"""
app/billing/webhooks.py
------------------------
Stripe webhook event dispatcher. Receives a verified stripe.Event object
(signature already checked by the route) and mutates the control DB accordingly.

Each event handler is self-contained and catches its own exceptions so that
one malformed event cannot abort processing of subsequent events in the same
delivery batch.

Public API:
  handle_event(event) -> None
"""

import logging
from datetime import datetime, timezone

logger = logging.getLogger(__name__)

# Maps Stripe subscription status strings to our internal subscription_status values.
_STRIPE_STATUS_MAP = {
    'trialing':   'trial',
    'active':     'active',
    'past_due':   'past_due',
    'canceled':   'cancelled',  # Stripe uses single 'l'
    'cancelled':  'cancelled',
    'incomplete': 'past_due',
    'incomplete_expired': 'cancelled',
    'unpaid':     'past_due',
    'paused':     'past_due',
}


def _ts_to_dt(ts) -> datetime | None:
    """Convert a Unix timestamp (int or None) to a naive UTC datetime."""
    if ts is None:
        return None
    return datetime.fromtimestamp(int(ts), tz=timezone.utc).replace(tzinfo=None)


def _lookup_tenant_by_customer(stripe_customer_id: str):
    """Return the Tenant ORM object (within an open session) or None."""
    from control.models import Tenant
    return None  # placeholder — caller must query within a control_session


def _get_base_url() -> str:
    from flask import current_app
    return (current_app.config.get('APP_BASE_URL') or '').rstrip('/')


def handle_event(event) -> None:
    """Dispatch a verified Stripe event to the appropriate handler."""
    event_type = event['type']
    data_obj   = event['data']['object']

    handlers = {
        'checkout.session.completed':          _on_checkout_completed,
        'customer.subscription.updated':       _on_subscription_updated,
        'customer.subscription.deleted':       _on_subscription_deleted,
        'invoice.payment_succeeded':           _on_payment_succeeded,
        'invoice.payment_failed':              _on_payment_failed,
        'customer.subscription.trial_will_end': _on_trial_will_end,
    }

    handler = handlers.get(event_type)
    if handler is None:
        logger.debug('BILLING WEBHOOK | unhandled | type=%s', event_type)
        return

    try:
        handler(data_obj)
    except Exception as exc:
        logger.error('BILLING WEBHOOK | handler_error | type=%s | err=%s', event_type, exc, exc_info=True)


# ── Individual event handlers ──────────────────────────────────────────────────

def _on_checkout_completed(obj):
    """checkout.session.completed — customer completed Stripe Checkout."""
    customer_id      = obj.get('customer')
    subscription_id  = obj.get('subscription')

    if not customer_id or not subscription_id:
        logger.warning('BILLING | checkout_completed_missing_fields | obj=%s', obj.get('id'))
        return

    from control.base import control_session
    from control.models import Tenant, TenantAudit
    from control.time_utils import now_eastern

    with control_session() as s:
        t = s.query(Tenant).filter_by(stripe_customer_id=customer_id).first()
        if t is None:
            logger.warning('BILLING | checkout_completed_no_tenant | customer=%s', customer_id)
            return

        t.stripe_subscription_id = subscription_id
        t.subscription_status    = 'active'
        t.trial_ends_at          = None  # trial period ended at checkout

        s.add(TenantAudit(
            action='billing_checkout_completed',
            tenant_id=t.id,
            details=f'subscription_id={subscription_id}',
        ))

    logger.info('BILLING | checkout_completed | tenant_id=%s sub=%s', t.id, subscription_id)


def _on_subscription_updated(obj):
    """customer.subscription.updated — sync status and plan from Stripe."""
    customer_id     = obj.get('customer')
    subscription_id = obj.get('id')
    stripe_status   = obj.get('status', '')
    period_end_ts   = obj.get('current_period_end')
    trial_end_ts    = obj.get('trial_end')

    # Extract the price ID from the first subscription item (plan change detection).
    items = obj.get('items', {}).get('data', [])
    new_price_id = items[0].get('price', {}).get('id') if items else None

    our_status = _STRIPE_STATUS_MAP.get(stripe_status)
    if our_status is None:
        logger.warning('BILLING | subscription_updated_unknown_status | status=%s', stripe_status)
        return

    from control.base import control_session
    from control.models import Tenant, Plan, TenantAudit

    with control_session() as s:
        t = s.query(Tenant).filter_by(stripe_customer_id=customer_id).first()
        if t is None:
            logger.warning('BILLING | subscription_updated_no_tenant | customer=%s', customer_id)
            return

        old_status  = t.subscription_status
        old_plan_id = t.plan_id

        t.subscription_status    = our_status
        t.stripe_subscription_id = subscription_id
        t.current_period_end     = _ts_to_dt(period_end_ts)
        if trial_end_ts:
            t.trial_ends_at = _ts_to_dt(trial_end_ts)

        # Sync plan when the price changes (upgrade / downgrade via portal).
        plan_detail = ''
        if new_price_id:
            matched_plan = s.query(Plan).filter_by(stripe_price_id=new_price_id).first()
            if matched_plan and matched_plan.id != old_plan_id:
                t.plan_id = matched_plan.id
                plan_detail = f' plan={old_plan_id}→{matched_plan.id}({matched_plan.code})'
                logger.info('BILLING | plan_changed | tenant_id=%s plan=%s→%s',
                            t.id, old_plan_id, matched_plan.id)

        s.add(TenantAudit(
            action='billing_subscription_updated',
            tenant_id=t.id,
            details=f'stripe_status={stripe_status} our_status={our_status} prev={old_status}{plan_detail}',
        ))

    logger.info('BILLING | subscription_updated | tenant_id=%s %s→%s', t.id, old_status, our_status)


def _on_subscription_deleted(obj):
    """customer.subscription.deleted — subscription was cancelled."""
    customer_id = obj.get('customer')

    from control.base import control_session
    from control.models import Tenant, TenantAudit
    from control.time_utils import now_eastern
    from app.billing.emails import send_billing_email

    with control_session() as s:
        t = s.query(Tenant).filter_by(stripe_customer_id=customer_id).first()
        if t is None:
            logger.warning('BILLING | subscription_deleted_no_tenant | customer=%s', customer_id)
            return

        t.subscription_status = 'cancelled'
        billing_email = t.billing_email

        s.add(TenantAudit(
            action='billing_subscription_cancelled',
            tenant_id=t.id,
            details=f'customer={customer_id}',
        ))

    logger.info('BILLING | subscription_deleted | tenant_id=%s', t.id)

    if billing_email:
        base_url = _get_base_url()
        send_billing_email(billing_email, 'subscription_cancelled', {
            'portal_url': f'{base_url}/billing/portal',
        })


def _on_payment_succeeded(obj):
    """invoice.payment_succeeded — payment went through, clear past_due."""
    customer_id = obj.get('customer')
    period_end  = obj.get('lines', {}).get('data', [{}])[0].get('period', {}).get('end')

    from control.base import control_session
    from control.models import Tenant, TenantAudit

    with control_session() as s:
        t = s.query(Tenant).filter_by(stripe_customer_id=customer_id).first()
        if t is None:
            return

        if t.subscription_status == 'past_due':
            t.subscription_status = 'active'
            t.past_due_since      = None
            t.dunning_stage       = 0
            t.dunning_sent_at     = None
            if period_end:
                t.current_period_end = _ts_to_dt(period_end)

            s.add(TenantAudit(
                action='billing_payment_recovered',
                tenant_id=t.id,
                details=f'customer={customer_id}',
            ))
            logger.info('BILLING | payment_succeeded_recovered | tenant_id=%s', t.id)


def _on_payment_failed(obj):
    """invoice.payment_failed — mark past_due and send dunning email."""
    customer_id = obj.get('customer')

    from control.base import control_session
    from control.models import Tenant, TenantAudit
    from app.billing.emails import send_billing_email

    with control_session() as s:
        t = s.query(Tenant).filter_by(stripe_customer_id=customer_id).first()
        if t is None:
            logger.warning('BILLING | payment_failed_no_tenant | customer=%s', customer_id)
            return

        t.subscription_status = 'past_due'
        if t.past_due_since is None:
            from control.time_utils import now_eastern
            t.past_due_since = now_eastern()
        billing_email = t.billing_email

        s.add(TenantAudit(
            action='billing_payment_failed',
            tenant_id=t.id,
            details=f'customer={customer_id}',
        ))

    logger.info('BILLING | payment_failed | tenant_id=%s', t.id)

    if billing_email:
        base_url = _get_base_url()
        send_billing_email(billing_email, 'payment_failed', {
            'portal_url': f'{base_url}/billing/portal',
        })


def _on_trial_will_end(obj):
    """customer.subscription.trial_will_end — sent 3 days before trial ends."""
    customer_id   = obj.get('customer')
    trial_end_ts  = obj.get('trial_end')

    from control.base import control_session
    from control.models import Tenant
    from app.billing.emails import send_billing_email

    with control_session() as s:
        t = s.query(Tenant).filter_by(stripe_customer_id=customer_id).first()
        if t is None:
            return
        billing_email = t.billing_email

    if billing_email:
        trial_dt = _ts_to_dt(trial_end_ts)
        trial_str = trial_dt.strftime('%B %d, %Y') if trial_dt else 'soon'
        base_url  = _get_base_url()
        send_billing_email(billing_email, 'trial_ending', {
            'trial_ends_at':  trial_str,
            'subscribe_url':  f'{base_url}/billing/subscribe',
        })
        logger.info('BILLING | trial_will_end_email_sent | customer=%s', customer_id)