from __future__ import annotations

import asyncio
import logging
from pathlib import Path
from typing import List, Optional, Tuple
from urllib.parse import unquote, urlparse

import aiohttp

from app.config import get_settings

_logger = logging.getLogger(__name__)
_settings = get_settings()


def create_session_timeout(total_seconds: Optional[float] = None) -> aiohttp.ClientTimeout:
    """Create an aiohttp timeout using the configured request timeout."""
    if total_seconds is None:
        total_seconds = _settings.request_timeout_ms / 1000
    return aiohttp.ClientTimeout(total=total_seconds)


async def download_url(
    url: str,
    *,
    timeout_seconds: float = 120,
    max_size_bytes: Optional[int] = None,
    chunk_size: int = 256 * 1024,
) -> Tuple[bytes, Optional[str]]:
    """Download a file from a URL with streaming and size guard.

    Returns (data, filename) where filename may be None.
    Consolidates _download_file from csv_analysis_service and
    _download_from_url from dataset_metadata_service.
    """
    timeout = aiohttp.ClientTimeout(total=timeout_seconds)
    try:
        async with aiohttp.ClientSession(timeout=timeout) as session:
            async with session.get(url) as resp:
                if resp.status != 200:
                    raise RuntimeError(f"HTTP {resp.status} when fetching {url}")

                if max_size_bytes and resp.content_length and resp.content_length > max_size_bytes:
                    raise RuntimeError(
                        f"Remote file advertises {resp.content_length} bytes, "
                        f"limit is {max_size_bytes}"
                    )

                chunks: List[bytes] = []
                total = 0
                async for chunk in resp.content.iter_chunked(chunk_size):
                    total += len(chunk)
                    if max_size_bytes and total > max_size_bytes:
                        raise RuntimeError(f"Download exceeded {max_size_bytes} bytes")
                    chunks.append(chunk)

                data = b"".join(chunks)
    except (aiohttp.ClientError, asyncio.TimeoutError) as exc:
        raise RuntimeError(f"Download failed for {url}: {exc}") from exc

    parsed = urlparse(url)
    filename = unquote(Path(parsed.path).name) if parsed.path else None
    return data, filename