import os
import random
import string
import httpx
from typing import Optional


def download_audio(url: str, temp_dir: str, timeout: int = 120) -> Optional[str]:
    os.makedirs(temp_dir, exist_ok=True)

    headers = {
        "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36",
        "Accept": "audio/mpeg,*/*",
    }

    file_ext = ".mp3"

    with httpx.Client(timeout=timeout, follow_redirects=True) as client:
        with client.stream("GET", url, headers=headers) as resp:
            if resp.status_code != 200:
                return None

            ct = resp.headers.get("content-type", "")
            if "ogg" in ct:
                file_ext = ".ogg"
            elif "wav" in ct:
                file_ext = ".wav"
            elif "m4a" in ct or "mp4" in ct:
                file_ext = ".m4a"

            cd = resp.headers.get("content-disposition", "")
            m = None
            if cd:
                import re
                m = re.search(r'filename=(.+)', cd)
            if m:
                fname = m.group(1).strip('"').strip("'")
            else:
                suffix = "".join(random.choices(string.ascii_lowercase, k=6))
                fname = f"call_{suffix}{file_ext}"

            local_path = os.path.join(temp_dir, fname)

            with open(local_path, "wb") as f:
                for chunk in resp.iter_bytes(chunk_size=8192):
                    f.write(chunk)

            return local_path