b3a7537364
- Certificate model: serial_number (unique), status (pending/rendering/completed/failed),
pdf_path, pdf_hash (SHA-256), verification_url, render_attempts, training_record FK
- renderer.py: LaTeX template → pdflatex subprocess → PDF; _escape_latex for XSS safety;
compute_pdf_hash for immutable verification metadata
- services.py: issue_certificate() generates serial, creates record, enqueues Celery task
- tasks.py: render_certificate_task (bind=True, autoretry 3x with 60s backoff);
sets RENDERING → COMPLETED with hash; FAILED with error on all retries exhausted
- API: /certificates/ (own list), /certificates/{id}/ (own detail)
- 15 unit + integration tests: hash consistency, LaTeX escaping, mocked render, retry behavior
Co-Authored-By: Paperclip <noreply@paperclip.ing>
109 lines
3.1 KiB
Python
109 lines
3.1 KiB
Python
"""
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LaTeX certificate renderer.
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Takes a certificate context dict and renders it to a PDF file via pdflatex.
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Returns the path to the rendered PDF.
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"""
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from __future__ import annotations
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import hashlib
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import os
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import shutil
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import subprocess
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import tempfile
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from pathlib import Path
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from string import Template
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LATEX_TEMPLATE = r"""
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\documentclass[12pt,a4paper]{article}
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\usepackage[margin=2cm]{geometry}
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\usepackage{fontenc}
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\usepackage[utf8]{inputenc}
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\usepackage{xcolor}
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\usepackage{graphicx}
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\pagestyle{empty}
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\begin{document}
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\begin{center}
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{\Huge\bfseries Certificate of Completion}\\[1.5cm]
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{\Large This certifies that}\\[0.8cm]
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{\LARGE\bfseries $recipient_name}\\[0.8cm]
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{\large has successfully completed}\\[0.5cm]
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{\Large\bfseries $course_title}\\[0.5cm]
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{\normalsize on $issued_date}\\[1.5cm]
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{\small Serial: $serial_number}\\[0.3cm]
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{\small Verify at: $verification_url}
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\end{center}
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\end{document}
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"""
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class RenderError(Exception):
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pass
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def _escape_latex(value: str) -> str:
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"""Escape special LaTeX characters in user-supplied strings."""
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special = {
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"&": r"\&",
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"%": r"\%",
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"$": r"\$",
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"#": r"\#",
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"_": r"\_",
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"{": r"\{",
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"}": r"\}",
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"~": r"\textasciitilde{}",
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"^": r"\^{}",
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"\\": r"\textbackslash{}",
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}
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return "".join(special.get(c, c) for c in value)
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def render_certificate_pdf(context: dict, output_path: str) -> str:
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"""
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Render a certificate PDF from the given context dict.
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Saves to output_path (must be a .pdf path).
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Returns output_path on success.
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Raises RenderError on failure.
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"""
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safe = {k: _escape_latex(str(v)) for k, v in context.items()}
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latex_source = Template(LATEX_TEMPLATE).safe_substitute(safe)
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with tempfile.TemporaryDirectory() as tmpdir:
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tex_file = os.path.join(tmpdir, "certificate.tex")
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with open(tex_file, "w", encoding="utf-8") as f:
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f.write(latex_source)
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try:
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result = subprocess.run(
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["pdflatex", "-interaction=nonstopmode", "-output-directory", tmpdir, tex_file],
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capture_output=True,
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text=True,
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timeout=30,
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)
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except FileNotFoundError:
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raise RenderError("pdflatex not found — ensure TeX Live is installed.")
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except subprocess.TimeoutExpired:
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raise RenderError("pdflatex timed out after 30 seconds.")
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if result.returncode != 0:
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raise RenderError(f"pdflatex failed:\n{result.stdout[-2000:]}")
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rendered_pdf = os.path.join(tmpdir, "certificate.pdf")
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if not os.path.exists(rendered_pdf):
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raise RenderError("pdflatex ran successfully but no PDF was produced.")
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os.makedirs(os.path.dirname(output_path), exist_ok=True)
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shutil.copy2(rendered_pdf, output_path)
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return output_path
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def compute_pdf_hash(pdf_path: str) -> str:
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"""Compute SHA-256 hex digest of a PDF file."""
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sha = hashlib.sha256()
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with open(pdf_path, "rb") as f:
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for chunk in iter(lambda: f.read(65536), b""):
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sha.update(chunk)
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return sha.hexdigest()
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