"""SSH connection layer — asyncssh based.

Provides run_command() which handles:
- Key-based auth (GPU, Mac mini)
- Password auth + sudo (company NAS)
- Timeout / retry
- Structured error classification
"""

from __future__ import annotations

import asyncio
from datetime import datetime, timezone

import asyncssh

from ..config import HostConfig, SSH_TIMEOUT, CMD_TIMEOUT, MAX_RETRIES


class SSHError(Exception):
    """Typed SSH error with error_type classification."""

    def __init__(self, error_type: str, message: str):
        self.error_type = error_type
        super().__init__(message)


def _now_iso() -> str:
    return datetime.now(timezone.utc).isoformat()


async def _connect(host: HostConfig) -> asyncssh.SSHClientConnection:
    """Open SSH connection with appropriate auth method."""
    kwargs: dict = {
        "host": host.ip,
        "username": host.user,
        "connect_timeout": SSH_TIMEOUT,
        "known_hosts": None,  # accept any host key (Tailscale internal network)
    }
    if host.auth == "password" and host.password:
        kwargs["password"] = host.password
        kwargs["client_keys"] = []  # don't try key auth
    # key auth is the default (uses ~/.ssh/)

    return await asyncssh.connect(**kwargs)


async def run_command(
    host: HostConfig,
    command: str,
    timeout: int = CMD_TIMEOUT,
    use_sudo: bool = False,
) -> tuple[str, str]:
    """Run a command on remote host. Returns (stdout, stderr).

    For NAS with sudo: wraps command with sudo using password via stdin.
    Raises SSHError with typed error_type on failure.
    """
    if use_sudo and host.needs_sudo and host.password:
        # Pipe password to sudo via stdin
        command = f"echo '{host.password}' | sudo -S {command}"

    last_error: Exception | None = None
    for attempt in range(1 + MAX_RETRIES):
        try:
            conn = await _connect(host)
            async with conn:
                result = await asyncio.wait_for(
                    conn.run(command, check=False),
                    timeout=timeout,
                )
                stdout = result.stdout or ""
                stderr = result.stderr or ""

                if result.exit_status != 0:
                    # Command ran but returned non-zero
                    # Filter out sudo password prompt from stderr
                    stderr_clean = "\n".join(
                        line for line in stderr.splitlines()
                        if "[sudo]" not in line and "Password:" not in line
                    )
                    raise SSHError(
                        "command_failed",
                        f"exit {result.exit_status}: {stderr_clean.strip() or stdout.strip()}"
                    )
                return stdout, stderr

        except SSHError:
            raise
        except asyncio.TimeoutError:
            raise SSHError("timeout", f"명령 실행 시간 초과 ({timeout}초)")
        except asyncssh.PermissionDenied:
            raise SSHError("auth", f"SSH 인증 실패: {host.user}@{host.ip}")
        except (OSError, asyncssh.Error) as e:
            last_error = e
            if attempt < MAX_RETRIES:
                await asyncio.sleep(1)
                continue
            raise SSHError("timeout", f"SSH 연결 실패: {host.ip} — {e}")

    raise SSHError("timeout", f"SSH 최대 재시도 초과: {host.ip}")


async def run_local(command: str, timeout: int = CMD_TIMEOUT) -> tuple[str, str]:
    """Run a command locally. Returns (stdout, stderr)."""
    try:
        proc = await asyncio.create_subprocess_shell(
            command,
            stdout=asyncio.subprocess.PIPE,
            stderr=asyncio.subprocess.PIPE,
        )
        stdout_bytes, stderr_bytes = await asyncio.wait_for(
            proc.communicate(), timeout=timeout
        )
        stdout = stdout_bytes.decode() if stdout_bytes else ""
        stderr = stderr_bytes.decode() if stderr_bytes else ""

        if proc.returncode != 0:
            raise SSHError("command_failed", f"exit {proc.returncode}: {stderr.strip() or stdout.strip()}")

        return stdout, stderr
    except asyncio.TimeoutError:
        raise SSHError("timeout", f"로컬 명령 시간 초과 ({timeout}초)")