"""Helper: turn an ir.attachment into a list of PIL.Image pages.

Kept separate from the adapters so future backends (Ollama-vision, Mindee)
that want PIL images directly don't have to re-implement the PDF rendering.
"""

import base64
import io
import logging

_logger = logging.getLogger(__name__)


def attachment_to_pages(attachment):
    """Decode an ir.attachment into a list of PIL.Image pages.

    Returns ``[]`` on failure (caller should treat as no pages).
    """
    try:
        from PIL import Image
        from pdf2image import convert_from_bytes
    except ImportError as e:
        _logger.warning("attachment_to_pages requires PIL + pdf2image: %s", e)
        return []

    if not attachment or not attachment.datas:
        return []

    try:
        data = base64.b64decode(attachment.datas)
    except Exception as e:
        _logger.warning("Could not decode attachment %s: %s", attachment.id, e)
        return []

    mimetype = attachment.mimetype or ''
    is_pdf = mimetype == 'application/pdf' or data[:4] == b'%PDF'
    try:
        if is_pdf:
            return convert_from_bytes(data, dpi=200)
        return [Image.open(io.BytesIO(data))]
    except Exception as e:
        _logger.warning("Could not render attachment %s: %s", attachment.id, e)
        return []