"""Maintenance-queue Celery tasks. Lightweight, user-triggered, non-ML."""
import logging
from celery import shared_task
from sqlalchemy import text

from app import db
from app.models import Tag

log = logging.getLogger(__name__)


@shared_task(
    name='app.tasks.maintenance.sync_character_fandoms',
    soft_time_limit=120,
    time_limit=180,
)
def sync_character_fandoms():
    """For every character tag with a non-null fandom_id, attach the fandom
    tag to every image tagged with the character but not the fandom.

    Additive only — never removes fandom tags.

    Returns a summary dict with counts.
    """
    chars = (
        Tag.query
        .filter_by(kind='character')
        .filter(Tag.fandom_id.isnot(None))
        .all()
    )
    total_added = 0
    failed = 0
    for char in chars:
        try:
            result = db.session.execute(
                text("""
                    INSERT INTO image_tags (image_id, tag_id)
                    SELECT it.image_id, :fandom_id
                    FROM image_tags it
                    WHERE it.tag_id = :char_id
                      AND NOT EXISTS (
                          SELECT 1 FROM image_tags it2
                          WHERE it2.image_id = it.image_id
                            AND it2.tag_id = :fandom_id
                      )
                """),
                {'char_id': char.id, 'fandom_id': char.fandom_id},
            )
            total_added += result.rowcount or 0
            db.session.commit()
        except Exception as e:
            db.session.rollback()
            failed += 1
            log.warning(
                "sync_character_fandoms: char tag %s (%s) failed: %s",
                char.id, char.name, e,
            )
    log.info(
        "sync_character_fandoms: scanned %d characters, added %d image↔fandom links, %d failed",
        len(chars), total_added, failed,
    )
    return {
        'characters_scanned': len(chars),
        'links_added': total_added,
        'characters_failed': failed,
    }