"""Raster images (.png/.jpg/.jpeg/.webp/.tiff/.bmp) -> PDF, one page per image.

Rendered directly by Pillow (img.save(format='PDF')) — no WeasyPrint in
this path, so image fidelity is exactly what the encoder produces.
Transparency (RGBA/P) is flattened to RGB over white. Images wider or
taller than MAX_DIM are downscaled proportionally to keep the PDF sane
for e.g. 12 MP camera photos.

An unopenable/corrupt file is a job error: "Invalid image: ..." (the
contract asserts 'image' in error.lower()).
"""
from __future__ import annotations

import io
from pathlib import Path

from PIL import Image

from . import common

MAX_DIM = 2000


def convert(path: Path, job_id: str, progress_cb=None, output_dir=None,
            source_name=None) -> str:
    """Render a raster image to a one-page PDF."""
    try:
        img = Image.open(path)
        img.load()  # force full decode: a truncated file fails here, not later
    except Exception as exc:  # noqa: BLE001 - PIL raises many types
        raise ValueError(f"Invalid image: {path.name} could not be opened ({exc})") from exc

    if img.mode in ("RGBA", "P"):
        bg = Image.new("RGB", img.size, (255, 255, 255))
        if img.mode == "P":
            img = img.convert("RGBA")
        bg.paste(img, mask=img.getchannel("A"))
        img = bg
    elif img.mode != "RGB":
        img = img.convert("RGB")

    w, h = img.size
    scale = min(1.0, MAX_DIM / max(w, h))
    if scale < 1.0:
        img = img.resize((max(1, int(w * scale)), max(1, int(h * scale))), Image.LANCZOS)

    common.report(progress_cb, 30.0, f"Rendering {path.name} (1/1)")
    buf = io.BytesIO()
    img.save(buf, format="PDF")
    out_dir = common.default_output_dir(output_dir)
    filename = common.derive_export_name(source_name or path.name, out_dir)
    return common.finalize_pdf(buf.getvalue(), out_dir, filename, job_id,
                               progress_cb=progress_cb)