#!/usr/bin/env python3
"""
NHTSA vPIC Database Downloader
Downloads and prepares the NHTSA vPIC database file for ETL processing
"""
import os
import logging
import requests
import zipfile
from pathlib import Path
from datetime import datetime
from typing import Optional

logger = logging.getLogger(__name__)

class NHTSADownloader:
    """Downloads and manages NHTSA vPIC database files"""
    
    def __init__(self, download_dir: str = "/app/data"):
        self.download_dir = Path(download_dir)
        self.download_dir.mkdir(exist_ok=True)
        
    def get_latest_database_url(self) -> str:
        """
        Get the latest NHTSA vPIC database URL
        Uses July 2025 version as specified
        """
        return "https://vpic.nhtsa.dot.gov/api/vPICList_lite_2025_07.bak.zip"
    
    def download_database(self, url: Optional[str] = None) -> Optional[Path]:
        """
        Download NHTSA vPIC database file
        
        Args:
            url: Database URL (defaults to latest)
            
        Returns:
            Path to downloaded .bak file or None if failed
        """
        if url is None:
            url = self.get_latest_database_url()
            
        logger.info(f"Starting download of NHTSA vPIC database from: {url}")
        
        try:
            # Extract filename from URL
            zip_filename = url.split('/')[-1]
            zip_path = self.download_dir / zip_filename
            
            # Download with progress
            response = requests.get(url, stream=True)
            response.raise_for_status()
            
            total_size = int(response.headers.get('content-length', 0))
            logger.info(f"Downloading {zip_filename} ({total_size:,} bytes)")
            
            with open(zip_path, 'wb') as f:
                downloaded = 0
                for chunk in response.iter_content(chunk_size=8192):
                    if chunk:
                        f.write(chunk)
                        downloaded += len(chunk)
                        if total_size > 0:
                            progress = (downloaded / total_size) * 100
                            if downloaded % (1024 * 1024 * 10) == 0:  # Log every 10MB
                                logger.info(f"Download progress: {progress:.1f}% ({downloaded:,}/{total_size:,} bytes)")
            
            logger.info(f"Successfully downloaded: {zip_path}")
            
            # Extract the .bak file
            bak_path = self.extract_bak_file(zip_path)
            
            # Clean up zip file
            zip_path.unlink()
            logger.info(f"Cleaned up zip file: {zip_path}")
            
            return bak_path
            
        except Exception as e:
            logger.error(f"Failed to download database: {e}")
            return None
    
    def extract_bak_file(self, zip_path: Path) -> Path:
        """
        Extract .bak file from zip archive
        
        Args:
            zip_path: Path to zip file
            
        Returns:
            Path to extracted .bak file
        """
        logger.info(f"Extracting .bak file from: {zip_path}")
        
        with zipfile.ZipFile(zip_path, 'r') as zip_ref:
            # Find the .bak file
            bak_files = [name for name in zip_ref.namelist() if name.endswith('.bak')]
            
            if not bak_files:
                raise ValueError("No .bak file found in zip archive")
            
            if len(bak_files) > 1:
                logger.warning(f"Multiple .bak files found, using first: {bak_files}")
            
            bak_filename = bak_files[0]
            logger.info(f"Extracting: {bak_filename}")
            
            # Extract to download directory
            zip_ref.extract(bak_filename, self.download_dir)
            
            bak_path = self.download_dir / bak_filename
            logger.info(f"Successfully extracted: {bak_path}")
            
            return bak_path
    
    def get_existing_bak_file(self) -> Optional[Path]:
        """
        Find an existing .bak file in preferred locations.
        Searches both the shared mount (/app/shared) and local download dir (/app/data).

        Returns:
            Path to most recent .bak file or None
        """
        search_dirs = [Path("/app/shared"), self.download_dir]
        candidates = []

        for d in search_dirs:
            try:
                if d.exists():
                    candidates.extend(list(d.glob("*.bak")))
            except Exception as e:
                logger.debug(f"Skipping directory {d}: {e}")

        if candidates:
            latest_bak = max(candidates, key=lambda p: p.stat().st_mtime)
            logger.info(f"Found existing .bak file: {latest_bak}")
            return latest_bak

        return None
    
    def ensure_database_file(self, force_download: bool = False) -> Optional[Path]:
        """
        Ensure we have a database file - download if needed
        
        Args:
            force_download: Force download even if file exists
            
        Returns:
            Path to .bak file or None if failed
        """
        if not force_download:
            existing_file = self.get_existing_bak_file()
            if existing_file:
                logger.info(f"Using existing database file: {existing_file}")
                return existing_file
        
        logger.info("Downloading fresh database file...")
        return self.download_database()
    
    def get_database_info(self, bak_path: Path) -> dict:
        """
        Get information about the database file
        
        Args:
            bak_path: Path to .bak file
            
        Returns:
            Dictionary with file info
        """
        if not bak_path.exists():
            return {"exists": False}
        
        stat = bak_path.stat()
        return {
            "exists": True,
            "path": str(bak_path),
            "size_mb": round(stat.st_size / (1024 * 1024), 1),
            "modified": datetime.fromtimestamp(stat.st_mtime).isoformat(),
            "name": bak_path.name
        }