"""
arma_modlist_tools.compat
~~~~~~~~~~~~~~~~~~~~~~~~~
OS detection and cross-platform utilities shared by all CLI scripts.

Supported platforms:
  - Windows / Windows Server  (sys.platform == "win32")
  - Ubuntu / Ubuntu Server    (sys.platform == "linux")

Typical usage::

    from arma_modlist_tools.compat import is_windows, get_os_label, fix_console_encoding

    fix_console_encoding()   # call once at script start on Windows
    print(get_os_label())    # "Windows Server", "Ubuntu", etc.
"""

from __future__ import annotations

import io
import platform
import sys


# ---------------------------------------------------------------------------
# Platform detection
# ---------------------------------------------------------------------------

def is_windows() -> bool:
    """Return ``True`` on Windows and Windows Server."""
    return sys.platform == "win32"


def is_linux() -> bool:
    """Return ``True`` on Linux (Ubuntu, Ubuntu Server, and other distros)."""
    return sys.platform == "linux"


def get_os_label() -> str:
    """
    Return a human-readable OS label.

    Possible values: ``"Windows"``, ``"Windows Server"``, ``"Ubuntu"``,
    ``"Ubuntu Server"``, ``"Linux"``, ``"Unknown"``.
    """
    if is_windows():
        ver = platform.version()
        # Windows Server versions contain "Server" in the version string
        # e.g. "10.0.17763 ... Windows Server 2019 ..."
        if "Server" in platform.version() or "Server" in platform.uname().version:
            return "Windows Server"
        return "Windows"

    if is_linux():
        # Read /etc/os-release for distro name
        os_release = _read_os_release()
        name = os_release.get("NAME", "").lower()

        if "ubuntu" in name:
            # Distinguish desktop vs server: server images have no display server
            if _is_headless():
                return "Ubuntu Server"
            return "Ubuntu"

        return "Linux"

    return "Unknown"


def _read_os_release() -> dict[str, str]:
    """Parse /etc/os-release into a dict (Linux only)."""
    result: dict[str, str] = {}
    try:
        with open("/etc/os-release", encoding="utf-8") as f:
            for line in f:
                line = line.strip()
                if "=" in line and not line.startswith("#"):
                    k, _, v = line.partition("=")
                    result[k] = v.strip('"')
    except OSError:
        pass
    return result


def _is_headless() -> bool:
    """Return True if no graphical display server is detected (headless/server)."""
    import os
    # Check for common display environment variables
    return not (os.environ.get("DISPLAY") or os.environ.get("WAYLAND_DISPLAY"))


# ---------------------------------------------------------------------------
# Console encoding
# ---------------------------------------------------------------------------

def fix_console_encoding() -> None:
    """
    Force UTF-8 output on Windows terminals that default to cp1252.

    Call once at the top of any CLI script that uses Unicode characters
    (checkmarks, arrows, etc.).  No-op on Linux.
    """
    if not is_windows():
        return
    if sys.stdout.encoding and sys.stdout.encoding.lower() == "utf-8":
        return
    sys.stdout = io.TextIOWrapper(sys.stdout.buffer, encoding="utf-8", errors="replace")
    sys.stderr = io.TextIOWrapper(sys.stderr.buffer, encoding="utf-8", errors="replace")