from enum import Enum


class ConstructionAgeBand(Enum):
    """A landlord-supplied construction age band, as resolved by the
    landlord-description-overrides context.

    Each member's value is the RdSAP England-&-Wales age-band **letter code**
    (A..M) the calculator's U-value cascades read from
    `SapBuildingPart.construction_age_band` — the same representation the gov-EPC
    API lodges. The construction-age-band Simulation Overlay
    (``domain/epc/property_overlays/construction_age_band_overlay.py``) sets the
    letter directly, so these values MUST stay the bare letter codes. Member
    names carry the year ranges for readability. ``UNKNOWN`` covers values the
    classifier cannot resolve (it leaves the lodged cert's age band untouched).
    """

    A_BEFORE_1900 = "A"
    B_1900_1929 = "B"
    C_1930_1949 = "C"
    D_1950_1966 = "D"
    E_1967_1975 = "E"
    F_1976_1982 = "F"
    G_1983_1990 = "G"
    H_1991_1995 = "H"
    I_1996_2002 = "I"
    J_2003_2006 = "J"
    K_2007_2011 = "K"
    L_2012_2022 = "L"
    M_2023_ONWARDS = "M"
    UNKNOWN = "Unknown"