"""Scheduled billing lifecycle jobs (``ENTITLEMENTS.md`` §5).

All tasks iterate tenants explicitly and bind ``current_tenant`` per row; none
runs "globally" against tenant-owned tables (``TENANCY.md`` §7).
"""

from __future__ import annotations

import logging
from datetime import timedelta

from celery import shared_task
from django.utils import timezone

from infrasynth.shared.enums import EntitlementStatus, SubscriptionStatus
from infrasynth.shared.settings_utils import get_setting
from infrasynth.tenancy.context import tenant_context

logger = logging.getLogger(__name__)


def _with_tenant(tenant):
    return tenant_context(tenant)


@shared_task(name="infrasynth.billing.sync_subscriptions")
def sync_subscriptions():
    """Pulls the latest state from each active gateway subscription."""
    from .models import Subscription
    from .services import BillingService

    service = BillingService()
    synced = 0
    subs = Subscription.all_objects.filter(
        status__in=[
            SubscriptionStatus.ACTIVE,
            SubscriptionStatus.PAST_DUE,
            SubscriptionStatus.TRIALING,
        ],
        gateway__isnull=False,
    ).select_related("gateway", "entitlement")
    for sub in subs:
        try:
            with _with_tenant(sub.tenant):
                service.sync_subscription(sub)
            synced += 1
        except Exception:  # noqa: BLE001
            logger.exception("Failed to sync subscription %s", sub.pk)
    return synced


@shared_task(name="infrasynth.billing.advance_entitlement_lifecycle")
def advance_entitlement_lifecycle():
    """Moves past-due entitlements to suspended once the grace window elapses."""
    from infrasynth.tenancy.models import Tenant

    from .models import Entitlement
    from .services import BillingService

    grace_days = int(get_setting("INFRASYNTH_BILLING", "GRACE_PERIOD_DAYS", 5))
    max_retries = int(get_setting("INFRASYNTH_BILLING", "MAX_RETRY_FAILED_PAYMENTS", 3))
    service = BillingService()
    suspended = 0

    candidates = Entitlement.all_objects.filter(
        status__in=[EntitlementStatus.PAST_DUE, EntitlementStatus.GRACE]
    ).select_related("tenant", "app")
    now = timezone.now()
    for entitlement in candidates:
        metadata = dict(entitlement.metadata or {})
        since_raw = metadata.get("past_due_since")
        if not since_raw:
            metadata["past_due_since"] = now.isoformat()
            entitlement.metadata = metadata
            entitlement.save(update_fields=["metadata"])
            continue
        from datetime import datetime

        try:
            since = datetime.fromisoformat(since_raw)
        except ValueError:
            continue
        attempts = int(metadata.get("failed_payments", 0))
        if now - since < timedelta(days=grace_days) and attempts < max_retries:
            continue
        with _with_tenant(entitlement.tenant):
            service.suspend_entitlement(entitlement)
        tenant = entitlement.tenant
        if tenant.status != Tenant.Status.SUSPENDED:
            tenant.status = Tenant.Status.SUSPENDED
            tenant.suspended_at = now
            tenant.save(update_fields=["status", "suspended_at"])
        suspended += 1
    return suspended


@shared_task(name="infrasynth.billing.expire_entitlements")
def expire_entitlements():
    """Expires cancelled-at-period-end entitlements whose period has ended."""
    from .models import Entitlement
    from .services import EntitlementService

    now = timezone.now()
    expired = 0
    candidates = Entitlement.all_objects.filter(
        status__in=[EntitlementStatus.ACTIVE, EntitlementStatus.TRIALING, EntitlementStatus.CANCELLED]
    ).select_related("tenant", "app")
    for entitlement in candidates:
        if not entitlement.cancel_at_period_end:
            continue
        if entitlement.current_period_end and entitlement.current_period_end > now:
            continue
        entitlement.status = EntitlementStatus.EXPIRED
        entitlement.save(update_fields=["status"])
        with _with_tenant(entitlement.tenant):
            EntitlementService().invalidate(entitlement.tenant, entitlement.app.slug)
        expired += 1
    return expired


@shared_task(name="infrasynth.billing.generate_renewal_invoices")
def generate_renewal_invoices():
    """Creates an open invoice ahead of each subscription renewal."""
    from django.db.models import Q

    from infrasynth.shared.enums import InvoiceStatus

    from .models import Invoice, Subscription
    from .services import BillingService

    days_ahead = int(get_setting("INFRASYNTH_BILLING", "INVOICE_GENERATION_DAYS_BEFORE_RENEWAL", 3))
    now = timezone.now()
    horizon = now + timedelta(days=days_ahead)
    service = BillingService()
    created = 0

    subs = Subscription.all_objects.filter(
        status=SubscriptionStatus.ACTIVE,
        current_period_end__lte=horizon,
        current_period_end__gt=now,
    ).select_related("tenant", "plan")
    for sub in subs:
        already = (
            Invoice.all_objects.filter(
                subscription=sub,
                status__in=[InvoiceStatus.DRAFT, InvoiceStatus.OPEN],
            )
            .filter(Q(due_date__isnull=True) | Q(due_date__gte=now))
            .exists()
        )
        if already:
            continue
        with _with_tenant(sub.tenant):
            service.generate_invoice(sub)
        created += 1
    return created