import re
from typing import List


def validate_email(email: str) -> bool:
    """
    Validate email format.
    
    Args:
        email: Email string to validate
        
    Returns:
        True if valid email format, False otherwise
    """
    pattern = r'^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$'
    return bool(re.match(pattern, email))


def validate_password(password: str) -> tuple[bool, str]:
    """
    Validate password strength.
    
    Args:
        password: Password string to validate
        
    Returns:
        Tuple of (is_valid, error_message)
    """
    if len(password) < 6:
        return False, "Password must be at least 6 characters long"
    
    # Bcrypt has a 72-byte limit
    if len(password.encode('utf-8')) > 72:
        return False, "Password is too long (max 72 bytes)"
    
    return True, ""


def validate_file_type(filename: str, allowed_types: List[str]) -> bool:
    """
    Validate file type by extension.
    
    Args:
        filename: Name of the file
        allowed_types: List of allowed extensions (e.g., ['pdf', 'docx'])
        
    Returns:
        True if file type is allowed, False otherwise
    """
    if '.' not in filename:
        return False
    
    extension = filename.rsplit('.', 1)[1].lower()
    return extension in allowed_types


def validate_file_size(file_size: int, max_size_mb: int = 10) -> bool:
    """
    Validate file size.
    
    Args:
        file_size: File size in bytes
        max_size_mb: Maximum allowed size in MB
        
    Returns:
        True if file size is within limit, False otherwise
    """
    max_size_bytes = max_size_mb * 1024 * 1024
    return file_size <= max_size_bytes