"""CircuitPython file download utility.

Downloads files over Wi-Fi in chunks to local flash or microSD card storage.
"""

import os
from sd_cp import SDCardManager

def download_file(url, dest_filename, session, use_sd=True):
    """Downloads a file from a URL over the network.

    Args:
        url (str): Source URL.
        dest_filename (str): Target filename.
        session (Session): adafruit_requests Session object.
        use_sd (bool): Save to microSD card if True, else local flash.
    """
    dest_path = dest_filename
    sd_manager = None

    if use_sd:
        sd_manager = SDCardManager(mount_point='/sd')
        if not sd_manager.mount():
            print("Download Error: Could not mount SD card.")
            return None
        dest_path = f"/sd/{dest_filename}"

    print(f"Starting download from: {url} -> {dest_path}")

    try:
        res = session.get(url)
    except Exception as e:
        print(f"HTTP Connection failed: {e}")
        return None

    if res.status_code != 200:
        print(f"HTTP Error: Received status code {res.status_code}")
        res.close()
        return None

    try:
        chunk_size = 4096
        total_downloaded = 0

        with open(dest_path, 'wb') as f:
            for chunk in res.iter_content(chunk_size):
                if not chunk:
                    break
                f.write(chunk)
                total_downloaded += len(chunk)

                if total_downloaded % (chunk_size * 25) == 0:
                    print(f"Downloaded {total_downloaded // 1024} KB...")

        print(f"Download complete! Saved {total_downloaded} bytes to '{dest_path}'.")
        return dest_path

    except Exception as e:
        print(f"Error writing to file: {e}")
        try:
            os.remove(dest_path)
        except:
            pass
        return None
    finally:
        res.close()