Wind speed
    # 5.2 5.2 5.0 4.4 4.3 3.9 4.0 3.8 4.1 4.4 4.6 4.9 (22)
    assert climate.monthly_wind_speed_m_per_s == (
        5.2, 5.2, 5.0, 4.4, 4.3, 3.9, 4.0, 3.8, 4.1, 4.4, 4.6, 4.9,
    )


def test_postcode_climate_parses_mixed_case() -> None:
    """Postcode is normalised to upper-case so "bd3 8aq" and "BD3 8AQ" hit
    the same record."""
    # Arrange
    lower = "bd4 7jr"
    upper = "BD4 7JR"

    # Act
    a = postcode_climate(lower)
    b = postcode_climate(upper)

    # Assert
    assert a is not None
    assert b is not None
    assert a == b


def test_postcode_climate_handles_two_digit_district() -> None:
    """Two-digit district numbers ("BD19") parse correctly — the digit
    consumption walks past the alpha prefix and grabs all digits."""
    # Arrange
    # Act
    climate = postcode_climate("bd19 3tf")

    # Assert
    assert climate is not None
    assert climate.area == "BD"
    assert climate.district == 19


def test_postcode_climate_returns_none_for_unknown_postcode() -> None:
    """Postcodes with no Table 172 entry (e.g. synthetic test data) yield
    None so callers can fall back to UK-average climate."""
    # Arrange
    # Act
    result = postcode_climate("ZZ99 9ZZ")

    # Assert
    assert result is None


def test_postcode_climate_returns_none_for_malformed() -> None:
    """Empty or letter-only postcodes return None rather than raising."""
    # Arrange
    # Act
    # Assert
    assert postcode_climate("") is None
    assert postcode_climate(None) is None
    assert postcode_climate("XYZ") is None