"""Install a desktop entry that does not depend on the GUI session's PATH."""

from __future__ import annotations

import argparse
import os
from pathlib import Path
import sys
from typing import Sequence


EXECUTABLE_TOKEN = "@PTLINUX_EXECUTABLE@"
ICON_TOKEN = "@PTLINUX_ICON@"


class DesktopEntryError(ValueError):
	"""Raised when a safe desktop entry cannot be rendered."""


def quote_exec_argument(value: str) -> str:
	"""Quote one Desktop Entry ``Exec`` argument without field-code expansion."""

	if not value or any(character in value for character in ("\x00", "\n", "\r")):
		raise DesktopEntryError("desktop executable path contains invalid characters")
	escaped = value.replace("\\", "\\\\\\\\")
	escaped = escaped.replace('"', '\\\\"')
	escaped = escaped.replace("`", "\\\\`")
	escaped = escaped.replace("$", "\\\\$")
	escaped = escaped.replace("%", "%%")
	return f'"{escaped}"'


def escape_icon_path(value: str) -> str:
	"""Escape one absolute Desktop Entry ``Icon`` path as a string value."""

	if not value or any(character in value for character in ("\x00", "\n", "\r")):
		raise DesktopEntryError("desktop icon path contains invalid characters")
	return value.replace("\\", "\\\\")


def render_desktop_entry(template: str, executable: Path, icon: Path) -> str:
	"""Replace launcher and icon tokens with validated absolute paths."""

	if template.count(EXECUTABLE_TOKEN) != 1:
		raise DesktopEntryError("desktop template must contain exactly one executable token")
	if template.count(ICON_TOKEN) != 1:
		raise DesktopEntryError("desktop template must contain exactly one icon token")
	launcher = executable.expanduser()
	if not launcher.is_absolute():
		raise DesktopEntryError("desktop launcher path must be absolute")
	if not launcher.is_file() or not os.access(launcher, os.X_OK):
		raise DesktopEntryError(f"desktop launcher is missing or not executable: {launcher}")
	icon_path = icon.expanduser()
	if not icon_path.is_absolute():
		raise DesktopEntryError("desktop icon path must be absolute")
	if not icon_path.is_file():
		raise DesktopEntryError(f"desktop icon is missing: {icon_path}")
	rendered = template.replace(EXECUTABLE_TOKEN, quote_exec_argument(str(launcher)))
	rendered = rendered.replace(ICON_TOKEN, escape_icon_path(str(icon_path)))
	return rendered if rendered.endswith("\n") else rendered + "\n"


def install_desktop_entry(
	template: Path,
	executable: Path,
	icon: Path,
	destination: Path,
) -> None:
	"""Render and atomically install one user-level desktop entry."""

	rendered = render_desktop_entry(
		template.read_text(encoding="utf-8"),
		executable,
		icon,
	)
	destination.parent.mkdir(parents=True, exist_ok=True)
	temporary = destination.with_name(f".{destination.name}.{os.getpid()}.tmp")
	try:
		temporary.write_text(rendered, encoding="utf-8")
		temporary.chmod(0o644)
		temporary.replace(destination)
	except BaseException:
		temporary.unlink(missing_ok=True)
		raise


def main(argv: Sequence[str] | None = None) -> int:
	parser = argparse.ArgumentParser(description="install the PristonTale EU desktop entry")
	parser.add_argument("template", type=Path)
	parser.add_argument("executable", type=Path)
	parser.add_argument("icon", type=Path)
	parser.add_argument("destination", type=Path)
	arguments = parser.parse_args(argv)
	try:
		install_desktop_entry(
			arguments.template,
			arguments.executable,
			arguments.icon,
			arguments.destination,
		)
	except (DesktopEntryError, OSError) as exc:
		print(f"Could not install desktop shortcut: {exc}", file=sys.stderr)
		return 1
	return 0


if __name__ == "__main__":
	raise SystemExit(main())