"""
Shared PDF generation helper for any model using the hospital letterhead (artboard).
"""

import io
import base64

from django.conf import settings
from django.template.loader import render_to_string
from weasyprint import HTML


def _img_to_data_uri(path):
    """Open an image file and return it as a base64 data URI."""
    try:
        from PIL import Image as PILImage

        img = PILImage.open(path)
        buf = io.BytesIO()
        img.save(buf, format="PNG", optimize=True)
        return "data:image/png;base64," + base64.b64encode(buf.getvalue()).decode()
    except Exception:
        return None


def _get_logo_data_uri():
    """Load the HH_P_ICON as a base64 data URI for embedding in PDF."""
    return _img_to_data_uri(settings.BASE_DIR / "static" / "img" / "HH_P_ICON.png")


def _get_letterhead_data_uri(obj):
    """Load the hospital letterhead (artboard) for the given object's hospital.

    Priority: hospital.letterhead upload → static fallback artboard image.
    """
    hospital = getattr(obj, "hospital", None)
    if hospital and hospital.letterhead:
        uri = _img_to_data_uri(hospital.letterhead.path)
        if uri:
            return uri
    # Static fallback
    return _img_to_data_uri(settings.BASE_DIR / "static" / "images" / "artboard" / "Artboard 1@3x.png")


def generate_letterhead_pdf(template_name, context, filename, obj=None):
    """Render a template with the hospital letterhead (artboard) and return an HttpResponse with the PDF.

    Args:
        template_name: Django template path.
        context: Dict of template context variables.
        filename: Output PDF filename.
        obj: The model instance (used to resolve hospital.letterhead). If None,
             falls back to the static artboard image.
    """
    from django.http import HttpResponse

    logo_path = _get_logo_data_uri()
    letterhead_path = _img_to_data_uri(settings.BASE_DIR / "static" / "images" / "artboard" / "Artboard 1@3x.png")
    if obj:
        letterhead_path = _get_letterhead_data_uri(obj)

    full_context = {**context, "logo_path": logo_path, "letterhead_path": letterhead_path}

    html_string = render_to_string(template_name, full_context)
    pdf_file = HTML(string=html_string, base_url=str(settings.BASE_DIR / "static")).write_pdf()

    response = HttpResponse(pdf_file, content_type="application/pdf")
    response["Content-Disposition"] = f'attachment; filename="{filename}"'
    return response