youtube-summarizer/backend/services/video_service.py

import re
import logging
from typing import Optional, List, Dict, Any
from backend.core.exceptions import (
    UserInputError, 
    ValidationError, 
    UnsupportedFormatError,
    ErrorCode
)

logger = logging.getLogger(__name__)


class VideoService:
    def __init__(self):
        self.supported_formats = [
            "https://youtube.com/watch?v=VIDEO_ID",
            "https://youtu.be/VIDEO_ID",
            "https://youtube.com/embed/VIDEO_ID",
            "https://m.youtube.com/watch?v=VIDEO_ID",
            "https://www.youtube.com/watch?v=VIDEO_ID"
        ]
        
        # Patterns that match any video ID length (for validation later)
        self.url_patterns = [
            r'(?:https?://)?(?:www\.)?youtube\.com/watch\?v=([a-zA-Z0-9_-]+)',
            r'(?:https?://)?(?:www\.)?youtu\.be/([a-zA-Z0-9_-]+)',
            r'(?:https?://)?(?:www\.)?youtube\.com/embed/([a-zA-Z0-9_-]+)',
            r'(?:https?://)?(?:m\.)?youtube\.com/watch\?v=([a-zA-Z0-9_-]+)',
            r'(?:https?://)?youtube\.com/watch\?v=([a-zA-Z0-9_-]+)'
        ]
        
        self.playlist_patterns = [
            r'(?:https?://)?(?:www\.)?youtube\.com/playlist\?list=',
            r'(?:https?://)?(?:www\.)?youtube\.com/watch\?.*&list=',
            r'(?:https?://)?(?:www\.)?youtube\.com/watch\?.*\?list='
        ]

    def extract_video_id(self, url: str) -> str:
        """
        Extract YouTube video ID from various URL formats.
        
        Args:
            url: YouTube URL to parse
            
        Returns:
            str: 11-character video ID
            
        Raises:
            ValidationError: If URL format is invalid
            UnsupportedFormatError: If URL is a playlist or other unsupported format
        """
        if not url:
            raise ValidationError(
                message="URL cannot be empty",
                details={"url": url, "supported_formats": self.supported_formats}
            )
        
        url = url.strip()
        
        # Check for playlist URLs first
        if self._is_playlist_url(url):
            logger.info(f"Playlist URL detected: {url}")
            raise UnsupportedFormatError(
                message="Playlist URLs are not yet supported. Please provide a single video URL.",
                details={
                    "url": url,
                    "detected_type": "playlist",
                    "suggestion": "You can copy the URL of a specific video from the playlist instead",
                    "supported_formats": self.supported_formats
                }
            )
        
        # Try to extract video ID using patterns
        for pattern in self.url_patterns:
            match = re.search(pattern, url)
            if match:
                video_id = match.group(1)
                
                # Validate video ID format
                if self._validate_video_id(video_id):
                    logger.info(f"Successfully extracted video ID: {video_id} from URL: {url}")
                    return video_id
                else:
                    raise ValidationError(
                        message=f"Invalid video ID format: {video_id}",
                        details={
                            "url": url,
                            "video_id": video_id,
                            "expected_format": "11 characters containing letters, numbers, underscores, or hyphens"
                        }
                    )
        
        # For any URL (YouTube or not) that doesn't match our patterns,
        # it's a validation error
        raise ValidationError(
            message="Invalid YouTube URL format",
            details={
                "url": url,
                "supported_formats": self.supported_formats,
                "suggestion": "Please provide a valid YouTube video URL with a video ID"
            }
        )
    
    def _validate_video_id(self, video_id: str) -> bool:
        """
        Validate that video ID is exactly 11 characters with valid format.
        
        Args:
            video_id: Video ID to validate
            
        Returns:
            bool: True if valid, False otherwise
        """
        if not video_id or len(video_id) != 11:
            return False
        
        # YouTube video IDs contain letters, numbers, underscores, and hyphens
        valid_pattern = r'^[a-zA-Z0-9_-]{11}$'
        return bool(re.match(valid_pattern, video_id))
    
    def _is_playlist_url(self, url: str) -> bool:
        """
        Check if URL is a playlist URL.
        
        Args:
            url: URL to check
            
        Returns:
            bool: True if playlist URL, False otherwise
        """
        for pattern in self.playlist_patterns:
            if re.search(pattern, url):
                return True
        return False
    
    def normalize_url(self, video_id: str) -> str:
        """
        Create a normalized YouTube URL from a video ID.
        
        Args:
            video_id: YouTube video ID
            
        Returns:
            str: Normalized YouTube URL
        """
        return f"https://youtube.com/watch?v={video_id}"
    
    def get_supported_formats(self) -> List[str]:
        """
        Get list of supported URL formats.
        
        Returns:
            List[str]: List of supported format examples
        """
        return self.supported_formats.copy()