"""
core/file_association.py

Self-registers LabUI as the handler for .labui files with the OS, so
double-clicking one launches the app — Windows (registry) and Linux (XDG).
User-scoped, no admin/root rights needed.

macOS doesn't need any of this: labui.spec builds a real .app bundle with
CFBundleDocumentTypes baked into Info.plist at build time, which is enough
for Finder to associate .labui files with it automatically.

Only meaningful for a packaged build (sys.frozen, set by PyInstaller) —
registering the bare Python interpreter as the handler for "python.exe
main.py" isn't useful, so callers should gate the UI action on that.
"""

from __future__ import annotations
import os
import sys
import subprocess
from typing import Optional

_PROG_ID   = "LabUI.Profile"
_EXT       = ".labui"
_MIME_TYPE = "application/x-labui"


def _exe_path() -> str:
    return sys.executable


def is_registered() -> bool:
    if sys.platform.startswith("win"):
        return _win_is_registered()
    if sys.platform.startswith("linux"):
        return _linux_is_registered()
    return False


def register() -> Optional[str]:
    """Register .labui with this app. Returns an error string, or None on success."""
    try:
        if sys.platform.startswith("win"):
            _win_register()
        elif sys.platform.startswith("linux"):
            _linux_register()
        else:
            return f"File association isn't needed on this platform ({sys.platform})."
        return None
    except Exception as e:
        return str(e)


def unregister() -> Optional[str]:
    """Remove the association. Returns an error string, or None on success."""
    try:
        if sys.platform.startswith("win"):
            _win_unregister()
        elif sys.platform.startswith("linux"):
            _linux_unregister()
        return None
    except Exception as e:
        return str(e)


# ── Windows ──────────────────────────────────────────────────────────────────

def _win_is_registered() -> bool:
    import winreg
    try:
        with winreg.OpenKey(winreg.HKEY_CURRENT_USER,
                             f"Software\\Classes\\{_EXT}") as k:
            value, _ = winreg.QueryValueEx(k, "")
            return value == _PROG_ID
    except FileNotFoundError:
        return False


def _win_register():
    import winreg
    exe = _exe_path()

    with winreg.CreateKey(winreg.HKEY_CURRENT_USER,
                           f"Software\\Classes\\{_EXT}") as k:
        winreg.SetValueEx(k, "", 0, winreg.REG_SZ, _PROG_ID)

    with winreg.CreateKey(winreg.HKEY_CURRENT_USER,
                           f"Software\\Classes\\{_PROG_ID}") as k:
        winreg.SetValueEx(k, "", 0, winreg.REG_SZ, "LabUI Profile")

    with winreg.CreateKey(winreg.HKEY_CURRENT_USER,
                           f"Software\\Classes\\{_PROG_ID}\\DefaultIcon") as k:
        winreg.SetValueEx(k, "", 0, winreg.REG_SZ, f'"{exe}",0')

    with winreg.CreateKey(winreg.HKEY_CURRENT_USER,
                           f"Software\\Classes\\{_PROG_ID}\\shell\\open\\command") as k:
        winreg.SetValueEx(k, "", 0, winreg.REG_SZ, f'"{exe}" "%1"')

    _win_notify_shell()


def _win_unregister():
    import winreg
    for path in (
        f"Software\\Classes\\{_PROG_ID}\\shell\\open\\command",
        f"Software\\Classes\\{_PROG_ID}\\shell\\open",
        f"Software\\Classes\\{_PROG_ID}\\shell",
        f"Software\\Classes\\{_PROG_ID}\\DefaultIcon",
        f"Software\\Classes\\{_PROG_ID}",
        f"Software\\Classes\\{_EXT}",
    ):
        try:
            winreg.DeleteKey(winreg.HKEY_CURRENT_USER, path)
        except FileNotFoundError:
            pass
    _win_notify_shell()


def _win_notify_shell():
    """Tell Explorer the file-type association changed — otherwise it keeps
    showing the old icon/handler until logoff or reboot."""
    try:
        import ctypes
        SHCNE_ASSOCCHANGED = 0x08000000
        SHCNF_IDLIST = 0x0000
        ctypes.windll.shell32.SHChangeNotify(SHCNE_ASSOCCHANGED, SHCNF_IDLIST, None, None)
    except Exception:
        pass


# ── Linux (XDG) ──────────────────────────────────────────────────────────────

def _xdg_data_home() -> str:
    return os.environ.get("XDG_DATA_HOME") or os.path.join(os.path.expanduser("~"), ".local", "share")


def _desktop_file_path() -> str:
    return os.path.join(_xdg_data_home(), "applications", "labui.desktop")


def _mime_package_path() -> str:
    return os.path.join(_xdg_data_home(), "mime", "packages", "labui-labui.xml")


def _linux_is_registered() -> bool:
    return os.path.isfile(_desktop_file_path())


def _linux_register():
    exe = _exe_path()

    desktop_path = _desktop_file_path()
    os.makedirs(os.path.dirname(desktop_path), exist_ok=True)
    with open(desktop_path, "w") as f:
        f.write(
            "[Desktop Entry]\n"
            "Type=Application\n"
            "Name=LabUI\n"
            f"Exec={exe} %f\n"
            "Terminal=false\n"
            f"MimeType={_MIME_TYPE};\n"
            "NoDisplay=true\n"
        )

    mime_path = _mime_package_path()
    os.makedirs(os.path.dirname(mime_path), exist_ok=True)
    with open(mime_path, "w") as f:
        f.write(
            '<?xml version="1.0" encoding="UTF-8"?>\n'
            '<mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">\n'
            f'  <mime-type type="{_MIME_TYPE}">\n'
            '    <comment>LabUI Profile</comment>\n'
            f'    <glob pattern="*{_EXT}"/>\n'
            '  </mime-type>\n'
            '</mime-info>\n'
        )

    # Best-effort — desktop-environment dependent, the glob-matched .desktop
    # file alone is often enough even if these tools/steps are unavailable.
    _run_best_effort(["update-desktop-database", os.path.join(_xdg_data_home(), "applications")])
    _run_best_effort(["update-mime-database", os.path.join(_xdg_data_home(), "mime")])
    _run_best_effort(["xdg-mime", "default", "labui.desktop", _MIME_TYPE])


def _linux_unregister():
    for path in (_desktop_file_path(), _mime_package_path()):
        try:
            os.remove(path)
        except FileNotFoundError:
            pass
    _run_best_effort(["update-desktop-database", os.path.join(_xdg_data_home(), "applications")])
    _run_best_effort(["update-mime-database", os.path.join(_xdg_data_home(), "mime")])


def _run_best_effort(cmd: list):
    try:
        subprocess.run(cmd, check=False, capture_output=True, timeout=5)
    except Exception:
        pass