import re
from typing import Optional

from .energy_climate_change_levy_data import CCL_RATES, CCL_RATES_HISTORY, CclRate
from .energy_climate_change_levy_types import CclCommodity, ClimateChangeLevy
from .math_round_div import RoundingMode, round_div
from .money_amount import money

ISO_DATE = re.compile(r"[0-9]{4}-[0-9]{2}-[0-9]{2}")
# quantity (thousandths of a unit) x rate (thousandths of a penny) is in
# millionths of a penny.
DIVISOR = 1_000_000
MAX_SAFE = 9007199254740991


def climate_change_levy(
    commodity: CclCommodity, quantity: int, on_date: str, qualifying_use: bool, mode: RoundingMode
) -> ClimateChangeLevy:
    """The Climate Change Levy on one supply, at the main rate in force on
    ``on_date``. A qualifying-use supply (domestic, charity non-business or
    de minimis) is outside the levy and comes back excluded, with a zero levy.
    """
    if not isinstance(on_date, str) or not ISO_DATE.fullmatch(on_date):
        raise ValueError('onDate must be an ISO date (YYYY-MM-DD), received "%s"' % (on_date,))
    if not isinstance(quantity, int) or isinstance(quantity, bool) or quantity < 0:
        raise ValueError(
            "quantity must be a whole number of thousandths of a unit, 0 or more, received %s" % (quantity,)
        )
    if not any(r.commodity == commodity for r in CCL_RATES):
        raise ValueError('unknown commodity "%s": expected electricity, gas, lpg or other' % (commodity,))
    best: Optional[CclRate] = None
    for r in CCL_RATES:
        if r.commodity != commodity or on_date < r.valid_from:
            continue
        if r.valid_to is not None and on_date > r.valid_to:
            continue
        if best is None or r.valid_from > best.valid_from:
            best = r
    if best is None:
        # A pruned build must not answer an old date with a newer rate.
        if CCL_RATES_HISTORY != "full":
            earliest = None
            for r in CCL_RATES:
                if r.commodity == commodity and (earliest is None or r.valid_from < earliest):
                    earliest = r.valid_from
            if earliest is not None and on_date < earliest:
                raise ValueError(
                    "no Climate Change Levy rate for %s on %s: this build was installed with history=%s, "
                    "so it only carries rates from %s. Reinstall with history=full for older supplies."
                    % (commodity, on_date, CCL_RATES_HISTORY, earliest)
                )
        raise ValueError("no Climate Change Levy rate for %s on %s" % (commodity, on_date))
    pence = 0
    if not qualifying_use:
        product = quantity * best.rate
        if product > MAX_SAFE:
            raise ValueError("levy too large to calculate exactly")
        pence = round_div(product, DIVISOR, mode)
    return ClimateChangeLevy(
        commodity=commodity,
        unit=best.unit,
        rate=best.rate,
        excluded=bool(qualifying_use),
        levy=money(pence, "GBP"),
        valid_from=best.valid_from,
        valid_to=best.valid_to,
    )