from itertools import takewhile
from pathlib import Path
from typing import Iterator, List

from .exceptions import ServiceException, SysCallError
from .general import SysCommand
from .output import error


def list_keyboard_languages() -> Iterator[str]:
	for line in SysCommand("localectl --no-pager list-keymaps", environment_vars={'SYSTEMD_COLORS': '0'}):
		yield line.decode('UTF-8').strip()


def list_locales() -> List[str]:
	entries = Path('/etc/locale.gen').read_text().splitlines()
	# Before the list of locales begins there's an empty line with a '#' in front
	# so we'll collect the locales from bottom up and halt when we're done.
	locales = list(takewhile(bool, map(lambda entry: entry.strip('\n\t #'), reversed(entries))))
	locales.reverse()
	return locales


def list_x11_keyboard_languages() -> Iterator[str]:
	for line in SysCommand("localectl --no-pager list-x11-keymap-layouts", environment_vars={'SYSTEMD_COLORS': '0'}):
		yield line.decode('UTF-8').strip()


def verify_keyboard_layout(layout :str) -> bool:
	for language in list_keyboard_languages():
		if layout.lower() == language.lower():
			return True
	return False


def verify_x11_keyboard_layout(layout :str) -> bool:
	for language in list_x11_keyboard_languages():
		if layout.lower() == language.lower():
			return True
	return False


def set_keyboard_language(locale :str) -> bool:
	if len(locale.strip()):
		if not verify_keyboard_layout(locale):
			error(f"Invalid keyboard locale specified: {locale}")
			return False

		try:
			SysCommand(f'localectl set-keymap {locale}')
		except SysCallError as err:
			raise ServiceException(f"Unable to set locale '{locale}' for console: {err}")

		return True

	return False


def list_timezones() -> Iterator[str]:
	for line in SysCommand("timedatectl --no-pager list-timezones", environment_vars={'SYSTEMD_COLORS': '0'}):
		yield line.decode('UTF-8').strip()