import os
import re
import requests

USER_AGENT = "VLC/3.0.9 LibVLC/3.0.9"
HEADERS = {'User-Agent': USER_AGENT}

def sanitize_filename(name):
    return re.sub(r'[\\/*?:\"<>|]', "", name).strip()

def aria2c_exists():
    return os.path.exists("./aria2c") or os.path.exists("./aria2c.exe")

def get_remote_file_size(url):
    try:
        with requests.head(url, headers=HEADERS, timeout=10) as head:
            head.raise_for_status()
            content_length = head.headers.get('content-length')
            return int(content_length) if content_length else 0
    except Exception:
        return 0

def download_with_aria2c(url, dest_path, max_connections=1):
    import subprocess
    os.makedirs(os.path.dirname(dest_path), exist_ok=True)
    remote_size = get_remote_file_size(url)
    if os.path.exists(dest_path):
        local_size = os.path.getsize(dest_path)
        if remote_size > 0 and local_size >= remote_size:
            print(f"✔ Already downloaded: {os.path.basename(dest_path)}")
            return
    aria2_bin = "aria2c.exe" if os.name == 'nt' else "./aria2c"
    cmd = [
        aria2_bin,
        "--dir", os.path.dirname(dest_path),
        "--out", os.path.basename(dest_path),
        "--max-connection-per-server=1",
        "--split=1",
        "--min-split-size=1M",
        "--console-log-level=warn",
        "--allow-overwrite=true",
        "--header", f"User-Agent: {USER_AGENT}",
        "--max-concurrent-downloads", str(max_connections),
        url
    ]
    print(f"\n⚡ Fast downloading with aria2c: {os.path.basename(dest_path)}")
    try:
        subprocess.run(cmd, check=True)
    except subprocess.CalledProcessError:
        print(f"⚠ aria2c failed. Falling back to Python downloader.")
        download_file_with_progress(url, dest_path, os.path.basename(dest_path))

def download_file_with_progress(url, dest_path, title):
    resume_byte_pos = 0
    local_exists = os.path.exists(dest_path)
    mode = 'wb'
    headers = HEADERS.copy()
    try:
        with requests.head(url, headers=headers, timeout=10) as head:
            head.raise_for_status()
            content_length = head.headers.get('content-length')
            remote_size = int(content_length) if content_length else 0
            accepts_ranges = head.headers.get('accept-ranges', 'none') == 'bytes'
    except Exception:
        remote_size = 0
        accepts_ranges = False

    if local_exists:
        local_size = os.path.getsize(dest_path)
        if remote_size > 0 and local_size >= remote_size:
            print(f"✔ Already downloaded: {title}")
            return
        elif remote_size > 0 and local_size < remote_size and accepts_ranges:
            resume_byte_pos = local_size
            headers['Range'] = f'bytes={resume_byte_pos}-'
            mode = 'ab'
            print(f"⏯ Resuming download for {title} at {local_size / (1024 ** 2):.2f} MB")
        else:
            print(f"⚠ Restarting download for {title}")
            mode = 'wb'

    with requests.get(url, headers=headers, stream=True, timeout=30) as response:
        response.raise_for_status()
        total = remote_size
        downloaded = resume_byte_pos
        with open(dest_path, mode) as f:
            for chunk in response.iter_content(chunk_size=1024 * 1024):
                if chunk:
                    f.write(chunk)
                    downloaded += len(chunk)
                    percent = (downloaded / total * 100) if total else 0
                    print(f"\rDownloading '{title}': {percent:.2f}%", end='', flush=True)
    print(f"\n✔ Download complete: {dest_path}")