"""
File validation utilities for CAE Mesh Generator
"""
import os
from pathlib import Path
from typing import Tuple, Optional

def validate_step_file(file_path: str) -> Tuple[bool, Optional[str]]:
    """
    Validate if uploaded file is a valid STEP file
    
    Args:
        file_path: Path to the uploaded file
        
    Returns:
        Tuple of (is_valid, error_message)
    """
    try:
        if not os.path.exists(file_path):
            return False, "File does not exist"
        
        # Check file size
        file_size = os.path.getsize(file_path)
        if file_size == 0:
            return False, "File is empty"
        
        if file_size > 100 * 1024 * 1024:  # 100MB limit
            return False, "File too large (max 100MB)"
        
        # Check file extension
        file_ext = Path(file_path).suffix.lower()
        if file_ext not in ['.step', '.stp']:
            return False, f"Invalid file extension: {file_ext}"
        
        # Basic STEP file content validation
        try:
            with open(file_path, 'r', encoding='utf-8', errors='ignore') as f:
                first_line = f.readline().strip()
                if not first_line.startswith('ISO-10303'):
                    return False, "Invalid STEP file format (missing ISO-10303 header)"
                
                # Check for basic STEP structure
                content = f.read(1000)  # Read first 1000 chars
                if 'HEADER;' not in content and 'DATA;' not in content:
                    return False, "Invalid STEP file structure"
                    
        except UnicodeDecodeError:
            return False, "File encoding error - not a valid text-based STEP file"
        
        return True, None
        
    except Exception as e:
        return False, f"File validation error: {str(e)}"

def get_file_info(file_path: str) -> dict:
    """
    Get detailed file information
    
    Args:
        file_path: Path to the file
        
    Returns:
        Dictionary with file information
    """
    try:
        stat = os.stat(file_path)
        return {
            'size': stat.st_size,
            'size_mb': round(stat.st_size / (1024 * 1024), 2),
            'modified': stat.st_mtime,
            'extension': Path(file_path).suffix.lower(),
            'exists': True
        }
    except Exception as e:
        return {
            'size': 0,
            'size_mb': 0,
            'modified': None,
            'extension': '',
            'exists': False,
            'error': str(e)
        }