"""Cross-platform OS compatibility helpers.

Odysseus began as a Linux/macOS/Docker-only app. This module centralizes the
small set of OS differences needed to run it *natively* on Windows so the rest
of the codebase can stay platform-agnostic. Import from here instead of
sprinkling ``os.name == "nt"`` checks (and POSIX-only calls) across modules.

Design rules:
  * Stdlib + ctypes only — no new third-party deps (no psutil/pywinpty).
  * POSIX behaviour is unchanged; Windows gets a faithful equivalent or a
    safe, documented no-op.
"""

from __future__ import annotations

import os
import ntpath
import shutil
import subprocess
from pathlib import Path
import sys
from typing import List, Optional
import platform

IS_WINDOWS = os.name == "nt"
IS_POSIX = not IS_WINDOWS
# Allows APFEL support and ARM-native binary recommendations on Apple Silicon Macs.
IS_APPLE_SILICON = (
    IS_POSIX
    and platform.system() == "Darwin"
    and platform.machine().lower()
    in {
        "arm64",
        "aarch64",
    }
)


# ── File permissions ────────────────────────────────────────────────────────
def safe_chmod(path, mode: int) -> bool:
    """``os.chmod`` that is a harmless no-op on Windows.

    On POSIX we apply the mode — used to lock secret/key files down to 0o600.
    Windows has no POSIX permission bits; files under the user profile are
    already ACL-restricted to that user, so we skip rather than raise. Returns
    True when the mode was actually applied.
    """
    if IS_WINDOWS:
        return False
    try:
        os.chmod(path, mode)
        return True
    except OSError:
        return False


# ── Process detach / liveness / teardown ────────────────────────────────────
def detached_popen_kwargs() -> dict:
    """Keyword args for :class:`subprocess.Popen` that fully detach a child so
    it outlives the request/stream that launched it.

    POSIX: ``start_new_session=True`` (setsid) — new session + process group.
    Windows: ``CREATE_NEW_PROCESS_GROUP | DETACHED_PROCESS`` — the child gets
    its own process group (so it isn't killed when the parent's console closes)
    and is detached from any console.
    """
    if IS_WINDOWS:
        flags = getattr(subprocess, "CREATE_NEW_PROCESS_GROUP", 0x00000200) | getattr(
            subprocess, "DETACHED_PROCESS", 0x00000008
        )
        return {"creationflags": flags}
    return {"start_new_session": True}


def pid_alive(pid: Optional[int]) -> bool:
    """True if a process with ``pid`` is currently running.

    POSIX uses the classic ``os.kill(pid, 0)`` probe. That is **unsafe on
    Windows**: CPython's ``os.kill`` calls ``TerminateProcess(handle, sig)`` for
    any signal other than CTRL_C/CTRL_BREAK, so ``os.kill(pid, 0)`` would *kill*
    the process it is checking. We instead open the process and read its exit
    code via the Win32 API.
    """
    if not pid:
        return False
    if IS_WINDOWS:
        import ctypes
        from ctypes import wintypes

        PROCESS_QUERY_LIMITED_INFORMATION = 0x1000
        STILL_ACTIVE = 259
        kernel32 = ctypes.windll.kernel32
        handle = kernel32.OpenProcess(
            PROCESS_QUERY_LIMITED_INFORMATION, False, int(pid)
        )
        if not handle:
            return False
        try:
            code = wintypes.DWORD()
            if kernel32.GetExitCodeProcess(handle, ctypes.byref(code)):
                return code.value == STILL_ACTIVE
            return False
        finally:
            kernel32.CloseHandle(handle)
    try:
        os.kill(pid, 0)
        return True
    except (OSError, ProcessLookupError):
        return False


def kill_process_tree(pid: Optional[int]) -> None:
    """Terminate ``pid`` and all of its descendants.

    POSIX: signal the whole process group (``killpg``), falling back to a plain
    ``kill`` if the pid isn't a group leader.
    Windows: ``taskkill /T /F`` walks and kills the child tree (there is no
    process-group signalling).
    """
    if not pid:
        return
    if IS_WINDOWS:
        try:
            subprocess.run(
                ["taskkill", "/F", "/T", "/PID", str(pid)],
                stdout=subprocess.DEVNULL,
                stderr=subprocess.DEVNULL,
                creationflags=getattr(subprocess, "CREATE_NO_WINDOW", 0),
            )
        except Exception:
            pass
        return
    import signal

    try:
        os.killpg(os.getpgid(pid), signal.SIGTERM)
    except Exception:
        try:
            os.kill(pid, signal.SIGTERM)
        except Exception:
            pass


# ── Shell / executable resolution ───────────────────────────────────────────
_BASH_CACHE: Optional[str] = None
_BASH_PROBED = False

# Common Git-for-Windows install locations to probe when bash isn't on PATH.
_WINDOWS_BASH_ROOT_ENV_VARS = (
    "ProgramFiles",
    "ProgramW6432",
    "ProgramFiles(x86)",
    "LocalAppData",
)
_WINDOWS_BASH_DEFAULT_ROOTS = (
    r"C:\Program Files\Git",
    r"C:\Program Files (x86)\Git",
)
_WINDOWS_BASH_RELATIVE_PATHS = (
    ("bin", "bash.exe"),
    ("usr", "bin", "bash.exe"),
)

# Paths to add to the remote SSH probe command to find tools like nvidia-smi that may not be on PATH.
_SSH_PATH_MEMBERS = (
    "/usr/bin",
    "/usr/local/bin",
    "/usr/local/cuda/bin",
    "/usr/lib/wsl/lib"
)
# Fallback locations for nvidia-smi on WSL and other Linux distros where it may not be on PATH.
NVIDIA_PATH_CANDIDATES = (
    "/usr/bin/nvidia-smi",
    "/usr/local/bin/nvidia-smi",
    "/usr/local/cuda/bin/nvidia-smi",
    "/usr/lib/wsl/lib/nvidia-smi",
)


def _ssh_path_override() -> str:
    """Build the PATH export snippet used for remote SSH shell probes."""
    return f"export PATH=\"$PATH:{':'.join(_SSH_PATH_MEMBERS)}\"; "


SSH_PATH_OVERRIDE = _ssh_path_override()


def _windows_bash_fallbacks() -> List[str]:
    roots: List[str] = []
    for env_name in _WINDOWS_BASH_ROOT_ENV_VARS:
        base = os.environ.get(env_name)
        if base:
            roots.append(ntpath.join(base, "Git"))
    roots.extend(_WINDOWS_BASH_DEFAULT_ROOTS)

    paths: List[str] = []
    seen = set()
    for root in roots:
        for rel in _WINDOWS_BASH_RELATIVE_PATHS:
            path = ntpath.join(root, *rel)
            key = path.lower()
            if key not in seen:
                seen.add(key)
                paths.append(path)
    return paths


def _is_windows_bash_stub(path: str) -> bool:
    lowered = path.lower()
    return (
        "system32\\bash.exe" in lowered
        or "sysnative\\bash.exe" in lowered
        or "windowsapps\\bash.exe" in lowered
    )


def git_bash_path(path: str | Path) -> str:
    """Convert a path to POSIX style suitable for Git Bash on Windows.

    Transforms drive letters (e.g., 'C:\\path') to POSIX '/c/path',
    and uses forward slashes.
    """
    p = Path(path)
    p_str = p.as_posix()
    if IS_WINDOWS and len(p_str) >= 2 and p_str[1] == ":":
        drive = p_str[0].lower()
        return f"/{drive}{p_str[2:]}"
    return p_str



def find_bash() -> Optional[str]:
    """Locate a real ``bash`` interpreter, or None.

    On Windows this is typically Git Bash / WSL. Many Odysseus features (the
    agent ``bash`` tool, background jobs, Cookbook scripts) emit bash syntax, so
    when a bash is present we use it and keep full parity with POSIX. Result is
    cached.
    """
    global _BASH_CACHE, _BASH_PROBED
    if _BASH_PROBED:
        return _BASH_CACHE
    _BASH_PROBED = True
    found = which_tool("bash")
    if found and IS_WINDOWS and _is_windows_bash_stub(found):
        found = None
    if not found and IS_WINDOWS:
        for cand in _windows_bash_fallbacks():
            if os.path.exists(cand):
                found = cand
                break
    _BASH_CACHE = found
    return found


def has_bash() -> bool:
    return find_bash() is not None


def which_tool(name: str) -> Optional[str]:
    """``shutil.which`` that also tries Windows executable suffixes.

    On Windows, Node/npm shims are ``npx.cmd``/``npm.cmd`` and binaries end in
    ``.exe``; a bare ``which("npx")`` can miss them depending on PATHEXT. We try
    the bare name first, then the common suffixes.
    """
    found = shutil.which(name)
    if found:
        return found
    if IS_WINDOWS:
        for ext in (".cmd", ".exe", ".bat"):
            found = shutil.which(name + ext)
            if found:
                return found
    return None


def run_script_argv(script_path) -> List[str]:
    """argv to execute a shell *script file*.

    Prefers bash (so existing ``.sh`` wrappers work verbatim, including on
    Windows via Git Bash). On Windows with no bash available, falls back to
    ``cmd.exe /c`` — simple commands still run, but bash-specific syntax won't.
    Callers that need guaranteed bash should check :func:`has_bash` first and
    surface a clear "install Git Bash" message.
    """
    bash = find_bash()
    if bash:
        return [bash, str(script_path)]
    if IS_WINDOWS:
        comspec = os.environ.get("ComSpec", "cmd.exe")
        return [comspec, "/c", str(script_path)]
    return ["sh", str(script_path)]


def is_wsl() -> bool:
    """True if running inside Windows Subsystem for Linux (WSL)."""
    import sys
    if sys.platform.startswith("linux") or os.name == "posix":
        try:
            with open("/proc/version", "r") as f:
                if "microsoft" in f.read().lower():
                    return True
        except Exception:
            pass
    return False


def translate_path(path_str: str) -> str:
    """Translate a path (possibly a Windows path) to the current OS format.

    Particularly handles Windows paths (e.g. C:\\foo or C:/foo) when running
    under WSL, translating them to /mnt/c/foo.
    Also handles standard path normalization to avoid string breakages.
    """
    if not path_str:
        return path_str

    if is_wsl():
        path_str = path_str.replace("\\", "/")
        import re
        m = re.match(r"^([a-zA-Z]):(.*)", path_str)
        if m:
            drive = m.group(1).lower()
            rest = m.group(2)
            if not rest.startswith("/"):
                rest = "/" + rest
            return f"/mnt/{drive}{rest}"

    try:
        return str(Path(path_str).resolve())
    except Exception:
        return path_str


def get_wsl_windows_user_profile() -> Optional[str]:
    """Retrieve the Windows host User Profile path from inside WSL."""
    if not is_wsl():
        return None
    try:
        r = run_wsl_windows_powershell("Write-Output $env:USERPROFILE", timeout=5)
        if r.returncode == 0 and r.stdout.strip():
            return translate_path(r.stdout.strip())
    except Exception:
        pass

    try:
        users_dir = "/mnt/c/Users"
        if os.path.isdir(users_dir):
            for entry in os.listdir(users_dir):
                if entry not in ("All Users", "Default", "Default User", "desktop.ini", "Public"):
                    path = os.path.join(users_dir, entry)
                    if os.path.isdir(path):
                        return path
    except Exception:
        pass
    return None


def _ssh_exec_argv(
    remote: str,
    ssh_port: str | None,
    *,
    remote_cmd: str | None = None,
    connect_timeout: int | None = None,
    strict_host_key_checking: bool | None = None,
) -> list[str]:
    """Build a consistent ssh argv for remote command execution."""
    argv = ["ssh"]
    if connect_timeout is not None:
        argv.extend(["-o", f"ConnectTimeout={int(connect_timeout)}"])
    if strict_host_key_checking is not None:
        argv.extend(
            [
                "-o",
                "StrictHostKeyChecking=yes"
                if strict_host_key_checking
                else "StrictHostKeyChecking=no",
            ]
        )
    if ssh_port and ssh_port != "22":
        argv.extend(["-p", str(ssh_port)])
    argv.append(remote)
    if remote_cmd is not None:
        argv.append(remote_cmd)
    return argv


def run_ssh_command(
    remote: str,
    ssh_port: str | None,
    remote_cmd: str,
    *,
    timeout: float,
    connect_timeout: int | None = None,
    strict_host_key_checking: bool | None = None,
    text: bool = True,
) -> subprocess.CompletedProcess:
    """Run an ssh command with centralized timeout and stderr/stdout capture."""
    return subprocess.run(
        _ssh_exec_argv(
            remote,
            ssh_port,
            remote_cmd=remote_cmd,
            connect_timeout=connect_timeout,
            strict_host_key_checking=strict_host_key_checking,
        ),
        timeout=timeout,
        capture_output=True,
        text=text,
    )


def _windows_powershell_argv(
    command: str,
    *,
    no_profile: bool = True,
    non_interactive: bool = True,
) -> List[str]:
    argv: List[str] = ["powershell.exe"]
    if no_profile:
        argv.append("-NoProfile")
    if non_interactive:
        argv.append("-NonInteractive")
    argv.extend(["-Command", command])
    return argv


def run_wsl_windows_powershell(
    command: str,
    *,
    timeout: float = 5,
) -> subprocess.CompletedProcess[str]:
    """Run a PowerShell command on the Windows host from WSL.

    Raises ``RuntimeError`` when called outside WSL.
    """

    if not is_wsl():
        raise RuntimeError("run_wsl_windows_powershell is only supported in WSL")
    return subprocess.run(
        _windows_powershell_argv(command),
        capture_output=True,
        text=True,
        timeout=timeout,
    )