"""Billing use cases.

Design rule, stated once and enforced here: **the internal usage ledger is the
source of truth.** A payment provider only moves money; it never decides what a
tenant owes. That is why ``summary`` computes totals from ``UsageLedgerRepository``
and not from any external invoice.

Credit is spent, not checked-then-spent: the debit is a single adjustment, so two
concurrent runs cannot both pass a stale affordability check.
"""

from __future__ import annotations

from datetime import datetime

from app.application.ports import PaymentProviderPort
from app.application.ports.realtime import emit_wallet_changed
from app.core.errors import NotFoundError, PermissionDeniedError, ValidationError
from app.domain.billing.models import (
    CreditKind,
    CreditWallet,
    Invoice,
    Payment,
    PaymentStatus,
    Subscription,
)
from app.infrastructure.repositories.audit import UsageLedgerRepository
from app.infrastructure.repositories.billing import (
    CreditWalletRepository,
    InvoiceRepository,
    PaymentRepository,
    PlanRepository,
    SubscriptionRepository,
)
from app.infrastructure.repositories.credit import CreditLedgerRepository

#: A tenant may not buy an arbitrary amount of credit in one action.
MIN_TOPUP = 1.0
MAX_TOPUP = 10_000.0


class BillingService:
    def __init__(
        self,
        *,
        wallets: CreditWalletRepository,
        invoices: InvoiceRepository,
        payments: PaymentRepository,
        plans: PlanRepository,
        subscriptions: SubscriptionRepository,
        ledger: UsageLedgerRepository,
        payment_provider: PaymentProviderPort,
    ) -> None:
        self.wallets = wallets
        self.invoices = invoices
        self.payments = payments
        self.plans = plans
        self.subscriptions = subscriptions
        self.ledger = ledger
        self.payment_provider = payment_provider
        # Settled payments are credited through the credit ledger, in the wallets' session.
        self.credit_ledger = CreditLedgerRepository(wallets.session)

    # -- reads ---------------------------------------------------------------

    async def wallet_for(self, organization_id: str) -> CreditWallet:
        return await self.wallets.ensure(organization_id)

    async def summary(
        self,
        *,
        organization_id: str,
        since: datetime | None = None,
        until: datetime | None = None,
    ) -> dict:
        wallet = await self.wallets.ensure(organization_id)
        breakdown = await self.ledger.breakdown(
            organization_id=organization_id, since=since, until=until
        )
        return {
            "balance": wallet.balance,
            "currency": wallet.currency,
            "low_balance": wallet.is_low,
            "low_balance_threshold": wallet.low_balance_threshold,
            "total_spend": breakdown.total_price,
            "by_unit": breakdown.by_unit,
            "by_employee": breakdown.by_employee,
            "by_project": breakdown.by_project,
        }

    async def list_usage_events(
        self, *, organization_id: str, limit: int = 100, offset: int = 0
    ) -> list:
        return await self.ledger.list_events(
            organization_id=organization_id, limit=limit, offset=offset
        )

    async def list_invoices(self, organization_id: str) -> list[Invoice]:
        return await self.invoices.list_for_org(organization_id)

    async def list_payments(self, organization_id: str) -> list[Payment]:
        return await self.payments.list_for_org(organization_id)

    async def current_subscription(self, organization_id: str) -> Subscription | None:
        return await self.subscriptions.get_for_org(organization_id)

    # -- writes --------------------------------------------------------------

    async def add_credit(
        self, *, organization_id: str, amount: float, allow_negative: bool = False
    ) -> CreditWallet:
        """Grant (or, for a platform owner, claw back) credit.

        Superseded by the owner-only ``CreditService``, which writes the credit ledger.

        ``allow_negative`` is reserved for the platform owner console; an org
        admin may only ever add credit.
        """
        if amount == 0:
            raise ValidationError("مقدار اعتبار نمی‌تواند صفر باشد.")
        if amount < 0 and not allow_negative:
            raise PermissionDeniedError("کسر اعتبار فقط توسط مالک سامانه انجام می‌شود.")
        if not allow_negative and amount > MAX_TOPUP:
            raise ValidationError(f"حداکثر افزایش اعتبار در هر عملیات {MAX_TOPUP} است.")

        wallet = await self.wallets.adjust(organization_id=organization_id, delta=amount)
        if wallet.balance < 0:
            # Refuse to leave a wallet in debt; undo and surface the conflict.
            await self.wallets.adjust(organization_id=organization_id, delta=-amount)
            raise ValidationError("اعتبار کافی برای این کسر وجود ندارد.")
        # Live push: the sidebar credit badge and the billing page follow the
        # wallet as it moves, whoever moved it.
        await emit_wallet_changed(
            organization_id=organization_id, balance=wallet.balance
        )
        return wallet

    async def start_checkout(
        self,
        *,
        organization_id: str,
        amount: float,
        success_url: str,
        cancel_url: str,
    ) -> tuple[Payment, str]:
        """Create a pending payment plus the provider's hosted checkout URL."""
        if amount < MIN_TOPUP:
            raise ValidationError(f"حداقل مبلغ شارژ {MIN_TOPUP} است.")
        if amount > MAX_TOPUP:
            raise ValidationError(f"حداکثر مبلغ شارژ {MAX_TOPUP} است.")

        wallet = await self.wallets.ensure(organization_id)
        payment = await self.payments.create(
            Payment(
                organization_id=organization_id,
                amount=amount,
                status=PaymentStatus.PENDING,
                provider="mock",
            )
        )
        session = await self.payment_provider.create_checkout(
            organization_id=organization_id,
            amount=amount,
            currency=wallet.currency,
            success_url=success_url,
            cancel_url=cancel_url,
        )
        updated = await self.payments.set_status(
            payment.id, PaymentStatus.PENDING, external_id=session.external_id
        )
        return (updated or payment), session.url

    async def settle_payment(
        self, *, organization_id: str, payment_id: str, succeeded: bool
    ) -> Payment:
        """Mark a payment final and credit the wallet when it succeeded.

        This is the only path that turns money into credit, so it is idempotent
        with respect to status: a payment that is already final is returned
        untouched rather than credited twice. The credit is one ``adjustment`` row in
        the credit ledger, written in this session, so it shows in the owner's credit
        history and updates ``last_credit_at``.
        """
        payment = next(
            (p for p in await self.payments.list_for_org(organization_id) if p.id == payment_id),
            None,
        )
        if payment is None:
            raise NotFoundError("پرداخت یافت نشد.")
        if payment.status != PaymentStatus.PENDING:
            return payment

        if succeeded:
            credit = await self.credit_ledger.apply(
                organization_id=organization_id,
                amount=payment.amount,
                kind=CreditKind.ADJUSTMENT,
                reason="billing/settle-payment",
            )
            final = await self.payments.set_status(payment_id, PaymentStatus.SUCCEEDED)
            await emit_wallet_changed(
                organization_id=organization_id, balance=credit.balance_after
            )
        else:
            final = await self.payments.set_status(payment_id, PaymentStatus.FAILED)
        return final or payment