from __future__ import annotations

import logging
import os
import shlex
import subprocess  # noqa: S404
from dataclasses import dataclass
from typing import TYPE_CHECKING

if TYPE_CHECKING:
    from collections.abc import Mapping
    from collections.abc import Sequence
    from pathlib import Path

logger = logging.getLogger("tussilago.control_plane.host_commands")

DEFAULT_INHERITED_ENV_KEYS: frozenset[str] = frozenset(
    {
        "HOME",
        "LANG",
        "LC_ALL",
        "LC_CTYPE",
        "LOGNAME",
        "PATH",
        "SSL_CERT_DIR",
        "SSL_CERT_FILE",
        "TMPDIR",
        "USER",
        "UV_CACHE_DIR",
        "VIRTUAL_ENV",
        "XDG_CACHE_HOME",
        "XDG_RUNTIME_DIR",
    },
)


@dataclass(frozen=True, slots=True)
class HostCommandResult:
    """Capture output from a completed host-side command."""

    args: tuple[str, ...]
    returncode: int
    stdout: str
    stderr: str


class HostCommandError(RuntimeError):
    """Raised when a host-side command fails or times out."""

    def __init__(
        self,
        message: str,
        *,
        args: Sequence[str],
        returncode: int | None,
        stdout: str,
        stderr: str,
    ) -> None:
        """Store captured command context for later error reporting."""
        super().__init__(message)
        self.command_args = tuple(args)
        self.returncode = returncode
        self.stdout = stdout
        self.stderr = stderr


def build_host_command_env(
    *,
    env_overrides: Mapping[str, str] | None = None,
    allowed_env_keys: frozenset[str] | None = None,
    inherited_env_keys: frozenset[str] = DEFAULT_INHERITED_ENV_KEYS,
) -> dict[str, str]:
    """Build a sanitized environment for host-side child processes.

    Returns:
        A filtered environment dictionary suitable for subprocess execution.

    Raises:
        ValueError: If env overrides are provided without an allowlist.
    """
    resolved_env = {key: value for key, value in os.environ.items() if key in inherited_env_keys}

    if env_overrides is None:
        return resolved_env

    if allowed_env_keys is None:
        msg = "allowed_env_keys is required when env_overrides are provided"
        raise ValueError(msg)

    disallowed_keys = sorted(set(env_overrides).difference(allowed_env_keys))
    if disallowed_keys:
        msg = f"env_overrides contains disallowed keys: {', '.join(disallowed_keys)}"
        raise ValueError(msg)

    resolved_env.update(env_overrides)
    return resolved_env


def run_host_command(
    *,
    command: Sequence[str],
    cwd: Path | None = None,
    env_overrides: Mapping[str, str] | None = None,
    allowed_env_keys: frozenset[str] | None = None,
    timeout_seconds: float = 60.0,
) -> HostCommandResult:
    """Run a host-side command with explicit environment and timeout controls.

    Returns:
        A result object containing the command, return code, and captured output.

    Raises:
        ValueError: If the command is empty or env overrides are not allowlisted.
        HostCommandError: If the command fails or times out.
    """
    normalized_command = tuple(command)
    if not normalized_command:
        msg = "command must not be empty"
        raise ValueError(msg)

    if any(not argument for argument in normalized_command):
        msg = "command arguments must be non-empty strings"
        raise ValueError(msg)

    resolved_env = build_host_command_env(
        env_overrides=env_overrides,
        allowed_env_keys=allowed_env_keys,
    )

    logger.debug(
        "Running host command executable=%s argc=%s (cwd=%s)",
        shlex.quote(normalized_command[0]),
        len(normalized_command),
        cwd,
    )

    try:
        completed = subprocess.run(  # noqa: S603
            normalized_command,
            check=True,
            capture_output=True,
            text=True,
            cwd=cwd,
            env=resolved_env,
            timeout=timeout_seconds,
        )
    except subprocess.CalledProcessError as error:
        msg_0 = "Host command failed."
        raise HostCommandError(
            msg_0,
            args=tuple(str(argument) for argument in error.cmd),
            returncode=error.returncode,
            stdout=error.stdout or "",
            stderr=error.stderr or "",
        ) from error
    except subprocess.TimeoutExpired as error:
        msg_0 = "Host command timed out."
        raise HostCommandError(
            msg_0,
            args=normalized_command,
            returncode=None,
            stdout=str(error.stdout) or "",
            stderr=str(error.stderr) or "",
        ) from error

    return HostCommandResult(
        args=normalized_command,
        returncode=completed.returncode,
        stdout=completed.stdout,
        stderr=completed.stderr,
    )