"""OS and architecture detection."""

import platform as _platform
import shutil
from dataclasses import dataclass
from typing import Optional


@dataclass
class PlatformInfo:
    os: str = "linux"          # "linux" or "macos"
    arch: str = "amd64"        # "amd64" or "arm64"
    platform: str = ""         # "linux-amd64", etc.

    def __post_init__(self):
        if not self.platform:
            self.platform = f"{self.os}-{self.arch}"


_OS_MAP = {"Darwin": "macos", "Linux": "linux"}
_ARCH_MAP = {"x86_64": "amd64", "aarch64": "arm64", "arm64": "arm64"}


def detect_platform() -> PlatformInfo:
    raw_os = _platform.system()
    os_name = _OS_MAP.get(raw_os)
    if os_name is None:
        raise RuntimeError(f"Unsupported operating system: {raw_os}")

    raw_arch = _platform.machine().lower()
    arch = _ARCH_MAP.get(raw_arch)
    if arch is None:
        raise RuntimeError(f"Unsupported architecture: {raw_arch}")

    return PlatformInfo(os=os_name, arch=arch, platform=f"{os_name}-{arch}")


def detect_container_runtime() -> Optional[str]:
    """Return 'docker' or 'podman' if available, else None."""
    for runtime in ("docker", "podman"):
        if shutil.which(runtime):
            return runtime
    return None