Add tools for rendering PDFs with electron-pdf

aleksis/core/util/pdf.py

+import glob
+import os
+import subprocess  # noqa
+from tempfile import mkstemp
+from typing import Union
+
+from django.http.request import HttpRequest
+from django.http.response import HttpResponse
+from django.shortcuts import render
+from django.template.loader import render_to_string
+from django.utils.translation import gettext as _
+
+from celery_progress.backend import ProgressRecorder
+
+from aleksis.core.settings import MEDIA_ROOT, MEDIA_URL, STATIC_ROOT
+from aleksis.core.util.core_helpers import (
+    DummyRecorder,
+    celery_optional,
+    celery_optional_progress,
+    is_celery_enabled,
+    path_and_rename,
+)
+
+
+@celery_optional_progress
+def generate_pdf(recorder: Union[ProgressRecorder, DummyRecorder], html_code: str, pdf_path: str):
+    """Generate a PDF file by rendering the HTML code using electron-pdf."""
+    recorder.total = 1
+
+    # Replace /static with STATIC_ROOT to get local file system paths
+    html_code = html_code.replace("/static", STATIC_ROOT)
+
+    # Write HTML code to a temporary file to make it available for electron-pdf
+    f, path = mkstemp(".html")
+    with open(path, "w") as f:
+        f.write(html_code)
+
+    subprocess.run(["electron-pdf", path, pdf_path])  # noqa
+
+    recorder.set_progress(1)
+
+
+def render_pdf(request: HttpRequest, template_name: str, context: dict = None) -> HttpResponse:
+    """Start PDF generation and show progress page.
+
+    The progress page will redirect to the PDF after completion.
+
+    .. warning::
+
+        If celery isn't enabled, this will render the template directly in the browser.
+    """
+    if not context:
+        context = {}
+    pdf_path = path_and_rename(None, "file.pdf", "pdfs")
+
+    html_template = render_to_string(template_name, context)
+
+    if is_celery_enabled():
+        result = generate_pdf(html_template, os.path.join(MEDIA_ROOT, pdf_path))
+
+        context = {
+            "title": _("Progress: Generate PDF file"),
+            "back_url": context.get("back_url", "index"),
+            "progress": {
+                "task_id": result.task_id,
+                "title": _("Generating PDF file …"),
+                "success": _("The PDF file has been generated successfully."),
+                "error": _("There was a problem while generating the PDF file."),
+                "redirect_on_success": MEDIA_URL + pdf_path,
+            },
+            "additional_button": {
+                "href": MEDIA_URL + pdf_path,
+                "caption": _("Download PDF"),
+                "icon": "picture_as_pdf",
+            },
+        }
+
+        # Render progress view
+        return render(request, "core/pages/progress.html", context)
+    else:
+        # Render PaperCSS view if Celery isn't enabled
+        return render(request, template_name, context)
+
+
+@celery_optional
+def clean_up_pdf_directory() -> None:
+    """Clean up directory with generated PDF files."""
+    files = glob.glob(os.path.join(MEDIA_ROOT, "pdfs", "*.pdf"))
+    for file in files:
+        os.remove(file)

docs/dev/01_setup.rst

@@ -30,6 +30,8 @@ Some system libraries are required to install AlekSIS::
 
   sudo apt install build-essential libpq-dev libpq5 libssl-dev python3-dev python3-pip python3-venv yarnpkg gettext
 
+If you want to use the PDF rendering feature, you have to install ``electron-pdf``
+according to the instructions at https://github.com/fraserxu/electron-pdf.
 
 Get Poetry
 ----------