"""
app/billing/emails.py
---------------------
Dunning / billing lifecycle emails sent via Flask-Mail in a background thread.
Sends multipart HTML + plain-text messages using Jinja2 templates in
app/templates/billing/email/.
"""

import logging
import threading
from flask import current_app, render_template
from flask_mail import Message
from app import mail

logger = logging.getLogger(__name__)

_SUBJECTS = {
    'payment_failed':         'Action Required: Payment failed for your JQC subscription',
    'trial_ending':           'Your JQC free trial ends in 3 days',
    'subscription_cancelled': 'Your JQC subscription has been cancelled',
}

_HTML_TEMPLATES = {
    'payment_failed':         'billing/email/payment_failed.html',
    'trial_ending':           'billing/email/trial_ending.html',
    'subscription_cancelled': 'billing/email/subscription_cancelled.html',
}

_PLAIN_BODIES = {
    'payment_failed': (
        "We were unable to process your most recent payment for your JQC subscription.\n\n"
        "Please update your payment method to avoid interruption to your service:\n"
        "  {portal_url}\n\n— The JQC Team"
    ),
    'trial_ending': (
        "Your JQC free trial will end on {trial_ends_at}.\n\n"
        "Subscribe now to keep your workspace active:\n"
        "  {subscribe_url}\n\n— The JQC Team"
    ),
    'subscription_cancelled': (
        "Your JQC subscription has been cancelled and your workspace access has been suspended.\n\n"
        "You can reactivate at any time:\n"
        "  {portal_url}\n\n— The JQC Team"
    ),
}


def send_billing_email(to_addr: str, event_type: str, context_dict: dict):
    """Send a billing lifecycle HTML+plain email in a background thread.

    Args:
        to_addr:      Recipient email address.
        event_type:   One of 'payment_failed', 'trial_ending', 'subscription_cancelled'.
        context_dict: Variables substituted into both the HTML template and plain body.
    """
    if not to_addr:
        logger.warning('BILLING EMAIL | skipped | event=%s | reason=no_recipient', event_type)
        return

    subject = _SUBJECTS.get(event_type, 'JQC Billing Notification')
    plain_tmpl = _PLAIN_BODIES.get(event_type, '')
    html_tmpl_path = _HTML_TEMPLATES.get(event_type)

    try:
        plain_body = plain_tmpl.format(**context_dict)
    except KeyError as exc:
        logger.error('BILLING EMAIL | plain_template_error | event=%s | key=%s', event_type, exc)
        plain_body = plain_tmpl

    app = current_app._get_current_object()

    def _send():
        try:
            with app.app_context():
                html_body = None
                if html_tmpl_path:
                    try:
                        html_body = render_template(html_tmpl_path, **context_dict)
                    except Exception as exc:
                        logger.error('BILLING EMAIL | html_render_failed | tmpl=%s | err=%s',
                                     html_tmpl_path, exc)

                msg = Message(
                    subject=subject,
                    recipients=[to_addr],
                    body=plain_body,
                    html=html_body,
                )
                mail.send(msg)
                logger.info('BILLING EMAIL | sent | event=%s | to=%s', event_type, to_addr)
        except Exception as exc:
            logger.error('BILLING EMAIL | send_failed | event=%s | to=%s | err=%s',
                         event_type, to_addr, exc)

    threading.Thread(target=_send, daemon=True).start()