thrillwiki_django_no_react/core/api/exceptions.py

"""
Custom exception handling for ThrillWiki API.
Provides standardized error responses following Django styleguide patterns.
"""

import logging
from typing import Any, Dict, Optional

from django.http import Http404
from django.core.exceptions import PermissionDenied, ValidationError as DjangoValidationError
from rest_framework import status
from rest_framework.response import Response
from rest_framework.views import exception_handler
from rest_framework.exceptions import ValidationError as DRFValidationError, NotFound, PermissionDenied as DRFPermissionDenied

from ..exceptions import ThrillWikiException
from ..logging import get_logger, log_exception

logger = get_logger(__name__)


def custom_exception_handler(exc: Exception, context: Dict[str, Any]) -> Optional[Response]:
    """
    Custom exception handler for DRF that provides standardized error responses.
    
    Returns:
        Response with standardized error format or None to fallback to default handler
    """
    # Call REST framework's default exception handler first
    response = exception_handler(exc, context)
    
    if response is not None:
        # Standardize the error response format
        custom_response_data = {
            'status': 'error',
            'error': {
                'code': _get_error_code(exc),
                'message': _get_error_message(exc, response.data),
                'details': _get_error_details(exc, response.data),
            },
            'data': None,
        }
        
        # Add request context for debugging
        if hasattr(context.get('request'), 'user'):
            custom_response_data['error']['request_user'] = str(context['request'].user)
        
        # Log the error for monitoring
        log_exception(logger, exc, context={'response_status': response.status_code}, request=context.get('request'))
        
        response.data = custom_response_data
    
    # Handle ThrillWiki custom exceptions
    elif isinstance(exc, ThrillWikiException):
        custom_response_data = {
            'status': 'error',
            'error': exc.to_dict(),
            'data': None,
        }
        
        log_exception(logger, exc, context={'response_status': exc.status_code}, request=context.get('request'))
        response = Response(custom_response_data, status=exc.status_code)
    
    # Handle specific Django exceptions that DRF doesn't catch
    elif isinstance(exc, DjangoValidationError):
        custom_response_data = {
            'status': 'error',
            'error': {
                'code': 'VALIDATION_ERROR',
                'message': 'Validation failed',
                'details': _format_django_validation_errors(exc),
            },
            'data': None,
        }
        
        log_exception(logger, exc, context={'response_status': status.HTTP_400_BAD_REQUEST}, request=context.get('request'))
        response = Response(custom_response_data, status=status.HTTP_400_BAD_REQUEST)
    
    elif isinstance(exc, Http404):
        custom_response_data = {
            'status': 'error',
            'error': {
                'code': 'NOT_FOUND',
                'message': 'Resource not found',
                'details': str(exc) if str(exc) else None,
            },
            'data': None,
        }
        
        log_exception(logger, exc, context={'response_status': status.HTTP_404_NOT_FOUND}, request=context.get('request'))
        response = Response(custom_response_data, status=status.HTTP_404_NOT_FOUND)
    
    elif isinstance(exc, PermissionDenied):
        custom_response_data = {
            'status': 'error',
            'error': {
                'code': 'PERMISSION_DENIED',
                'message': 'Permission denied',
                'details': str(exc) if str(exc) else None,
            },
            'data': None,
        }
        
        log_exception(logger, exc, context={'response_status': status.HTTP_403_FORBIDDEN}, request=context.get('request'))
        response = Response(custom_response_data, status=status.HTTP_403_FORBIDDEN)
    
    return response


def _get_error_code(exc: Exception) -> str:
    """Extract or determine error code from exception."""
    if hasattr(exc, 'default_code'):
        return exc.default_code.upper()
    
    if isinstance(exc, DRFValidationError):
        return 'VALIDATION_ERROR'
    elif isinstance(exc, NotFound):
        return 'NOT_FOUND'
    elif isinstance(exc, DRFPermissionDenied):
        return 'PERMISSION_DENIED'
    
    return exc.__class__.__name__.upper()


def _get_error_message(exc: Exception, response_data: Any) -> str:
    """Extract user-friendly error message."""
    if isinstance(response_data, dict):
        # Handle DRF validation errors
        if 'detail' in response_data:
            return str(response_data['detail'])
        elif 'non_field_errors' in response_data:
            errors = response_data['non_field_errors']
            return errors[0] if isinstance(errors, list) and errors else str(errors)
        elif isinstance(response_data, dict) and len(response_data) == 1:
            key, value = next(iter(response_data.items()))
            if isinstance(value, list) and value:
                return f"{key}: {value[0]}"
            return f"{key}: {value}"
    
    # Fallback to exception message
    return str(exc) if str(exc) else 'An error occurred'


def _get_error_details(exc: Exception, response_data: Any) -> Optional[Dict[str, Any]]:
    """Extract detailed error information for debugging."""
    if isinstance(response_data, dict) and len(response_data) > 1:
        return response_data
    
    if hasattr(exc, 'detail') and isinstance(exc.detail, dict):
        return exc.detail
    
    return None


def _format_django_validation_errors(exc: DjangoValidationError) -> Dict[str, Any]:
    """Format Django ValidationError for API response."""
    if hasattr(exc, 'error_dict'):
        # Field-specific errors
        return {
            field: [str(error) for error in errors]
            for field, errors in exc.error_dict.items()
        }
    elif hasattr(exc, 'error_list'):
        # Non-field errors
        return {
            'non_field_errors': [str(error) for error in exc.error_list]
        }
    
    return {'non_field_errors': [str(exc)]}


# Removed _log_api_error - using centralized logging instead