import logging
from pathlib import Path

from app.celery_app import celery_app
from app.core.config import settings

logger = logging.getLogger(__name__)

THUMB_SIZES = [(400, 400), (200, 200)]


@celery_app.task(bind=True, max_retries=3, default_retry_delay=10)
def generate_thumbnail(self, image_path: str):
    """Generate thumbnail variants for an uploaded image."""
    try:
        from PIL import Image

        if settings.STORAGE_BACKEND != "local":
            logger.info("Thumbnail generation skipped for non-local storage: %s", image_path)
            return {"status": "skipped", "reason": "non-local storage"}

        full_path = Path(settings.LOCAL_STORAGE_PATH) / image_path.lstrip("/")
        if not full_path.exists():
            logger.warning("Image not found: %s", full_path)
            return {"status": "error", "reason": "file not found"}

        results = []
        img = Image.open(full_path)
        if img.mode in ("RGBA", "P"):
            img = img.convert("RGB")

        for w, h in THUMB_SIZES:
            thumb = img.copy()
            thumb.thumbnail((w, h), Image.LANCZOS)
            suffix = full_path.suffix or ".jpg"
            thumb_name = f"{full_path.stem}_{w}x{h}{suffix}"
            thumb_path = full_path.parent / thumb_name
            thumb.save(str(thumb_path), quality=85, optimize=True)
            results.append(str(thumb_path))
            logger.info("Generated thumbnail: %s", thumb_path)

        return {"status": "ok", "thumbnails": results}

    except Exception as exc:
        logger.exception("Thumbnail generation failed for %s", image_path)
        raise self.retry(exc=exc)