import os
import shutil
import subprocess
from pathlib import Path
from tempfile import mkdtemp
from typing import Callable, Optional

import pypdfium2
from docx.document import Document
from PIL import Image, ImageChops


def get_libreoffice_cmd(raise_if_unavailable: bool = False) -> Optional[str]:
    """Return the libreoffice cmd and optionally test it."""

    libreoffice_cmd = (
        shutil.which("libreoffice")
        or shutil.which("soffice")
        or (
            "/Applications/LibreOffice.app/Contents/MacOS/soffice"
            if os.path.isfile("/Applications/LibreOffice.app/Contents/MacOS/soffice")
            else None
        )
    )

    if raise_if_unavailable:
        if libreoffice_cmd is None:
            raise RuntimeError("Libreoffice not found")

        # The following test will raise if the libreoffice_cmd cannot be used
        subprocess.run(
            [
                libreoffice_cmd,
                "-h",
            ],
            stdout=subprocess.DEVNULL,
            stderr=subprocess.DEVNULL,
            check=True,
        )

    return libreoffice_cmd


def get_docx_to_pdf_converter() -> Optional[Callable]:
    """
    Detects the best available DOCX to PDF tool and returns a conversion function.
    The returned function accepts (input_path, output_path).
    Returns None if no tool is available.
    """

    # Try LibreOffice
    libreoffice_cmd = get_libreoffice_cmd()

    if libreoffice_cmd:

        def convert_with_libreoffice(input_path, output_path):
            subprocess.run(
                [
                    libreoffice_cmd,
                    "--headless",
                    "--convert-to",
                    "pdf",
                    "--outdir",
                    os.path.dirname(output_path),
                    input_path,
                ],
                stdout=subprocess.DEVNULL,
                stderr=subprocess.DEVNULL,
                check=True,
            )

            expected_output = os.path.join(
                os.path.dirname(output_path),
                os.path.splitext(os.path.basename(input_path))[0] + ".pdf",
            )
            if expected_output != output_path:
                os.rename(expected_output, output_path)

        return convert_with_libreoffice

    ## Space for other DOCX to PDF converters if available

    # No tools found
    return None


def crop_whitespace(image: Image.Image, bg_color=None, padding=0) -> Image.Image:
    if bg_color is None:
        bg_color = image.getpixel((0, 0))

    bg = Image.new(image.mode, image.size, bg_color)
    diff = ImageChops.difference(image, bg)
    bbox = diff.getbbox()

    if bbox:
        left, upper, right, lower = bbox
        left = max(0, left - padding)
        upper = max(0, upper - padding)
        right = min(image.width, right + padding)
        lower = min(image.height, lower + padding)
        return image.crop((left, upper, right, lower))
    else:
        return image


def get_pil_from_dml_docx(
    docx: Document, converter: Optional[Callable]
) -> Optional[Image.Image]:
    if converter is None:
        return None

    temp_dir = Path(mkdtemp())
    temp_docx = Path(temp_dir / "drawing_only.docx")
    temp_pdf = Path(temp_dir / "drawing_only.pdf")

    # 1) Save docx temporarily
    docx.save(str(temp_docx))

    # 2) Export to PDF
    converter(temp_docx, temp_pdf)

    # 3) Load PDF as PNG
    pdf = pypdfium2.PdfDocument(temp_pdf)
    page = pdf[0]
    image = crop_whitespace(page.render(scale=2).to_pil())
    page.close()
    pdf.close()

    shutil.rmtree(temp_dir, ignore_errors=True)

    return image