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"""Subprocess supervision helpers for ``ts serve``."""

from __future__ import annotations

import asyncio
import contextlib
import logging
import os
import sys
import time

logger = logging.getLogger(__name__)

_GATEWAY_MODULE = "smg"
_ENGINE_MODULE_DEFAULT = "smg_grpc_servicer.tokenspeed"
_PIPE_LINE_LIMIT = 64 * 1024 * 1024


async def spawn_engine(
    args: list[str],
    *,
    host: str,
    port: int,
) -> asyncio.subprocess.Process:
    """Spawn the engine subprocess with PIPE stdio."""
    module = os.environ.get("TS_SERVE_ENGINE_MODULE", _ENGINE_MODULE_DEFAULT)
    cmd = [
        sys.executable,
        "-m",
        module,
        "--host",
        host,
        "--port",
        str(port),
        *args,
    ]
    logger.info("spawn engine: %s", " ".join(cmd))
    return await asyncio.create_subprocess_exec(
        *cmd,
        stdout=asyncio.subprocess.PIPE,
        stderr=asyncio.subprocess.PIPE,
        limit=_PIPE_LINE_LIMIT,
    )


async def spawn_gateway(
    args: list[str],
    *,
    engine_host: str,
    engine_port: int,
) -> asyncio.subprocess.Process:
    """Spawn ``python -m smg launch`` with PIPE stdio."""
    cmd = [
        sys.executable,
        "-m",
        _GATEWAY_MODULE,
        "launch",
        "--worker-urls",
        f"grpc://{engine_host}:{engine_port}",
        "--disable-retries",
        "--disable-circuit-breaker",
        *args,
    ]
    logger.info("spawn gateway: %s", " ".join(cmd))
    return await asyncio.create_subprocess_exec(
        *cmd,
        stdout=asyncio.subprocess.PIPE,
        stderr=asyncio.subprocess.PIPE,
        limit=_PIPE_LINE_LIMIT,
    )


async def wait_grpc_serving(
    target: str,
    *,
    timeout: float,
    poll_interval: float = 1.0,
) -> None:
    """Poll ``grpc.health.v1.Health.Check`` on ``target`` until SERVING."""
    import grpc
    from grpc_health.v1 import health_pb2, health_pb2_grpc

    deadline = time.monotonic() + timeout
    last_err: Exception | None = None
    async with grpc.aio.insecure_channel(target) as channel:
        stub = health_pb2_grpc.HealthStub(channel)
        while time.monotonic() < deadline:
            try:
                resp = await stub.Check(
                    health_pb2.HealthCheckRequest(service=""),
                    timeout=2.0,
                )
                if resp.status == health_pb2.HealthCheckResponse.SERVING:
                    return
            except Exception as exc:  # noqa: BLE001
                last_err = exc
            await asyncio.sleep(poll_interval)
    detail = f" (last error: {last_err!r})" if last_err is not None else ""
    raise TimeoutError(
        f"engine never reached SERVING on {target} within {timeout:.0f}s{detail}"
    )


async def wait_http_ready(
    url: str,
    *,
    timeout: float,
    poll_interval: float = 1.0,
) -> None:
    """Poll HTTP ``GET <url>`` until 200, or raise ``TimeoutError``."""
    import aiohttp

    deadline = time.monotonic() + timeout
    last_err: Exception | None = None
    async with aiohttp.ClientSession() as session:
        while time.monotonic() < deadline:
            try:
                async with session.get(
                    url, timeout=aiohttp.ClientTimeout(total=2.0)
                ) as resp:
                    if resp.status == 200:
                        return
            except Exception as exc:  # noqa: BLE001
                last_err = exc
            await asyncio.sleep(poll_interval)
    detail = f" (last error: {last_err!r})" if last_err is not None else ""
    raise TimeoutError(
        f"gateway never reached 200 on {url} within {timeout:.0f}s{detail}"
    )


async def terminate_then_kill(proc, *, drain_timeout: float) -> None:
    """SIGTERM, wait up to ``drain_timeout``, then SIGKILL if still alive."""
    if proc.returncode is not None:
        return
    proc.terminate()
    try:
        await asyncio.wait_for(proc.wait(), timeout=drain_timeout)
    except asyncio.TimeoutError:
        with contextlib.suppress(ProcessLookupError):
            proc.kill()
        with contextlib.suppress(Exception):
            await proc.wait()