from typing import Dict, List, Sequence

from .legal_time_billing_types import FeeEarnerRate, FeeEarnerTotal, TimeBill, TimeBillLine, TimeEntry
from .math_round_div import round_div
from .math_round_div_types import RoundingMode
from .money_amount import Money, money
from .time_round_to_increment import round_to_increment


def time_billing(entries: Sequence[TimeEntry], rates: Sequence[FeeEarnerRate], unit_minutes: int, mode: RoundingMode) -> TimeBill:
    """Price time entries in whole billing units at each fee earner's hourly rate."""
    if len(rates) == 0:
        raise ValueError("rates must not be empty")
    currency = rates[0].hourly_rate.currency
    card: Dict[str, Money] = {}
    for rate in rates:
        if rate.fee_earner in card:
            raise ValueError('duplicate rate for fee earner "%s"' % (rate.fee_earner,))
        if rate.hourly_rate.currency != currency:
            raise ValueError("currency mismatch: %s and %s" % (currency, rate.hourly_rate.currency))
        if rate.hourly_rate.minor < 0:
            raise ValueError("hourly rates must not be negative, received %s" % (rate.hourly_rate.minor,))
        card[rate.fee_earner] = rate.hourly_rate

    lines: List[TimeBillLine] = []
    order: List[str] = []
    totals: Dict[str, List[int]] = {}
    units = 0
    billed_minutes = 0
    total = 0
    for entry in entries:
        hourly_rate = card.get(entry.fee_earner)
        if hourly_rate is None:
            raise ValueError('no rate for fee earner "%s"' % (entry.fee_earner,))
        # Rounded per entry: seven 1-minute emails are seven units, not two.
        billed = round_to_increment(entry.minutes, unit_minutes, mode)
        line_units = billed // unit_minutes
        fee = round_div(billed * hourly_rate.minor, 60, "half-up")
        lines.append(
            TimeBillLine(
                fee_earner=entry.fee_earner,
                minutes=entry.minutes,
                billed_minutes=billed,
                units=line_units,
                hourly_rate=hourly_rate,
                fee=money(fee, currency),
            )
        )
        if entry.fee_earner not in totals:
            totals[entry.fee_earner] = [0, 0]
            order.append(entry.fee_earner)
        totals[entry.fee_earner][0] += line_units
        totals[entry.fee_earner][1] += fee
        units += line_units
        billed_minutes += billed
        total += fee
    by_fee_earner = [FeeEarnerTotal(fee_earner=c, units=totals[c][0], fee=money(totals[c][1], currency)) for c in order]
    return TimeBill(lines=lines, by_fee_earner=by_fee_earner, units=units, billed_minutes=billed_minutes, total=money(total, currency))