"""Listing expiry warning and expired notification emails.

Two sweeps (called from nightly systemd timer):
  - warn_expiring(days=3): send one warning email per listing expiring within N days
    that hasn't already received one.
  - notify_expired(): send "your listing expired" email for newly-expired listings
    that haven't been notified yet.

We track state via a JSON field on the listing.  Rather than adding columns, we
use the existing `attributes` JSON and a private `_notified` sub-key so no migration
is required.  The key is prefixed with `_` to avoid colliding with user attributes.
"""
from datetime import datetime, timedelta
from app.utils.time import utcnow
from flask import current_app
from app.extensions import db
from app.models.listing import Listing
from app.models.enums import ListingStatus
from app.services.email import send_email


def _already_notified(listing, key: str) -> bool:
    attrs = listing.attributes or {}
    return bool(attrs.get(key))


def _mark_notified(listing, key: str):
    attrs = dict(listing.attributes or {})
    attrs[key] = utcnow().isoformat()
    listing.attributes = attrs


def warn_expiring(days: int = 3) -> int:
    """Send warning emails for listings expiring within `days` days. Returns count."""
    now = utcnow()
    window_end = now + timedelta(days=days)
    soon = (Listing.query
            .filter(Listing.status == ListingStatus.active,
                    Listing.expires_at > now,
                    Listing.expires_at <= window_end)
            .all())
    sent = 0
    for listing in soon:
        if _already_notified(listing, "_warn_sent"):
            continue
        user = listing.user
        if not user or not user.email:
            continue
        days_left = (listing.expires_at - now).days
        subject = f"Your listing '{listing.title[:50]}' expires in {days_left} day(s)"
        body = (
            f"Hi {user.display_name},\n\n"
            f"Your listing \"{listing.title}\" will expire in {days_left} day(s) "
            f"({listing.expires_at.strftime('%Y-%m-%d')}).\n\n"
            f"To keep it active, edit and re-save it, or purchase a boost.\n\n"
            f"View your listing: {current_app.config.get('SERVER_NAME', '')}/listings/{listing.id}\n\n"
            f"— Classifieds"
        )
        if send_email(user.email, subject, body):
            _mark_notified(listing, "_warn_sent")
            db.session.commit()
            sent += 1
    return sent


def notify_expired() -> int:
    """Send 'your listing expired' emails for newly-expired listings. Returns count."""
    expired = (Listing.query
               .filter(Listing.status == ListingStatus.expired)
               .all())
    sent = 0
    for listing in expired:
        if _already_notified(listing, "_expired_sent"):
            continue
        user = listing.user
        if not user or not user.email:
            continue
        subject = f"Your listing '{listing.title[:50]}' has expired"
        body = (
            f"Hi {user.display_name},\n\n"
            f"Your listing \"{listing.title}\" expired on "
            f"{listing.expires_at.strftime('%Y-%m-%d')}.\n\n"
            f"To re-list it, create a new listing or upgrade your plan for longer listing life.\n\n"
            f"— Classifieds"
        )
        if send_email(user.email, subject, body):
            _mark_notified(listing, "_expired_sent")
            db.session.commit()
            sent += 1
    return sent