"""Kontostände (in Kontowährung) und Umrechnung in die Hauptwährung.

Saldo = Anfangssaldo + Einnahmen - Ausgaben - Transfers-raus + Transfers-rein.
Transfers werden in der jeweiligen Kontowährung verrechnet (bei währungsüber-
greifenden Transfers am Zielkonto der gutgeschriebene Betrag ``to_amount_cents``).
"""

from datetime import date

from sqlalchemy import func
from sqlalchemy.orm import Session

from ..models import Account, Transaction, TxnType
from . import currency


def _sum(query) -> int:
    return int(query.scalar() or 0)


def account_balance_cents(db: Session, account: Account) -> int:
    income = _sum(
        db.query(func.sum(Transaction.amount_cents)).filter(
            Transaction.account_id == account.id, Transaction.type == TxnType.income
        )
    )
    expense = _sum(
        db.query(func.sum(Transaction.amount_cents)).filter(
            Transaction.account_id == account.id, Transaction.type == TxnType.expense
        )
    )
    transfer_out = _sum(
        db.query(func.sum(Transaction.amount_cents)).filter(
            Transaction.account_id == account.id, Transaction.type == TxnType.transfer
        )
    )
    transfer_in = _sum(
        db.query(
            func.sum(func.coalesce(Transaction.to_amount_cents, Transaction.amount_cents))
        ).filter(
            Transaction.to_account_id == account.id, Transaction.type == TxnType.transfer
        )
    )
    return account.opening_balance_cents + income - expense - transfer_out + transfer_in


def account_balance_base_cents(
    db: Session, account: Account, base_currency: str, on: date
) -> int:
    """Saldo in die Hauptwährung umgerechnet (aktueller Kurs). Fällt auf den
    nativen Wert zurück, wenn kein Kurs verfügbar ist."""
    native = account_balance_cents(db, account)
    if account.currency == base_currency:
        return native
    conv = currency.convert(db, native, account.currency, base_currency, on)
    return conv if conv is not None else native


def net_worth_cents(db: Session, accounts: list[Account], base_currency: str, on: date) -> int:
    return sum(
        account_balance_base_cents(db, a, base_currency, on)
        for a in accounts
        if not a.is_archived
    )