import atexit
import json
import logging
from pathlib import Path
from typing import Union, Dict, List, Callable, Tuple

import discord

import utils
from . import vNoneTov1_0

logger = logging.getLogger(__name__)

# Functions used to convert between configuration versions, in a dictionary of: old_version -> converter
# Each converter takes the old configuration and returns the converted configuration and the new version
config_version_converters: Dict[Union[None, str], Callable[[Dict], Tuple[Dict, str]]] = {
	None: vNoneTov1_0.convert
}


class ChannelsConfigFile:
	"""
	Wrapper for the channels configuration file, telling which channels to watch and which channels were created by the bot.
	"""
	version = "1.0"

	@staticmethod
	def empty_config() -> Dict:
		"""
		:return: An empty configuration, used to initialise the configuration file
		"""
		return {
			"__version__": ChannelsConfigFile.version,
		}

	def __init__(self, config_file_path: Union[str, Path]):
		self.config_file = None  # File descriptor to the on-disk config file
		self.config = None  # In-memory configuration

		# Loading configuration from disk
		logger.debug("Loading channels configuration file")
		config_file_path = Path(config_file_path).absolute()
		if config_file_path.exists():
			if not config_file_path.is_file():
				raise ValueError(f"Config file {config_file_path} exists but is not a regular file")

			self.config_file = config_file_path.open("r+")

			if config_file_path.stat().st_size == 0:  # Config file is empty
				logger.warning(f"Config file {config_file_path} is empty, using empty config")
				self.config = self.empty_config()
				self.save_to_file()  # So that the file is proper json
			else:  # Config file is not empty
				has_been_converted = self.reload_from_disk()
				if has_been_converted:
					self.save_to_file()
		else:  # Config file does not exist
			self.config_file = config_file_path.open("w+")
			self.config = self.empty_config()
			self.save_to_file()  # So that the file is proper json

		# Verifying that attributes have been initialised properly
		assert self.config_file is not None and self.config is not None
		logger.debug("Channels configuration file successfully initialised")

		atexit.register(self.save_to_file)

	def reload_from_disk(self) -> bool:
		"""
		Reload the configuration from the on-disk file

		:return: Whether the configuration had to be converted to a more recent version because the on-file was an earlier version
		:except json.JSONDecodeError: if the file is not valid json
		:except ValueError: if the version of the configuration in the file is not known or can not be converted to a more recent one
		"""
		logger.debug("Loading channels configuration file from disk")
		self.config_file.seek(0)  # Moving to beginning of file
		try:
			self.config = json.load(self.config_file)
		except json.JSONDecodeError as e:
			logger.critical(f"JSON Error when parsing channels config file: {e}")
			raise e
		# Checking configuration version and converting if needed
		config_version = self.config["__version__"] if "__version__" in self.config else None
		has_been_converted = False
		if config_version != self.version:
			logger.info(f"Channels configuration file is an older version, converting (on-file: {config_version}, current: {self.version})...")

			# Performing the conversion
			while config_version != self.version:
				if config_version in config_version_converters:
					logger.debug(f"Converting from {config_version}")
					self.config, config_version = config_version_converters[config_version](self.config)
					logger.debug(f"Converted to {config_version}")
				else:
					logger.critical(f"Impossible to find converter to convert from {config_version}")
					raise ValueError(f"Configuration loading: impossible to convert on-file config to current version")
			has_been_converted = True

		assert self.config["__version__"] == self.version

		logger.debug("Loaded channels configuration file from disk")
		return has_been_converted

	def save_to_file(self, indent = 2) -> None:
		"""
		Save the configuration to the on-fisk file
		:param indent: Indentation to use for pretty-printing json
		"""
		logger.debug("Writing channels configuration file to disk")
		self.config_file.seek(0)
		self.config_file.truncate()
		json.dump(self.config, self.config_file, indent = indent)
		self.config_file.flush()
		logger.debug("Written channels configuration file to disk")

	def _get_guild_configuration(self, guild: discord.Guild) -> Dict:
		str_guild_id = str(guild.id)
		if str_guild_id not in self.config:
			self.config[str_guild_id] = {
				"_name": guild.name,
				"watched_channels": [],
				"created_channels": [],
			}
		return self.config[str_guild_id]

	def get_watched_channels_ids(self, guild: discord.Guild) -> List[int]:
		"""
		:return: The list of IDs of watched channels for the given guild. Beware that the returned list is not a copy, it should not be modified.
		"""
		guild_configuration = self._get_guild_configuration(guild)
		if "watched_channels" not in guild_configuration:
			guild_configuration["watched_channels"] = []
		return guild_configuration["watched_channels"]

	def add_channel_to_watched(self, guild: discord.Guild, channel: Union[discord.VoiceChannel, discord.Object]) -> bool:
		"""
		Add a voice channel to the list of channels that the bot should watch
		:return: True if the channel has been added, False if it was already present
		"""
		watched_channels = self.get_watched_channels_ids(guild)
		if channel.id in watched_channels:
			return False
		else:
			watched_channels.append(channel.id)
			self.save_to_file()
			return True

	def remove_channel_from_watched(self, guild: discord.Guild, channel: Union[discord.VoiceChannel, discord.Object]) -> bool:
		"""
		Attempt to remove a voice channel from the list of channels that the bot should watch
		:return: True if the channel was in the list and has been removed, False if it was not in the list
		"""
		watched_channels = self.get_watched_channels_ids(guild)
		size_before = len(watched_channels)
		utils.list_remove_all_occurrences(watched_channels, channel.id)  # Removing all occurrences of the channel, just in case
		if len(watched_channels) != size_before:  # Size differs: something must have been removed
			self.save_to_file()
			return True
		else:  # Same size: list has not been modified
			return False

	def clear_watched_channels(self, guild: discord.Guild) -> None:
		"""
		Remove all channels from the watched channels list
		"""
		self.get_watched_channels_ids(guild).clear()
		self.save_to_file()

	def is_watched(self, guild: discord.Guild, channel: discord.VoiceChannel) -> bool:
		"""
		:return: Whether the given channel is watched
		"""
		return channel.id in self.get_watched_channels_ids(guild)

	def _get_created_channels(self, guild: discord.Guild) -> List[int]:
		guild_configuration = self._get_guild_configuration(guild)
		if "created_channels" not in guild_configuration:
			guild_configuration["created_channels"] = []
		return guild_configuration["created_channels"]

	def add_channel_to_created(self, guild: discord.Guild, channel: discord.VoiceChannel) -> None:
		"""
		Add a voice channel to the list of channels that the bot has created and manages.
		"""
		self._get_created_channels(guild).append(channel.id)
		self.save_to_file()

	def remove_channel_from_created(self, guild: discord.Guild, channel: Union[discord.VoiceChannel, discord.Object]):
		"""
		Remove a voice channel from the list of channels that have been created by the bot
		"""
		created_channels = self._get_created_channels(guild)
		utils.list_remove_all_occurrences(created_channels, channel.id)
		# We could update the on-disk file, but we avoid it to limit the number of writes to disk.
		# It is not critical if this information is lost, and it will probably be updated properly anyway the next time the file is written
		# self.save_to_file()
		pass

	def is_created(self, guild: discord.Guild, channel: Union[discord.VoiceChannel, discord.Object]):
		"""
		:return: Whether the given channel is one of the channels that have been created by the bot
		"""
		return channel.id in self._get_created_channels(guild)