from __future__ import annotations

from dataclasses import replace
from decimal import Decimal

from broker_sync.fx import FxCache, convert_to_gbp
from broker_sync.models import Activity, ActivityType

_QTY_PRICE_TYPES = {ActivityType.BUY, ActivityType.SELL}


def normalise_to_gbp(activity: Activity, *, cache: FxCache) -> Activity:
    """Return a copy of `activity` with amount_gbp/fx_rate_gbp/fx_rate_source set.

    Two cases:
    - BUY/SELL: amount_gbp = quantity * unit_price * rate.
    - Everything else (DIVIDEND/DEPOSIT/FEE/...): amount_gbp = amount * rate.

    Source is always the cache's source tag (ECB_LIVE or HMRC_MONTHLY).
    """
    on_date = activity.date.date()
    if activity.activity_type in _QTY_PRICE_TYPES:
        assert activity.quantity is not None and activity.unit_price is not None
        native_total: Decimal = activity.quantity * activity.unit_price
    else:
        assert activity.amount is not None
        native_total = activity.amount

    amount_gbp, rate, source = convert_to_gbp(native_total, activity.currency, on_date, cache=cache)
    return replace(
        activity,
        amount_gbp=amount_gbp,
        fx_rate_gbp=rate,
        fx_rate_source=source,
    )