# app/exceptions/error_renderer.py
"""
Error Page Renderer
Renders context-aware error pages using Jinja2 templates.
Handles fallback logic and context-specific customization.
"""
import logging
from pathlib import Path
from typing import Optional, Dict, Any
from fastapi import Request
from fastapi.responses import HTMLResponse
from fastapi.templating import Jinja2Templates
from middleware.context_middleware import RequestContext, get_request_context
logger = logging.getLogger(__name__)
class ErrorPageRenderer:
"""Renders context-aware error pages using Jinja2 templates."""
# Map status codes to friendly names
STATUS_CODE_NAMES = {
400: "Bad Request",
401: "Unauthorized",
403: "Forbidden",
404: "Not Found",
422: "Validation Error",
429: "Too Many Requests",
500: "Internal Server Error",
502: "Bad Gateway",
503: "Service Unavailable",
}
# Map status codes to user-friendly messages
STATUS_CODE_MESSAGES = {
400: "The request could not be processed due to invalid data.",
401: "You need to be authenticated to access this resource.",
403: "You don't have permission to access this resource.",
404: "The page you're looking for doesn't exist or has been moved.",
422: "The submitted data contains validation errors.",
429: "Too many requests. Please slow down and try again later.",
500: "Something went wrong on our end. We're working to fix it.",
502: "Unable to reach the service. Please try again later.",
503: "The service is temporarily unavailable. Please try again later.",
}
@staticmethod
def get_templates_dir() -> Path:
"""Get the templates directory path."""
# Assuming templates are in app/templates/
base_dir = Path(__file__).resolve().parent.parent
return base_dir / "templates"
@staticmethod
def render_error_page(
request: Request,
status_code: int,
error_code: str,
message: str,
details: Optional[Dict[str, Any]] = None,
show_debug: bool = False,
) -> HTMLResponse:
"""
Render appropriate error page based on request context.
Template Selection Priority:
1. Context-specific error page: {context}/errors/{status_code}.html
2. Context-specific generic: {context}/errors/generic.html
3. Fallback error page: fallback/{status_code}.html
4. Fallback generic: fallback/generic.html
Args:
request: FastAPI request object
status_code: HTTP status code
error_code: Application error code
message: Error message
details: Additional error details
show_debug: Whether to show debug information
Returns:
HTMLResponse with rendered error page
"""
# Get request context
context_type = get_request_context(request)
# Prepare template data
template_data = ErrorPageRenderer._prepare_template_data(
request=request,
context_type=context_type,
status_code=status_code,
error_code=error_code,
message=message,
details=details,
show_debug=show_debug,
)
# Find and render template
templates_dir = ErrorPageRenderer.get_templates_dir()
templates = Jinja2Templates(directory=str(templates_dir))
# Try to find appropriate template
template_path = ErrorPageRenderer._find_template(
context_type=context_type,
status_code=status_code,
)
logger.info(
f"Rendering error page: {template_path} for {status_code} in {context_type.value} context",
extra={
"status_code": status_code,
"error_code": error_code,
"context": context_type.value,
"template": template_path,
}
)
try:
# Render template
return templates.TemplateResponse(
template_path,
{
"request": request,
**template_data,
},
status_code=status_code,
)
except Exception as e:
logger.error(
f"Failed to render error template {template_path}: {e}",
exc_info=True
)
# Return basic HTML as absolute fallback
return ErrorPageRenderer._render_basic_html_fallback(
status_code=status_code,
error_code=error_code,
message=message,
)
@staticmethod
def _find_template(
context_type: RequestContext,
status_code: int,
) -> str:
"""
Find appropriate error template based on context and status code.
Priority:
1. {context}/errors/{status_code}.html
2. {context}/errors/generic.html
3. fallback/{status_code}.html
4. fallback/generic.html
"""
templates_dir = ErrorPageRenderer.get_templates_dir()
# Map context type to folder name
context_folders = {
RequestContext.ADMIN: "admin",
RequestContext.VENDOR_DASHBOARD: "vendor",
RequestContext.SHOP: "shop",
RequestContext.API: "fallback", # API shouldn't get here, but just in case
RequestContext.FALLBACK: "fallback",
}
context_folder = context_folders.get(context_type, "fallback")
# Try context-specific status code template
specific_template = f"{context_folder}/errors/{status_code}.html"
if (templates_dir / specific_template).exists():
return specific_template
# Try context-specific generic template
generic_template = f"{context_folder}/errors/generic.html"
if (templates_dir / generic_template).exists():
return generic_template
# Try fallback status code template
fallback_specific = f"fallback/{status_code}.html"
if (templates_dir / fallback_specific).exists():
return fallback_specific
# Use fallback generic template (must exist)
return "fallback/generic.html"
@staticmethod
def _prepare_template_data(
request: Request,
context_type: RequestContext,
status_code: int,
error_code: str,
message: str,
details: Optional[Dict[str, Any]],
show_debug: bool,
) -> Dict[str, Any]:
"""Prepare data dictionary for error template."""
# Get friendly status name
status_name = ErrorPageRenderer.STATUS_CODE_NAMES.get(
status_code, f"Error {status_code}"
)
# Get default user-friendly message
default_message = ErrorPageRenderer.STATUS_CODE_MESSAGES.get(
status_code, "An error occurred while processing your request."
)
# Use provided message or default
user_message = message if message else default_message
# Determine if we should show debug info
# Only show to admins (we can check user role if available)
display_debug = show_debug and ErrorPageRenderer._is_admin_user(request)
# Get context-specific data
context_data = ErrorPageRenderer._get_context_data(request, context_type)
return {
"status_code": status_code,
"status_name": status_name,
"error_code": error_code,
"message": user_message,
"details": details or {},
"show_debug": display_debug,
"context_type": context_type.value,
"path": request.url.path,
**context_data,
}
@staticmethod
def _get_context_data(request: Request, context_type: RequestContext) -> Dict[str, Any]:
"""Get context-specific data for error templates."""
data = {}
# Add vendor information if available (for shop context)
if context_type == RequestContext.SHOP:
vendor = getattr(request.state, "vendor", None)
if vendor:
# Pass minimal vendor info for templates
data["vendor"] = {
"id": vendor.id,
"name": vendor.name,
"subdomain": vendor.subdomain,
"logo": getattr(vendor, "logo", None),
}
# Add theme information if available
theme = getattr(request.state, "theme", None)
if theme:
# Theme can be a dict or object, handle both
if isinstance(theme, dict):
data["theme"] = theme
else:
# If it's an object, convert to dict
data["theme"] = {
"colors": getattr(theme, "colors", {}),
"fonts": getattr(theme, "fonts", {}),
"branding": getattr(theme, "branding", {}),
"custom_css": getattr(theme, "custom_css", None),
}
return data
@staticmethod
def _is_admin_user(request: Request) -> bool:
"""
Check if current user is an admin (for debug info display).
This is a placeholder - implement based on your auth system.
"""
# TODO: Implement actual admin check based on JWT/session
# For now, check if we're in admin context
context_type = get_request_context(request)
return context_type == RequestContext.ADMIN
@staticmethod
def _render_basic_html_fallback(
status_code: int,
error_code: str,
message: str,
) -> HTMLResponse:
"""
Render a basic HTML error page as absolute fallback.
Used when template rendering fails.
"""
html_content = f"""
{status_code} - Error
{status_code}
Error
{message}
Error Code: {error_code}
"""
return HTMLResponse(content=html_content, status_code=status_code)