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This commit is contained in:
beabigegg
507
backend/app/services/pdf_generator.py
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507
backend/app/services/pdf_generator.py
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"""
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Tool_OCR - PDF Generator Service
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Converts Markdown to layout-preserved PDFs using Pandoc + WeasyPrint
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"""
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import logging
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import subprocess
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from pathlib import Path
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from typing import Optional, Dict
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from datetime import datetime
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from weasyprint import HTML, CSS
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from markdown import markdown
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from app.core.config import settings
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logger = logging.getLogger(__name__)
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class PDFGenerationError(Exception):
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"""Exception raised when PDF generation fails"""
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pass
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class PDFGenerator:
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"""
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PDF generation service with layout preservation
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Supports two generation methods:
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1. Pandoc (preferred): Markdown → HTML → PDF via pandoc command
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2. WeasyPrint (fallback): Direct Python-based HTML → PDF conversion
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"""
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# Default CSS template for layout preservation
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DEFAULT_CSS = """
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@page {
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size: A4;
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margin: 2cm;
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}
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body {
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font-family: "Noto Sans CJK SC", "Noto Sans CJK TC", "Microsoft YaHei", "SimSun", sans-serif;
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font-size: 11pt;
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line-height: 1.6;
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color: #333;
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}
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h1 {
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font-size: 24pt;
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font-weight: bold;
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margin-top: 0;
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margin-bottom: 12pt;
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color: #000;
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page-break-after: avoid;
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}
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h2 {
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font-size: 18pt;
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font-weight: bold;
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margin-top: 18pt;
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margin-bottom: 10pt;
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color: #000;
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page-break-after: avoid;
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}
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h3 {
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font-size: 14pt;
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font-weight: bold;
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margin-top: 14pt;
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margin-bottom: 8pt;
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color: #000;
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page-break-after: avoid;
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}
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p {
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margin: 0 0 10pt 0;
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text-align: justify;
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}
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table {
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width: 100%;
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border-collapse: collapse;
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margin: 12pt 0;
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page-break-inside: avoid;
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}
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table th {
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background-color: #f0f0f0;
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border: 1px solid #ccc;
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padding: 8pt;
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text-align: left;
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font-weight: bold;
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}
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table td {
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border: 1px solid #ccc;
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padding: 8pt;
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text-align: left;
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}
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code {
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font-family: "Courier New", monospace;
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font-size: 10pt;
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background-color: #f5f5f5;
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padding: 2pt 4pt;
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border-radius: 3px;
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}
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pre {
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background-color: #f5f5f5;
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border: 1px solid #ddd;
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border-radius: 5px;
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padding: 10pt;
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overflow-x: auto;
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page-break-inside: avoid;
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}
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pre code {
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background-color: transparent;
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padding: 0;
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}
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img {
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max-width: 100%;
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height: auto;
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display: block;
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margin: 12pt auto;
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page-break-inside: avoid;
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}
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blockquote {
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border-left: 4px solid #ddd;
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padding-left: 12pt;
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margin: 12pt 0;
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color: #666;
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font-style: italic;
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}
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ul, ol {
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margin: 10pt 0;
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padding-left: 20pt;
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}
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li {
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margin: 5pt 0;
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}
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hr {
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border: none;
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border-top: 1px solid #ccc;
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margin: 20pt 0;
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}
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.page-break {
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page-break-after: always;
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}
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"""
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# Academic paper template
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ACADEMIC_CSS = """
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@page {
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size: A4;
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margin: 2.5cm;
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}
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body {
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font-family: "Times New Roman", "Noto Serif CJK SC", serif;
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font-size: 12pt;
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line-height: 1.8;
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color: #000;
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}
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h1 {
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font-size: 20pt;
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text-align: center;
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margin-bottom: 24pt;
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page-break-after: avoid;
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}
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h2 {
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font-size: 16pt;
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margin-top: 20pt;
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margin-bottom: 12pt;
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page-break-after: avoid;
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}
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h3 {
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font-size: 14pt;
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margin-top: 16pt;
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margin-bottom: 10pt;
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page-break-after: avoid;
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}
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p {
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text-indent: 2em;
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text-align: justify;
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margin: 0 0 12pt 0;
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}
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table {
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width: 100%;
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border-collapse: collapse;
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margin: 16pt auto;
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page-break-inside: avoid;
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}
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table caption {
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font-weight: bold;
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margin-bottom: 8pt;
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}
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"""
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# Business report template
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BUSINESS_CSS = """
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@page {
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size: A4;
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margin: 2cm 2.5cm;
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}
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body {
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font-family: "Arial", "Noto Sans CJK SC", sans-serif;
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font-size: 11pt;
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line-height: 1.5;
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color: #333;
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}
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h1 {
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font-size: 22pt;
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color: #0066cc;
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border-bottom: 3px solid #0066cc;
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padding-bottom: 8pt;
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margin-bottom: 20pt;
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page-break-after: avoid;
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}
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h2 {
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font-size: 16pt;
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color: #0066cc;
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margin-top: 20pt;
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margin-bottom: 12pt;
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page-break-after: avoid;
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}
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table {
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width: 100%;
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border-collapse: collapse;
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margin: 16pt 0;
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}
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table th {
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background-color: #0066cc;
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color: white;
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padding: 10pt;
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font-weight: bold;
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}
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table td {
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border: 1px solid #ddd;
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padding: 10pt;
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}
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table tr:nth-child(even) {
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background-color: #f9f9f9;
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}
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"""
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def __init__(self):
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"""Initialize PDF generator"""
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self.css_templates = {
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"default": self.DEFAULT_CSS,
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"academic": self.ACADEMIC_CSS,
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"business": self.BUSINESS_CSS,
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}
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def check_pandoc_available(self) -> bool:
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"""
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Check if Pandoc is installed and available
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Returns:
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bool: True if pandoc is available, False otherwise
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"""
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try:
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result = subprocess.run(
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["pandoc", "--version"],
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capture_output=True,
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text=True,
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timeout=5
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)
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return result.returncode == 0
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except (subprocess.TimeoutExpired, FileNotFoundError):
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logger.warning("Pandoc not found or timed out")
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return False
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def generate_pdf_pandoc(
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self,
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markdown_path: Path,
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output_path: Path,
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css_template: str = "default",
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metadata: Optional[Dict] = None
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) -> Path:
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"""
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Generate PDF using Pandoc (preferred method)
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Args:
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markdown_path: Path to input Markdown file
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output_path: Path to output PDF file
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css_template: CSS template name or custom CSS string
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metadata: Optional metadata dict (title, author, date)
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Returns:
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Path: Path to generated PDF file
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Raises:
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PDFGenerationError: If PDF generation fails
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"""
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try:
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# Create temporary CSS file
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css_content = self.css_templates.get(css_template, css_template)
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css_file = output_path.parent / f"temp_{datetime.now().timestamp()}.css"
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css_file.write_text(css_content, encoding="utf-8")
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# Build pandoc command
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pandoc_cmd = [
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"pandoc",
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str(markdown_path),
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"-o", str(output_path),
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"--pdf-engine=weasyprint",
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"--css", str(css_file),
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"--standalone",
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"--from=markdown+tables+fenced_code_blocks+footnotes",
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]
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# Add metadata if provided
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if metadata:
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if metadata.get("title"):
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pandoc_cmd.extend(["--metadata", f"title={metadata['title']}"])
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if metadata.get("author"):
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pandoc_cmd.extend(["--metadata", f"author={metadata['author']}"])
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if metadata.get("date"):
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pandoc_cmd.extend(["--metadata", f"date={metadata['date']}"])
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# Execute pandoc
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logger.info(f"Executing pandoc: {' '.join(pandoc_cmd)}")
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result = subprocess.run(
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pandoc_cmd,
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capture_output=True,
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text=True,
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timeout=60 # 60 second timeout for large documents
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)
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# Clean up temporary CSS file
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css_file.unlink(missing_ok=True)
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if result.returncode != 0:
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error_msg = f"Pandoc failed: {result.stderr}"
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logger.error(error_msg)
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raise PDFGenerationError(error_msg)
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if not output_path.exists():
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raise PDFGenerationError(f"PDF file not created: {output_path}")
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logger.info(f"PDF generated successfully via Pandoc: {output_path}")
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return output_path
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except subprocess.TimeoutExpired:
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css_file.unlink(missing_ok=True)
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raise PDFGenerationError("Pandoc execution timed out")
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except Exception as e:
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css_file.unlink(missing_ok=True)
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raise PDFGenerationError(f"Pandoc PDF generation failed: {str(e)}")
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def generate_pdf_weasyprint(
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self,
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markdown_path: Path,
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output_path: Path,
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css_template: str = "default",
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metadata: Optional[Dict] = None
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) -> Path:
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"""
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Generate PDF using WeasyPrint directly (fallback method)
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Args:
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markdown_path: Path to input Markdown file
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output_path: Path to output PDF file
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css_template: CSS template name or custom CSS string
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metadata: Optional metadata dict (title, author, date)
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Returns:
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Path: Path to generated PDF file
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Raises:
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PDFGenerationError: If PDF generation fails
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"""
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try:
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# Read Markdown content
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markdown_content = markdown_path.read_text(encoding="utf-8")
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# Convert Markdown to HTML
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html_content = markdown(
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markdown_content,
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extensions=[
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'tables',
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'fenced_code',
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'codehilite',
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'nl2br',
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'sane_lists',
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]
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)
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# Wrap HTML with proper structure
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title = metadata.get("title", markdown_path.stem) if metadata else markdown_path.stem
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full_html = f"""
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<!DOCTYPE html>
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<html lang="zh-CN">
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<head>
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<meta charset="UTF-8">
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<title>{title}</title>
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</head>
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<body>
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{html_content}
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</body>
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</html>
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"""
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# Get CSS content
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css_content = self.css_templates.get(css_template, css_template)
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# Generate PDF
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logger.info(f"Generating PDF via WeasyPrint: {output_path}")
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html = HTML(string=full_html, base_url=str(markdown_path.parent))
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css = CSS(string=css_content)
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html.write_pdf(str(output_path), stylesheets=[css])
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if not output_path.exists():
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raise PDFGenerationError(f"PDF file not created: {output_path}")
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logger.info(f"PDF generated successfully via WeasyPrint: {output_path}")
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return output_path
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except Exception as e:
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raise PDFGenerationError(f"WeasyPrint PDF generation failed: {str(e)}")
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def generate_pdf(
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self,
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markdown_path: Path,
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output_path: Path,
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css_template: str = "default",
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metadata: Optional[Dict] = None,
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prefer_pandoc: bool = True
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) -> Path:
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"""
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Generate PDF from Markdown with automatic fallback
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Args:
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markdown_path: Path to input Markdown file
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output_path: Path to output PDF file
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css_template: CSS template name ("default", "academic", "business") or custom CSS
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metadata: Optional metadata dict (title, author, date)
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prefer_pandoc: Use Pandoc if available, fallback to WeasyPrint
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Returns:
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Path: Path to generated PDF file
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Raises:
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PDFGenerationError: If both methods fail
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"""
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if not markdown_path.exists():
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raise PDFGenerationError(f"Markdown file not found: {markdown_path}")
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# Ensure output directory exists
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output_path.parent.mkdir(parents=True, exist_ok=True)
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# Try Pandoc first if preferred and available
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if prefer_pandoc and self.check_pandoc_available():
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try:
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return self.generate_pdf_pandoc(markdown_path, output_path, css_template, metadata)
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except PDFGenerationError as e:
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logger.warning(f"Pandoc failed, falling back to WeasyPrint: {e}")
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# Fall through to WeasyPrint
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# Use WeasyPrint (fallback or direct)
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return self.generate_pdf_weasyprint(markdown_path, output_path, css_template, metadata)
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def get_available_templates(self) -> Dict[str, str]:
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"""
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Get list of available CSS templates
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Returns:
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Dict mapping template names to descriptions
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"""
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return {
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"default": "通用排版模板，適合大多數文檔",
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"academic": "學術論文模板，適合研究報告",
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"business": "商業報告模板，適合企業文檔",
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}
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def save_custom_template(self, template_name: str, css_content: str) -> None:
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"""
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Save a custom CSS template
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Args:
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template_name: Template name
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css_content: CSS content
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"""
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self.css_templates[template_name] = css_content
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logger.info(f"Custom CSS template saved: {template_name}")
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Reference in New Issue
Block a user