"""
Validation utilities for security and input validation
"""
import os
import re
from typing import Optional
from urllib.parse import urlparse


class ValidationError(Exception):
    """Custom exception for validation errors."""
    pass


class Validators:
    """Collection of validation functions for security and input validation."""
    
    # Regex patterns for validation - allow numbers, letters, hyphens, underscores, dots
    HUGGINGFACE_MODEL_PATTERN = re.compile(r'^[a-zA-Z0-9_\-\.]+/[a-zA-Z0-9_\-\.]+$')
    SAFE_FILENAME_PATTERN = re.compile(r'^[a-zA-Z0-9_\-\.]+$')
    
    @staticmethod
    def validate_model_path(model_path: str) -> bool:
        """
        Validate that a custom model path is safe and follows expected patterns.
        
        Args:
            model_path: The model path to validate
            
        Returns:
            bool: True if valid, False otherwise
            
        Raises:
            ValidationError: If the model path is invalid
        """
        if not model_path or not isinstance(model_path, str):
            raise ValidationError("Model path cannot be empty")
        
        # Trim whitespace
        model_path = model_path.strip()
        
        # Check for dangerous characters (excluding single forward slash for HuggingFace format)
        dangerous_chars = ['..', '\\', '|', ';', '&', '$', '`', '<', '>']
        if any(char in model_path for char in dangerous_chars):
            raise ValidationError("Model path contains invalid characters")
        
        # Check for multiple slashes or leading/trailing slashes
        if '//' in model_path or model_path.startswith('/') or model_path.endswith('/'):
            raise ValidationError("Model path contains invalid characters")
        
        # Check if it looks like a HuggingFace model path (user/model format)
        if not Validators.HUGGINGFACE_MODEL_PATTERN.match(model_path):
            raise ValidationError("Model path must follow the format 'organization/model-name'")
        
        # Check length limits
        if len(model_path) > 200:
            raise ValidationError("Model path is too long")
        
        return True
    
    @staticmethod
    def validate_filename(filename: str) -> bool:
        """
        Validate that a filename is safe for upload.
        
        Args:
            filename: The filename to validate
            
        Returns:
            bool: True if valid, False otherwise
            
        Raises:
            ValidationError: If the filename is invalid
        """
        if not filename or not isinstance(filename, str):
            raise ValidationError("Filename cannot be empty")
        
        # Check for dangerous characters and patterns
        dangerous_patterns = ['..', '/', '\\', '|', ';', '&', '$', '`', '<', '>']
        if any(pattern in filename for pattern in dangerous_patterns):
            raise ValidationError("Filename contains invalid characters")
        
        # Check if filename starts with a dot (hidden files)
        if filename.startswith('.'):
            raise ValidationError("Hidden files are not allowed")
        
        # Check length
        if len(filename) > 255:
            raise ValidationError("Filename is too long")
        
        return True
    
    @staticmethod
    def validate_file_extension(filename: str, allowed_extensions: set) -> bool:
        """
        Validate that a file has an allowed extension.
        
        Args:
            filename: The filename to check
            allowed_extensions: Set of allowed extensions (e.g., {'.txt', '.py'})
            
        Returns:
            bool: True if valid, False otherwise
            
        Raises:
            ValidationError: If the extension is not allowed
        """
        if not filename:
            raise ValidationError("Filename cannot be empty")
        
        _, ext = os.path.splitext(filename.lower())
        if ext not in allowed_extensions:
            allowed_list = ', '.join(sorted(allowed_extensions))
            raise ValidationError(f"File type '{ext}' not allowed. Allowed types: {allowed_list}")
        
        return True
    
    @staticmethod
    def validate_file_size(file_size: int, max_size: int) -> bool:
        """
        Validate that a file size is within limits.
        
        Args:
            file_size: Size of the file in bytes
            max_size: Maximum allowed size in bytes
            
        Returns:
            bool: True if valid, False otherwise
            
        Raises:
            ValidationError: If the file is too large
        """
        if file_size > max_size:
            max_mb = max_size / (1024 * 1024)
            current_mb = file_size / (1024 * 1024)
            raise ValidationError(f"File too large: {current_mb:.1f}MB (max: {max_mb:.1f}MB)")
        
        return True
    
    @staticmethod
    def validate_text_input(text: str, max_length: int = 1000000) -> bool:
        """
        Validate text input for processing.
        
        Args:
            text: The text to validate
            max_length: Maximum allowed length
            
        Returns:
            bool: True if valid, False otherwise
            
        Raises:
            ValidationError: If the text is invalid
        """
        if not isinstance(text, str):
            raise ValidationError("Text input must be a string")
        
        if len(text) > max_length:
            raise ValidationError(f"Text too long: {len(text)} characters (max: {max_length})")
        
        return True
    
    @staticmethod
    def sanitize_model_path(model_path: str) -> str:
        """
        Sanitize a model path by removing potentially dangerous elements.
        
        Args:
            model_path: The model path to sanitize
            
        Returns:
            str: Sanitized model path
        """
        if not model_path:
            return ""
        
        # Remove whitespace
        sanitized = model_path.strip()
        
        # Remove any path traversal attempts
        sanitized = sanitized.replace('..', '')
        sanitized = sanitized.replace('/', '')
        sanitized = sanitized.replace('\\', '')
        
        return sanitized
    
    @staticmethod
    def is_safe_path(path: str, base_path: str) -> bool:
        """
        Check if a path is safe and within the expected base directory.
        
        Args:
            path: The path to check
            base_path: The base directory that the path should be within
            
        Returns:
            bool: True if the path is safe, False otherwise
        """
        try:
            # Resolve both paths to absolute paths
            abs_path = os.path.abspath(path)
            abs_base = os.path.abspath(base_path)
            
            # Check if the path is within the base directory
            return abs_path.startswith(abs_base)
        except (OSError, ValueError):
            return False


# Global instance
validators = Validators()