"""Minimal HTTP health endpoint using raw asyncio.

No external dependencies — just a bare TCP server that speaks enough
HTTP to return JSON status. Runs on a separate port from the NTCP2
transport (default 9701).
"""

from __future__ import annotations

import asyncio
import json
import logging

logger = logging.getLogger(__name__)


async def start_health_server(
    get_status_fn,
    host: str = "0.0.0.0",
    port: int = 9701,
) -> asyncio.Server:
    """Start a minimal HTTP health server.

    Parameters
    ----------
    get_status_fn:
        Callable that returns a dict with router status.
    host:
        Bind address.
    port:
        Listen port (default 9701).

    Returns
    -------
    asyncio.Server
        The running server instance.
    """

    async def handle_request(
        reader: asyncio.StreamReader,
        writer: asyncio.StreamWriter,
    ) -> None:
        try:
            # Read the request line (we don't care about the path)
            await asyncio.wait_for(reader.readline(), timeout=5.0)
            # Drain remaining headers
            while True:
                line = await asyncio.wait_for(reader.readline(), timeout=5.0)
                if line in (b"\r\n", b"\n", b""):
                    break

            status = get_status_fn()
            body = json.dumps(status, indent=2).encode()
            response = (
                b"HTTP/1.1 200 OK\r\n"
                b"Content-Type: application/json\r\n"
                b"Connection: close\r\n"
                b"Content-Length: " + str(len(body)).encode() + b"\r\n"
                b"\r\n" + body
            )
            writer.write(response)
            await writer.drain()
        except Exception:
            pass
        finally:
            writer.close()
            try:
                await writer.wait_closed()
            except Exception:
                pass

    server = await asyncio.start_server(handle_request, host, port)
    logger.info("Health server started on %s:%d", host, port)
    return server