dangerzone.py

#!/usr/bin/env python3
"""
Here are the steps, with progress bar percentages for each step:

document_to_pixels
- 0%-3%: Convert document into a PDF (skipped if the input file is a PDF)
- 3%-5%: Split PDF into individual pages, and count those pages
- 5%-50%: Convert each page into pixels (each page takes 45/n%, where n is the number of pages)

pixels_to_pdf:
- 50%-95%: Convert each page of pixels into a PDF (each page takes 45/n%, where n is the number of pages)
- 95%-100%: Compress the final PDF
"""

import glob
import json
import os
import shutil
import subprocess
import sys
from typing import Dict, List, Optional

import magic
from PIL import Image

# timeout in seconds for any single subprocess
DEFAULT_TIMEOUT: float = 60


def run_command(
    args: List[str],
    *,
    error_message: str,
    timeout_message: str,
    timeout: float = DEFAULT_TIMEOUT,
) -> subprocess.CompletedProcess:
    """
    Runs a command and returns the result.

    :raises RuntimeError: if the process returns a non-zero exit status
    :raises TimeoutError: if the process times out
    """
    try:
        return subprocess.run(
            args,
            stdout=subprocess.DEVNULL,
            stderr=subprocess.DEVNULL,
            timeout=timeout,
            check=True,
        )
    except subprocess.CalledProcessError as e:
        raise RuntimeError(error_message) from e
    except subprocess.TimeoutExpired as e:
        raise TimeoutError(timeout_message) from e


class DangerzoneConverter:
    def __init__(self) -> None:
        self.percentage: float = 0.0

    def document_to_pixels(self) -> None:

        conversions: Dict[str, Dict[str, Optional[str]]] = {
            # .pdf
            "application/pdf": {"type": None},
            # .docx
            "application/vnd.openxmlformats-officedocument.wordprocessingml.document": {
                "type": "libreoffice",
                "libreoffice_output_filter": "writer_pdf_Export",
            },
            # .doc
            "application/msword": {
                "type": "libreoffice",
                "libreoffice_output_filter": "writer_pdf_Export",
            },
            # .docm
            "application/vnd.ms-word.document.macroEnabled.12": {
                "type": "libreoffice",
                "libreoffice_output_filter": "writer_pdf_Export",
            },
            # .xlsx
            "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet": {
                "type": "libreoffice",
                "libreoffice_output_filter": "calc_pdf_Export",
            },
            # .xls
            "application/vnd.ms-excel": {
                "type": "libreoffice",
                "libreoffice_output_filter": "calc_pdf_Export",
            },
            # .pptx
            "application/vnd.openxmlformats-officedocument.presentationml.presentation": {
                "type": "libreoffice",
                "libreoffice_output_filter": "impress_pdf_Export",
            },
            # .ppt
            "application/vnd.ms-powerpoint": {
                "type": "libreoffice",
                "libreoffice_output_filter": "impress_pdf_Export",
            },
            # .odt
            "application/vnd.oasis.opendocument.text": {
                "type": "libreoffice",
                "libreoffice_output_filter": "writer_pdf_Export",
            },
            # .odg
            "application/vnd.oasis.opendocument.graphics": {
                "type": "libreoffice",
                "libreoffice_output_filter": "impress_pdf_Export",
            },
            # .odp
            "application/vnd.oasis.opendocument.presentation": {
                "type": "libreoffice",
                "libreoffice_output_filter": "impress_pdf_Export",
            },
            # .ops
            "application/vnd.oasis.opendocument.spreadsheet": {
                "type": "libreoffice",
                "libreoffice_output_filter": "calc_pdf_Export",
            },
            # .jpg
            "image/jpeg": {"type": "convert"},
            # .gif
            "image/gif": {"type": "convert"},
            # .png
            "image/png": {"type": "convert"},
            # .tif
            "image/tiff": {"type": "convert"},
            "image/x-tiff": {"type": "convert"},
        }

        # Detect MIME type
        mime = magic.Magic(mime=True)
        mime_type = mime.from_file("/tmp/input_file")

        # Validate MIME type
        if mime_type not in conversions:
            raise ValueError(f"The document format is not supported")

        # Convert input document to PDF
        conversion = conversions[mime_type]
        if conversion["type"] is None:
            pdf_filename = "/tmp/input_file"
        elif conversion["type"] == "libreoffice":
            self.update_progress("Converting to PDF using LibreOffice")
            args = [
                "libreoffice",
                "--headless",
                "--convert-to",
                f"pdf:{conversion['libreoffice_output_filter']}",
                "--outdir",
                "/tmp",
                "/tmp/input_file",
            ]
            run_command(
                args,
                error_message="Conversion to PDF with LibreOffice failed",
                timeout_message=f"Error converting document to PDF, LibreOffice timed out after {DEFAULT_TIMEOUT} seconds",
            )
            pdf_filename = "/tmp/input_file.pdf"
        elif conversion["type"] == "convert":
            self.update_progress("Converting to PDF using GraphicsMagick")
            args = [
                "gm",
                "convert",
                "/tmp/input_file",
                "/tmp/input_file.pdf",
            ]
            run_command(
                args,
                error_message="Conversion to PDF with GraphicsMagick failed",
                timeout_message=f"Error converting document to PDF, GraphicsMagick timed out after {DEFAULT_TIMEOUT} seconds",
            )
            pdf_filename = "/tmp/input_file.pdf"
        else:
            raise ValueError(
                f"Invalid conversion type {conversion['type']} for MIME type {mime_type}"
            )
        self.percentage += 3

        # Separate PDF into pages
        self.update_progress("Separating document into pages")
        args = ["pdftk", pdf_filename, "burst", "output", "/tmp/page-%d.pdf"]
        run_command(
            args,
            error_message="Separating document into pages failed",
            timeout_message=f"Error separating document into pages, pdfseparate timed out after {DEFAULT_TIMEOUT} seconds",
        )

        page_filenames = glob.glob("/tmp/page-*.pdf")

        self.percentage += 2

        # Convert to RGB pixel data
        percentage_per_page = 45.0 / len(page_filenames)
        for page in range(1, len(page_filenames) + 1):
            pdf_filename = f"/tmp/page-{page}.pdf"
            png_filename = f"/tmp/page-{page}.png"
            rgb_filename = f"/tmp/page-{page}.rgb"
            width_filename = f"/tmp/page-{page}.width"
            height_filename = f"/tmp/page-{page}.height"
            filename_base = f"/tmp/page-{page}"

            self.update_progress(
                f"Converting page {page}/{len(page_filenames)} to pixels"
            )

            # Convert to png
            run_command(
                ["pdftocairo", pdf_filename, "-png", "-singlefile", filename_base],
                error_message="Conversion from PDF to PNG failed",
                timeout_message=f"Error converting from PDF to PNG, pdftocairo timed out after {DEFAULT_TIMEOUT} seconds",
            )

            # Save the width and height
            with Image.open(png_filename, "r") as im:
                width, height = im.size
            with open(width_filename, "w") as f:
                f.write(str(width))
            with open(height_filename, "w") as f:
                f.write(str(height))

            # Convert to RGB pixels
            run_command(
                [
                    "gm",
                    "convert",
                    png_filename,
                    "-depth",
                    "8",
                    f"rgb:{rgb_filename}",
                ],
                error_message="Conversion from PNG to RGB failed",
                timeout_message=f"Error converting from PNG to pixels, convert timed out after {DEFAULT_TIMEOUT} seconds",
            )

            # Delete the png
            os.remove(png_filename)
            self.percentage += percentage_per_page

        self.update_progress("Converted document to pixels")

        # Move converted files into /dangerzone
        for filename in (
            glob.glob("/tmp/page-*.rgb")
            + glob.glob("/tmp/page-*.width")
            + glob.glob("/tmp/page-*.height")
        ):
            shutil.move(filename, "/dangerzone")

    def pixels_to_pdf(self) -> None:
        self.percentage = 50.0

        num_pages = len(glob.glob("/dangerzone/page-*.rgb"))

        # Convert RGB files to PDF files
        percentage_per_page = 45.0 / num_pages
        for page in range(1, num_pages + 1):
            filename_base = f"/dangerzone/page-{page}"
            rgb_filename = f"{filename_base}.rgb"
            width_filename = f"{filename_base}.width"
            height_filename = f"{filename_base}.height"
            png_filename = f"/tmp/page-{page}.png"
            ocr_filename = f"/tmp/page-{page}"
            pdf_filename = f"/tmp/page-{page}.pdf"

            with open(width_filename) as f:
                width = f.read().strip()
            with open(height_filename) as f:
                height = f.read().strip()

            if os.environ.get("OCR") == "1":  # OCR the document
                self.update_progress(
                    f"Converting page {page}/{num_pages} from pixels to searchable PDF"
                )
                run_command(
                    [
                        "gm",
                        "convert",
                        "-size",
                        f"{width}x{height}",
                        "-depth",
                        "8",
                        f"rgb:{rgb_filename}",
                        f"png:{png_filename}",
                    ],
                    error_message=f"Page {page}/{num_pages} conversion to PNG failed",
                    timeout_message=f"Error converting pixels to PNG, convert timed out after {DEFAULT_TIMEOUT} seconds",
                )
                run_command(
                    [
                        "tesseract",
                        png_filename,
                        ocr_filename,
                        "-l",
                        os.environ.get("OCR_LANGUAGE"),  # type: ignore
                        "--dpi",
                        "70",
                        "pdf",
                    ],
                    error_message=f"Page {page}/{num_pages} OCR failed",
                    timeout_message=f"Error converting PNG to searchable PDF, tesseract timed out after {DEFAULT_TIMEOUT} seconds",
                )

            else:  # Don't OCR
                self.update_progress(
                    f"Converting page {page}/{num_pages} from pixels to PDF"
                )
                run_command(
                    [
                        "gm",
                        "convert",
                        "-size",
                        f"{width}x{height}",
                        "-depth",
                        "8",
                        f"rgb:{rgb_filename}",
                        f"pdf:{pdf_filename}",
                    ],
                    error_message=f"Page {page}/{num_pages} conversion to PDF failed",
                    timeout_message=f"Error converting RGB to PDF, convert timed out after {DEFAULT_TIMEOUT} seconds",
                )

            self.percentage += percentage_per_page

        # Merge pages into a single PDF
        self.update_progress(f"Merging {num_pages} pages into a single PDF")
        args = ["pdfunite"]
        for page in range(1, num_pages + 1):
            args.append(f"/tmp/page-{page}.pdf")
        args.append(f"/tmp/safe-output.pdf")
        run_command(
            args,
            error_message="Merging pages into a single PDF failed",
            timeout_message=f"Error merging pages into a single PDF, pdfunite timed out after {DEFAULT_TIMEOUT} seconds",
        )

        self.percentage += 2

        # Compress
        self.update_progress(f"Compressing PDF")
        compress_timeout = num_pages * 3
        run_command(
            ["ps2pdf", "/tmp/safe-output.pdf", "/tmp/safe-output-compressed.pdf"],
            timeout_message=f"Error compressing PDF, ps2pdf timed out after {compress_timeout} seconds",
            error_message="Compressing PDF failed",
            timeout=compress_timeout,
        )

        self.percentage = 100.0
        self.update_progress("Safe PDF created")

        # Move converted files into /safezone
        shutil.move("/tmp/safe-output.pdf", "/safezone")
        shutil.move("/tmp/safe-output-compressed.pdf", "/safezone")

    def update_progress(self, text: str, *, error: bool = False) -> None:
        print(
            json.dumps(
                {"error": error, "text": text, "percentage": int(self.percentage)}
            )
        )
        sys.stdout.flush()


def main() -> int:
    if len(sys.argv) != 2:
        print(f"Usage: {sys.argv[0]} [document-to-pixels]|[pixels-to-pdf]")
        return -1

    converter = DangerzoneConverter()

    try:
        if sys.argv[1] == "document-to-pixels":
            converter.document_to_pixels()
        elif sys.argv[1] == "pixels-to-pdf":
            converter.pixels_to_pdf()
    except (RuntimeError, TimeoutError, ValueError) as e:
        converter.update_progress(str(e), error=True)
        return 1
    else:
        return 0  # Success!


if __name__ == "__main__":
    sys.exit(main())