from __future__ import annotations

import json
import os
import secrets
import shlex
import subprocess
import stat
import string
import sys
import time
import re
import urllib.parse
from urllib.request import Request, urlopen
import urllib.error
import pathlib
from datetime import datetime, date
from enum import Enum
from typing import Callable, Optional, Dict, Any, List, Union, Iterator, TYPE_CHECKING
from select import epoll, EPOLLIN, EPOLLHUP
from shutil import which

from .exceptions import RequirementError, SysCallError
from .output import debug, error, info
from .storage import storage


if TYPE_CHECKING:
	from .installer import Installer


def generate_password(length :int = 64) -> str:
	haystack = string.printable # digits, ascii_letters, punctiation (!"#$[] etc) and whitespace
	return ''.join(secrets.choice(haystack) for i in range(length))


def locate_binary(name :str) -> str:
	if path := which(name):
		return path
	raise RequirementError(f"Binary {name} does not exist.")


def clear_vt100_escape_codes(data :Union[bytes, str]) -> Union[bytes, str]:
	# https://stackoverflow.com/a/43627833/929999
	vt100_escape_regex = r'\x1B\[[?0-9;]*[a-zA-Z]'
	if isinstance(data, bytes):
		return re.sub(vt100_escape_regex.encode(), b'', data)
	return re.sub(vt100_escape_regex, '', data)


def jsonify(obj: Any, safe: bool = True) -> Any:
	"""
	Converts objects into json.dumps() compatible nested dictionaries.
	Setting safe to True skips dictionary keys starting with a bang (!)
	"""

	compatible_types = str, int, float, bool
	if isinstance(obj, dict):
		return {
			key: jsonify(value, safe)
			for key, value in obj.items()
			if isinstance(key, compatible_types)
			and not (isinstance(key, str) and key.startswith("!") and safe)
		}
	if isinstance(obj, Enum):
		return obj.value
	if hasattr(obj, 'json'):
		# json() is a friendly name for json-helper, it should return
		# a dictionary representation of the object so that it can be
		# processed by the json library.
		return jsonify(obj.json(), safe)
	if hasattr(obj, '__dump__'):
		return obj.__dump__()
	if isinstance(obj, (datetime, date)):
		return obj.isoformat()
	if isinstance(obj, (list, set, tuple)):
		return [jsonify(item, safe) for item in obj]
	if isinstance(obj, pathlib.Path):
		return str(obj)
	if hasattr(obj, "__dict__"):
		return vars(obj)
	return str(obj)

class JSON(json.JSONEncoder, json.JSONDecoder):
	"""
	A safe JSON encoder that will omit private information in dicts (starting with !)
	"""

	def encode(self, obj: Any) -> str:
		return super().encode(jsonify(obj))


class UNSAFE_JSON(json.JSONEncoder, json.JSONDecoder):
	"""
	UNSAFE_JSON will call/encode and keep private information in dicts (starting with !)
	"""

	def encode(self, obj: Any) -> str:
		return super().encode(jsonify(obj, safe=False))


class SysCommandWorker:
	def __init__(
		self,
		cmd :Union[str, List[str]],
		callbacks :Optional[Dict[str, Any]] = None,
		peek_output :Optional[bool] = False,
		environment_vars :Optional[Dict[str, Any]] = None,
		logfile :Optional[None] = None,
		working_directory :Optional[str] = './',
		remove_vt100_escape_codes_from_lines :bool = True
	):
		callbacks = callbacks or {}
		environment_vars = environment_vars or {}

		if isinstance(cmd, str):
			cmd = shlex.split(cmd)

		if cmd:
			if cmd[0][0] != '/' and cmd[0][:2] != './': # pathlib.Path does not work well
				cmd[0] = locate_binary(cmd[0])

		self.cmd = cmd
		self.callbacks = callbacks
		self.peek_output = peek_output
		# define the standard locale for command outputs. For now the C ascii one. Can be overridden
		self.environment_vars = {**storage.get('CMD_LOCALE',{}),**environment_vars}
		self.logfile = logfile
		self.working_directory = working_directory

		self.exit_code :Optional[int] = None
		self._trace_log = b''
		self._trace_log_pos = 0
		self.poll_object = epoll()
		self.child_fd :Optional[int] = None
		self.started :Optional[float] = None
		self.ended :Optional[float] = None
		self.remove_vt100_escape_codes_from_lines :bool = remove_vt100_escape_codes_from_lines

	def __contains__(self, key: bytes) -> bool:
		"""
		Contains will also move the current buffert position forward.
		This is to avoid re-checking the same data when looking for output.
		"""
		assert isinstance(key, bytes)

		index = self._trace_log.find(key, self._trace_log_pos)
		if index >= 0:
			self._trace_log_pos += index + len(key)
			return True

		return False

	def __iter__(self, *args :str, **kwargs :Dict[str, Any]) -> Iterator[bytes]:
		last_line = self._trace_log.rfind(b'\n')
		lines = filter(None, self._trace_log[self._trace_log_pos:last_line].splitlines())
		for line in lines:
			if self.remove_vt100_escape_codes_from_lines:
				line = clear_vt100_escape_codes(line)  # type: ignore

			yield line + b'\n'

		self._trace_log_pos = last_line

	def __repr__(self) -> str:
		self.make_sure_we_are_executing()
		return str(self._trace_log)

	def __str__(self) -> str:
		try:
			return self._trace_log.decode('utf-8')
		except UnicodeDecodeError:
			return str(self._trace_log)

	def __enter__(self) -> 'SysCommandWorker':
		return self

	def __exit__(self, *args :str) -> None:
		# b''.join(sys_command('sync')) # No need to, since the underlying fs() object will call sync.
		# TODO: https://stackoverflow.com/questions/28157929/how-to-safely-handle-an-exception-inside-a-context-manager

		if self.child_fd:
			try:
				os.close(self.child_fd)
			except:
				pass

		if self.peek_output:
			# To make sure any peaked output didn't leave us hanging
			# on the same line we were on.
			sys.stdout.write("\n")
			sys.stdout.flush()

		if len(args) >= 2 and args[1]:
			debug(args[1])

		if self.exit_code != 0:
			raise SysCallError(
				f"{self.cmd} exited with abnormal exit code [{self.exit_code}]: {str(self)[-500:]}",
				self.exit_code,
				worker=self
			)

	def is_alive(self) -> bool:
		self.poll()

		if self.started and self.ended is None:
			return True

		return False

	def write(self, data: bytes, line_ending :bool = True) -> int:
		assert type(data) == bytes  # TODO: Maybe we can support str as well and encode it

		self.make_sure_we_are_executing()

		if self.child_fd:
			return os.write(self.child_fd, data + (b'\n' if line_ending else b''))

		return 0

	def make_sure_we_are_executing(self) -> bool:
		if not self.started:
			return self.execute()
		return True

	def tell(self) -> int:
		self.make_sure_we_are_executing()
		return self._trace_log_pos

	def seek(self, pos :int) -> None:
		self.make_sure_we_are_executing()
		# Safety check to ensure 0 < pos < len(tracelog)
		self._trace_log_pos = min(max(0, pos), len(self._trace_log))

	def peak(self, output: Union[str, bytes]) -> bool:
		if self.peek_output:
			if isinstance(output, bytes):
				try:
					output = output.decode('UTF-8')
				except UnicodeDecodeError:
					return False

			peak_logfile = pathlib.Path(f"{storage['LOG_PATH']}/cmd_output.txt")

			change_perm = False
			if peak_logfile.exists() is False:
				change_perm = True

			with peak_logfile.open("a") as peek_output_log:
				peek_output_log.write(str(output))

			if change_perm:
				os.chmod(str(peak_logfile), stat.S_IRUSR | stat.S_IWUSR | stat.S_IRGRP)

			sys.stdout.write(str(output))
			sys.stdout.flush()

		return True

	def poll(self) -> None:
		self.make_sure_we_are_executing()

		if self.child_fd:
			got_output = False
			for fileno, event in self.poll_object.poll(0.1):
				try:
					output = os.read(self.child_fd, 8192)
					got_output = True
					self.peak(output)
					self._trace_log += output
				except OSError:
					self.ended = time.time()
					break

			if self.ended or (not got_output and not _pid_exists(self.pid)):
				self.ended = time.time()
				try:
					wait_status = os.waitpid(self.pid, 0)[1]
					self.exit_code = os.waitstatus_to_exitcode(wait_status)
				except ChildProcessError:
					try:
						wait_status = os.waitpid(self.child_fd, 0)[1]
						self.exit_code = os.waitstatus_to_exitcode(wait_status)
					except ChildProcessError:
						self.exit_code = 1

	def execute(self) -> bool:
		import pty

		if (old_dir := os.getcwd()) != self.working_directory:
			os.chdir(str(self.working_directory))

		# Note: If for any reason, we get a Python exception between here
		#   and until os.close(), the traceback will get locked inside
		#   stdout of the child_fd object. `os.read(self.child_fd, 8192)` is the
		#   only way to get the traceback without losing it.

		self.pid, self.child_fd = pty.fork()

		# https://stackoverflow.com/questions/4022600/python-pty-fork-how-does-it-work
		if not self.pid:
			history_logfile = pathlib.Path(f"{storage['LOG_PATH']}/cmd_history.txt")
			try:
				change_perm = False
				if history_logfile.exists() is False:
					change_perm = True

				try:
					with history_logfile.open("a") as cmd_log:
						cmd_log.write(f"{time.time()} {self.cmd}\n")

					if change_perm:
						os.chmod(str(history_logfile), stat.S_IRUSR | stat.S_IWUSR | stat.S_IRGRP)
				except (PermissionError, FileNotFoundError):
					# If history_logfile does not exist, ignore the error
					pass
				except Exception as e:
					exception_type = type(e).__name__
					error(f"Unexpected {exception_type} occurred in {self.cmd}: {e}")
					raise e

				os.execve(self.cmd[0], list(self.cmd), {**os.environ, **self.environment_vars})
				if storage['arguments'].get('debug'):
					debug(f"Executing: {self.cmd}")

			except FileNotFoundError:
				error(f"{self.cmd[0]} does not exist.")
				self.exit_code = 1
				return False
		else:
			# Only parent process moves back to the original working directory
			os.chdir(old_dir)

		self.started = time.time()
		self.poll_object.register(self.child_fd, EPOLLIN | EPOLLHUP)

		return True

	def decode(self, encoding :str = 'UTF-8') -> str:
		return self._trace_log.decode(encoding)


class SysCommand:
	def __init__(self,
		cmd :Union[str, List[str]],
		callbacks :Dict[str, Callable[[Any], Any]] = {},
		start_callback :Optional[Callable[[Any], Any]] = None,
		peek_output :Optional[bool] = False,
		environment_vars :Optional[Dict[str, Any]] = None,
		working_directory :Optional[str] = './',
		remove_vt100_escape_codes_from_lines :bool = True):

		self._callbacks = callbacks.copy()
		if start_callback:
			self._callbacks['on_start'] = start_callback

		self.cmd = cmd
		self.peek_output = peek_output
		self.environment_vars = environment_vars
		self.working_directory = working_directory
		self.remove_vt100_escape_codes_from_lines = remove_vt100_escape_codes_from_lines

		self.session :Optional[SysCommandWorker] = None
		self.create_session()

	def __enter__(self) -> Optional[SysCommandWorker]:
		return self.session

	def __exit__(self, *args :str, **kwargs :Dict[str, Any]) -> None:
		# b''.join(sys_command('sync')) # No need to, since the underlying fs() object will call sync.
		# TODO: https://stackoverflow.com/questions/28157929/how-to-safely-handle-an-exception-inside-a-context-manager

		if len(args) >= 2 and args[1]:
			error(args[1])

	def __iter__(self, *args :List[Any], **kwargs :Dict[str, Any]) -> Iterator[bytes]:
		if self.session:
			for line in self.session:
				yield line

	def __getitem__(self, key :slice) -> Optional[bytes]:
		if not self.session:
			raise KeyError(f"SysCommand() does not have an active session.")
		elif type(key) is slice:
			start = key.start or 0
			end = key.stop or len(self.session._trace_log)

			return self.session._trace_log[start:end]
		else:
			raise ValueError("SysCommand() doesn't have key & value pairs, only slices, SysCommand('ls')[:10] as an example.")

	def __repr__(self, *args :List[Any], **kwargs :Dict[str, Any]) -> str:
		return self.decode('UTF-8', errors='backslashreplace') or ''

	def __json__(self) -> Dict[str, Union[str, bool, List[str], Dict[str, Any], Optional[bool], Optional[Dict[str, Any]]]]:
		return {
			'cmd': self.cmd,
			'callbacks': self._callbacks,
			'peak': self.peek_output,
			'environment_vars': self.environment_vars,
			'session': self.session is not None
		}

	def create_session(self) -> bool:
		"""
		Initiates a :ref:`SysCommandWorker` session in this class ``.session``.
		It then proceeds to poll the process until it ends, after which it also
		clears any printed output if ``.peek_output=True``.
		"""
		if self.session:
			return True

		with SysCommandWorker(
			self.cmd,
			callbacks=self._callbacks,
			peek_output=self.peek_output,
			environment_vars=self.environment_vars,
			remove_vt100_escape_codes_from_lines=self.remove_vt100_escape_codes_from_lines,
			working_directory=self.working_directory) as session:

			self.session = session

			while not self.session.ended:
				self.session.poll()

		if self.peek_output:
			sys.stdout.write('\n')
			sys.stdout.flush()

		return True

	def decode(self, *args, **kwargs) -> Optional[str]:
		if self.session:
			return self.session._trace_log.decode(*args, **kwargs)
		return None

	@property
	def exit_code(self) -> Optional[int]:
		if self.session:
			return self.session.exit_code
		else:
			return None

	@property
	def trace_log(self) -> Optional[bytes]:
		if self.session:
			return self.session._trace_log
		return None


def _pid_exists(pid: int) -> bool:
	try:
		return any(subprocess.check_output(['/usr/bin/ps', '--no-headers', '-o', 'pid', '-p', str(pid)]).strip())
	except subprocess.CalledProcessError:
		return False


def run_custom_user_commands(commands :List[str], installation :Installer) -> None:
	for index, command in enumerate(commands):
		script_path = f"/var/tmp/user-command.{index}.sh"
		chroot_path = installation.target / script_path
		
		info(f'Executing custom command "{command}" ...')
		chroot_path.write_text(command)
		SysCommand(f"arch-chroot {installation.target} bash {script_path}")
		
		os.unlink(chroot_path)


def json_stream_to_structure(configuration_identifier : str, stream :str, target :dict) -> bool :
	"""
	Load a JSON encoded dictionary from a stream and merge it into an existing dictionary.
	A stream can be a filepath, a URL or a raw JSON string.
	Returns True if the operation succeeded, False otherwise.
	+configuration_identifier is just a parameter to get meaningful, but not so long messages
	"""

	raw: Optional[str] = None
	# Try using the stream as a URL that should be grabbed
	if urllib.parse.urlparse(stream).scheme:
		try:
			with urlopen(Request(stream, headers={'User-Agent': 'ArchInstall'})) as response:
				raw = response.read()
		except urllib.error.HTTPError as err:
			error(f"Could not fetch JSON from {stream} as {configuration_identifier}: {err}")
			return False

	# Try using the stream as a filepath that should be read
	if raw is None and (path := pathlib.Path(stream)).exists():
		try:
			raw = path.read_text()
		except Exception as err:
			error(f"Could not read file {stream} as {configuration_identifier}: {err}")
			return False

	try:
		# We use `or` to try the stream as raw JSON to be parsed
		structure = json.loads(raw or stream)
	except Exception as err:
		error(f"{configuration_identifier} contains an invalid JSON format: {err}")
		return False
	if not isinstance(structure, dict):
		error(f"{stream} passed as {configuration_identifier} is not a JSON encoded dictionary")
		return False
	target.update(structure)
	return True


def secret(x :str):
	""" return * with len equal to to the input string """
	return '*' * len(x)