youtube-summarizer/backend/core/exceptions.py

from enum import Enum
from typing import Optional, Dict, Any
from fastapi import status


class ErrorCode(str, Enum):
    INVALID_URL = "INVALID_URL"
    UNSUPPORTED_FORMAT = "UNSUPPORTED_FORMAT"
    VIDEO_NOT_FOUND = "VIDEO_NOT_FOUND"
    TRANSCRIPT_NOT_AVAILABLE = "TRANSCRIPT_NOT_AVAILABLE"
    TRANSCRIPT_UNAVAILABLE = "TRANSCRIPT_UNAVAILABLE"
    AI_SERVICE_ERROR = "AI_SERVICE_ERROR"
    RATE_LIMIT_EXCEEDED = "RATE_LIMIT_EXCEEDED"
    INTERNAL_ERROR = "INTERNAL_ERROR"
    TOKEN_LIMIT_EXCEEDED = "TOKEN_LIMIT_EXCEEDED"
    COST_LIMIT_EXCEEDED = "COST_LIMIT_EXCEEDED"
    AI_SERVICE_UNAVAILABLE = "AI_SERVICE_UNAVAILABLE"


class BaseAPIException(Exception):
    def __init__(
        self,
        message: str,
        error_code: ErrorCode,
        status_code: int = status.HTTP_500_INTERNAL_SERVER_ERROR,
        details: Optional[Dict[str, Any]] = None,
        recoverable: bool = False
    ):
        self.message = message
        self.error_code = error_code
        self.status_code = status_code
        self.details = details or {}
        self.recoverable = recoverable
        super().__init__(message)


class UserInputError(BaseAPIException):
    def __init__(
        self, 
        message: str, 
        error_code: ErrorCode, 
        details: Optional[Dict[str, Any]] = None
    ):
        super().__init__(
            message=message,
            error_code=error_code,
            status_code=status.HTTP_400_BAD_REQUEST,
            details=details,
            recoverable=True
        )


class ValidationError(UserInputError):
    def __init__(self, message: str, details: Optional[Dict[str, Any]] = None):
        super().__init__(
            message=message,
            error_code=ErrorCode.INVALID_URL,
            details=details
        )


class UnsupportedFormatError(UserInputError):
    def __init__(self, message: str, details: Optional[Dict[str, Any]] = None):
        super().__init__(
            message=message,
            error_code=ErrorCode.UNSUPPORTED_FORMAT,
            details=details
        )


class YouTubeError(BaseAPIException):
    """Base exception for YouTube-related errors"""
    def __init__(self, message: str, details: Optional[Dict[str, Any]] = None):
        super().__init__(
            message=message,
            error_code=ErrorCode.VIDEO_NOT_FOUND,
            status_code=status.HTTP_400_BAD_REQUEST,
            details=details
        )


class TranscriptExtractionError(BaseAPIException):
    """Base exception for transcript extraction failures"""
    pass


class AIServiceError(BaseAPIException):
    """Base exception for AI service errors"""
    pass


class TokenLimitExceededError(AIServiceError):
    """Raised when content exceeds model token limit"""
    def __init__(self, token_count: int, max_tokens: int):
        super().__init__(
            message=f"Content ({token_count} tokens) exceeds model limit ({max_tokens} tokens)",
            error_code=ErrorCode.TOKEN_LIMIT_EXCEEDED,
            status_code=status.HTTP_400_BAD_REQUEST,
            details={
                "token_count": token_count,
                "max_tokens": max_tokens,
                "suggestions": [
                    "Use chunked processing for long content",
                    "Choose a briefer summary length",
                    "Split content into smaller sections"
                ]
            }
        )


class CostLimitExceededError(AIServiceError):
    """Raised when processing cost exceeds limits"""
    def __init__(self, estimated_cost: float, cost_limit: float):
        super().__init__(
            message=f"Estimated cost ${estimated_cost:.3f} exceeds limit ${cost_limit:.2f}",
            error_code=ErrorCode.COST_LIMIT_EXCEEDED,
            status_code=status.HTTP_400_BAD_REQUEST,
            details={
                "estimated_cost": estimated_cost,
                "cost_limit": cost_limit,
                "cost_reduction_tips": [
                    "Choose 'brief' summary length",
                    "Remove less important content from transcript",
                    "Process content in smaller segments"
                ]
            }
        )


class AIServiceUnavailableError(AIServiceError):
    """Raised when AI service is temporarily unavailable"""
    def __init__(self, message: str = "AI service is temporarily unavailable"):
        super().__init__(
            message=message,
            error_code=ErrorCode.AI_SERVICE_UNAVAILABLE,
            status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
            details={
                "suggestions": [
                    "Please try again in a few moments",
                    "Check API status page for any ongoing issues"
                ]
            },
            recoverable=True
        )


class PipelineError(BaseAPIException):
    """Base exception for pipeline processing errors"""
    def __init__(
        self, 
        message: str, 
        stage: str = "unknown",
        recoverable: bool = True,
        details: Optional[Dict[str, Any]] = None
    ):
        super().__init__(
            message=message,
            error_code=ErrorCode.INTERNAL_ERROR,
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            details={
                "stage": stage,
                **(details or {})
            },
            recoverable=recoverable
        )


class ServiceError(BaseAPIException):
    """General service error for business logic failures"""
    def __init__(
        self,
        message: str,
        service: str = "unknown",
        recoverable: bool = True,
        details: Optional[Dict[str, Any]] = None
    ):
        super().__init__(
            message=message,
            error_code=ErrorCode.INTERNAL_ERROR,
            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
            details={
                "service": service,
                **(details or {})
            },
            recoverable=recoverable
        )