"""Unit tests for rec/districts.py and services/district_service.py."""
from rec.districts import get_districts, get_district_by_name
from services.district_service import get_all_districts, get_district_names, validate_districts


class TestGetDistricts:
    def test_returns_non_empty_dict(self) -> None:
        districts = get_districts()
        assert isinstance(districts, dict)
        assert len(districts) > 0

    def test_values_start_with_region_prefix(self) -> None:
        for name, region_id in get_districts().items():
            assert region_id.startswith("REGION^"), (
                f"District '{name}' has value '{region_id}' that doesn't start with REGION^"
            )

    def test_contains_expected_london_boroughs(self) -> None:
        districts = get_districts()
        for borough in ("Camden", "Westminster", "Hackney"):
            assert borough in districts, f"Expected borough '{borough}' not found"


class TestGetDistrictByName:
    def test_valid_name_returns_region_id(self) -> None:
        result = get_district_by_name("Camden")
        assert result == "REGION^93941"

    def test_invalid_name_returns_none(self) -> None:
        result = get_district_by_name("Nonexistent District")
        assert result is None


class TestGetDistrictNames:
    def test_returns_list_matching_dict_keys(self) -> None:
        names = get_district_names()
        assert isinstance(names, list)
        assert names == list(get_districts().keys())


class TestGetAllDistricts:
    def test_returns_same_as_get_districts(self) -> None:
        assert get_all_districts() == get_districts()


class TestValidateDistricts:
    def test_all_valid_returns_empty_list(self) -> None:
        result = validate_districts(["Camden", "Westminster", "Hackney"])
        assert result == []

    def test_some_invalid_returns_invalid_ones(self) -> None:
        result = validate_districts(["Camden", "Faketown", "Westminster", "Nowhere"])
        assert result == ["Faketown", "Nowhere"]

    def test_all_invalid_returns_all(self) -> None:
        invalid = ["Faketown", "Nowhere", "Neverland"]
        result = validate_districts(invalid)
        assert result == invalid

    def test_empty_list_returns_empty_list(self) -> None:
        result = validate_districts([])
        assert result == []