environment.py

from __future__ import annotations

import os
import platform
import shutil
from dataclasses import dataclass
from typing import Literal

from kaos.path import KaosPath


def _windows_shell_candidates() -> list[KaosPath]:
    """PowerShell executables to probe, in order.

    Prefer PowerShell 7+ (`pwsh`) when present, then fall back to Windows PowerShell 5.1
    (`powershell.exe`), matching common developer installs while remaining usable on systems
    that only ship the inbox shell.
    """
    candidates: list[KaosPath] = []
    seen: set[str] = set()

    def add(path: str) -> None:
        normalized = os.path.normcase(os.path.normpath(path))
        if normalized not in seen:
            seen.add(normalized)
            candidates.append(KaosPath(path))

    pwsh = shutil.which("pwsh")
    if pwsh:
        add(pwsh)

    program_files = os.environ.get("ProgramW6432") or os.environ.get(
        "ProgramFiles", r"C:\Program Files"
    )
    add(os.path.join(program_files, "PowerShell", "7", "pwsh.exe"))

    system_root = os.environ.get("SYSTEMROOT", r"C:\Windows")
    add(
        os.path.join(
            system_root, "System32", "WindowsPowerShell", "v1.0", "powershell.exe"
        )
    )

    powershell = shutil.which("powershell")
    if powershell:
        add(powershell)

    add("powershell.exe")
    return candidates


@dataclass(slots=True, frozen=True, kw_only=True)
class Environment:
    os_kind: Literal["Windows", "Linux", "macOS"] | str
    os_arch: str
    os_version: str
    shell_name: Literal["bash", "sh", "Windows PowerShell"]
    shell_path: KaosPath

    @staticmethod
    async def detect() -> Environment:
        match platform.system():
            case "Darwin":
                os_kind = "macOS"
            case "Windows":
                os_kind = "Windows"
            case "Linux":
                os_kind = "Linux"
            case system:
                os_kind = system

        os_arch = platform.machine()
        os_version = platform.version()

        if os_kind == "Windows":
            shell_name = "Windows PowerShell"
            fallback_path = KaosPath("powershell.exe")
            for path in _windows_shell_candidates():
                if await path.is_file():
                    shell_path = path
                    break
            else:
                shell_path = fallback_path
        else:
            possible_paths = [
                KaosPath("/bin/bash"),
                KaosPath("/usr/bin/bash"),
                KaosPath("/usr/local/bin/bash"),
            ]
            fallback_path = KaosPath("/bin/sh")
            for path in possible_paths:
                if await path.is_file():
                    shell_name = "bash"
                    shell_path = path
                    break
            else:
                shell_name = "sh"
                shell_path = fallback_path

        return Environment(
            os_kind=os_kind,
            os_arch=os_arch,
            os_version=os_version,
            shell_name=shell_name,
            shell_path=shell_path,
        )