"""
PDF generation utilities with corporate identity support
"""
import os
import base64
from io import BytesIO
from django.conf import settings
from django.template.loader import render_to_string
from django.http import HttpResponse
from django.utils import timezone

# Try to import WeasyPrint, fall back gracefully if not available
try:
    from weasyprint import HTML, CSS
    from weasyprint.text.fonts import FontConfiguration
    WEASYPRINT_AVAILABLE = True
    IMPORT_ERROR = None
except ImportError as e:
    # WeasyPrint dependencies not available
    HTML = None
    CSS = None
    FontConfiguration = None
    WEASYPRINT_AVAILABLE = False
    IMPORT_ERROR = str(e)
except OSError as e:
    # System dependencies missing (like pango)
    HTML = None
    CSS = None
    FontConfiguration = None
    WEASYPRINT_AVAILABLE = False
    IMPORT_ERROR = str(e)

from stiftung.models import AppConfiguration


class PDFGenerator:
    """Corporate identity PDF generator"""
    
    def __init__(self):
        if WEASYPRINT_AVAILABLE:
            self.font_config = FontConfiguration()
        else:
            self.font_config = None
    
    def is_available(self):
        """Check if PDF generation is available"""
        return WEASYPRINT_AVAILABLE
        
    def get_corporate_settings(self):
        """Get corporate identity settings from configuration"""
        return {
            'stiftung_name': AppConfiguration.get_setting('corporate_stiftung_name', 'Stiftung'),
            'logo_path': AppConfiguration.get_setting('corporate_logo_path', ''),
            'primary_color': AppConfiguration.get_setting('corporate_primary_color', '#2c3e50'),
            'secondary_color': AppConfiguration.get_setting('corporate_secondary_color', '#3498db'),
            'address_line1': AppConfiguration.get_setting('corporate_address_line1', ''),
            'address_line2': AppConfiguration.get_setting('corporate_address_line2', ''),
            'phone': AppConfiguration.get_setting('corporate_phone', ''),
            'email': AppConfiguration.get_setting('corporate_email', ''),
            'website': AppConfiguration.get_setting('corporate_website', ''),
            'footer_text': AppConfiguration.get_setting('corporate_footer_text', 'Dieser Bericht wurde automatisch generiert.'),
        }
    
    def get_logo_base64(self, logo_path):
        """Convert logo to base64 for embedding in PDF"""
        if not logo_path:
            return None
            
        # Try different possible paths
        possible_paths = [
            logo_path,
            os.path.join(settings.MEDIA_ROOT, logo_path),
            os.path.join(settings.STATIC_ROOT or '', logo_path),
            os.path.join(settings.BASE_DIR, 'static', logo_path),
        ]
        
        for path in possible_paths:
            if os.path.exists(path):
                try:
                    with open(path, 'rb') as img_file:
                        img_data = base64.b64encode(img_file.read()).decode('utf-8')
                        # Determine MIME type
                        ext = os.path.splitext(path)[1].lower()
                        if ext in ['.jpg', '.jpeg']:
                            mime_type = 'image/jpeg'
                        elif ext == '.png':
                            mime_type = 'image/png'
                        elif ext == '.svg':
                            mime_type = 'image/svg+xml'
                        else:
                            mime_type = 'image/png'  # default
                        
                        return f"data:{mime_type};base64,{img_data}"
                except Exception:
                    continue
        
        return None
    
    def get_base_css(self, corporate_settings):
        """Generate base CSS for corporate identity"""
        primary_color = corporate_settings.get('primary_color', '#2c3e50')
        secondary_color = corporate_settings.get('secondary_color', '#3498db')
        
        return f"""
        @page {{
            size: A4;
            margin: 2cm 1.5cm 2cm 1.5cm;
            @bottom-center {{
                content: "Seite " counter(page) " von " counter(pages);
                font-size: 10pt;
                color: #666;
            }}
        }}
        
        body {{
            font-family: 'Segoe UI', 'DejaVu Sans', Arial, sans-serif;
            font-size: 10pt;
            line-height: 1.4;
            color: #333;
            margin: 0;
            padding: 0;
        }}
        
        .header {{
            border-bottom: 2px solid {primary_color};
            padding-bottom: 15px;
            margin-bottom: 25px;
            page-break-inside: avoid;
        }}
        
        .header-content {{
            display: flex;
            justify-content: space-between;
            align-items: flex-start;
        }}
        
        .header-left {{
            flex: 1;
        }}
        
        .header-right {{
            text-align: right;
            flex-shrink: 0;
            margin-left: 20px;
        }}
        
        .logo {{
            max-height: 60px;
            max-width: 150px;
            margin-bottom: 10px;
        }}
        
        .stiftung-name {{
            font-size: 20pt;
            font-weight: bold;
            color: {primary_color};
            margin: 0;
            line-height: 1.2;
        }}
        
        .document-title {{
            font-size: 16pt;
            color: {secondary_color};
            margin: 5px 0 0 0;
        }}
        
        .header-info {{
            font-size: 9pt;
            color: #666;
            margin-top: 10px;
        }}
        
        .contact-info {{
            font-size: 8pt;
            color: #666;
            line-height: 1.3;
        }}
        
        h1, h2, h3 {{
            color: {primary_color};
            page-break-inside: avoid;
            page-break-after: avoid;
        }}
        
        h1 {{
            font-size: 14pt;
            margin: 20px 0 15px 0;
            border-bottom: 1px solid {secondary_color};
            padding-bottom: 5px;
        }}
        
        h2 {{
            font-size: 12pt;
            margin: 15px 0 10px 0;
        }}
        
        h3 {{
            font-size: 11pt;
            margin: 10px 0 8px 0;
        }}
        
        table {{
            width: 100%;
            border-collapse: collapse;
            margin: 10px 0;
            page-break-inside: avoid;
        }}
        
        th, td {{
            border: 1px solid #ddd;
            padding: 6px 8px;
            text-align: left;
            vertical-align: top;
        }}
        
        th {{
            background-color: #f8f9fa;
            font-weight: 600;
            color: {primary_color};
        }}
        
        tr:nth-child(even) {{
            background-color: #f9f9f9;
        }}
        
        .amount {{
            text-align: right;
            font-family: 'Courier New', monospace;
            font-weight: 500;
        }}
        
        .status-badge {{
            padding: 2px 6px;
            border-radius: 3px;
            font-size: 8pt;
            font-weight: 500;
        }}
        
        .status-beantragt {{ background-color: #fff3cd; color: #856404; }}
        .status-genehmigt {{ background-color: #d1ecf1; color: #0c5460; }}
        .status-ausgezahlt {{ background-color: #d4edda; color: #155724; }}
        .status-abgelehnt {{ background-color: #f8d7da; color: #721c24; }}
        .status-storniert {{ background-color: #e2e3e5; color: #383d41; }}
        
        .footer {{
            margin-top: 30px;
            padding-top: 15px;
            border-top: 1px solid #ddd;
            font-size: 8pt;
            color: #666;
            text-align: center;
        }}
        
        .stats-grid {{
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
            gap: 15px;
            margin: 15px 0;
        }}
        
        .stat-card {{
            border: 1px solid #ddd;
            border-radius: 4px;
            padding: 12px;
            text-align: center;
            background: #f8f9fa;
        }}
        
        .stat-value {{
            font-size: 14pt;
            font-weight: bold;
            color: {primary_color};
        }}
        
        .stat-label {{
            font-size: 8pt;
            color: #666;
            margin-top: 3px;
        }}
        
        .section {{
            margin-bottom: 20px;
            page-break-inside: avoid;
        }}
        
        .no-page-break {{
            page-break-inside: avoid;
        }}
        
        .page-break-before {{
            page-break-before: always;
        }}
        """
    
    def generate_pdf_response(self, html_content, filename, css_content=None):
        """Generate PDF response from HTML content"""
        if not WEASYPRINT_AVAILABLE:
            # Return HTML fallback if WeasyPrint is not available
            error_html = f"""
            <!DOCTYPE html>
            <html>
            <head>
                <title>PDF Export - {filename}</title>
                <style>
                    body {{ font-family: Arial, sans-serif; padding: 20px; max-width: 1200px; margin: 0 auto; }}
                    .warning {{ background: #fff3cd; color: #856404; padding: 15px; border: 1px solid #ffeaa7; border-radius: 5px; margin-bottom: 20px; }}
                    .content {{ border: 1px solid #ddd; padding: 20px; border-radius: 5px; }}
                    {css_content or ''}
                </style>
            </head>
            <body>
                <div class="warning">
                    <h2>⚠️ PDF Generation Not Available</h2>
                    <p><strong>WeasyPrint dependencies are missing:</strong> {IMPORT_ERROR}</p>
                    <p>Showing content as HTML preview instead. You can print this page to PDF using your browser.</p>
                </div>
                <div class="content">
                    {html_content}
                </div>
            </body>
            </html>
            """
            response = HttpResponse(error_html, content_type='text/html')
            response['Content-Disposition'] = f'inline; filename="{filename.replace(".pdf", "_preview.html")}"'
            return response
        
        try:
            # Create CSS string
            if css_content:
                css = CSS(string=css_content, font_config=self.font_config)
            else:
                css = None
            
            # Generate PDF
            html_doc = HTML(string=html_content)
            pdf_bytes = html_doc.write_pdf(stylesheets=[css] if css else None,
                                         font_config=self.font_config)
            
            # Create response
            response = HttpResponse(pdf_bytes, content_type='application/pdf')
            response['Content-Disposition'] = f'attachment; filename="{filename}"'
            return response
            
        except Exception as e:
            # Fallback: return error message as HTML
            error_html = f"""
            <!DOCTYPE html>
            <html>
            <head>
                <title>PDF Generation Error</title>
                <style>
                    body {{ font-family: Arial, sans-serif; padding: 20px; }}
                    .error {{ color: #d32f2f; border: 1px solid #d32f2f; padding: 15px; border-radius: 5px; margin-bottom: 20px; }}
                    .content {{ border: 1px solid #ddd; padding: 20px; border-radius: 5px; }}
                </style>
            </head>
            <body>
                <h1>PDF Generation Error</h1>
                <div class="error">
                    <p>An error occurred while generating the PDF:</p>
                    <p><strong>{str(e)}</strong></p>
                    <p>Showing content as HTML preview instead.</p>
                </div>
                <div class="content">
                    <h2>Original Content</h2>
                    {html_content}
                </div>
            </body>
            </html>
            """
            
            response = HttpResponse(error_html, content_type='text/html')
            response['Content-Disposition'] = f'inline; filename="error_{filename.replace(".pdf", ".html")}"'
            return response
    
    def export_data_list_pdf(self, data, fields_config, title, filename_prefix, request_user=None):
        """
        Export a list of data as formatted PDF
        
        Args:
            data: QuerySet or list of model instances
            fields_config: dict with field names as keys and display names as values
            title: Document title
            filename_prefix: Prefix for the generated filename
            request_user: User making the request (for audit purposes)
        """
        corporate_settings = self.get_corporate_settings()
        logo_base64 = self.get_logo_base64(corporate_settings.get('logo_path', ''))
        
        # Prepare context
        context = {
            'corporate_settings': corporate_settings,
            'logo_base64': logo_base64,
            'title': title,
            'data': data,
            'fields_config': fields_config,
            'generation_date': timezone.now(),
            'generated_by': (request_user.get_full_name() 
                           if hasattr(request_user, 'get_full_name') and request_user.get_full_name() 
                           else request_user.username 
                           if hasattr(request_user, 'username') and request_user.username 
                           else 'System'),
            'total_count': len(data) if hasattr(data, '__len__') else data.count(),
        }
        
        # Render HTML
        html_content = render_to_string('pdf/data_list.html', context)
        
        # Generate CSS
        css_content = self.get_base_css(corporate_settings)
        
        # Generate filename
        timestamp = timezone.now().strftime('%Y%m%d_%H%M%S')
        filename = f"{filename_prefix}_{timestamp}.pdf"
        
        return self.generate_pdf_response(html_content, filename, css_content)


# Global instance
pdf_generator = PDFGenerator()